A Randomized, Double-Blind, Phase 3 Safety and Efficacy Study of Ridinilazole Versus Vancomycin for Treatment of Clostridioides difficile Infection: Clinical Outcomes With Microbiome and Metabolome Correlates of Response

BACKGROUND

Exposure to antibiotics predisposes to dysbiosis and Clostridioides difficile infection (CDI) that can be severe, recurrent (rCDI), and life-threatening. Nonselective drugs that treat CDI and perpetuate dysbiosis are associated with rCDI, in part due to loss of microbiome-derived secondary bile acid (SBA) production. Ridinilazole is a highly selective drug designed to treat CDI and prevent rCDI.

METHODS

In this phase 3 superiority trial, adults with CDI, confirmed with a stool toxin test, were randomized to receive 10 days of ridinilazole (200 mg twice daily) or vancomycin (125 mg 4 times daily). The primary endpoint was sustained clinical response (SCR), defined as clinical response and no rCDI through 30 days after end of treatment. Secondary endpoints included rCDI and change in relative abundance of SBAs.

RESULTS

Ridinilazole and vancomycin achieved an SCR rate of 73% versus 70.7%, respectively, a treatment difference of 2.2% (95% CI: -4.2%, 8.6%). Ridinilazole resulted in a 53% reduction in recurrence compared with vancomycin (8.1% vs 17.3%; 95% CI: -14.1%, -4.5%; P = .0002). Subgroup analyses revealed consistent ridinilazole benefit for reduction in rCDI across subgroups. Ridinilazole preserved microbiota diversity, increased SBAs, and did not increase the resistome. Conversely, vancomycin worsened CDI-associated dysbiosis, decreased SBAs, increased Proteobacteria abundance (∼3.5-fold), and increased the resistome.

CONCLUSIONS

Although ridinilazole did not meet superiority in SCR, ridinilazole greatly reduced rCDI and preserved microbiome diversity and SBAs compared with vancomycin. These findings suggest that treatment of CDI with ridinilazole results in an earlier recovery of gut microbiome health. Clinical Trials Registration.Ri-CoDIFy 1 and 2: NCT03595553 and NCT03595566.

Tryptophan Metabolites And Their Predicted Microbial Sources In Fecal Samples From Healthy Individuals

Gut microbiota produce tryptophan metabolites (TMs) important to homeostasis. However, measuring TM levels in stool and determining their microbial sources can be difficult. Here, we measured TMs from the indole pathway in fecal samples from 21 healthy adults with the goal to: 1) determine fecal TM concentrations in healthy individuals; 2) link TM levels to bacterial abundance using 16S and whole genome shotgun (WGS) sequencing data; and 3) predict likely bacterial sources of TM production. Within our samples, we identified 151 genera (16S) and 592 bacterial species (WGS). Eight TMs were found in ≥17 fecal samples, including four in all persons. To our knowledge, we are the first to report fecal levels for indole-3-lactate, indole-3-propionate, and 3-indoleacrylate levels in healthy persons. Overall, indole, indole-3-acetate (IAA), and skatole accounted for 86% of the eight TMs measured. Significant correlations were found between seven TMs and 29 bacterial species.  Predicted multiple TM sources support the notion of a complex network of TM production and regulation. Further, the data suggest key roles for Collinsella aerofaciens and IAA, a metabolite reported to maintain intestinal homeostasis through enhanced barrier integrity and anti-inflammatory/antioxidant activities. These findings extend our understanding of TMs and their relationship to the microbial species that act as effectors and/or regulators in the healthy intestine and may lead to novel strategies designed to manipulate tryptophan metabolism to prevent disease and/or restore health to the dysbiotic gut.

Modulating a prebiotic food source influences inflammation and immune-regulating gut microbes and metabolites: insights from the BE GONE trial

BACKGROUND

Accessible prebiotic foods hold strong potential to jointly target gut health and metabolic health in high-risk patients. The BE GONE trial targeted the gut microbiota of obese surveillance patients with a history of colorectal neoplasia through a straightforward bean intervention.

METHODS

This low-risk, non-invasive dietary intervention trial was conducted at MD Anderson Cancer Center (Houston, TX, USA). Following a 4-week equilibration, patients were randomized to continue their usual diet without beans (control) or to add a daily cup of study beans to their usual diet (intervention) with immediate crossover at 8-weeks. Stool and fasting blood were collected every 4 weeks to assess the primary outcome of intra and inter-individual changes in the gut microbiome and in circulating markers and metabolites within 8 weeks. This study was registered on ClinicalTrials.gov as NCT02843425, recruitment is complete and long-term follow-up continues.

FINDINGS

Of the 55 patients randomized by intervention sequence, 87% completed the 16-week trial, demonstrating an increase on-intervention in diversity [n = 48; linear mixed effect and 95% CI for inverse Simpson index: 0.16 (0.02, 0.30); p = 0.02] and shifts in multiple bacteria indicative of prebiotic efficacy, including increased Faecalibacterium, Eubacterium and Bifidobacterium (all p < 0.05). The circulating metabolome showed parallel shifts in nutrient and microbiome-derived metabolites, including increased pipecolic acid and decreased indole (all p < 0.002) that regressed upon returning to the usual diet. No significant changes were observed in circulating lipoproteins within 8 weeks; however, proteomic biomarkers of intestinal and systemic inflammatory response, fibroblast-growth factor-19 increased, and interleukin-10 receptor-α decreased (p = 0.01).

INTERPRETATION

These findings underscore the prebiotic and potential therapeutic role of beans to enhance the gut microbiome and to regulate host markers associated with metabolic obesity and colorectal cancer, while further emphasizing the need for consistent and sustainable dietary adjustments in high-risk patients.

FUNDING

This study was funded by the American Cancer Society.

Tumor-resident Lactobacillus iners confer chemoradiation resistance through lactate-induced metabolic rewiring

Tumor microbiota can produce active metabolites that affect cancer and immune cell signaling, metabolism, and proliferation. Here, we explore tumor and gut microbiome features that affect chemoradiation response in patients with cervical cancer using a combined approach of deep microbiome sequencing, targeted bacterial culture, and in vitro assays. We identify that an obligate L-lactate-producing lactic acid bacterium found in tumors, Lactobacillus iners, is associated with decreased survival in patients, induces chemotherapy and radiation resistance in cervical cancer cells, and leads to metabolic rewiring, or alterations in multiple metabolic pathways, in tumors. Genomically similar L-lactate-producing lactic acid bacteria commensal to other body sites are also significantly associated with survival in colorectal, lung, head and neck, and skin cancers. Our findings demonstrate that lactic acid bacteria in the tumor microenvironment can alter tumor metabolism and lactate signaling pathways, causing therapeutic resistance. Lactic acid bacteria could be promising therapeutic targets across cancer types.

Functional Genomics of Gastrointestinal Escherichia coli Isolated from Patients with Cancer and Diarrhea

We describe the epidemiology and clinical characteristics of 29 patients with cancer and diarrhea in whom Enteroaggregative Escherichia coli (EAEC) was initially identified by GI BioFire panel multiplex. E. coli strains were successfully isolated from fecal cultures in 14 of 29 patients. Six of the 14 strains were identified as EAEC and 8 belonged to other diverse E. coli groups of unknown pathogenesis. We investigated these strains by their adherence to human intestinal organoids, cytotoxic responses, antibiotic resistance profile, full sequencing of their genomes, and annotation of their functional virulome. Interestingly, we discovered novel and enhanced adherence and aggregative patterns for several diarrheagenic pathotypes that were not previously seen when co-cultured with immortalized cell lines. EAEC isolates displayed exceptional adherence and aggregation to human colonoids compared not only to diverse GI E. coli , but also compared to prototype strains of other diarrheagenic E. coli . Some of the diverse E. coli strains that could not be classified as a conventional pathotype also showed an enhanced aggregative and cytotoxic response. Notably, we found a high carriage rate of antibiotic resistance genes in both EAEC strains and diverse GI E. coli isolates and observed a positive correlation between adherence to colonoids and the number of metal acquisition genes carried in both EAEC and the diverse E. coli strains. This work indicates that E. coli from cancer patients constitute strains of remarkable pathotypic and genomic divergence, including strains of unknown disease etiology with unique virulomes. Future studies will allow for the opportunity to re-define E. coli pathotypes with greater diagnostic accuracy and into more clinically relevant groupings.

Bacteroides ovatus alleviates dysbiotic microbiota-induced intestinal graft-versus-host disease

Acute gastrointestinal intestinal GVHD (aGI-GVHD) is a serious complication of allogeneic hematopoietic stem cell transplantation, and the intestinal microbiota is known to impact on its severity. However, an association between treatment response of aGI-GVHD and the intestinal microbiota has not been well-studied. In a cohort of patients with aGI-GVHD (n=37), we found that non-response to standard therapy with corticosteroids was associated with prior treatment with carbapenem antibiotics and loss of Bacteroides ovatus from the microbiome. In a mouse model of carbapenem-aggravated GVHD, introducing Bacteroides ovatus reduced severity of GVHD and improved survival. Bacteroides ovatus reduced degradation of colonic mucus by another intestinal commensal, Bacteroides thetaiotaomicron, via its ability to metabolize dietary polysaccharides into monosaccharides, which then inhibit mucus degradation by Bacteroides thetaiotaomicron and reduce GVHD-related mortality.

Risk Factors Associated with Severe Clostridioides difficile Infection in Patients with Cancer

INTRODUCTION

Antibiotic use is a risk factor for Clostridioides difficile infection (CDI). Few studies have correlated use of prior antibiotic classes with CDI, microbiome composition, and disease severity in patients with cancer. We hypothesized that previous antibiotic exposure and fecal microbiome composition at time of presentation are risk factors for severe CDI in patients with cancer.

METHODS

This non-interventional, prospective, cohort study examined 200 patients with cancer who had their first episode or first recurrence of CDI. C. difficile was identified using nucleic acid amplification testing. Univariate analysis was used to determine significant risk factors for severe CDI. Fecal microbiome composition was determined by sequencing the V3/V4 region of 16 s rDNA encoding gene. Differential abundance analyses were used to single out significant microbial features which differed across severity levels.

RESULTS

On univariate analysis, factors associated with severe CDI included the presence of toxin A/B in stools (odds ratio [OR] 2.14 [1.05-4.36] p = 0.04 and prior 90-day metronidazole use (OR 2.66 [1.09-6.50] p = 0.03). Although alpha and beta diversity was similar between disease severity groups and toxin A/B in stools, increased abundance of Bacteroides uniformis, Ruminococcaceae, and Citrobacter koseri were associated with protection from severe CDI (p < 0.05) and depletion of anaerobes was higher in patients with prior metronidazole exposure.

CONCLUSION

Use of metronidazole for non-CDI indications within 90 days prior to diagnosis and presence of toxin A/B in stools were associated with severe CDI. Findings provide valuable insights into risk factors for severe CDI in an underserved population with cancer that warrants further exploration.

730. A Phase 3, Randomized, Double-Blind Study to Evaluate the Efficacy and Safety of Ridinilazole Compared with Vancomycin for the Treatment of Clostridioides difficile Infection

Background

Vancomycin (VAN) therapy for C. difficile infection (CDI) is effective with &gt; 80% clinical response (CR) but is associated with 20–30% recurrence rate (rCDI). Secondary bile acids (2° BAs) inhibit C. difficile germination and help prevent rCDI. VAN depletes the gut microbiome decreasing the conversion of primary bile acids to 2° BAs. Ridinilazole (RDZ) is a highly selective anti-CDI, DNA-binding antibiotic in development for the treatment of CDI and prevention of rCDI.

Methods

A global, double-blinded, randomized Phase 3 trial assessed a 10-day treatment with RDZ 200 mg BID vs VAN 125 mg QID for CDI. The primary endpoint was sustained clinical response (SCR) defined as CR and no rCDI through 30 days post-end of treatment (EOT). Other endpoints included rCDI, microbiome diversity and composition, and microbiome-derived 2° BAs concentration. rCDI was defined as a new episode of diarrhea with confirmed positive free toxin test (FTT), requiring additional CDI therapy. All participants were monitored for treatment emergent adverse events (TEAE).

Results

Of the 759 patients (pts) enrolled, 745 were included in the mITT population (RDZ n=370, VAN n=375). RDZ achieved a numerically higher SCR rate than VAN (73.0% vs 70.7%) p=0.4672. RDZ resulted in a significant reduction in rCDI rate (8.1% vs 17.3%, p=0.0002) (Fig 1). In a pre-specified subpopulation, this was most notable in pts not receiving other antibiotics (rCDI 6.7% in RDZ vs 16.5% in VAN, p=0.0005). Microbiome alpha diversity was higher for RDZ vs VAN at EOT and EOT+30d (p&lt; 0.0001 and p≤ 0.0007 respectively, Fig 2) as were relative abundance (p&lt; 0.0001 and p=0.0203 respectively), and concentrations of 2° BAs (Fig 3). Higher microbiome diversity and concentrations of 2° BAs at EOT were associated with both lower rCDI and higher SCR rates. RDZ was well tolerated (pts with ≥ 1 TEAE: RDZ 36.4% vs VAN 35.5%, treatment discontinuation due to TEAE: RDZ 0.8% vs. VAN 2.9%).

Conclusion

RDZ was effective for sustained clinical response and safe for the treatment of patients with CDI. This was most notable in pts not receiving antibiotics. Compared to VAN, RDZ patients had faster recovery of fecal 2° BA, consistent with the preservation of microbiome diversity, resulting in a significantly lower rate of rCDI.

Disclosures

Pablo C. Okhuysen, MD, AstraZeneca: Stocks/Bonds|Beam Therapeutics: Stocks/Bonds|Biontech: Stocks/Bonds|Deinove: Grant/Research Support|Ferring: Advisor/Consultant|Glaxo Smith Kleine: Stocks/Bonds|Johnson and Johnson: Stocks/Bonds|Melinta: Grant/Research Support|Merck Sharp & Dohme Corp: Grant/Research Support|Moderna: Stocks/Bonds|Napo Pharmaceuticals: Advisor/Consultant|Napo Pharmaceuticals: Grant/Research Support|Novavax: Stocks/Bonds|Pfizer: Stocks/Bonds|Summit: Advisor/Consultant|Summit: Grant/Research Support Kevin W. Garey, PharmD, MS, Acurx: Grant/Research Support|cidara: Advisor/Consultant|cidara: Grant/Research Support|Paratek: Grant/Research Support|Seres Health: Grant/Research Support|Summit: Grant/Research Support Thomas J. Louie, MD, adiso therapeutics: Advisor/Consultant|adiso therapeutics: Grant/Research Support|crestone: Advisor/Consultant|crestone: Grant/Research Support|Finch: Advisor/Consultant|Finch: Grant/Research Support|Seres Therapeutics: Advisor/Consultant|Seres Therapeutics: Grant/Research Support|Seres Therapeutics: Honoraria|summit plc: Grant/Research Support|vedanta biosciences: Advisor/Consultant|vedanta biosciences: Grant/Research Support Jianling LI, MS, Abbott: Stocks/Bonds|Abbvie: Stocks/Bonds|ALX Oncology: Stocks/Bonds|BioNTech: Stocks/Bonds|Bluebird Bio: Stocks/Bonds|Cytokinetics: Stocks/Bonds|I-Mab: Stocks/Bonds|Johnson & Johnson: Stocks/Bonds|Moderna: Stocks/Bonds|TG Therapeutics: Stocks/Bonds Esther Duperchy, PhD, Summit Plc: Employee Jose G. Montoya, MD, Summit: Honoraria|Summit: Stocks/Bonds Lori Styles, MD, Abbvie: Stocks/Bonds|Summit Therapeutics: employee|Summit Therapeutics: Stocks/Bonds Fong Clow, Sc. D, Summit Therapeutics: Employee Danelle James, MD, Summit Therapeutics: Employee.

2108. Evaluation of Bezlotoxumab for the Prevention of Recurrent Clostridioides difficile Infection in Patients Living With Cancer at a Large Comprehensive Cancer Center

Background

Bezlotoxumab is a fully human monoclonal antibody that binds and neutralizes Clostridioides difficile toxin B. Administration of bezlotoxumab along with standard of care antibiotic (SoC) treatment of C. difficile infections (CDI) is associated with lower rates of CDI recurrence (rCDI). We aimed to determine the real-world incidence of rCDI in patients with cancer within 12 weeks after receiving bezlotoxumab.

Methods

This is a retrospective, single-center, descriptive study of patients with cancer that received bezlotoxumab from Jan 2018 through Oct 2021 at a large cancer center. rCDI was defined as a clinical illness associated with a positive stool nucleic acid amplification test with or without a confirmatory toxin assay for which CDI SoC was prescribed.

Results

A total of 131 patients were included in the study (median age of 63 years, 47% male, 77% Caucasian, 21% ICU admission), with 31% having one or more CDI episodes ≤ 6 months prior to receiving bezlotoxumab. The most common primary cancer type was leukemia (36%) followed by a solid organ tumor (35%), lymphoma (21%), and myeloma (8%). Cytotoxic chemotherapy or immune checkpoint inhibitors were prescribed within 6 months in 78% of cases and 60% of patients were given antibiotics not related to CDI. Fidaxomicin was most frequently administered as SoC (56%), followed by oral vancomycin (44%) with or without intravenous metronidazole. Within 12 weeks following bezlotoxumab treatment, rCDI occurred in 14 (10.7%, 95% Cl 5.4% to 16.0%) patients. Using univariate analysis, patients with rCDI were more likely to have received levofloxacin before and during bezlotoxumab treatment (86% versus 47%; OR 6.76, 95% CI 1.45 - 31.56, p=0.009).

Conclusion

In this real-world study, the rate of rCDI following use of bezlotoxumab during SoC antibiotics was comparable to that seen in clinical trials. Use of levofloxacin as prophylaxis for prolonged neutropenia in hematologic malignancies was associated with significantly higher rates of rCDI in patients that received bezlotoxumab. Our study suggests that neutropenia and antibiotic induced dysbiosis are risk factors for rCDI despite bezlotoxumab administration.

Disclosures

Pablo C. Okhuysen, MD, AstraZeneca: Stocks/Bonds|Beam Therapeutics: Stocks/Bonds|Biontech: Stocks/Bonds|Deinove: Grant/Research Support|Ferring: Advisor/Consultant|Glaxo Smith Kleine: Stocks/Bonds|Johnson and Johnson: Stocks/Bonds|Melinta: Grant/Research Support|Merck Sharp & Dohme Corp: Grant/Research Support|Moderna: Stocks/Bonds|Napo Pharmaceuticals: Advisor/Consultant|Napo Pharmaceuticals: Grant/Research Support|Novavax: Stocks/Bonds|Pfizer: Stocks/Bonds|Summit: Advisor/Consultant|Summit: Grant/Research Support.

1844. Mortality associated with Stenotrophomonas maltophilia bloodstream infection in patients with leukemia

Background

Patients with leukemia are disproportionately vulnerable to infections caused by S. maltophilia and mortality approaches 100% in patients with hemorrhagic pneumonia. Trimethoprim-sulfamethoxazole (SXT) is the drug of choice for treatment of infections caused by S. maltophilia however allergies, toxicity, and resistance may preclude its use. We sought to characterize clinical outcomes of patients with leukemia and S. maltophilia bloodstream infection (BSI).

Methods

Patients with leukemia are disproportionately vulnerable to infections caused by S. maltophilia and mortality approaches 100% in patients with hemorrhagic pneumonia. Trimethoprim-sulfamethoxazole (SXT) is the drug of choice for treatment of infections caused by S. maltophilia however allergies, toxicity, and resistance may preclude its use. We sought to characterize clinical outcomes of patients with leukemia and S. maltophilia bloodstream infection (BSI).

Results

Ninety-six patients with leukemia and S. maltophilia BSI were identified. The most common diagnosis was acute myeloid leukemia (60%); 31% had prior stem cell transplant. The most common single identified source was respiratory (31%) followed by central venous catheter (CVC, 26%). A single clear source was unable to be identified in 33%.Overall 14-day mortality was 31%. After excluding eleven patients who died within 24 hours, most patients received SXT (72%), followed by ceftazidime (40%), tigecycline (TGC, 40%), and minocycline (26%). SXT was associated with reduced mortality (hazard ratio [HR] 0.15, 95% confidence interval [CI] 0.05 – 0.44, p < 0.01) while TGC was associated with increased mortality (HR 3.13, 95% CI 1.00 – 9.73, p = 0.05). All patients who died were neutropenic at baseline and none had a CVC infection.

Conclusion

S. maltophilia BSI is associated with high mortality in patients with leukemia, particularly those with neutropenia at baseline. CVC infection alone was not associated with mortality. SXT is associated with reduced mortality relative to other antimicrobials. Alternative agents should be used with caution in these vulnerable patients.

Disclosures

Samuel L. Aitken, PharmD, MPH, Entasis Therapeutics: Advisor/Consultant|GlaxoSmithKline: Advisor/Consultant|Melinta: Grant/Research Support|Shionogi: Advisor/Consultant Pablo C. Okhuysen, MD, AstraZeneca: Stocks/Bonds|Beam Therapeutics: Stocks/Bonds|Biontech: Stocks/Bonds|Deinove: Grant/Research Support|Ferring: Advisor/Consultant|Glaxo Smith Kleine: Stocks/Bonds|Johnson and Johnson: Stocks/Bonds|Melinta: Grant/Research Support|Merck Sharp & Dohme Corp: Grant/Research Support|Moderna: Stocks/Bonds|Napo Pharmaceuticals: Advisor/Consultant|Napo Pharmaceuticals: Grant/Research Support|Novavax: Stocks/Bonds|Pfizer: Stocks/Bonds|Summit: Advisor/Consultant|Summit: Grant/Research Support.

Diet-derived metabolites and mucus link the gut microbiome to fever after cytotoxic cancer treatment

Not all patients with cancer and severe neutropenia develop fever, and the fecal microbiome may play a role. In a single-center study of patients undergoing hematopoietic cell transplant (n = 119), the fecal microbiome was characterized at onset of severe neutropenia. A total of 63 patients (53%) developed a subsequent fever, and their fecal microbiome displayed increased relative abundances of Akkermansia muciniphila, a species of mucin-degrading bacteria (P = 0.006, corrected for multiple comparisons). Two therapies that induce neutropenia, irradiation and melphalan, similarly expanded A. muciniphila and additionally thinned the colonic mucus layer in mice. Caloric restriction of unirradiated mice also expanded A. muciniphila and thinned the colonic mucus layer. Antibiotic treatment to eradicate A. muciniphila before caloric restriction preserved colonic mucus, whereas A. muciniphila reintroduction restored mucus thinning. Caloric restriction of unirradiated mice raised colonic luminal pH and reduced acetate, propionate, and butyrate. Culturing A. muciniphila in vitro with propionate reduced utilization of mucin as well as of fucose. Treating irradiated mice with an antibiotic targeting A. muciniphila or propionate preserved the mucus layer, suppressed translocation of flagellin, reduced inflammatory cytokines in the colon, and improved thermoregulation. These results suggest that diet, metabolites, and colonic mucus link the microbiome to neutropenic fever and may guide future microbiome-based preventive strategies.

Fully resolved assembly of Cryptosporidium parvum

Background

Cryptosporidium parvum is an apicomplexan parasite commonly found across many host species with a global infection prevalence in human populations of 7.6%. Understanding its diversity and genomic makeup can help in fighting established infections and prohibiting further transmission. The basis of every genomic study is a high-quality reference genome that has continuity and completeness, thus enabling comprehensive comparative studies.

Findings

Here, we provide a highly accurate and complete reference genome of Cryptosporidium parvum. The assembly is based on Oxford Nanopore reads and was improved using Illumina reads for error correction. We also outline how to evaluate and choose from different assembly methods based on 2 main approaches that can be applied to other Cryptosporidium species. The assembly encompasses 8 chromosomes and includes 13 telomeres that were resolved. Overall, the assembly shows a high completion rate with 98.4% single-copy BUSCO genes.

Conclusions

This high-quality reference genome of a zoonotic IIaA17G2R1 C. parvum subtype isolate provides the basis for subsequent comparative genomic studies across the Cryptosporidium clade. This will enable improved understanding of diversity, functional, and association studies.

Clostridioides difficile infection in cancer patients receiving immune checkpoint inhibitors

Background

Immune checkpoint inhibitors (ICIs) have revolutionized cancer treatment, but are associated with immune-mediated diarrhea and colitis (IMDC). Clostridioides difficile infection (CDI) can cause infectious diarrhea with overlapping symptoms. Thus, we sought to elucidate the characteristics of CDI in patients treated with ICI, in the context of IMDC.

Methods

We conducted a retrospective, single-center study of adult cancer patients (N=421) with ICI exposure from 2015-2020 and a positive stool nucleic acid amplification test and/or enzyme immunoassay for CDI. Baseline characteristics, treatments, and outcomes were compared between patients with and without concurrent IMDC.

Results

Forty-one eligible patients were included, 27 with concurrent IMDC and 14 without. Twenty-seven patients were taking programmed death-1 or its ligand inhibitors and 14 were taking cytotoxic T-lymphocyte-associated antigen 4 inhibitors. Patients with concurrent CDI and IMDC had a longer symptom duration (20 vs. 5 days, P=0.003) and a higher rate of grade 3-4 diarrhea (41% vs. 7%, P=0.033). Among patients with concurrent IMDC, preceding antibiotics (P=0.050) and proton pump inhibitors (PPI) (P=0.038) were used more frequently among individuals who developed CDI after immunosuppressant exposure. Thirty-eight patients received antibiotics for CDI, while 5 required fecal microbiota transplantation for concurrent CDI & IMDC.

Conclusions

CDI is common in ICI-treated cancer patients, especially those with IMDC requiring immunosuppressants. Antibiotics did not alter the need for immunosuppressants in those with concurrent IMDC. Use of PPI and antibiotics while receiving immunosuppressants for IMDC was associated with a greater risk of CDI. Further large-scale studies are warranted to clarify the role of CDI, antibiotics and immunosuppression treatment in IMDC patients.

700. Risk Factors and Molecular Epidemiology of Acute and Chronic Norovirus Infection at a Large Tertiary Care Cancer Center

Background

Norovirus (NoV) is the leading cause of viral diarrhea in patients with cancer. In this study, we describe risk factors associated with acute and chronic NoV infection in this patient population.

Methods

We identified 132 patients with NoV diarrhea (using stool RT PCR) between 2016-2020 at University of Texas MD Anderson Cancer Center (MDACC). Patient data, including demographics, clinical characteristics, NoV treatments, and complications were retrospectively extracted from charts. Stool samples were analyzed for NoV genogroups and genotypes. We compared characteristics and outcomes of patients with acute diarrhea (< 14day; AD) versus chronic diarrhea ( >14day or recurrences within 12 weeks; CD) and analyzed the data using Pearson Chi square or Fisher’s exact for categorical variables and Wilcoxon rank-sum test for continuous variables.

Results

Of 132 patients identified, 124 had an underlying cancer (39 solid tumor, 85 hematological malignancies, Table 1). On univariate analysis, CD patients were more likely to have a hematological malignancy (p=0.002), be a hematopoietic stem cell recipient (p= 0.013), have a history of gastrointestinal graft versus host disease (p= 0.011), or have received immunosuppressants or steroids in the 90 days before diarrhea onset (p=0.001, Table 2). CD patients had significantly lower white blood cell counts (p=0.038), absolute neutrophil counts (p=0.049), IgG levels (p= 0.001), and serum albumin levels (p=0.002) at the time of NoV diagnosis (Table 3). Patients with CD more often received symptomatic or NoV targeting treatment, including anti-diarrheal (p=0.005), nitazoxanide (p< 0.001), intravenous immune globulin (p=0.017), and oral IgG (p=0.042). CD patients more often had diarrheal recurrence in the first 4 weeks (p=0.001) or the second month (p< 0.001) after initial diagnosis and needed enteral or parenteral nutrition (p=0.004). We genotyped NoV in 67 patients (Figure 1), resulting in identification of the following genogroups: GI (n=9, 13%), GII.4 (n=23, 34%), and other types of GII (n=35, 52%). Genotype diversity was higher in patients with CD than AD (Figure 1).

Conclusion

In patients with cancer, CD from NoV is associated with severe immunosuppression, is refractory to therapy and can be caused by a variety of NoV genotypes/genogroups.

Disclosures

Robert L. Atmar, MD, Takeda Vaccines, Inc. (Grant/Research Support) Mary Estes, PhD, Takeda Vaccines (Consultant, Grant/Research Support) Pablo C. Okhuysen, MD, FACP, FIDSA, Deinove Pharmaceuticals (Grant/Research Support)Ferring Pharmaceuticals (Consultant)Melinta Therapeutics (Grant/Research Support)Merck & Co. (Grant/Research Support)Napo Pharmaceuticals (Consultant, Scientific Research Study Investigator, Research Grant or Support)Singulex (Consultant)Summit Therapeutics (Grant/Research Support)

1410. Isoniazid Therapy for Latent Tuberculosis Infection in Patients with Cancer Treated with Checkpoint Inhibitors Immunotherapy

Background

Data on the efficacy and tolerability of latent tuberculosis infection (LTBI) treatment in cancer patients receiving checkpoint inhibitor immunotherapy (CPI) is limited. We sought to assess LTBI therapy and its adverse events and outcomes in patients treated with CPI.

Methods

We performed a retrospective cohort study at MD Anderson Cancer Center of adult patients, between April 2016 and May 2021, who were receiving CPI and were diagnosed with LTBI based on positive T-SPOT TB test. We then compared those patients treated with isoniazid (INH) 5mg/kg daily versus those that did not receive INH therapy.

Results

We identified 35 patients treated with CPI who had a diagnosis of LTBI. Patients were divided into 2 groups: CPI alone (23 patients, 65.7%) and CPI+INH (12 patients, 34.3%). The majority of patients in both groups had renal cell carcinoma (34.3%) and melanoma (17.1%). Nivolumab as monotherapy was the most commonly used CPI agent in both groups (37.1%), whereas nivolumab and ipilimumab combination was mainly used in the CPI group (34.7%) compared to CPI+INH group (8.3%). In the CPI+INH group, 7 patients (58.3%) developed moderate to severe hepatoxicity that led to discontinuation of INH and CPI therapy versus none in the CPI group (p= 0.001). There was no statistically significant difference in the alanine aminotransferase (ALT) at baseline between both groups (p=0.117), whereas the median ALT level was significantly higher during CPI+INH therapy compared to CPI alone (135 U/L vs 24 U/L respectively, p=0.025. Furthermore, immune-related adverse events were reported in a total of 12 of 35 patients (34.2%). None of the patients in either group developed tuberculosis reactivation during a follow up period of up to 1148 days.

Conclusion

Our data suggest that latent tuberculosis reactivation is rare in cancer patients on CPI immunotherapy. Hepatotoxicity remains a concern in this patient population with LTBI treated with CPI and INH. With the widespread use of CPI, close laboratory and clinical monitoring is required to avoid life-threatening drug-induced liver injury and interruption of LTBI therapy and immunotherapy. Further clinical studies are warranted to determine the optimal management of LTBI during CPI therapy.

Disclosures

Pablo C. Okhuysen, MD, FACP, FIDSA, Deinove Pharmaceuticals (Grant/Research Support)Ferring Pharmaceuticals (Consultant)Melinta Therapeutics (Grant/Research Support)Merck & Co. (Grant/Research Support)Napo Pharmaceuticals (Consultant, Scientific Research Study Investigator, Research Grant or Support)Singulex (Consultant)Summit Therapeutics (Grant/Research Support) Dimitrios P. Kontoyiannis, MD, Astellas (Consultant)Cidara Therapeutics (Advisor or Review Panel member)Gilead Sciences (Consultant, Grant/Research Support, Other Financial or Material Support, Honoraria)

Bihemispheric Cortical Infarcts in an Adult Secondary to Escherichia coli K1 Meningitis

Cerebral ischemia is a known complication of meningitis. Most Escherichia coli meningitis-induced infarcts have been reported in the neonatal and pediatric population. To the best of our knowledge, there have been no previous reports describing bilateral cortical infarcts in an adult secondary to a K1 strain of E. coli meningitis, and herein we report a case in a 25-year-old female. The challenge in treating this patient was determining the duration of systemic antibiotic treatment and whether or not to use steroids. This study demonstrates the necessity of early diagnosis and treatment of E. coli meningitis to prevent neurological complications, including stroke.

Clostridioides difficile Infection in Cancer and Immunocompromised Patients: Relevance of a Two-step Diagnostic Algorithm and Infecting Ribotypes on Clinical Outcomes

BACKGROUND

Patients with cancer are particularly vulnerable to Clostridioides difficile infection (CDI). Guidelines recommend a two-step diagnostic algorithm to differentiate carriers from CDI; however, there are limited data for this approach while including other confounding risk factors for diarrhea such as radiation, cytotoxic chemotherapy, and adoptive cell based therapies.

METHODS

We conducted a prospective, non-interventional, single center, cohort study of cancer patients with acute diarrhea and C. difficile, identified in stools by nucleic acid amplification tests (NAAT) and culture. Fecal toxin A/B was detected by enzyme immunoassay (EIA) and isolates were ribotyped using 16s rRNA fluorescent sequencing. Patients were followed for 90 days to compare outcomes according to malignancy type, infecting ribotype, and EIA status.

RESULTS

We followed 227 patients with a positive NAAT. Of these, 87% were hospitalized and 83% had an active malignancy. EIA was confirmed positive in 80/227 (35%) of patients. Those with EIA+ were older (60 ± 18 years vs 54 ± 19 years., P = .01), more likely to fail therapy [24/80 (30%) vs 26/147 (18%), P = .04] and experience recurrence [20/80 (25%) vs 21/147(14%), P < .05]. We found a low prevalence (22%) of ribotypes historically associated with poor outcomes (002, 018, 027, 56, F078-126, 244) but their presence were associated with treatment failure [17/50 (34%) vs 33/177 (19%), P = .02].

CONCLUSIONS

When compared to cancer patients with fecal NAAT+/EIA-, patients with NAAT+/EIA+ CDI are less likely to respond to therapy and more likely to experience recurrence, particularly when due to ribotypes associated with poor outcomes.

Enteropathogenic Escherichia coli Infection in Cancer and Immunosuppressed Patients

BACKGROUND

The role of enteropathogenic Escherichia coli (EPEC) as a cause of diarrhea in cancer and immunocompromised patients is controversial. Quantitation of fecal bacterial loads has been proposed as a method to differentiate colonized from truly infected patients.

METHODS

We studied 77 adult cancer and immunosuppressed patients with diarrhea and EPEC identified in stools by FilmArray, 25 patients with pathogen-negative diarrhea, and 21 healthy adults without diarrhea. Stools were studied by quantitative polymerase chain reaction (qRT-PCR) for EPEC genes eaeA and lifA/efa-1 and strains characterized for virulence factors and adherence to human intestinal enteroids (HIEs).

RESULTS

Patients with EPEC were more likely to have community-acquired diarrhea (odds ratio, 3.82 [95% confidence interval, 1.5-10.0]; P = .008) compared with pathogen-negative cases. Although EPEC was identified in 3 of 21 (14%) healthy subjects by qPCR, the bacterial burden was low compared to patients with diarrhea (≤55 vs median, 6 × 104 bacteria/mg stool; P < .001). Among EPEC patients, the bacterial burden was higher in those who were immunosuppressed (median, 6.7 × 103 vs 55 bacteria/mg; P < .001) and those with fecal lifA/ifa-1 (median, 5 × 104 vs 120 bacteria/mg; P = .015). Response to antimicrobial therapy was seen in 44 of 48 (92%) patients with EPEC as the sole pathogen. Antimicrobial resistance was common and strains exhibited distinct patterns of adherence with variable cytotoxicity when studied in HIEs. Cancer care was delayed in 13% of patients.

CONCLUSIONS

Immunosuppressed cancer patients with EPEC-associated diarrhea carry high burden of EPEC with strains that are resistant to antibiotics, exhibit novel patterns of adherence when studied in HIEs, and interfere with cancer care.

Abstract LB223: Beans to Enrich the Gut microbiome vs. Obesity's Negative Effects: First results from the BE GONE Trial in high-risk colorectal patients

Background: Dry beans are a prebiotic food source rich in bioactive compounds with anti-inflammatory, anti-lipidemic and chemopreventive properties. The BE GONE trial tested the impact of an increase in dry bean consumption on gut microbiota and blood lipid profiles in high-risk colorectal (CR) patients otherwise consuming their usual diet. Methods: Following initiation of the pilot protocol (July 2016) among patients with a high-risk BMI and/or waist circumference and history of precancerous CR polyps, the crossover trial was expanded to patients with a history of CR cancer (May 2017). Patients were block randomized according to no vs. regular use of chronic disease medications commonly prescribed in the target population. Following a 4-week run-in/equilibration period, participants were randomized to continue the control diet (usual diet, no dry beans) or to begin the intervention diet (usual diet + dry beans). The intervention included a 2-week ramp-up to 1 cup/day navy beans (12 g dietary fiber; 14 g protein; 200 kcal) continued for an additional 6 weeks. Dietary habits, body weight, and other lifestyle parameters were monitored throughout the 20-week study. We characterized the 16Sv4 rDNA microbiome (Illumina MiSeq) and CLIA cholesterol panel in serial stool and fasting blood samples collected at baseline, week 4, and week 8 for each crossover period (n=249). Longitudinal analyses were conducted using generalized linear mixed models with random intercept and slope adjusted for chronic disease medication use examining the post-intervention effect from baseline to 4 weeks and baseline to 8 weeks. Results: Eligible patients were enrolled in the 4-week run-in/equilibration (n=69). Of these, 55 were randomized and 50 completed the 20-week trial in December 2019 with &gt;80% compliance. Primary reasons for withdrawal were work/travel/family obligations. Half (54%) of the participants were male, 74% were CR cancer survivors, 76% were white (non-Hispanic) and 40% were on statins and/or metformin. Pre-study dietary profiles were characterized by low mean intake of legumes (&lt;3 servings/month) and dietary fiber (17 g/day). The 8-week increase in bean intake significantly increased the inverse Simpson index [effect estimate and 95% CI: 1.59 (0.10, 3.08)], a diversity measure reflecting a greater variety of bacteria with a more even relative abundance. Longitudinal analyses restricted to taxa present in &gt;80% of patients at baseline, revealed significantly decreased Anaerostipes and Streptococcus at week 4 and increased Faecalibacterium at week 8, along with temporal fluctuations in other known specialized (e.g., pectin) and versatile fiber-fermenting bacteria of the Lachnospiraceae and Ruminococcaceae families. A modest decrease in LDL cholesterol was observed at 8-weeks [-2.64 (-6.91, 1.62)] Conclusions: Early results of the BE GONE trial suggest that an 8-week increase in dry bean intake may be sufficient to balance or enrich the gut microbiome of high-risk CR patients. Continued sample processing and analysis, including stool metagenomics and blood metabolomics should continue to shed light on functional interactions relevant to the human host.

Citation Format: Xiaotao Zhang, Kristi L. Hoffman, Fangyu Li, Ehsan Irajizad, Gladys Browman, Karen Basen-Engquist, Samir Hanash, Paul Scheet, Pablo C. Okhuysen, Scott Kopetz, Joseph Petrosino, Carrie R. Daniel. Beans to Enrich the Gut microbiome vs. Obesity's Negative Effects: First results from the BE GONE Trial in high-risk colorectal patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr LB223.

Norovirus in Cancer Patients: A Review

Norovirus (NoV) is the leading cause of viral-related diarrhea in cancer patients, in whom it can be chronic, contributing to decreased quality of life, interruption of cancer care, malnutrition, and altered mucosal barrier function. Immunosuppressed cancer patients shed NoV for longer periods of time than immunocompetent hosts, favoring quasispecies development and emergence of novel NoV variants. While nucleic acid amplification tests (NAATs) for NoV diagnosis have revolutionized our understanding of NoV burden of disease, not all NAATs provide information on viral load or infecting genotype. There is currently no effective antiviral or vaccine for chronic NoV infections. Screening for inhibitors of NoV replication in intestinal organoid culture models and creation of NoV-specific adoptive T cells are promising new strategies to develop treatments for chronic NoV in immunosuppressed patients. Herein we summarize data on the epidemiology, clinical manifestations, diagnostic challenges, and treatment of NoV infection in patients with cancer.

The impact of cancer-related diarrhea on changes in cancer therapy patterns

12111

Background: We studied the impact that cancer related diarrhea (CRD) has on cancer therapy and treatment patterns, including persistence, discontinuation, adherence, and switching of chemotherapy and targeted therapies in patients with and without CRD. Methods: We performed a longitudinal observational study among adult ( > 18 yrs) patients with CRD identified by diagnosis codes or pharmacy claims compared to matched (1:1) non-CRD patients using claims data derived from the IQVIA PharMetrics Plus database. Index date was defined as the date of the first cancer claim, and we re-indexed patients based on CRD claims. Each patient had a 6-month pre-index period and a minimum 3-month follow-up post-index period. To adjust for selection bias and baseline differences, we directly matched the CRD patients to non-CRD patients. Treatment patterns were evaluated and stratified for the first cancer therapy with or without CRD (chemotherapy vs targeted therapy vs both targeted and chemotherapy). Discontinuation was defined as a 30-day gap for chemotherapy and a 14-day gap for targeted therapies from index therapy; switching was a new chemotherapy or targeted therapy prescription within 30 days following discontinuation of index therapy. We computed adherence as the proportion of days covered over the 12-month post-index period and persistence as mean number of days on index therapy. A Cox proportional hazards model was used to estimate the difference in risk of discontinuation of index therapy between CRD and non-CRD cohorts. Results: We evaluated a total of 104,135 matched pairs of CRD and non-CRD adult patients with solid or hematologic cancer; each group further grouped by those receiving either chemotherapy (n = 47,220), targeted therapy (n = 2,427), or both treatments (n = 5,313). Patients with CRD discontinued the index therapy more frequently than non-CRD patients for chemotherapy (81.5% vs 62.3%), targeted therapy (69.2% vs 64.3%) or both (96.0% vs 85.5%) (p < 0.0001). Also, the overall percentage of discontinuation (82.4% vs. 64.6%) was significantly higher among patients with CRD. The mean time to discontinuation (59.6±54.1 vs. 68.3±76.6 days) was significantly lower (p < 0.0001) in patients with CRD. The mean time to switch (72.0±48.6 vs. 96.9±84.0 days), mean persistence (95.1±98.1 vs. 154.3±142.7 days), and mean adherence (25.5%±37.2 vs. 47.9±41%) were significantly lower (all p < 0.0001) among patients with CRD compared to non-CRD. The percentage of patients requiring a dose titration for their index cancer therapy was significantly higher (21.8%) for the CRD cohort versus 8.5% for non-CRD patients (p < 0.0001). Conclusions: Patients with CRD were 40% (adjusted) more likely to discontinue the index therapy than patients without CRD. The persistence of index cancer therapy and time to switch were also lower for patients with CRD. Strategies to control CRD and continue cancer therapy are urgently needed.

Characterizing unplanned resource utilization associated with cancer-related diarrhea

e18625

Background: In clinical oncology practice, diarrhea is a very common and severe side effect of cancer treatments including from radiotherapy, chemotherapy, and targeted therapies. Cancer-related diarrhea (CRD) leads to increased healthcare resource consumption due to unscheduled outpatient visits, and , increased hospital stays requiring intensive supportive care measures. We evaluated CRD patients receiving chemotherapy, targeted therapy, or both, requiring emergency department (ED), physician office visits, hospitalizations, and length of stay (LOS) compared to a matched cohort of non-CRD patients. Methods: We performed a longitudinal study among adult patients ( > 18 yrs) with CRD identified by diagnosis codes or pharmacy claims compared to matched non-CRD patients using claims data derived from the IQVIA PharMetrics Plus database. Index date was the first cancer claim date and patients were re-indexed based on their CRD claim. Each patient had a 6-month pre-index period, a minimum 3-month post-index period and had ≥12 months of continuous enrollment following the CRD index date. To adjust for selection bias and baseline differences, we matched CRD patients to non-CRD patients (1:1) by age, gender, geography and payer type. Patients were stratified by cancer therapy type (chemotherapy, targeted therapy or both treatments). We reported proportion of patients with hospitalizations, average length of stay (LOS), and ED visits. A generalized estimating equation model with log link and binomial distribution adjusted for type of cancer, therapy, and Charlson Comorbidity Index (CCI) was built to estimate the difference in occurrence of hospitalization between CRD and non-CRD cohorts. Results: We evaluated a total of 104,135 matched pairs of CRD and non-CRD adult patients with solid or hematologic cancer with 12-month continuous enrollment. The proportion of patients with ED visits (36.2% vs 18.9%, p < 0.0001) and hospitalizations (29.6% vs 12.8%, p < 0.0001) were significantly higher among CRD versus non-CRD cohort. When compared to non-CRD patients, CRD patients were more likely to be hospitalized (adjusted OR 2.28. 95% CI of 2.23-2.33). Mean CRD-specific office/hospital visits were significantly higher in the CRD cohort compared to the non-CRD cohort over the 12-month post-index period and patients had more CRD-specific visits to ED (7.5% vs 1.8%); physician’s offices (14.7% vs 3.8%); laboratory testing (11.6% vs 3.2%) and outpatient ancillary services (10.9% vs 2.6%) (all p < 0.0001). Mean hospital LOS among patients with CRD was higher than non-CRD patients (6.6±8.9 vs 5.8±10.5 days, p < 0.0001). Conclusions: Patients with CRD used significantly more resources, including outpatient services, ED visits, and hospitalizations. Effective prevention of CRD remains an unmet strategy to reduce the overall cost of cancer care.

Healthcare utilization and costs associated with cancer-related diarrhea

e18623

Background: Diarrhea is a common toxicity of cancer treatments, including radiotherapy, chemotherapy, and/or targeted therapies. Cancer-related diarrhea (CRD) leads to increased healthcare utilization and cost. This study evaluated the all-cause and CRD-specific healthcare utilization and cost of patients with CRD compared to a matched non-CRD cohort. Methods: We conducted a longitudinal observational study among adult patients ( > 18 years) with CRD using diagnosis codes or pharmacy claims compared to matched non-CRD patients using claims data from the IQVIA PharMetrics Plus database (October 2015 to March 2020). The index date was the date of the first cancer claim, and we re-indexed patients based on their CRD claim. Each patient had a 6-month pre-index period and a minimum 3-month post-index period. Patients were also required to have ≥12 months of continuous enrollment following the CRD index date. We directly matched patients 1:1 from the CRD cohort to the non-CRD cohort to adjust for selection bias and baseline differences. Our aim was to compare all-cause healthcare costs over a fixed 12-month post-index period, converting all costs to 2020 USD using the Consumer Price Index's medical component. We analyzed healthcare utilization for CRD-treated, CRD-inadequately treated, and CRD-untreated sub-cohorts (per Buono et al., J Econ 2017). Secondary endpoints included healthcare cost (proportion of patients, per-patient mean and median) and healthcare utilization (prescription fills and visits to the emergency department [ED], physician office, lab/pathology and outpatient ancillary services). We built one generalized estimating equation model with log link and gamma distribution adjusted for type of cancer, therapy and Charlson Comorbidity Index (CCI) to estimate the difference in total healthcare cost between CRD and non-CRD cohorts. Results: We evaluated a total of 104,135 matched pairs of CRD and non-CRD adult patients with solid or hematologic cancer receiving either targeted or chemotherapy, with 12-month continuous enrollment. Patients with CRD incurred significantly higher mean ($104,880 vs $39,664, p < 0.0001) and median ($59,969 vs $8,914, p < 0.0001) all-cause healthcare cost compared to patients without CRD over the 12-month post-index period. Inadequately treated CRD patients had the mean highest cost ($129,531) vs adequately CRD-treated ($107,050) or untreated CRD patients ($56,350) (all p < 0.0001). Mean pharmacy cost for CRD and non-CRD patients were ($35,190 vs $15,883); visits to the ED ($1,107 vs $431), physician office ($3,457 vs $2,058), lab/pathology ($4,074 vs $1,404), and outpatient ancillary services ($15,805 vs $4,940) (all p-values < 0.0001). Conclusions: Our findings show that patients with CRD had nearly 2.9 times higher all-cause total cost than patients without CRD after adjusting for covariates. Prevention of CRD may result in a significant reduction in cancer-treatment cost.

Disseminated cryptococcosis and anti-granulocyte-macrophage colony-stimulating factor autoantibodies: An underappreciated association

The development of disseminated cryptococcosis has historically occurred in patients living with advanced human immunodeficiency virus or other immunosuppressive conditions affecting T-cell function. Recently, patients with anti-cytokine neutralising autoantibodies have been recognised to be at risk for disseminated infections by opportunistic intracellular pathogens, including Cryptococcus species. Herein, we present a previously healthy 26-year-old man who was evaluated with disseminated cryptococcosis involving the bone, lung, mediastinum and brain. The patient's serum cryptococcal antigen titres were >1:1,100,000, and evaluation for an underlying immunodeficiency revealed high titres for anti-granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies. We also review the literature of all published cases of disseminated cryptococcosis associated with the presence of anti-GM-CSF autoantibodies. Clinicians should have a heightened awareness of anti-cytokine autoantibodies in patients without a known immunodeficiency and development disseminated infections by opportunistic intracellular pathogens.

798. Metronidazole Exposure Prior to Clostridiodes difficile Infection (CDI) is a Risk Factor for Severe C. difficile Disease in Cancer Patients

Background

Antibiotic use is a risk factor for CDI. Few studies have correlated use of prior antibiotics with CDI severity in cancer patients. This study identified clinical and microbiology risk factors associated with severe CDI in patients with cancer. We hypothesized that previous antibiotic exposure and microbiome composition at time of CDI presentation, are risk factors for severe disease in cancer patients.

Methods

This non-interventional, prospective, single-center cohort study examined patients with cancer who had their first episode or first recurrence of CDI between Oct 27, 2016 and Jul 1, 2019. C. difficile was identified using nucleic acid amplification testing. Multivariate analysis was used to determine significant clinical risk factors for severe CDI as defined in the 2018 IDSA/SHEA guidelines. Alpha, and beta diversities were calculated to measure the average species diversity and the overall microbial composition. Differential abundance analysis and progressive permutation analysis were used to single out the significant microbial features that differed across CDI severity levels.

Results

Patient (n=200) demographics show mean age of 60 yrs., 53% female, majority White (76%) and non-Hispanic (85%). Prior 90 day metronidazole use (Odds Ratio OR 4.68 [1.47-14.91] p0.009) was a significant risk factor for severe CDI. Other factors included Horn’s Index > 2 (OR 7.75 [1.05-57.35] p0.045), Leukocytosis (OR 1.29 [1.16-1.43] p< 0.001), Neutropenia (OR 6.01 [1.34-26.89] p0.019) and Serum Creatinine >0.95 mg/dL (OR 25.30 [8.08-79.17] p< 0.001). Overall, there were no significant differences in alpha and beta diversity between severity levels. However, when identifying individual microbial features, the high presence of Bacteroides uniformis, Ruminococceae, Citrobacter koseri and Salmonella were associated with protection from severe CDI (p< 0.05).

Table 1 - Results of multivariate logistic regression analysis of factors associated with severe CDI

Figure 1. Microbiome features identified by progressive permutation analysis as seen in a volcano plot.

Conclusion

A number of risk factors for severe CDI were identified among this population, including prior 90 day metronidazole use. Also, increased relative abundance of Bacteroides uniformis, Ruminococceae, Citrobacter koseri and Salmonella were linked to protection from severe CDI. Reducing metronidazole use in patients with cancer may help prevent subsequent severe CDI.

Disclosures

Adilene Olvera, MPH MLS (ASCP), MERK (Grant/Research Support, Scientific Research Study Investigator) Kevin W. Garey, PharmD, MS, FASHP, Merck & Co. (Grant/Research Support, Scientific Research Study Investigator) Ryan J. Dillon, MSc, Merck & Co., Inc., (Employee) Engels N. Obi, PhD, Merck & Co. (Employee)

51. A Review of Human Herpesvirus 6 and Central Nervous System Disease in Oncology Patients

Background

Human herpesvirus 6 (HHV-6) infects most of the human population. With immunosuppression it can reactivate and cause clinical syndromes of central nervous system (CNS) dysfunction. Much of the literature describes cases after hematopoietic stem cell transplantation (HSCT), ranging from encephalitis to a defined post-transplant acute limbic encephalitis syndrome (PALE). Outside of HSCT, studies of HHV-6 encephalitis in cancer patients are limited to case reports.

Methods

In this retrospective review, we present data from all patients admitted to MD Anderson Cancer Center between March 2016 and December 2018 that met established definitions for encephalitis, aseptic meningitis or HHV-6 PALE with detectable HHV-6 DNA in the cerebrospinal fluid (CSF) detected using either the Viracor or Biofire® Meningitis Encephalitis (ME) Panel testing platforms and no other identified etiology. We extracted demographic features, known risk factors, imaging findings, CSF analysis, treatments and patient outcomes from medical records.

Results

725 patients underwent HHV-6 testing during the study timeframe, with 19 (2.6%) cases of HHV-6 mediated CNS disease identified. Most patients, 13/19 (68%), had undergone HSCT. Median time to presentation was 31 days post-transplant. Survival at 240 days after transplant was 62% often with long-term neurologic sequelae. CSF tended to have lymphocyte predominance and nearly all patients had peripheral lymphopenia. Other at risk populations identified included 2/19 (11%) patients who received chimeric antigen receptor (CAR) T-cell therapy, 2/19 (11%) who received biologic immunotherapy, and 2/19 (11%) who had non-HSCT hematologic malignancy. Notable discordance among testing platforms was found in 5/9 (55%) of patients receiving both testing platforms.

CSF and Laboratory Analytes

Findings and Outcomes in HSCT Patients

Findings and Outcomes in Non-HSCT Patients

Conclusion

In addition to HSCT patients, HHV-6 reactivation leading to CNS disease also occurs in settings such as following adoptive T cell therapy or biologic immunotherapy. Significant diagnostic discordance exists between testing platforms.

Disclosures

Rodrigo Hasbun, MD, MPH, Biofire (Consultant)

1098. Norovirus Infection in Cancer Patients Undergoing Chimeric Antigen Receptor T-cell Immunotherapy (CAR-T)

Background

CAR-T is used to treat certain refractory hematological malignancies. B-cell aplasia and immunosuppression used to treat CAR-T side effects increase infection risk. Little data are available describing Norovirus (NoV) infections in CAR-T recipients.

Methods

We reviewed the medical records of 134 patients with NoV diarrhea (identified by nucleic acid amplification test) between 2016-2019. Of these patients, nine received CAR-T prior to developing NoV. Here we describe their demographics, clinical characteristics, treatments, and complications.

Results

The median age was 49 years (Table 1). Patients’ underlying malignancies included Non-Hodgkin’s Lymphoma (4), Acute Lymphoblastic Leukemia (3), Chronic Lymphocytic Leukemia (1) and metastatic Sarcoma (1). Prior to development of NoV, six patients had undergone hematopoietic stem cell transplant, and 1 had received checkpoint inhibitor therapy. Five patients experienced cytokine release syndrome after CAR-T, and 1 experienced CAR-T-related encephalopathy syndrome (Table 2). Two patients received interleukin-6 antagonist therapy, and one received high dose steroids. Time to diarrhea onset post-CAR-T cell infusion was variable(median 256days, IQR 26-523 days).Six had an absolute lymphocyte count< 1000/mm3 at diarrhea onset. Three had diarrhea for >14 days; median diarrhea duration in the other 6 patients was 4 days. Other GI complaints included abdominal pain (3), nausea (4), and vomiting (3). For NoV treatment, three received oral immunoglobulin, and 8 received Nitazoxanide. Complications included development of concomitant GI-GVHD(5), ileus (2), need for TPN (3), renal failure requiring dialysis (2), ICU stay (3), and death (2). Two patients were co-infected with other enteropathogens such as rotavirus, enteropathogenic and enteroaggregative E.Coli and Clostridioides difficile. Three patients with diarrhea lasting >14 days had serial samples collected over time; NoV shedding lasted 81-546 days. NoV was genotyped in 6 patients(Table 3) and included GII.2(2), GII.4(2), GII.6(1) and GII.12(1).

Table 1: Patient characteristics (N=9)

Table 2: CAR-T related factors

Table 3: NoV Genotypes

Conclusion

NoV belonging to various genotypes is an important cause of acute and chronic diarrhea in patients receiving CAR-T cell therapy.

Disclosures

Adilene Olvera, MPH MLS (ASCP), MERK (Grant/Research Support, Scientific Research Study Investigator) Robert L. Atmar, MD, Takeda Vaccines, Inc. (Grant/Research Support) Mary K. Estes, PhD, Takeda Vaccines (Consultant, Grant/Research Support)

Enteroaggregative E. coli Adherence to Human Heparan Sulfate Proteoglycans Drives Segment and Host Specific Responses to Infection

Enteroaggregative Escherichia coli (EAEC) is a significant cause of acute and chronic diarrhea, foodborne outbreaks, infections of the immunocompromised, and growth stunting in children in developing nations. There is no vaccine and resistance to antibiotics is rising. Unlike related E. coli pathotypes that are often associated with acute bouts of infection, EAEC is associated with persistent diarrhea and subclinical long-term colonization. Several secreted virulence factors have been associated with EAEC pathogenesis and linked to disease in humans, less certain are the molecular drivers of adherence to the intestinal mucosa. We previously established human intestinal enteroids (HIEs) as a model system to study host-EAEC interactions and aggregative adherence fimbriae A (AafA) as a major driver of EAEC adherence to HIEs. Here, we report a large-scale assessment of the host response to EAEC adherence from all four segments of the intestine across at least three donor lines for five E. coli pathotypes. The data demonstrate that the host response in the duodenum is driven largely by the infecting pathotype, whereas the response in the colon diverges in a patient-specific manner. Major pathways altered in gene expression in each of the four enteroid segments differed dramatically, with responses observed for inflammation, apoptosis and an overwhelming response to different mucin genes. In particular, EAEC both associated with large mucus droplets and specific mucins at the epithelial surface, binding that was ameliorated when mucins were removed, a process dependent on AafA. Pan-screening for glycans for binding to purified AafA identified the human ligand as heparan sulfate proteoglycans (HSPGs). Removal of HSPG abrogated EAEC association with HIEs. These results may mean that the human intestine responds remarkably different to distinct pathobionts that is dependent on the both the individual and intestinal segment in question, and uncover a major role for surface heparan sulfate proteoglycans as tropism-driving factor in adherence and/or colonization.

Gastrointestinal Adverse Events Observed After Chimeric Antigen Receptor T-Cell Therapy

BACKGROUND

Chimeric antigen receptor T-cell (CART) therapy can significantly improve outcomes for patients with certain hematologic malignancies. The most notable drawbacks of CART are cytokine release syndrome and CART-related encephalopathy syndrome. Gastrointestinal adverse events (GI-AEs) have not yet been reported in association with CART. Herein, we describe the incidence and clinical features of GI-AEs observed after CART.

MATERIALS AND METHODS

We report a case series of patients with hematologic malignancies who received CART, in a clinical trial or as the standard of care, and subsequently suffered from GI-AEs between 2012 and 2018.

RESULTS

In our cohort, 37 of 132 (28%) patients experienced GI-AEs. All 37 experienced diarrhea with a median onset of 7 days (interquartile range, 4 to 25 d) after CART infusion. The median age of these patients was 58 years. Most had diffuse large B-cell lymphoma (51%). Seventeen patients experienced cytokine release syndrome, and 9 experienced CART-related encephalopathy syndrome. The interleukin-6 antagonist was required in 15 patients. Overall, 49% of patients had grade 1 diarrhea, 32% had grade 2, and 15% had grade 3. Other gastrointestinal symptoms in these patients were abdominal pain (41%), nausea and vomiting (49%), fever (8%), bloody stools (3%), and abdominal distension (5%). The median duration of symptoms was 6 days (interquartile range, 3 to 9 d). In 32 patients who underwent imaging, 8 (25%) had findings suggestive of gastrointestinal tract inflammation. Nine (24%) patients experienced GI-AE recurrence after initial improvement. The symptoms were attributed to an alternative cause in 17 (13%) cases and to CART in 20 (15%) cases. One patient developed CART-related refractory colitis that eventually responded to antibiotics for pneumonia.

CONCLUSION

CART-related GI-AEs occur in 15% of patients treated with CART. These symptoms are typically mild and self-limiting, requiring only symptomatic treatment. Nevertheless, CART may, in rare cases, lead to refractory colitis.

The BE GONE trial study protocol: a randomized crossover dietary intervention of dry beans targeting the gut microbiome of overweight and obese patients with a history of colorectal polyps or cancer

BACKGROUND

Mouse and human studies support the promise of dry beans to improve metabolic health and to lower cancer risk. In overweight/obese patients with a history of colorectal polyps or cancer, the Beans to Enrich the Gut microbiome vs. Obesity's Negative Effects (BE GONE) trial will test whether and how an increase in the consumption of pre-cooked, canned dry beans within the context of usual diet and lifestyle can enhance the gut landscape to improve metabolic health and reduce cancer risk.

METHODS/DESIGN

This randomized crossover trial is designed to characterize changes in (1) host markers spanning lipid metabolism, inflammation, and obesity-related cancer risk; (2) compositional and functional profiles of the fecal microbiome; and (3) host and microbial metabolites. With each subject serving as their own control, the trial will compare the participant's usual diet with (intervention) and without (control) dry beans. Canned, pre-cooked dry beans are provided to participants and the usual diet continually assessed and monitored. Following a 4-week run-in and equilibration period, each participant provides a total of 5 fasting blood and 6 stool samples over a total period of 16 weeks. The intervention consists of a 2-week ramp-up of dry bean intake to 1 cup/d, which is then continued for an additional 6 weeks. Intra- and inter-individual outcomes are assessed across each crossover period with consideration of the joint or modifying effects of the usual diet and baseline microbiome.

DISCUSSION

The BE GONE trial is evaluating a scalable dietary prevention strategy targeting the gut microbiome of high-risk patients to mitigate the metabolic and inflammatory effects of adiposity that influence colorectal cancer risk, recurrence, and survival. The overarching scientific goal is to further elucidate interactions between diet, the gut microbiome, and host metabolism. Improved understanding of the diet-microbiota interplay and effective means to target these relationships will be key to the future of clinical and public health approaches to cancer and other major diet- and obesity-related diseases.

TRIAL REGISTRATION

This protocol is registered with the U.S. National Institutes of Health trial registry, ClinicalTrials.gov, under the identifier NCT02843425. First posted July 25, 2016; last verified January 25, 2019.

Conservation and global distribution of non-canonical antigens in Enterotoxigenic Escherichia coli

BACKGROUND

Enterotoxigenic Escherichia coli (ETEC) cause significant diarrheal morbidity and mortality in children of resource-limited regions, warranting development of effective vaccine strategies. Genetic diversity of the ETEC pathovar has impeded development of broadly protective vaccines centered on the classical canonical antigens, the colonization factors and heat-labile toxin. Two non-canonical ETEC antigens, the EtpA adhesin, and the EatA mucinase are immunogenic in humans and protective in animal models. To foster rational vaccine design that complements existing strategies, we examined the distribution and molecular conservation of these antigens in a diverse population of ETEC isolates.

METHODS

Geographically diverse ETEC isolates (n = 1159) were interrogated by PCR, immunoblotting, and/or whole genome sequencing (n = 46) to examine antigen conservation. The most divergent proteins were purified and their core functions assessed in vitro.

RESULTS

EatA and EtpA or their coding sequences were present in 57.0% and 51.5% of the ETEC isolates overall, respectively; and were globally dispersed without significant regional differences in antigen distribution. These antigens also exhibited >93% amino acid sequence identity with even the most divergent proteins retaining the core adhesin and mucinase activity assigned to the prototype molecules.

CONCLUSIONS

EtpA and EatA are well-conserved molecules in the ETEC pathovar, suggesting that they serve important roles in virulence and that they could be exploited for rational vaccine design.

2380. Fecal Collinsella Abundance is Negatively Associated with Toxin A/B Production in Cancer Patients with Clostridioides difficile

Background

The detection of C. difficile (CDI) by nucleic acid amplification test (NAAT) with negative toxin enzyme immunoassay (EIA-) is difficult to interpret in cancer patients. Markers that differentiate true infection from colonization, and are associated with clinical outcomes are needed. We hypothesized that the microbiome composition and inflammatory fecal markers in EIA- patients differed from those who are EIA+ and were associated with disease severity and recurrence.

Methods

We studied the fecal microbiome composition (16s rRNA, V3) of 147 cancer patients with CDI diagnosed by a two-step testing algorithm. Clinical data, CDI bacterial quantity (BQ) by qPCR and markers of intestinal inflammation (calprotectin, lactoferrin, IL-1β and IL-8) were analyzed. Data were stratified according to cancer type [hematologic (H) n = 49, solid tumor (ST) n = 66, or stem cell transplant (SCT) n = 32].

Results

Demographic characteristics and symptoms were similar between the three groups. At baseline, species diversity by Shannon index was similar in all three groups regardless of EIA detection and did not correlate with clinical presentation, response to therapy or recurrence. Microbiome composition did not correlate with inflammatory response except in H in whom a higher diversity correlated with increased IL-8 (P = 0.021) and calprotectin (P = 0.01) levels. At the genus level across all strata and when compared with EIA- cases, EIA+ cases presented with a higher abundance of Peptoclostridium (P = 0.0008) which correlated with CDI BQ qPCR (log of BQ/mg 2.38 ± 1.49 vs 0.92 ± 1.28, P < 0.001). In contrast, EIA- cases had a higher abundance of Collinsella (P = 0.001). SCT patients carried fewer Peptoclostridium when compared with other groups, whereas all three patient groups carried similar amounts of Collinsella. The relative abundance of Peptoclostridium and Collinsella was not associated with response to therapy, or fecal markers of inflammation. Principal component analysis did not demonstrate differences between the three groups studied.

Conclusion

In this study, the presence of Collinsella, a known butyrate and bile salt hydrolase producer, was associated with the lack of CDI toxin A/B production. Loss of Collinsella may represent a novel risk factor for active CDI.

Disclosures

All authors: No reported disclosures.

2235. Fecal Biomarkers for Clostridioides difficile Infection in Cancer Patients

Background

The diagnosis of C. difficile infection (CDI) relies on using a nucleic acid amplification test (NAAT) followed by confirmatory toxin enzyme immunoassay (EIA). This study examined the utility of fecal biomarkers and C. difficile bacterial quantity (BQ) in differentiating patients with true infection (NAAT+/EIA+) from patients with colonization (NAAT+/EIA-) in the context of C. difficile ribotypes.

Methods

We studied 136 patients with diarrhea and CDI identified by NAAT in stools for which a confirmatory toxin A, B, EIA was performed. Fecal IL-8, IL-1β, calprotectin, and lactoferrin were studied by ELISA. C. difficile BQ was determined by 16S rRNA qPCR. Data were stratified according to cancer diagnosis into three groups [hematologic (H) n = 43, solid tumor (ST) n = 62, or stem cell transplant (SCT) n = 31].

Results

Stools were EIA+ in 36/136 (26%) of the cohort. Although ST patients had a higher Charlson co-morbidity index when compared with the other two groups (P < 0.002), demographic characteristics and symptoms at the time of presentation were similar between groups regardless of EIA status. Most common ribotypes identified included F106 and F014-020. Ribotype distribution differed according to oncologic diagnosis as determined by the Shannon diversity index. There were fewer distinct C. difficile ribotypes in the SCT (n = 8) vs. ST (n = 15) and H (n = 15) groups (P < 0.001 and P < 0.002, respectively). BQ were higher in EIA+ than EIA- across all strata (log of BQ/mg 2.38 ± 1.49 vs. 0.92 ± 1.28, P > 0.001). Similarly, higher levels of fecal IL-8 (1.72 ± 1.9 vs. 0.83 ± 1.6 ng/mL), IL-1β (3.74 ± 13.7 vs.. 1.21 ± 4.6) and calprotectin (14.9 ± 27 vs. 6 ±1.8 ug/mL) levels were seen in EIA+ patients. While IL-8, IL-1β, and calprotectin were increased in EIA+ ST and H, no differences were seen in the SCT group. A sensitivity analysis using ROC curves, revealed that BQ resulted in a greater area under the curve than fecal markers of inflammation (A = 0.77, P < 0.001, 95% CI [0.67–0.86]).

Conclusion

In this study in cancer and immunocompromised patients, C. difficile bacterial burden regardless of infecting ribotype and fecal cytokines showed to be a helpful assay in distinguishing true CDI from colonization.

Disclosures

All authors: No reported disclosures.

Impact of antibiotic therapy on the development and response to treatment of immune checkpoint inhibitor-mediated diarrhea and colitis

Background

The gut microbiome impacts the efficacy of immune checkpoint inhibitor (ICI) therapy and the development of ICI-mediated diarrhea and/or colitis (IMDC). Antibiotic therapy,especially that with anaerobic activity, has profound effects on the gut microbiome. Therefore, we sought to assess the effect of antibiotics on the development of IMDC.

Methods

Patients who received ICI therapy from January 2016 to January 2018 were examined retrospectively. A Cox regression model was used to assess factors associated with overall survival.

Results

A total of 826 patients were included. Of these patients, 51.6% received inhibitors of programmed cell death protein-1 or its ligand, 32.0% received inhibitors of cytotoxic T-lymphocyte-associated antigen-4, and 16.5% received a combination of the two. IMDC occurred in 52.5% of the patients after a median of 8 weeks. Overall, 569 patients (68.9%) received antibiotic therapy. Antibiotic use at any time was associated with reduced IMDC occurrence and recurrence rates but also with frequent hospitalization and intensive care unit admission for IMDC as well as increased IMDC severity. Compared with patients who received antibiotic therapy only before ICI therapy initiation, those receiving it after ICI had a higher IMDC rate and more often needed immunosuppressive therapy and hospitalization for IMDC. Antibiotics with anaerobic activity were included in 51% of the antibiotic therapy regimens and were associated with increased immunosuppressant use, hospitalization, intensive care unit admission for IMDC, and severe IMDC grades. Forty-one patients received empiric prophylactic antibiotic therapy at IMDC onset. These patients more often needed immunosuppressive therapy, intravenous steroids, and infliximab/vedolizumab; had more frequent and longer hospitalization for IMDC and higher IMDC grades; and more frequently had IMDC recurrence than did patients who did not receive antibiotic therapy at the time of IMDC symptom onset.

Conclusions

Whereas antibiotic therapy appeared to be protective against IMDC onset, use of antibiotics, especially those with anaerobic activity, after ICI therapy was associated with increased risk of severe IMDC.

Electronic supplementary material

The online version of this article (10.1186/s40425-019-0714-x) contains supplementary material, which is available to authorized users.

Fecal Microbiome, Metabolites, and Stem Cell Transplant Outcomes: A Single-Center Pilot Study

Background

Accumulating evidence suggests that the intestinal microbiome may dramatically affect the outcomes of hematopoietic stem cell transplant (HSCT) recipients. Providing 16S ribosomal RNA based microbiome characterization in a clinically actionable time frame is currently problematic. Thus, determination of microbial metabolites as surrogates for microbiome composition could offer practical biomarkers.

Methods

Longitudinal fecal specimens (n = 451) were collected from 44 patients before HSCT through 100 days after transplantation, as well as 1-time samples from healthy volunteers (n = 18) as controls. Microbiota composition was determined using 16S ribosomal RNA V4 sequencing. Fecal indole and butyrate levels were determined using liquid chromatography tandem mass spectrometry.

Results

Among HSCT recipients, both fecal indole and butyrate levels correlated with the Shannon diversity index at baseline (P = .02 and P = .002, respectively) and directly after transplantation (P = .006 and P < .001, respectively). Samples with high butyrate levels were enriched for Clostridiales, whereas samples containing high indole were also enriched for Bacteroidales. A lower Shannon diversity index at the time of engraftment was associated with increased incidence of acute intestinal graft-vs-host disease (iGVHD) (P = .02) and transplant-related deaths (P = .03). Although fecal metabolites were not associated with acute iGVHD or overall survival, patients contracting bloodstream infections within 30 days after transplantation had significantly lower levels of fecal butyrate (P = .03).

Conclusions

Longitudinal analysis of fecal microbiome and metabolites after HSCT identified butyrate and indole as potential surrogate markers for microbial diversity and specific taxa. Further studies are needed to ascertain whether fecal metabolites can be used as biomarkers of acute iGVHD or bacteremia after HSCT.

Diagnosis of Yersinia enterocolitica Infection in Cancer Patients With Diarrhea in the Era of Molecular Diagnostics for Gastrointestinal Infections

Background

Yersinia enterocolitica is an uncommon cause of diarrhea, mesenteric adenitis and bacteremia in the United States. There is limited information regarding the clinical course in immunocompromised patients. We describe the clinical presentations and outcomes in patients with cancer with Y. enterocolitica diagnosed at a US cancer center before and after introduction of gastrointestinal multiplex panel (GIMP) nucleic acid amplification tests (NAATs).

Methods

We reviewed medical records of all patients with Y. enterocolitica isolated from cultures or identified by means of NAATs from 2000 to 2018. We then extracted demographic information, clinical characteristics, treatment, and overall mortality rate at 30 days after the diagnosis of yersiniosis.

Results

We identified 17 cases: 6 cases by culture before April 2016 and 11 cases by NAATs after that; 4 of the latter were confirmed by means of culture (36%). This represented an 8-fold increase for overall detection and a 3-fold increase in culture-proved infections when adjusted per 1000 admissions. The most common presenting symptom was diarrhea (11 of 14 [79%]), followed by abdominal pain (9 of 14 [64%]) and nausea and vomiting (6 of 14 [43%]). In 1 patient, the infection resolved spontaneously; the other patients received antibiotic treatment, the majority with a fluoroquinolone. The 30-day mortality rate was 7.1%, and the cause of death was a complication of advanced cancer.

Conclusion

Since implementing use of the GIMP, we observed an increase in Y. enterocolitica cases, possibly related to increasing number of patients with cancer at our institution who are receiving intensive immunosuppression, increased testing due to ease and availability, and increased sensitivity of NAATs. GIMP NAATs are redefining the epidemiology of Y. enterocolitica infection in patients with cancer.

Use and Interpretation of Enteropathogen Multiplex Nucleic Acid Amplification Tests in Patients With Suspected Infectious Diarrhea

Acute diarrheal illness due to gastrointestinal infection is a significant cause of morbidity and mortality in the United States and around the world. Determining the causative organism in a timely manner assists with patient care, identifying outbreaks, providing infection control, and administering antimicrobial therapy when indicated. Traditional diagnostic modalities based on culture and immunoassays are limited by their low sensitivity and long turnaround time. Nucleic acid amplification tests (NAATs) for enteric pathogens allow for the syndromic testing of stool for multiple pathogens simultaneously and have higher sensitivity with a shorter turnaround time. However, by not isolating the organism, NAATs do not provide drug susceptibility or confirmatory identification. Furthermore, NAATs cannot distinguish between true infection and carrier states. Nevertheless, several studies have demonstrated the cost-effectiveness of multiplex NAATs by reducing the length of hospital stay and cost of isolation. Five platforms are currently approved by the US Food and Drug Administration that can detect different bacteria, parasites, and viruses. The sensitivity and specificity of each platform depends on the targeted pathogens and whether the tests are performed on fresh stool, frozen stool, or in transport media. Overall, these tests have high sensitivity and specificity of more than 90% when used in symptomatic patients. Thus, multiplex NAAT gastrointestinal platforms offer several advantages compared to traditional methods. However, the interpretation of the results requires acknowledging the limitations of the tests and exercising clinical judgment. More studies are needed to establish the cost-effectiveness of multiplex NAATs and their impact on antibiotic stewardship and clinical outcomes.

Gut microbiome modulates response to anti-PD-1 immunotherapy in melanoma patients

Preclinical mouse models suggest that the gut microbiome modulates tumor response to checkpoint blockade immunotherapy; however, this has not been well-characterized in human cancer patients. Here we examined the oral and gut microbiome of melanoma patients undergoing anti-programmed cell death 1 protein (PD-1) immunotherapy (n = 112). Significant differences were observed in the diversity and composition of the patient gut microbiome of responders versus nonresponders. Analysis of patient fecal microbiome samples (n = 43, 30 responders, 13 nonresponders) showed significantly higher alpha diversity (P < 0.01) and relative abundance of bacteria of the Ruminococcaceae family (P < 0.01) in responding patients. Metagenomic studies revealed functional differences in gut bacteria in responders, including enrichment of anabolic pathways. Immune profiling suggested enhanced systemic and antitumor immunity in responding patients with a favorable gut microbiome as well as in germ-free mice receiving fecal transplants from responding patients. Together, these data have important implications for the treatment of melanoma patients with immune checkpoint inhibitors.

Ribotypes Matter, Significance of Clostridium difficile Ribotypes in Cancer Patients with Diarrhea

Background

Cancer patients are at increased risk for Clostridium difficile infection (CDI) due to frequent health care contact, chemotherapy, use of antibiotics, and immunosuppression. Distinct ribotypes are associated with CDI adverse outcomes. Ribotypes 14-020 are the predominant ribotypes in many hospitals. We examined the contribution of C. difficile ribotypes to CDI severity, response to therapy and outcomes in this population.

Methods

Demographic and clinical data were collected from 90 cancer patients with a first episode or first recurrence of CDI identified by two-step PCR followed by EIA for A/B toxins. Fluorescent PCR ribotyping (FPCR) was performed on fecal isolates. We identified 27 distinct ribotypes between October 2016 and January 2017. Clinical outcomes were studied in three FPCR subgroups. Group I (GI, n = 27) included F014-020, group II (GII, n = 17) included virulent types 002, 027, 078–126, 244 and group III (GIII, n = 46) included the rest. Treatment failure was defined as no response after at least 3 days of a CDI treatment regimen. CDI severity was determined using Zar’s criteria, presence of bacteremia and ICU stay.

Results

The proportion of patients >50 yrs. old, with health care onset CDI (31%), primary CDI (92.2%), and on active chemotherapy (70%) was similar across the three groups. At presentation, disease severity was similar in all groups; However, patients in GII were more likely to have detectable toxin A/B by EIA compared with GI and GIII (53% vs. 23%, P = 0.015) and higher treatment failure rates (56%) when compared with GI (15% P = 0.007) and GIII (16%, P = 0.004). Bacteremia was more common in GIII (28%) compared with GII (0%) P = 0.041 and GI 7% P = 0.007. Patients in GI experienced fewer complications when compared with those in GIII P = 0.025. No differences in sustained clinical response, recurrence, ICU stay or all cause 90-day mortality were found between the groups.

Conclusion

Cancer patients with CDI due to GII ribotypes are more likely to excrete fecal toxin A/B and fail conventional therapy. In contrast, patients in GI and GIII were more likely to respond to therapy. GI was associated with fewer complications. Of interest, GIII was associated with bacteremia. Evaluation of C. difficile ribotypes is clinically relevant in cancer patients with CDI.

Disclosures

All authors: No reported disclosures.

Clinical features and molecular epidemiology of diarrheagenic Escherichia coli pathotypes identified by fecal gastrointestinal multiplex nucleic acid amplification in patients with cancer and diarrhea

Diarrheagenic Escherichia coli (DEC) pathotypes with differing epidemiology and clinical features, are known causes of disease with worldwide occurrence. At a major cancer center in the U.S., we studied patients with cancer and diarrhea for whom a GI Biofire FilmArray multiplex GI panel (BFM) was performed. An enteropathogen was identified in 382 of 2017 (19%) samples distributed across 311 patients. Of these, 60/311(19%) were positive for DEC. Patients receiving hematopoietic stem cell transplants (HSCT) 29/60 (48%) or with a hematologic malignancy 17/60 (28%) accounted for the majority of DEC cases. Enteropathogenic E. coli (EPEC, n=35 [58%]), enteroaggregative E. coli (EAEC, n=10 [17%]) and Shiga toxin producing E. coli (STEC, n=3 [5%]) were the most common DEC identified and peaked in the summer months. Stool cultures confirmed infections in 6/10 (60%) EAEC (five typical AggR⁺), and EPEC was recovered in 8/35 (22%) samples (all atypical eaeA⁺, bfp^-). DEC was identified in 22 cases (37%) that developed diarrhea >48hours after admission suggesting health care acquisition. Chronic infections were found in 2 EPEC and 1 EAEC cases that were tested at 1month or beyond with shedding that ranged from 58 to >125days. Two patients that underwent hematopoietic stem cell transplantation carried EAEC strains resistant to multiple antibiotics including fluoroquinolones and expressed extended spectrum beta lactamases. While in some instances BFM results were not verified in culture and could represent false positives, DEC pathotypes, especially EPEC and EAEC, caused chronic infections with antimicrobial-resistant strains in a subset of immunosuppressed cancer patients.

Viral associated diarrhea in immunocompromised and cancer patients at a large comprehensive cancer center: a 10-year retrospective study

BACKGROUND

Viral associated diarrhea (VAD) due to Norovirus (NV), Rotavirus (RV) and Adenovirus (AV) is common in immunocompromised and cancer patients. We sought to determine if the clinical characteristics, morbidity and seasonality of infection differed according to the type of enteric virus identified.

METHODS

Cases of NV, RV and AV were identified in stool specimens submitted to the clinical microbiology laboratory between November 2005 and February 2015. Clinical characteristics of patients, potential risk factors and outcomes were compared.

RESULTS

A total of 97 VAD cases were identified: NV (n = 49), RV (n = 34) and AV (n = 14). The majority of cases were in patients with leukemia and lymphoma. NV (59%), RV (74%) and AV (78%) were identified in hematopoietic stem cell transplant (HSCT) recipients; and in patients with graft versus host disease (GVHD): NV (34%), RV (46%) and AV (57%). Nine cases of NV were genotyped; all were due to genotype II. Nine of 49 (18%) cases of NV, 7 of 34 (20%) cases of RV and 2 of 14 (14%) cases of AV were considered to be health care acquired (HCA). In multivariate analysis, immunosuppression (OR 2.8 95% CI 1.26-6.60, p = .01) and neutropenia (OR 4.8 95% CI 1.27-18.5, p = .01) were identified as risk factors for NV diarrhea compared to RV and AV.

CONCLUSIONS

In our study, agents responsible for VAD occurred year round but predominated in the winter time; caused prolonged illness and were frequently health care associated. Presentations were atypical in many cases without upper gastrointestinal symptoms such as nausea and vomiting.

Cryptosporidium muris: infectivity and illness in healthy adult volunteers

Although Cryptosporidium parvum and C. hominis cause the majority of human cryptosporidiosis cases, other Cryptosporidium species are also capable of infecting humans, particularly when individuals are immunocompromised. Ten C. muris cases have been reported, primarily in human immunodeficiency virus (HIV) -positive patients with diarrhea. However, asymptomatic cases were reported in two HIV-negative children, and in another case, age and immune status were not described. This study examines the infectivity of C. muris in six healthy adults. Volunteers were challenged with 10(5) C. muris oocysts and monitored for 6 weeks for infection and/or illness. All six patients became infected. Two patients experienced a self-limited diarrheal illness. Total oocysts shed during the study ranged from 6.7 × 10(6) to 4.1 × 10(8), and the number was slightly higher in volunteers with diarrhea (2.8 × 10(8)) than asymptomatic shedders (4.4 × 10(7)). C. muris-infected subjects shed oocysts longer than occurred with other species studied in healthy volunteers. Three volunteers shed oocysts for 7 months. Physical examinations were normal, with no reported recurrence of diarrhea or other gastrointestinal complaints. Two persistent shedders were treated with nitazoxanide, and the infection was resolved. Thus, healthy adults are susceptible to C. muris, which can cause mild diarrhea and result in persistent, asymptomatic infection.

Does chemotherapy cause viral relapse in cancer patients with hepatitis C infection successfully treated with antivirals?

Authors have reported conflicting results on the persistence of hepatitis C virus (HCV) infection in patients having sustained virologic response (SVR) to treatment. Therefore, we sought to determine whether chemotherapy leads to viral relapse in 30 HCV-infected patients who had SVR before cancer diagnosis. Half of them had hematologic malignancies. Most (60%) received HCV therapy with interferon and ribavirin. Chemotherapy was started at a median of 72 months after SVR and included rituximab (27%), cyclophosphamide (23%), cisplatin (17%), or corticosteroids (37%). No patient had post-SVR viral relapse. Therapeutically induced resolution of HCV appears to be permanent and not affected by chemotherapy.

Persistent abdominal symptoms in US adults after short-term stay in Mexico

BACKGROUND

Postinfectious irritable bowel syndrome (PI-IBS) has been reported as a complication of bacterial diarrhea including travelers' diarrhea (TD). This study assessed the role of TD among US students in Mexico in triggering the onset of persistent abdominal symptoms (PAS) and IBS.

METHODS

We conducted a 6-month follow-up of a cohort of 817 US students in Mexico as short-term study to assess the frequency of PAS and IBS. Using Rome II criteria for IBS, groups of students with PAS were then categorized as PI-IBS if they met the symptom criteria for IBS or as suffering from functional abdominal disorder (FAD) if they did not meet the criteria.

RESULTS

FAD and IBS were commonly found in US students 6 months after leaving Mexico. Important variables in their development were younger adult age, longer stays in Mexico and occurrence of acute diarrhea while in Mexico. Diarrhea while in Mexico occurred more commonly for those later diagnosed with FAD, 101/196 (52%), relative risk (RR) = 1.5 [confidence interval (CI) 1.2-1.8; p = 0.001]; IBS, 20/32 (63%), RR = 2.5 (CI 1.2-5.0; p = 0.007); and PAS (FAD + IBS), 121/228 (53%), RR = 1.5 (CI 1.2-1.8; p < 0.001) compared with subjects who had experienced diarrhea while in Mexico but were not diagnosed with PAS at 6 months, 227/589 (39%). Diarrhea caused by heat-labile enterotoxin-producing enterotoxigenic Escherichia coli or Providencia ssp. demonstrated a greater risk of developing PAS.

CONCLUSIONS

PAS occurred commonly in a subset of younger adult travelers who stayed longer in Mexico and experienced acute diarrhea while there. Further studies with this cohort will focus on host genetic associations with the development of PAS.

Seroepidemiology of norovirus-associated travelers' diarrhea

BACKGROUND

Noroviruses (NoVs) are the most common cause of epidemic gastroenteritis, responsible for at least 50% of all gastroenteritis outbreaks worldwide and were recently identified as a leading cause of travelers' diarrhea (TD) in US and European travelers to Mexico, Guatemala, and India.

METHODS

Serum and diarrheic stool samples were collected from 75 US student travelers to Cuernavaca, Mexico, who developed TD. NoV RNA was detected in acute diarrheic stool samples using reverse transcription-polymerase chain reaction (RT-PCR). Serology assays were performed using GI.1 Norwalk virus (NV) and GII.4 Houston virus (HOV) virus-like particles (VLPs) to measure serum levels of immunoglobulin A (IgA) and IgG by dissociation-enhanced lanthanide fluorescent immunoassay (DELFIA); serum IgM was measured by capture enzyme-linked immunosorbent assay (ELISA), and the 50% antibody-blocking titer (BT50 ) was determined by a carbohydrate-blocking assay.

RESULTS

NoV infection was identified in 12 (16%; 9 GI-NoV and 3 GII-NoV) of 75 travelers by either RT-PCR or fourfold or more rise in antibody titer. Significantly more individuals had detectable preexisting IgA antibodies against HOV (62/75, 83%) than against NV (49/75, 65%) (p = 0.025) VLPs. A significant difference was observed between NV- and HOV-specific preexisting IgA antibody levels (p = 0.0037), IgG (p = 0.003), and BT50 (p = <0.0001). None of the NoV-infected TD travelers had BT50  > 200, a level that has been described previously as a possible correlate of protection.

CONCLUSIONS

We found that GI-NoVs are commonly associated with TD cases identified in US adults traveling to Mexico, and seroprevalence rates and geometric mean antibody levels to a GI-NoV were lower than to a GII-NoV strain.

Cryptosporidium meleagridis: infectivity in healthy adult volunteers

Most Cryptosporidium infections in humans are caused by C. parvum or C. hominis. However, genotyping techniques have identified infections caused by unusual Cryptosporidium species. Cryptosporidium meleagridis has been identified in ≤ 1% of persons with diarrhea, although prevalence is higher in developing nations. We examined the infectivity of C. meleagridis in healthy adults. Five volunteers were challenged with 10(5) C. meleagridis oocysts and monitored six weeks for fecal oocysts and clinical manifestations. Four volunteers had diarrhea; three had detectable fecal oocysts; and one infected volunteer remained asymptomatic. Fecal DNA from two volunteers was amplified by using a polymerase chain reaction specific for the Cryptosporidium small subunit ribosomal RNA gene. Nucleotide sequence of these amplicons was diagnostic for C. meleagridis. All infections were self-limited; oocysts were cleared within ≤ 12 days of challenge. These studies establish that healthy adults can be infected and become ill from ingestion of C. meleagridis oocysts.

A randomized, double-blind, pilot study of rifaximin 550 mg versus placebo in the prevention of travelers' diarrhea in Mexico during the dry season

BACKGROUND

Rifaximin has been shown to be effective in treating and preventing travelers' diarrhea (TD) during the summer season.

METHODS

The goal of this double-blinded multicenter trial was to assess the efficacy and safety of rifaximin 550 mg administered once daily for 14 days compared with placebo in the prevention of TD during the dry season in Mexico.

RESULTS

There were 101 participants randomized. Overall, 25 participants developed TD during the 3 weeks of the study: 22% from the rifaximin group and 29% from the placebo group (p = 0.4). Mild diarrhea (defined as only one or two unformed stools during a 24-h period plus at least one abdominal symptoms) developed in only 3 (6%) participants taking rifaximin compared with 10 (21%) taking placebo during the first week of study (p = 0.03). No clinically significant or serious adverse events were reported.

CONCLUSIONS

Antibiotic prophylaxis of TD in Mexico during the dry season needs to be further studied and its benefits weighed against the benefits of self-treatment.

Single nucleotide polymorphisms in the promoter of the gene encoding the lipopolysaccharide receptor CD14 are associated with bacterial diarrhea in US and Canadian travelers to Mexico

BACKGROUND

Under normal conditions, the expression of CD14, which is the principal receptor for bacterial lipopolysaccharide, is down-regulated in the intestinal mucosa but increases in response to inflammatory stimuli. The aim of the present study was to investigate whether fecal CD14 levels increased in response to infection with diarrheagenic Escherichia coli and whether single nucleotide polymorphisms (SNPs) in the CD14 gene were associated with an increased susceptibility to traveler's diarrhea (TD) in US visitors to Mexico.

METHODS

Six SNPs located at the promoter, exon, and untranslated regions of CD14 were typed in a prospective cohort study of 1360 visitors to Mexico at risk for TD. Stools from visitors with TD were studied for enteric pathogens by culture, colony hybridization, and polymerase chain reaction. Fecal soluble CD14 (sCD14) was measured in a subgroup of 203 adults with diarrhea and 66 healthy controls by enzyme-linked immunosorbent assay.

RESULTS

The minor allele frequencies for CD14 SNPs were significantly different among the various racial and ethnic groups studied. Two SNPs in the promoter region of CD14 (-159 C > T; rs2569190 and -4191 C > T; rs5744441) were found to be associated with TD in White visitors. The -159 TT genotype was associated with a higher risk for TD (Relative risk [RR], 1.21; 95% confidence interval [CI], 1.05-1.38; P = .008), whereas individuals with the -4191 TT genotype were protected from infection (RR, 0.82; 95% CI, 0.71-0.92; P = .006). Subjects with TD excreted higher levels of fecal CD14 than did healthy controls (33,480 pg/mL vs 6178 pg/mL; P < .02). Fecal sCD14 levels were higher in stool samples from visitors with TD and the -159 TT genotype than they were in visitors with the CC/CT genotypes (P = .02), and stool samples from subjects with the -4191 CC genotype had higher fecal sCD14 levels than did stool samples from visitors with the CT/TT (P = .005) genotype. In a multivariate analysis with haplotypes constructed with the 6 SNPs studied, subjects with the haplotype containing the -159 C and the -4191 T allele were less likely to acquire TD (P = .015).

CONCLUSIONS

Our study suggests that CD14 levels increase in response to bacterial diarrhea and that polymorphisms in the CD14 gene influence susceptibility to TD. Intestinal CD14 plays an important role in the innate immune response to enteric pathogens.