Overdiagnosis of Clostridium difficile Infection in the Molecular Test Era

Evaluation of a Fluorescence Immunoassay for Detection of Clostridioides difficile Glutamate Dehydrogenase and Toxin Antigens

BACKGROUND

Clostridioides difficile infection (CDI) is a leading cause of nosocomial infections in the United States, causing longer hospital stays, significant morbidity, and increased healthcare costs. Accurate CDI diagnosis is essential for timely treatment and infection control. Laboratory diagnosis of CDI commonly involves the detection of glutamate dehydrogenase (GDH) and/or toxins A and B by immunoassays or the toxin genes by nucleic acid amplification. This study assesses the performance of a new commercial test, the Sofia® 2 C. difficile Fluorescent Immunoassay (Sofia 2; FIA; QuidelOrtho), for detecting C. difficile GDH and toxins.

METHODS

Sofia 2 was compared to enzyme immunoassays (EIAs) C. diff Quik Chek Complete (Techlab Inc.) and Immunocard (Meridian Bioscience) using remnant stool samples from 262 patients with suspected CDI.

RESULTS

Sofia 2 demonstrated high agreement with the EIA methods for GDH (positive percentage agreement (PPA): 100%, negative percentage agreement (NPA): 94%, overall percentage of agreement (OPA): 95%) and toxins (PPA: 100%, NPA: 99%, OPA: 99%) detection. Compared to standard-of-care (SOC) testing including toxin gene PCR with the following toxin antigen test, Sofia 2 demonstrates strong PPA (100%), NPA (98%), positive predictive value (71%), and negative predictive value (100%).

CONCLUSIONS

Sofia 2 C. difficile FIA generates rapid results that are comparable to other commercial immunoassays with a simple workflow, supporting its use for CDI diagnosis in clinical practice.

High Prevalence of Multistep Algorithms in Diagnostic Clostridioides difficile Laboratory Testing

CONTEXT.—

Laboratory testing practices for diagnosis of Clostridioides difficile infection (CDI) have evolved in response to published guidelines, availability of highly sensitive nucleic acid amplification tests (NAATs), perceived problems with the specificity of NAATs, and CDI reporting requirements.

OBJECTIVE.—

To assess the current state of laboratory practice for diagnostic CDI testing.

DESIGN.—

An optional 8-item supplemental questionnaire was distributed in December 2019 to the 1374 laboratories participating in the College of American Pathologists C difficile Detection (CDF) proficiency testing program challenge CDF-C.

RESULTS.—

Of 1374 CDF-C participants, 1160 (84.4%) responded, predominantly representing laboratories based in the United States (1077 of 1160; 92.8%). The majority reported using a multistep testing algorithm (684 of 1159; 59.0%). Initial testing with a glutamate dehydrogenase and toxin A/B combination test followed by NAAT for discrepant results was the most common testing method (360 of 1146; 31.4%). NAAT alone (299 of 1146; 26.1%) was next, then NAAT followed by an assay that included toxin A/B enzyme immunoassay if NAAT is positive (258 of 1146; 22.5%). Only 5.4% (62 of 1146) reported using toxin A/B immunoassay alone. Most respondents (1093 of 1131; 96.6%) reported rejecting CDI tests on formed stool, but rejection of CDI testing in pediatric patients was uncommon (211 of 1131; 18.7%). Rejection of CDI testing in patients using laxatives was reported more often by US-based respondents (379 of 1054 [36.0%] versus 9 of 77 [11.7%], P < .001).

CONCLUSIONS.—

Multistep algorithms for CDI diagnosis are widely used in line with published recommendations. Most respondents reported rejection of formed stool for CDI testing, but few reported rejection of testing in infants and patients taking laxatives, suggesting these may be areas of opportunity for laboratories to pursue in improving CDI testing practices.

Clinical Outcome of Inflammatory Bowel Disease with Clostridioides difficile Polymerase Chain Reaction Toxin-Positive/Enzyme Immunoassay Toxin-Negative: A Retrospective Cohort Study

BACKGROUND

Clostridioides difficile infection (CDI) frequently occurs concurrently in patients with inflammatory bowel disease (IBD), and differential diagnosis from IBD flares is critical. However, clinical management of C. difficile in IBD patients with polymerase chain reaction toxin-positive (tPCR+)/enzyme immunoassay toxin-negative (tEIA-) results has not yet been investigated.

AIMS

We aimed to assess the clinical significance of C. difficile tPCR+/tEIA- in patients with IBD and the impact of antibiotic treatment on IBD outcomes.

METHODS

This single-center, retrospective cohort study included patients with IBD with CDI test results between January 01, 2018, and August 01, 2022. First, the clinical outcomes of IBD, such as medication escalation, hospitalization, and surgery, were compared between patients with IBD with tPCR-/tEIA- and those with tPCR+/tEIA- using Cox regression and propensity score matching. Next, the clinical outcomes of IBD were assessed based on whether antibiotic treatment for CDI was administered to both groups.

RESULTS

Among 412 patients with IBD with PCR test, 71 (17.2%) showed tPCR+/tEIA- results. The tPCR+/tEIA- group showed no statistically significant difference in IBD outcomes compared to the tPCR-/tEIA- group. The antibiotic-treated tPCR+/tEIA- group showed a higher risk of drug escalation and admission than the tPCR-/tEIA- group, while the antibiotic-untreated tPCR+/tEIA- group did not. After drug escalation during the follow-up, the treated tPCR+/tEIA- group showed IBD outcomes similar to those of the tPCR-/tEIA- group.

CONCLUSIONS

In patients with IBD with indeterminate CDI, the need for antibiotics should be thoroughly assessed and proper management of underlying IBD such as drug escalation may lead to favorable outcomes.

Determination of the performance of a novel diagnostic test for Clostridioides difficile toxins A and B using latent class analysis

The diagnosis of Clostridioides difficile infection (CDI) remains challenging. Nucleic acid amplification tests (NAAT) targeting the C. difficile (CD) toxin B gene suffer from suboptimal specificity for CDI due to CD asymptomatic colonization. Enzyme immunoassays (EIAs) that detect the presence of CD toxins are more specific for CDI but suffer from low sensitivity. To address this challenge, assays detecting CD toxins were developed using single-molecule array (SIMOA) technology, which have much lower limits of toxin detection than conventional EIAs. In this study, stool specimens from 708 symptomatic patients were aliquoted for testing by cell cytotoxicity neutralization assay (CCNA), toxigenic culture, NAAT, conventional CD toxin EIA, and SIMOA CD toxin EIAs. Using latent class analysis, we calculated the sensitivity and specificity of each of these diagnostic tests for detecting, separately, the presence of CD bacterium, CD toxin gene, and CD toxin. We estimated that the prevalence of CDI in our cohort was 14% (95% credible interval [CI]: 0.11-0.17). While the specificity of NAAT for detecting the presence of CD toxin was 95% (95% CI: 0.94-0.97), its positive predictive value was poor due to the low prevalence of CDI. The specificity of the conventional CD toxin EIA for CDI was excellent, but the sensitivity was only 48% (95% CI: 0.41-0.55). In comparison, the sensitivities of the SIMOA toxins A and B EIAs were 76% (95% CI: 0.67-0.84) and 77% (95% CI: 0.67-0.84), respectively, while maintaining excellent specificity. We conclude that SIMOA CD toxin EIAs are significantly more sensitive than conventional CD toxin EIAs.

IMPORTANCE

Clostridioides difficile infection (CDI) is the most important infectious cause of hospital-associated diarrhea worldwide, but its diagnosis remains challenging. Nucleic acid amplification tests (NAATs) targeting the C. difficile (CD) toxin B gene have suboptimal specificity due to the presence of CD asymptomatic colonization, while enzyme immunoassays (EIAs) that detect the toxin itself are much more specific but are limited by low sensitivity. New assays for detecting CD toxins were developed using single-molecule array (SIMOA) technology, which have much lower limits of toxin detection than conventional EIAs, potentially improving the sensitivity of these conventional EIAs while remaining highly specific. In this study, we use latent class analysis to evaluate the sensitivity and specificity of different diagnostic tests for CD, including the novel SIMOA toxin assays, in detecting the different CD targets: the presence of CD bacterium, the presence of CD toxin gene, and the presence of CD toxin.

Three stages of laboratory stewardship in improving appropriate Clostridioides difficile testing in a community-based setting

Objective

Assess the efficacy of staged interventions aimed to reduce inappropriate Clostridioides difficile testing and hospital-onset C. difficile infection (HO-CDI) rates.

Design

Interrupted time series.

Setting

Community-based.

Methods/Interventions

National Healthcare Safety Network (NHSN) C. difficile metrics from January 2019 to November 2022 were analyzed after three interventions at a community-based healthcare system. Interventions included: (1) an electronic medical record (EMR) based hard stop requiring confirming ≥3 loose or liquid stools over 24 h, (2) an infectious diseases (ID) review and approval of testing >3 days of hospital admission, and (3) an infection control practitioner (ICP) reviews combined with switching to a reverse two-tiered clinical testing algorithm.

Results

After all interventions, the number of C. difficile tests per 1,000 patient-days (PD) and HO-CDI cases per 10,000 PD decreased from 20.53 to 6.92 and 9.80 to 0.20, respectively. The EMR hard stop resulted in a (28%) reduction in the CDI testing rate (adjusted incidence rate ratio ((aIRR): 0.72; 95% confidence interval [CI], 0.53 to 0.96)) and ID review resulted in a (42%) reduction in the CDI testing rate (aIRR: 0.58; 95% CI, 0.42-0.79). Changing to the reverse testing algorithm reduced reported HO-CDI rate by (95%) (cIRR: 0.05; 95% CI; 0.01-0.40).

Conclusions

Staged interventions aimed at improving diagnostic stewardship were effective in overall reducing CDI testing in a community healthcare system.

Infectious Enterocolitis in Hematopoietic Cell Transplant with Post-Transplant Cyclophosphamide

Despite the high incidence of diarrhea in hematopoietic cell transplant (HCT) and the frequent involvement of infections, evidence concerning patients receiving post-transplant cyclophosphamide (PTCy) as graft-versus-host disease (GVHD) prophylaxis in the molecular diagnostic era is limited. This study aimed to evaluate the characteristics, incidence, risk factors, and outcomes impact of infectious enterocolitis in patients with hematologic malignancies undergoing HCT from matched sibling, matched unrelated, and haploidentical donors using PTCy as GVHD prophylaxis. Retrospective analysis of infectious enterocolitis episodes in 399 patients undergoing HCT at a single institution. Uniform GVHD prophylaxis with PTCy, sirolimus, and mycophenolate mofetil was given, irrespective of donor type or conditioning intensity. Levofloxacin was used prophylactically until myeloid engraftment. Infectious enterocolitis episodes were diagnosed by both molecular-based techniques and stool cultures. Infectious enterocolitis affected 21% of patients, with 19% having more than one episode. The median onset and duration was of 83 and 13 days, respectively, 20% were nosocomial and 58% were managed ambulatorily. The 1-year cumulative incidence was 19%, with 39% occurring beyond day 100, and was similar for Clostridioides difficile infection (CDI; 7%), non-CDI bacterial (8%), and viral enterocolitis (6%), with no differences in clinical features. However, toxin-positive CDI lasted longer (22 days) than toxin-negative cases (10 days, P = .03) Bone marrow HCT significantly increased the risk of overall infectious enterocolitis, while moderate-severe chronic GVHD increased all-cause and viral enterocolitis incidence. Infectious enterocolitis did not significantly impact overall survival, GVHD disease-free relapse-free survival, and non-relapse mortality. Approximately one-fifth of PTCy-based HCT recipients develop infectious enterocolitis in the first year, typically resolving within 2 weeks, with higher incidence in bone marrow recipients and those with moderate-severe chronic GVHD. CDI, non-CDI bacterial, and viral infections had similar incidences and clinical features. While infectious enterocolitis does not significantly impact transplant outcomes, its diagnosis remains challenging.

Fidaxomicin's Role in Overcoming Vancomycin Failure in Clostridium difficile Infections: A Case Series and Literature Review

Clostridium difficile infection (CDI), characterized by diarrheal illness with serious complications, is a common pathology in clinical practice. We present a series of five patients with CDI who underwent treatment with fidaxomicin following the failure of oral vancomycin. To our knowledge, no evidence in the literature suggests that fidaxomicin is more effective than vancomycin in treating acute infection. This paper emphasizes the importance of utilizing a large study to determine the relative effectiveness of vancomycin versus fidaxomicin in treating CDI. We also provide a literature review on CDI and management evolution.

Real-world Effectiveness of Fecal Microbiota Transplantation for First or Second Clostridioides difficile Infection

BACKGROUND & AIMS

Clostridioides difficile infection (CDI) is associated with high mortality. Fecal microbiota transplantation (FMT) is an established treatment for recurrent CDI, but its use for first or second CDI remains experimental. We aimed to investigate the effectiveness of FMT for first or second CDI in a real-world clinical setting.

METHODS

This multi-site Danish cohort study included patients with first or second CDI treated with FMT from June 2019 to February 2023. The primary outcome was cure of C. difficile-associated diarrhea (CDAD) 8 weeks after the last FMT treatment. Secondary outcomes included CDAD cure 1 and 8 weeks after the first FMT treatment and 90-day mortality following positive C. difficile test.

RESULTS

We included 467 patients, with 187 (40%) having their first CDI. The median patient age was 73 years (interquartile range [IQR], 58-82 years). Notably, 167 (36%) had antibiotic-refractory CDI, 262 (56%) had severe CDI, and 89 (19%) suffered from fulminant CDI. Following the first FMT treatment, cure of CDAD was achieved in 353 patients (76%; 95% confidence interval [CI], 71%-79%) at week 1. At week 8, 255 patients (55%; 95% CI, 50%-59%) maintained sustained effect. In patients without initial effect, repeated FMT treatments led to an overall cure of CDAD in 367 patients (79%; 95% CI, 75%-82%). The 90-day mortality was 10% (95% CI, 8%-14%).

CONCLUSION

Repeated FMT treatments demonstrate high effectiveness in managing patients with first or second CDI. Forwarding FMT in CDI treatment guidelines could improve patient survival.

CLINICALTRIALS

gov, Number: NCT03712722.

Risk factors for the development of Clostridioides difficile infection in patients colonized with toxigenic Clostridioides difficile

OBJECTIVE

Asymptomatic patients colonized with toxigenic Clostridioides difficile are at risk of progressing to C. difficile infection (CDI), but risk factors associated with progression are poorly understood. The objectives of this study were to estimate the incidence and identify risk factors to progression of hospital-onset CDI (HO-CDI) among colonized patients.

METHODS

This was a nested case-control study at an academic medical center including adult patients colonized with toxigenic C. difficile, detected via polymerase chain reaction (PCR) on a rectal swab collected on admission from 2017 to 2020. Patients with prior CDI or symptoms on admission, neutropenia, prior rectal surgery, or hospitalization less than 24 hours were excluded. Colonized patients that developed HO-CDI were matched 1:3 to colonized patients who did not based on PCR test date. Bivariate and multivariable-adjusted Cox regression analyses were used to identify risk factors.

RESULTS

Of 2,150 colonized patients, 109 developed HO-CDI, with an incidence of 5.1%. After exclusions, 321 patients (69 with HO-CDI) were included, with an estimated incidence of 4.2%. Risk factors included cirrhosis (aHR 1.94), ICU admission (aHR 1.76), malignancy (aHR 1.88), and hospitalization within six months (aHR 1.6). Prior antibiotic exposure in the past three months (aHR 2.14) and receipt of at-risk antibiotics were also identified as potential risk factors (aHR 2.17).

CONCLUSIONS

Progression to HO-CDI among colonized patients was not uncommon. This study highlights key risk factors associated with progression, underscoring the importance of enhanced monitoring and prevention efforts tailored to high-risk populations to mitigate HO-CDI.

Curbing inappropriate C. difficile treatment in patients receiving concomitant laxatives

In the setting of universal Clostridioides difficile screening, we implemented an alert that triggered when C. difficile treatment was ordered in patients who recently received laxatives. This resulted in C. difficile treatment avoidance in 37% of patients and was associated with drug cost savings of $143,905 over a 10-month period.

Diagnosis and Management of Clostridioides difficile in Inflammatory Bowel Disease

Patients with inflammatory bowel disease (IBD) have an increased risk of Clostridioides difficile infection (CDI), which can lead to worse IBD outcomes. The diagnosis of CDI in patients with IBD is complicated by higher C. difficile colonization rates and shared clinical symptoms of intestinal inflammation. Traditional risk factors for CDI, such as antibiotic exposure, may be lacking in patients with IBD because of underlying intestinal microbiota dysbiosis. Although CDI disproportionately affects people with IBD, patients with IBD are typically excluded from CDI clinical trials creating a knowledge gap in the diagnosis and management of these 2 diseases. This narrative review aims to provide a comprehensive overview of the diagnosis, treatment, and prevention of CDI in patients with IBD. Distinguishing CDI from C. difficile colonization in the setting of an IBD exacerbation is important to avoid treatment delays. When CDI is diagnosed, extended courses of anti- C. difficile antibiotics may lead to better CDI outcomes. Regardless of a diagnosis of CDI, the presence of C. difficile in a patient with IBD should prompt a disease assessment of the underlying IBD. Microbiota-based therapies and bezlotoxumab seem to be effective in preventing CDI recurrence in patients with IBD. Patients with IBD should be considered at high risk of CDI recurrence and evaluated for a preventative strategy when diagnosed with CDI. Ultimately, the comanagement of CDI in a patient with IBD requires a nuanced, patient-specific approach to distinguish CDI from C. difficile colonization, prevent CDI recurrence, and manage the underlying IBD.

Management of Recurrent Clostridioides difficile Infection (rCDI): A Systematic Literature Review to Assess the Feasibility of Indirect Treatment Comparison (ITC)

Recurrent Clostridioides difficile infection (rCDI) is a major cause of increased morbidity, mortality, and healthcare costs. Fecal-microbiota-based therapies are recommended for rCDI on completion of standard-of-care (SoC) antibiotics to prevent further recurrence: these therapies include conventional fecal-microbiota transplantation and the US Food and Drug Administration-approved therapies REBYOTA® (RBL) and VOWST Oral Spores™ (VOS). As an alternative to microbiota-based therapies, bezlotoxumab, a monoclonal antibody, is used as adjuvant to SoC antibiotics to prevent rCDI. There are no head-to-head clinical trials comparing different microbiota-based therapies or bezlotoxumab for rCDI. To address this gap, we conducted a systematic literature review to identify clinical trials on rCDI treatments and assess the feasibility of using them to conduct an indirect treatment comparison (ITC). The feasibility analysis determined that trial heterogeneity, particularly relating to inclusion criteria, may significantly compromise ITC and prevent cross-trial comparisons. Our analysis underlines the need to adopt standardized protocols to ensure comparability across trials.

Clinical significance of toxin EIA positivity in patients with suspected Clostridioides difficile infection: systematic review and meta-analysis

The laboratory diagnosis of Clostridioides difficile infection (CDI) is controversial. Nucleic acid amplification tests (NAAT) and toxin enzyme immunoassays (EIA) are most widely used, often in combination. However, the interpretation of a positive NAAT and negative toxin immunoassay (NAAT+/EIA-) is uncertain. PubMed and EMBASE were searched for studies reporting clinical outcomes in NAAT+/EIA- versus NAAT+/EIA+ patients. Forty-six studies comprising 33,959 patients were included in this meta-analysis. All-cause mortality (RR 0.96, 95% CI 0.80-1.15), attributable mortality (RR 0.61, 95% CI 0.20-1.91), fulminant CDI (RR 0.83, 95% CI 0.57-1.20), radiographic evidence of CDI (RR 0.87, 95% CI 0.65-1.16), total CDI complications (RR 0.95, 95% CI 0.59-1.53), colectomies (RR 0.78, 95% CI 0.34-1.79), and ICU admission (RR 1.04, 95% CI 0.84-1.30) did not significantly differ between NAAT+/EIA- and NAAT+/EIA+ patients. However, rates of recurrent (RR 0.62, 95% CI 0.50-0.77) or severe (RR 0.74, 95% CI 0.63-0.88) CDI were significantly lower in NAAT+/EIA- patients than in NAAT+/EIA+ patients. The pooled prevalence of NAAT+/EIA- patients who were treated with antibiotics for CDI was 73.4% (pooled proportion 0.72, 95% CI 0.52-0.88). NAAT+/EIA- patients have lower rates of recurrence and are at reduced risk for severe CDI compared with NAAT+/EIA+ patients but have a risk of CDI-related complications and mortality comparable to that of NAAT+/EIA+ patients. Toxin results cannot rule in or rule out CDI, and the decision whether to treat symptomatic NAAT+/EIA- patients for CDI should be based on clinical presentation and not on the toxin result.IMPORTANCEClostridioides difficile infection (CDI) is a common cause of healthcare-associated infections and the leading cause of antibiotic-associated diarrhea. However, the laboratory diagnosis of CDI, primarily done by nucleic acid amplification test (NAAT) and enzyme immunoassay (EIA), is controversial, especially in patients who test positive by NAAT but negative by EIA. In this systematic review, we compared the clinical outcomes of NAAT+/EIA- versus NAAT+/EIA+ patients and found that the two groups have similar risk of mortality and CDI-related complications. However, NAAT+/EIA- patients had significantly lower rates of recurrence and severe CDI than NAAT+/EIA+ patients, and most NAAT+/EIA- patients received CDI therapy. Toxin testing can help to predict the likelihood of CDI recurrence or severe infection, but the toxin result should not be a determining factor in the administration of CDI therapy. The decision on whether to treat NAAT+/EIA- patients should be based on clinical assessment.

Heterogeneity of Clostridioides difficile asymptomatic colonization prevalence: a systematic review and meta-analysis

BACKGROUND

Asymptomatic carriers significantly influence the transmission dynamics of C. difficile. This study aimed to assess the prevalence of toxigenic C. difficile asymptomatic colonization (tCDAC) and investigate its heterogeneity across different populations. We searched MEDLINE, Web of Science, and Scopus for articles published between 2000 and 2023 on tCDAC. Studies including asymptomatic adults with laboratory-confirmed tCDAC were eligible. We performed a random-effects meta-analysis to estimate the pooled prevalence by clinical characteristics, settings, and geographic areas. In addition, we used outlier analyses and meta-regression to explore sources of prevalence variability.

RESULTS

Fifty-one studies involving 39,447 patients were included. The tCDAC prevalence ranged from 0.5 to 51.5%. Among pooled estimates, a high prevalence was observed in patients with cystic fibrosis, outbreak settings, and cancer patients, whereas the lowest rates were found in healthy individuals and healthcare workers. Similar colonization rates were observed between admitted and hospitalized patients. Our meta-regression analysis revealed lower rates in healthy individuals and higher rates in cystic fibrosis patients and studies from North America. Additionally, compared with that among healthy individuals, the prevalence significantly increased by 15-47% among different populations and settings.

CONCLUSION

Our study revealed that tCDAC is a common phenomenon. We found high prevalence estimates that showed significant variability across populations. This heterogeneity could be partially explained by population characteristics and settings, supporting their role in the pathogenesis and burden of this disease. This highlights the need to identify high-risk groups to improve infection control strategies, decrease transmission dynamics, and better understand the natural history of this disease.

Diagnosis of Clostridioides difficile infection and impact of testing

Diagnosis of Clostridioides difficile infection (CDI) remains challenging as it involves in the first instance recognition (clinical awareness) of the patients' symptoms for clinical suspicion of CDI to warrant testing, and secondly, different laboratory tests have been described for CDI. Due to the overwhelming amount of information in the literature on CDI tests and their performance, with separately published guidelines, this review aims to provide a comprehensive but concise summary of the current state of CDI diagnostic testing. Current knowledge and the impact of using different laboratory diagnostic procedures for CDI, including the most recommended approach as a two-step algorithm and the concept of diagnostic stewardship, are being discussed. This review provides an updated overview and valuable take-home messages in the field of CDI laboratory testing and highlights that timely diagnosis is important for the clinical management of CDI and that the recommended testing procedures are increasingly becoming more widely accepted.

Multiplexed gastrointestinal PCR panels for the evaluation of diarrhea in patients with acute leukemia

OBJECTIVE

To better delineate multiplexed gastrointestinal polymerase chain reaction (PCR) panel (MGPP) diagnostic and therapeutic stewardship for patients undergoing treatment for acute leukemia including indications and benefits of testing, optimal timing, and interpretation of results.

STUDY DESIGN

We retrieved all MGPP ordered on 662 consecutive patients admitted with newly diagnosed acute leukemia between June 2015 and May 2024.

SETTING

Regional referral center for acute leukemia.

RESULTS

Fifty-one (17%) of 305 MGPP obtained on the 198 patients who underwent testing identified at least one and 4 (1%) more than one diarrheagenic pathogen. The probability of a positive result was greater if obtained as an outpatient [20/52(38%)], but was not related to type of leukemia, sex, or age. Among the positive results, the pathogens identified included Clostridioides difficile (78% of tests), norovirus (16%), diarrheagenic Escherichia coli (6%), adenovirus 40/41 (4%), and Giardia lamblia (4%). The results of 30 of the 305 tests resulted in a change in treatment (28 C. difficile, 2 G. lamblia). For the MGPP C. difficile results with an accompanying toxin determination, this included treatment following 16/19 tests with a positive toxin result and 11/19 with a negative. Actionable results other than C. difficile were rarely seen in the inpatient population.

CONCLUSIONS

MGPP testing is most useful when administered as an outpatient and of little benefit for inpatients with hospital-onset diarrhea. Since MGPP is sensitive and does not distinguish between colonization and causes of diarrhea, caution is needed in interpretation of results, especially for toxin-negative C. difficile.

Informing estimates of probability of Clostridioides difficile infection for testing and treatment: expert consensus from a modified-Delphi procedure

Background

Clostridioides difficile infection (CDI) may be misdiagnosed if testing is performed in the absence of signs or symptoms of disease. This study sought to support appropriate testing by estimating the impact of signs, symptoms, and healthcare exposures on pre-test likelihood of CDI.

Methods

A panel of fifteen experts in infectious diseases participated in a modified UCLA/RAND Delphi study to estimate likelihood of CDI. Consensus, defined as agreement by >70% of panelists, was assessed via a REDCap survey. Items without consensus were discussed in a virtual meeting followed by a second survey.

Results

All fifteen panelists completed both surveys (100% response rate). In the initial survey, consensus was present on 6 of 15 (40%) items related to risk of CDI. After panel discussion and clarification of questions, consensus (>70% agreement) was reached on all remaining items in the second survey. Antibiotics were identified as the primary risk factor for CDI and grouped into three categories: high-risk (likelihood ratio [LR] 7, 93% agreement among panelists in first survey), low-risk (LR 3, 87% agreement in first survey), and minimal-risk (LR 1, 71% agreement in first survey). Other major factors included new or unexplained severe diarrhea (e.g., ≥ 10 liquid bowel movements per day; LR 5, 100% agreement in second survey) and severe immunosuppression (LR 5, 87% agreement in second survey).

Conclusion

Infectious disease experts concurred on the importance of signs, symptoms, and healthcare exposures for diagnosing CDI. The resulting risk estimates can be used by clinicians to optimize CDI testing and treatment.

Acute diarrhea in the hospitalized immunocompromised patient: what is new on diagnostic and treatment?

PURPOSE OF REVIEW

This article aims to provide an intuitive framework for diagnosing and managing healthcare-associated diarrhea (HCAD) in the immunocompromised (IC) host.

RECENT FINDINGS

Our understanding of diarrhea in hospitalized IC patients has significantly evolved. However, the challenge lies in distinguishing between these patients' numerous causes of diarrhea. The incorporation of gastrointestinal (GI) multiplex polymerase chain reaction (PCR) panels has led to a paradigm shift in our approach to diarrhea. However, using these panels judiciously is of utmost importance, as their misuse can lead to over-testing, overtreatment, and increased hospital costs. We propose a stepwise diagnostic algorithm that ensures diagnostic stewardship, optimal patient care, and resource utilization.

SUMMARY

Diarrhea is a common complication in hospitalized IC patients and is associated with significant morbidity and rare mortality. The advent of new diagnostics, such as GI multiplex PCR panels, holds promise in facilitating the detection of recognized pathogens and may allow for improved outcomes using pathogen-targeted therapy.

Therapeutics involved in managing initial and recurrent Clostridium difficile infection: An updated literature review

Clostridium difficile infection (CDI) has been increasing due to the effect of recurrent hospitalizations. The use of antibiotics has been shown to alter the gut microbiome and lead to CDIs. The treatment is limited to three major antibiotics; however, the incidence of recurrent CDIs has been increasing and drug resistance is a major concern. This aspect is a growing concern in modern medicine especially in the elderly population, critical care patients, and immunocompromised individuals who are at high risk of developing CDIs. Clostridium difficile can lead to various complications including septic shock and fulminant colitis that could prove to be lethal in these patients. Newer modalities of treatment have been developed including bezlotoxumab, a monoclonal antibody and fecal microbiota transplant. There have been studies showing asymptomatic carriers and drug resistance posing a major threat to the healthcare system. Newer treatment options are being studied to treat and prevent CDIs. This review will provide an insight into the current treatment modalities, prevention and newer modalities of treatment and challenges faced in the treatment of CDIs.

Emerging Diagnostics in Clostridioides difficile Infection

Clostridioides difficile detection in community settings is time-intensive, resulting in delays in diagnosing and quarantining infected individuals. However, with the advent of semi-automated devices and improved algorithms in recent decades, the ability to discern CDI infection from asymptomatic carriage has significantly improved. This, in turn, has led to efficiently regulated monitoring systems, further reducing endemic risk, with recent concerns regarding a possible surge in hospital-acquired Clostridioides difficile infections post-COVID failing to materialize. This review highlights established and emerging technologies used to detect community-acquired Clostridioides difficile in research and clinical settings.

Multiplexed Gastrointestinal PCR Panels for the Evaluation of Diarrhea in Hematopoietic Stem Cell Transplantation Recipients

Multiplexed gastrointestinal PCR panels (MGPPs) are frequently used to aid the diagnosis and management of diarrhea in hematopoietic stem cell transplantation (HCT) recipients. Many issues related to the optimal use of MGPPs in HCT patients remain to be clarified. We aimed to better define MGPP diagnostic and therapeutic stewardship in HCT recipients, including indications for and benefits of testing, optimal timing of tests, and interpretation of results. We retrieved 463 consecutive MGPPs ordered on 651 consecutive first HCT (312 allogeneic, 339 autologous) performed at our institution between June 2015 and June 2023. One hundred and sixteen of the 463 MGPPs (25%) identified at least 1 diarrheagenic pathogen, and 12 (3%) identified more than 1 diarrheagenic pathogen. A positive result was more likely if the test was ordered within 48 hours of a hospital admission (41%; 32 of 78) or as an outpatient (41%; 46 of 111) compared with evaluation of hospital-onset diarrhea (14%; 38 of 274). Among the positive results, the most frequent pathogens identified included Clostridioides difficile (64%), diarrheagenic Escherichia coli (20%), norovirus (9%), and adenovirus 40/41 (5%). Thirty-eight percent of the positive C. difficile MGPP determinations were associated with a positive test for toxin. In our allogeneic HCT cohort, 3% of MGPPs for hospital-onset diarrhea yielded an organism other than C. difficile. Fifty-six percent of positive and 14% of all submitted tests resulted in a change in treatment. For organisms other than C. difficile, only 1% of all tests and 5% of positive tests resulted in initiation of therapy. For patients at risk for acute graft-versus-host disease (aGVHD), a positive or negative MGPP result was not predictive of a new diagnosis of aGVHD in proximity to diarrhea onset. These results suggest that MGPP testing is most useful when performed at hospital admission or on an outpatient basis. Because MGPPs are sensitive and do not distinguish between colonization and causes of diarrhea, caution is needed when interpreting results, especially for toxin-negative C. difficile and diarrheagenic gram-negative organisms.

Impact of an electronic smart order-set for diagnostic stewardship of Clostridiodes difficile infection (CDI) in a community healthcare system in South Florida

BACKGROUND

Inappropriate testing for Clostridiodes difficile infection (CDI) increases health care onset cases and contributes to overdiagnosis and overtreatment of patients in a community health care system.

METHODS

An electronic smart order set for the testing of CDI was created and implemented to improve the appropriateness of testing. A retrospective review of patients who were tested for CDI, pre and post, was conducted to determine if inappropriate stool testing for CDI decreased post-implementation of the order set.

RESULTS

224 patients were tested for CDI during the study period with the post-implementation period having a higher proportion of patients who met appropriate testing criteria defined by presence of diarrhea (80.5% vs 61.3%; P = .002). The rate of inappropriate CDI stool testing decreased from 31.1% to 11.0% after implementation (P < .001). A higher proportion of CDI patients were readmitted within 30 days of discharge (54.2% vs 33.0%; P = 0.001) during the post-implementation period.

CONCLUSIONS

There was a significant reduction in inappropriate CDI testing following the implementation of the order set. There was an observed increase in the proportion of patients who underwent recent gastrointestinal surgery which may have contributed to the increase in 30-day readmission rates during the post-implementation period.

An ultrasensitive genosensor for detection of toxigenic and non-toxigenic Clostridioides difficile based on a conserved sequence in surface layer protein coding gene

Clostridioides difficile (C. difficile) is the most common agent of antibiotic-associated diarrhea, leading to intestinal infection through the secretion of two major toxins. Not all strains of this bacterium are toxigenic, but some of them cause infection via their accessory virulence factors, such as surface layer protein (SlpA). SlpA is conserved in both toxigenic and non-toxigenic strains of C. difficile. In the present work, an amplification-free electrochemical genosensor was designed for the detection of the slpA gene. A glassy carbon electrode coated with gold nanoparticle-reduced graphene oxide nanocomposite was used as the working electrode, and its surface was modified using a simple thiolated linear oligonucleotide as the bioreceptor. Moreover, the hexaferrocenium tri[hexa(isothiocyanato) iron(III)] trihydroxonium (HxFc) complex was used as an intercalator, and its redox signal was recorded using differential pulse voltammetry. Scan rate studies indicated a quasi-reversible adsorption-controlled process for the HxFc complex. This genosensor showed high sensitivity with a limit of detection of 0.2 fM, a linear response range of 0.46-1900 fM, and a satisfactory specificity toward the synthetic slpA target gene. Also, the genosensor indicated responses in the mentioned linear range toward the genome extracted from either toxigenic or non-toxigenic strains of C. difficile.

Clinical Characteristics and Risk Factors for Clostridioides difficile Infection in the Hematopoietic Cell Transplantation Population

Background

Hematopoietic cell transplantation (HCT) recipients are at increased risk of developing primary and recurrent Clostridioides difficile infection (CDI). The objective of our study was to characterize the risk factors for primary and recurrent CDI in a large cohort of patients hospitalized for HCT.

Methods

We conducted a retrospective cohort study of adults who underwent HCT from 2010-2023 to analyze the epidemiology, timing, and risk factors for CDI. We compared patients who developed CDI with those who did not, controlling for patient demographics, comorbidities, transplant factors, medications, and laboratory values.

Results

Of the 2,725 adults who underwent HCT, 252 (9.3%) developed primary CDI within one-year of transplantation. The incidence was higher among allogenic HCT recipients (17.8%) compared to autologous recipients (4.1%). Independent risk factors for primary CDI included receipt of penicillin antibiotics, prior chemotherapy, and umbilical cord stem cells. Receipt of macrolide antibiotics was an independent risk factor for recurrent CDI, while receipt of autologous HCT was associated with a reduced risk of both primary and recurrent CDI.

Conclusions

CDI presents an early complication after HCT, particularly in allogenic recipients who experience higher incidence rates and severe complications. Early recognition and management of these risk factors are essential to prevent these adverse outcomes.

Multiplex Gastrointestinal Panel Testing in Hospitalized Patients With Acute Diarrhea in Thailand

Background

Multiplex gastrointestinal (GI) panel testing is widely used for outpatient diagnosis of diarrhea. However, the clinical practicality of multiplex testing in hospitalized diarrheal subjects has not yet been thoroughly elucidated.

Methods

We enrolled hospitalized subjects with acute diarrhea. The subjects' stool samples were collected in triplicate; 1 sample was tested using traditional diagnoses, and the other 2 were tested using Allplex (AP) and FilmArray (FA) GI panel testing. Clinical data were reviewed and analyzed.

Results

Of the 199 subjects, 92 (46.5%) were male, and the mean age was 66.3 years. The median (interquartile range) onset of diarrhea was 6 (2--14) days after hospitalization. One hundred fifty-one patients (75.9%) had sepsis, and 166 (83.4%) had received prior or were receiving current antimicrobial therapy. Positive stool cultures were obtained from 4/89 (4.5%), and Clostridioides difficile toxin gene tests were positive in 14/188 (7.4%) patients. AP and FA multiplex tests were positive for GI pathogens in 49/199 (24.6%) and 40/199 (20.1%), respectively. The target most frequently detected by AP was Aeromonas spp. Both assays commonly detected enteropathogenic E. coli (EPEC), C. difficile toxin gene, and Salmonella spp.; neither assay detected pathogens in 75.4% and 79.9%. Fever (odds ratio [OR], 2.05; 95% CI, 1.08-3.88; P = .028), watery diarrhea (OR, 2.69; 95% CI, 1.25-5.80; P = .011), and antimicrobial therapy (OR, 2.60; 95% CI, 1.18-5.71; P = .018) were independent factors associated with the negative multiplex test result.

Conclusions

Multiplex GI panel testing effectively detects enteric pathogens associated with diarrhea in hospitalized subjects. The etiology remains undiagnosed in >75% of cases. Factors contributing to negative test results should be considered before implementing the tests.

Use of PCR Cycle Threshold and Clinical Interventions to Aid in the Management of Pediatric Clostridioides difficile Patients

Better diagnostic tools are needed to improve the diagnosis of Clostridioides difficile infections (CDI) and reduce the overtreatment of colonized children. In this study, we evaluated two polymerase chain reaction (PCR) assays (Cepheid GeneXpert C. difficile and the Gastroenteritis PCR Panel by QIAstat-Dx) as a standalone method in combination with the PCR cycle threshold (Ct) value in positive samples to predict the presence of free toxins. We also evaluated the clinical impact of reporting toxin production results and provided comments alongside the PCR results in our pediatric population. PCR-positive stool samples from pediatric patients (aged 2 to 18 years old) were included in our study and tested for the presence of toxins A and B using the C. difficile Quik Chek Complete kit. For the clinical intervention, the CDI treatment rates 6 months pre- and post-intervention were compared. The use of PCR Ct value showed excellent sensitivity (100%) at a Ct value cutoff of 26.1 and 27.2 using the Cepheid GeneXpert C. difficile and the Gastroenteritis PCR Panel by QIAstat-Dx, respectively, while the toxin test showed inferior sensitivity of 64% in the PCR-positive samples. In addition, CDI treatment rates were decreased by 23% post-intervention. The results of our study suggest that nucleic acid amplification test (NAAT) assays supplemented by the use of PCR Ct value for positive samples can be used as standalone tests to differentiate CDI from colonization. Furthermore, the reporting of toxin production along with the PCR results can help reduce the unnecessary treatment of colonized children.

Comparison of rectal swabs and fecal samples for the detection of Clostridioides difficile infections with a new in-house PCR assay

The detection of Clostridioides difficile infections (CDI) relies on testing the stool of patients by toxin antigen detection or PCR methods. Although PCR and antigenic methods have significantly reduced the time to results, delays in stool collection can significantly add to the turnaround time. The use of rectal swabs to detect C. difficile could considerably reduce the time to diagnosis of CDI. We developed a new rapid PCR assay for the detection of C. difficile and evaluated this PCR assay on both stool and rectal swab specimens. We recruited a total of 623 patients suspected of C. difficile infection. Stool samples and rectal swabs were collected from each patient and tested by our PCR assay. Stool samples were also tested by the cell cytotoxicity neutralization assay (CCNA) as a reference. The PCR assay detected C. difficile in 60 stool specimens and 61 rectal swabs for the 64 patients whose stool samples were positive for C. difficile by CCNA. The PCR assay detected an additional 35 and 36 stool and rectal swab specimens positive for C. difficile, respectively, for sensitivity with stools and rectal swabs of 93.8% and 95.3%, specificity of 93.7% and 93.6%, positive predictive values of 63.2% and 62.9%, and negative predictive values of 99.2% and 99.4%. Detection of C. difficile using PCR on stools or rectal swabs yielded reliable and similar results. The use of PCR tests on rectal swabs could reduce turnaround time for CDI detection, thus improving CDI management and control of C. difficile transmission.

IMPORTANCE

Clostridioides difficile infection (CDI) is the leading cause of healthcare-associated diarrhea, resulting in high morbidity, mortality, and economic burden. In clinical laboratories, CDI testing is currently performed on stool samples collected from patients with diarrhea. However, the diagnosis of CDI can be delayed by the time required to collect stool samples. Barriers to sample collection could be overcome by using a rectal swab instead of a stool sample. Our study showed that CDI can be identified rapidly and reliably by a new PCR assay developed in our laboratory on both stool and rectal swab specimens. The use of PCR tests on rectal swabs could reduce the time for the detection of CDI and improve the management of this infection. It should also provide a useful alternative for infection-control practitioners to better control the spread of C. difficile.

Clostridioides difficile Colitis

Clostridioides difficile colitis is an important source of hospital-acquired diarrhea associated with antibiotic use. Symptoms are profuse watery diarrhea, typically following a course of antibiotics; however, some cases of fulminant disease may manifest with shock, ileus, or megacolon. Nonfulminant colitis is treated with oral fidaxomicin. C difficile colitis has a high potential for recurrence, and recurrent episodes are also treated with fidaxomicin. Bezlotoxumab is another medication that may be used in populations at high risk for further recurrence. Fulminant disease is treated with maximal medical therapy and early surgical consultation. Antibiotic stewardship is critical to preventing C difficile colitis.

C. difficile biomarkers, pathogenicity and detection

BACKGROUND

Clostridioides difficile infection (CDI) is the main etiologic agent of antibiotic-associated diarrhea. CDI contributes to gut inflammation and can lead to disruption of the intestinal epithelial barrier. Recently, the rate of CDI cases has been increased. Thus, early diagnosis of C. difficile is critical for controlling the infection and guiding efficacious therapy.

APPROACH

A search strategy was set up using the terms C. difficile biomarkers and diagnosis. The found references were classified into two general categories; conventional and advanced methods.

RESULTS

The pathogenicity and biomarkers of C. difficile, and the collection manners for CDI-suspected specimens were briefly explained. Then, the conventional CDI diagnostic methods were subtly compared in terms of duration, level of difficulty, sensitivity, advantages, and disadvantages. Thereafter, an extensive review of the various newly proposed techniques available for CDI detection was conducted including nucleic acid isothermal amplification-based methods, biosensors, and gene/single-molecule microarrays. Also, the detection mechanisms, pros and cons of these methods were highlighted and compared with each other. In addition, approximately complete information on FDA-approved platforms for CDI diagnosis was collected.

CONCLUSION

To overcome the deficiencies of conventional methods, the potential of advanced methods for C. difficile diagnosis, their direction, perspective, and challenges ahead were discussed.

Validation of clinical risk tools for recurrent Clostridioides difficile infection

OBJECTIVE

We sought to validate available tools for predicting recurrent C. difficile infection (CDI) including recurrence risk scores (by Larrainzar-Coghen, Reveles, D'Agostino, Cobo, and Eyre et al) alongside consensus guidelines risk criteria, the leading severity score (ATLAS), and PCR cycle threshold (as marker of fecal organism burden) using electronic medical records.

DESIGN

Retrospective cohort study validating previously described tools.

SETTING

Tertiary care academic hospital.

PATIENTS

Hospitalized adult patients with CDI at University of Virginia Medical Center.

METHODS

Risk scores were calculated within ±48 hours of index CDI diagnosis using a large retrospective cohort of 1,519 inpatient infections spanning 7 years and compared using area under the receiver operating characteristic curve (AUROC) and the DeLong test. Recurrent CDI events (defined as a repeat positive test or symptom relapse within 60 days requiring retreatment) were confirmed by clinician chart review.

RESULTS

Reveles et al tool achieved the highest AUROC of 0.523 (and 0.537 among a subcohort of 1,230 patients with their first occurrence of CDI), which was not substantially better than other tools including the current IDSA/SHEA C. difficile guidelines or PCR cycle threshold (AUROC: 0.564), regardless of prior infection history.

CONCLUSIONS

All tools performed poorly for predicting recurrent C. difficile infection (AUROC range: 0.488-0.564), especially among patients with a prior history of infection (AUROC range: 0.436-0.591). Future studies may benefit from considering novel biomarkers and/or higher-dimensional models that could augment or replace existing tools that underperform.

Impact of the Reverse 2-Step Algorithm for Clostridioides difficile Testing in the Microbiology Laboratory on Hospitalized Patients

Background

Multistep laboratory testing is recommended for the diagnosis of Clostridioides difficile infection (CDI). The aim of this study was to present the impact of multistep CDI diagnostic testing in an academic hospital system and evaluate the toxin B gene polymerase chain reaction (PCR) cycle threshold (Ct) values of PCR-positive tests.

Methods

In October 2022, our system began reflex testing all PCR-positive stool samples with the C. DIFF QUIK CHEK COMPLETE (Techlab), an enzyme immunoassay-based test with results for the glutamate dehydrogenase antigen (GDH) and C difficile toxin A/B. Hospital-onset (HO) CDI and CDI antibiotic use before and after testing were tracked. Ct values were obtained from the Infectious Diseases Diagnostic Laboratory. Receiver operating curve analysis was used to examine the sensitivity and specificity for identifying GDH+/toxin+ and GDH-/toxin- at various Ct thresholds.

Results

The HO-CDI rate decreased from 0.352 cases per 1000 patient-days to 0.115 cases per 1000 patient-days post-reflex testing (P < .005). Anti-CDI antibiotics use decreased, but the decrease was not commensurate with CDI rates following reflex testing. PCR+/GDH+/toxin+ samples had a lower mean Ct value than PCR+/GDH-/toxin- samples (23.3 vs 33.5, P < .0001). A Ct value of 28.65 could distinguish between those 2 groups. Fifty-four percent of PCR+/GDH+/toxin- samples had a Ct value below that cut-off, suggesting the possibility of CDI with a negative toxin test.

Conclusions

Reflex testing for a laboratory diagnosis of CDI results in rapid, systemwide decreases in the rate of HO-CDI. Additional research is needed to distinguish CDI from C difficile colonization in patients with discordant testing.

Potential underreporting of treated patients using a Clostridioides difficile testing algorithm that screens with a nucleic acid amplification test

OBJECTIVE

Patients tested for Clostridioides difficile infection (CDI) using a 2-step algorithm with a nucleic acid amplification test (NAAT) followed by toxin assay are not reported to the National Healthcare Safety Network as a laboratory-identified CDI event if they are NAAT positive (+)/toxin negative (-). We compared NAAT+/toxin- and NAAT+/toxin+ patients and identified factors associated with CDI treatment among NAAT+/toxin- patients.

DESIGN

Retrospective observational study.

SETTING

The study was conducted across 36 laboratories at 5 Emerging Infections Program sites.

PATIENTS

We defined a CDI case as a positive test detected by this 2-step algorithm during 2018-2020 in a patient aged ≥1 year with no positive test in the previous 8 weeks.

METHODS

We used multivariable logistic regression to compare CDI-related complications and recurrence between NAAT+/toxin- and NAAT+/toxin+ cases. We used a mixed-effects logistic model to identify factors associated with treatment in NAAT+/toxin- cases.

RESULTS

Of 1,801 cases, 1,252 were NAAT+/toxin-, and 549 were NAAT+/toxin+. CDI treatment was given to 866 (71.5%) of 1,212 NAAT+/toxin- cases versus 510 (95.9%) of 532 NAAT+/toxin+ cases (P < .0001). NAAT+/toxin- status was protective for recurrence (adjusted odds ratio [aOR], 0.65; 95% CI, 0.55-0.77) but not CDI-related complications (aOR, 1.05; 95% CI, 0.87-1.28). Among NAAT+/toxin- cases, white blood cell count ≥15,000/µL (aOR, 1.87; 95% CI, 1.28-2.74), ≥3 unformed stools for ≥1 day (aOR, 1.90; 95% CI, 1.40-2.59), and diagnosis by a laboratory that provided no or neutral interpretive comments (aOR, 3.23; 95% CI, 2.23-4.68) were predictors of CDI treatment.

CONCLUSION

Use of this 2-step algorithm likely results in underreporting of some NAAT+/toxin- cases with clinically relevant CDI. Disease severity and laboratory interpretive comments influence treatment decisions for NAAT+/toxin- cases.

Clinical outcomes and treatment necessity in patients with toxin-negative Clostridioides difficile stool samples

PURPOSE

The clinical significance of negative toxin enzyme immunoassays (EIA) for Clostridioides difficile infections (CDIs) is unclear. Our study aimed to investigate the significance of toxin EIA-negative in the diagnosis and prognosis of CDI.

METHODS

All stool specimens submitted for C. difficile toxin EIA testing were cultured to isolate C. difficile. In-house PCR for tcdA, tcdB, cdtA, and cdtB genes were performed using C. difficile isolates. Stool specimens were tested with C. difficile toxins A and B using EIA kit (RIDASCREEN Clostridium difficile toxin A/B, R-Biopharm AG, Darmstadt, Germany). Characteristics and subsequent CDI episodes of toxin EIA-negative and -positive patients were compared.

RESULTS

Among 190 C. difficile PCR-positive patients, 83 (43.7%) were toxin EIA-negative. Multivariate analysis revealed independent associations toxin EIA-negative results and shorter hospital stays (OR = 0.98, 95% CI 0.96-0.99, p = 0.013) and less high-risk antibiotic exposure in the preceding month (OR = 0.38, 95% CI 0.16-0.94, p = 0.035). Toxin EIA-negative patients displayed a significantly lower white blood cell count rate (11.0 vs. 35.4%, p < 0.001). Among the 54 patients who were toxin EIA-negative and did not receive CDI treatment, three (5.6%) were diagnosed with CDI after 7-21 days without complication.

CONCLUSION

Our study demonstrates that toxin EIA-negative patients had milder laboratory findings and no complications, despite not receiving treatment. Prolonged hospitalisation and exposure to high-risk antibiotics could potentially serve as markers for the development of toxin EIA-positive CDI.

Clostridioides difficile infection is associated with differences in transcriptionally active microbial communities

Clostridioides difficile infection (CDI) is responsible for around 300,000 hospitalizations yearly in the United States, with the associated monetary cost being billions of dollars. Gut microbiome dysbiosis is known to be important to CDI. To the best of our knowledge, metatranscriptomics (MT) has only been used to characterize gut microbiome composition and function in one prior study involving CDI patients. Therefore, we utilized MT to investigate differences in active community diversity and composition between CDI+ (n = 20) and CDI- (n = 19) samples with respect to microbial taxa and expressed genes. No significant (Kruskal-Wallis, p > 0.05) differences were detected for richness or evenness based on CDI status. However, clustering based on CDI status was significant for both active microbial taxa and expressed genes datasets (PERMANOVA, p ≤ 0.05). Furthermore, differential feature analysis revealed greater expression of the opportunistic pathogens Enterocloster bolteae and Ruminococcus gnavus in CDI+ compared to CDI- samples. When only fungal sequences were considered, the family Saccharomycetaceae expressed more genes in CDI-, while 31 other fungal taxa were identified as significantly (Kruskal-Wallis p ≤ 0.05, log(LDA) ≥ 2) associated with CDI+. We also detected a variety of genes and pathways that differed significantly (Kruskal-Wallis p ≤ 0.05, log(LDA) ≥ 2) based on CDI status. Notably, differential genes associated with biofilm formation were expressed by C. difficile. This provides evidence of another possible contributor to C. difficile's resistance to antibiotics and frequent recurrence in vivo. Furthermore, the greater number of CDI+ associated fungal taxa constitute additional evidence that the mycobiome is important to CDI pathogenesis. Future work will focus on establishing if C. difficile is actively producing biofilms during infection and if any specific fungal taxa are particularly influential in CDI.

Breaking Boundaries in Pneumonia Diagnostics: Transitioning from Tradition to Molecular Frontiers with Multiplex PCR

The advent of rapid molecular microbiology testing has revolutionized infectious disease diagnostics and is now impacting pneumonia diagnosis and management. Molecular platforms offer highly multiplexed assays for diverse viral and bacterial detection, alongside antimicrobial resistance markers, providing the potential to significantly shape patient care. Despite the superiority in sensitivity and speed, debates continue regarding the clinical role of multiplex molecular testing, notably in comparison to standard methods and distinguishing colonization from infection. Recent guidelines endorse molecular pneumonia panels for enhanced sensitivity and rapidity, but implementation requires addressing methodological differences and ensuring clinical relevance. Diagnostic stewardship should be leveraged to optimize pneumonia testing, emphasizing pre- and post-analytical strategies. Collaboration between clinical microbiologists and bedside providers is essential in developing implementation strategies to maximize the clinical utility of multiplex molecular diagnostics in pneumonia. This narrative review explores these multifaceted issues, examining the current evidence on the clinical performance of multiplex molecular assays in pneumonia, and reflects on lessons learned from previous microbiological advances. Additionally, given the complexity of pneumonia and the sensitivity of molecular diagnostics, diagnostic stewardship is discussed within the context of current literature, including implementation strategies that consider pre-analytical and post-analytical modifications to optimize the clinical utility of advanced technologies like multiplex PCR.

Diagnostic stewardship to improve patient outcomes and healthcare-associated infection (HAI) metrics

Diagnostic stewardship seeks to improve ordering, collection, performance, and reporting of tests. Test results play an important role in reportable HAIs. The inclusion of HAIs in public reporting and pay for performance programs has highlighted the value of diagnostic stewardship as part of infection prevention initiatives. Inappropriate testing should be discouraged, and approaches that seek to alter testing solely to impact a reportable metric should be avoided. HAI definitions should be further adapted to new testing technologies, with focus on actionable and clinically relevant test results that will improve patient care.

Present and Future Non-Culture-Based Diagnostics: Stewardship Potentials and Considerations

The medical microbiologist plays a key role in the transition from culture-based to molecular test methods for diagnosis of infectious diseases. They must understand the scientific and technical bases underlying these tests along with their associated benefits and limitations and be able to educate administrators and patient providers on their proper use. Coordination of testing practices between clinical departments and the spectrum of public health and research laboratories is essential to optimize health care delivery.

Clostridioides difficile detection and infection in children: are they just small adults?

Clostridioides difficile is a well-recognized healthcare-associated pathogen, with its significance widely recognized in adult populations. Despite this, there is limited data on the significance of detection within paediatric populations, both for individual patient management and wider transmission risk-based considerations. High rates of colonization are understood to occur in infants, with increasing levels up to 11 months, and colonization rates similar to adults by 8 years old. Sources of C. difficile are ubiquitous, with detection in companion animals and food sources, as well as within the clinical and wider environment. Due to the close interactions that occur between children and the environment, it is understandable that increasing recognition is afforded to the community acquisition of C. difficile in children. Other risk factors for the detection of C. difficile in children are similar to those observed in adults, including prior hospitalization and underlying conditions affecting gut health and motility. Recent studies have shown rising awareness of the role of asymptomatic carriage of C. difficile in healthcare transmission. Prior to this, paediatric patient populations were less likely to be screened due to uncertainty regarding the significance of detection; however, this increased awareness has led to a review of possible carriage testing pathways. Despite this increased attention, C. difficile infection remains poorly defined in paediatric populations, with limited dedicated paediatric data sets making comparison challenging. This is further complicated by the fact that infection in children frequently self resolves without additional therapies. Due to this, C. difficile remains a management challenge in paediatric settings.

Health care-associated Clostridioides difficile infection: Learning the perspectives of health care workers to build successful strategies

BACKGROUND

Clostridioides difficile (C difficile) is one of the most common health care-associated infections that negatively impact patient care and health care costs. This study takes a unique approach to C difficile infection (CDI) control by investigating key prevention obstacles through the perspectives of Stanford health care (SHC) frontline health care personnel.

METHODS

An anonymous qualitative survey was distributed at SHC, focusing on knowledge and practice of CDI prevention guidelines, as well as education, communication, and perspectives regarding CDI at SHC.

RESULTS

112 survey responses were analyzed. Our findings unveiled gaps in personnel's knowledge of C difficile diagnostic guidelines and revealed a need for targeted communication and guideline-focused education. Health care staff shared preferences and recommendations, with the majority recommending enhanced communication of guidelines and information as a strategy for reducing CDI rates. The findings were then used to design and propose internal recommendations for SHC to mitigate the gaps found.

DISCUSSION

Many guidelines and improvement strategies are based on strong scientific and medical foundations; however, it is important to ask whether these guidelines are effectively translated into practice. Frontline health care workers hold empirical perspectives that could be key in infection control.

CONCLUSIONS

Our findings emphasize the importance of including frontline health care personnel in infection prevention decision-making processes and the strategies presented here can be applied to mitigating infections in different health care settings.

Clinical Outcomes and Management of NAAT-Positive/Toxin-Negative Clostridioides difficile Infection: A Systematic Review and Meta-Analysis

BACKGROUND

Standalone nucleic acid amplification tests (NAATs) are frequently used to diagnose Clostridioides difficile infections (CDI), although they may be unable to distinguish colonization from disease. A 2-stage algorithm pairing NAATs with toxin immunoassays (Toxin) may improve specificity. We evaluated clinical outcomes of patients who were NAAT+/Toxin+ versus NAAT+/Toxin- and treated versus untreated NAAT+/Toxin- cases through systematic review and meta-analysis.

METHODS

We searched EMBASE and MEDLINE from inception to April 1, 2023 for articles comparing CDI outcomes among symptomatic patients tested by NAAT and Toxin tests. The risk differences (RD) of all-cause mortality and CDI recurrence were computed by random effects meta-analysis between patients who were NAAT+/Toxin+ and NAAT+/Toxin-, as well as between patients who were NAAT+/Toxin- and treated or untreated.

RESULTS

Twenty-six observational studies comprising 12 737 patients were included. The 30-day all-cause mortality was not significantly different between those who were NAAT+/Toxin+ (8.4%) and NAAT+/Toxin- (6.7%) (RD = 0.41%, 95% confidence interval [CI] = -.67, 1.49). Recurrence at 60 days was significantly higher among patients who were NAAT+/Toxin+ (19.8%) versus NAAT+/Toxin- (11.0%) (RD = 7.65%, 95% CI = 4.60, 10.71). Among treated compared to untreated NAAT+/Toxin- cases, the all-cause 30-day mortalities were 5.0% and 12.7%, respectively (RD = -7.45%, 95% CI = -12.29, -2.60), but 60-day recurrence was not significantly different (11.6% vs 7.0%, respectively; RD = 5.25%, 95% CI -1.71, 12.22).

CONCLUSIONS

Treatment of patients who were NAAT+/Toxin- was associated with reduced all-cause mortality but not recurrence. Although subject to the inherent limitations of observational studies, these results suggest that some patients who are NAAT+/Toxin- may benefit from treatment.

Clostridioides difficile Infection: Diagnosis and Treatment Challenges

Clostridioides difficile is the most important cause of healthcare-associated diarrhea in the United States. The high incidence and recurrence rates of C. difficile infection (CDI), associated with high morbidity and mortality, pose a public health challenge. Although antibiotics targeting C. difficile bacteria are the first treatment choice, antibiotics also disrupt the indigenous gut flora and, therefore, create an environment that is favorable for recurrent CDI. The challenge of treating CDI is further exacerbated by the rise of antibiotic-resistant strains of C. difficile, placing it among the top five most urgent antibiotic resistance threats in the USA. The evolution of antibiotic resistance in C. difficile involves the acquisition of new resistance mechanisms, which can be shared among various bacterial species and different C. difficile strains within clinical and community settings. This review provides a summary of commonly used diagnostic tests and antibiotic treatment strategies for CDI. In addition, it discusses antibiotic treatment and its resistance mechanisms. This review aims to enhance our current understanding and pinpoint knowledge gaps in antimicrobial resistance mechanisms in C. difficile, with an emphasis on CDI therapies.

Rapid discrimination between clinical Clostridioides difficile infection and colonization by quantitative detection of TcdB toxin using a real-time cell analysis system

Objectives

It is important to accurately discriminate between clinical Clostridioides difficile infection (CDI) and colonization (CDC) for effective antimicrobial treatment.

Methods

In this study, 37 stool samples were collected from 17 CDC and 20 CDI cases, and each sample were tested in parallel through the real-time cell analysis (RTCA) system, real-time PCR assay (PCR), and enzyme-linked immunosorbent assay (ELISA).

Results

RTCA-measured functional and toxical C. difficile toxin B (TcdB) concentrations in the CDI group (302.58 ± 119.15 ng/mL) were significantly higher than those in the CDC group (18.15 ± 11.81 ng/mL) (p = 0.0008). Conversely, ELISA results revealed no significant disparities in TcdB concentrations between the CDC (26.21 ± 3.57 ng/mL) and the CDI group (17.07 ± 3.10 ng/mL) (p = 0.064). PCR results indicated no significant differences in tcdB gene copies between the CDC (774.54 ± 357.89 copies/μL) and the CDI group (4,667.69 ± 3,069.87 copies/μL) (p = 0.407). Additionally, the functional and toxical TcdB concentrations secreted from C. difficile isolates were measured by the RTCA. The results from the CDC (490.00 ± 133.29 ng/mL) and the CDI group (439.82 ± 114.66 ng/mL) showed no significant difference (p = 0.448). Notably, RTCA-measured functional and toxical TcdB concentration was significantly decreased when mixed with pooled CDC samples supernatant (p = 0.030).

Conclusion

This study explored the novel application of the RTCA assay in effectively discerning clinical CDI from CDC cases.

Use of electronic health record data to identify hospital-associated Clostridioides difficile infections: a validation study

Background

Clinical research focused on the burden and impact of Clostridioides difficile infection (CDI) often relies upon accurate identification of cases using existing health record data. Use of diagnosis codes alone can lead to misclassification of cases. Our goal was to develop and validate a multi-component algorithm to identify hospital-associated CDI (HA-CDI) cases using electronic health record (EHR) data.

Methods

We performed a validation study using a random sample of adult inpatients at a large academic hospital setting in Portland, Oregon from January 2018 to March 2020. We excluded patients with CDI on admission and those with short lengths of stay (< 4 days). We tested a multi-component algorithm to identify HA-CDI; case patients were required to have received an inpatient course of metronidazole, oral vancomycin, or fidaxomicin and have at least one of the following: a positive C. difficile laboratory test or the International Classification of Diseases, Tenth Revision (ICD-10) code for non-recurrent CDI. For a random sample of 80 algorithm-identified HA-CDI cases and 80 non-cases, we performed manual EHR review to identify gold standard of HA-CDI diagnosis. We then calculated overall percent accuracy, sensitivity, specificity, and positive and negative predictive value for the algorithm overall and for the individual components.

Results

Our case definition algorithm identified HA-CDI cases with 94% accuracy (95% Confidence Interval (CI): 88% to 97%). We achieved 100% sensitivity (94% to 100%), 89% specificity (81% to 95%), 88% positive predictive value (78% to 94%), and 100% negative predictive value (95% to 100%). Requiring a positive C. difficile test as our gold standard further improved diagnostic performance (97% accuracy [93% to 99%], 93% PPV [85% to 98%]).

Conclusions

Our algorithm accurately detected true HA-CDI cases from EHR data in our patient population. A multi-component algorithm performs better than any isolated component. Requiring a positive laboratory test for C. difficile strengthens diagnostic performance even further. Accurate detection could have important implications for CDI tracking and research.

Diagnostic Guidance for C. difficile Infections

Diagnosis of Clostridioides difficile infection (CDI) can be challenging. First of all, there has been debate on which of the two reference assays, cell cytotoxicity neutralization assay (CCNA) or toxigenic culture (TC), should be considered the gold standard for CDI detection. Although the CCNA suffers most from suboptimal storage conditions and subsequent toxin degradation, TC is reported to falsely increase CDI detection rates as it cannot differentiate CDI patients from patients asymptomatically colonised by toxigenic C. difficile. Several rapid assays are available for CDI detection and fall into three broad categories: (1) enzyme immunoassays for glutamate dehydrogenase, (2) enzyme immunoassays or single-molecule array assays for toxins A/B and (3) nucleic acid amplification tests detecting toxin genes. All three categories have their own limitations, being suboptimal specificity and/or sensitivity or the inability to discern colonised patients from CDI patients. In light of these limitations, multi-step algorithmic testing has been advocated by international guidelines (IDSA/SHEA and ESCMID) in order to optimize diagnostic accuracy. As a result, a survey performed in 2018-2019 in Europe revealed that most of all hospital sites reported using more than one test to diagnose CDI. CDI incidence rates are also influenced by sample selection criteria, as several studies have shown that if not all unformed stool samples are tested for CDI, many cases may be missed due to an absence of clinical suspicion. Since methods for diagnosing CDI remain imperfect, there has been a growing interest in alternative testing strategies like faecal microbiota biomarkers, immune modulating interleukins, cytokines and imaging methods. At the moment, these alternative methods might play an adjunctive role, but they are not suitable to replace conventional CDI testing strategies.

The Need for European Surveillance of CDI

Since the turn of the millennium, the epidemiology of Clostridioides difficile infection (CDI) has continued to challenge. Changes in clinical presentation, severity of disease, descriptions of new risk factors and the occurrence of outbreaks all emphasised the importance of early diagnosis and standardised surveillance systems. However, a lack of consensus on case definitions, clinical guidelines and optimal laboratory diagnostics across Europe has led to the underestimation of CDI and impeded comparison between countries. These inconsistencies have prevented the true burden of disease from being appreciated.Acceptance that a multi-country CDI surveillance program and optimised diagnostic strategies are required has built the foundations for a more robust, unified surveillance. The concerted efforts of the European Centre for Disease Prevention and Control (ECDC) CDI networks led to the development of the European surveillance protocol and an over-arching long-term CDI surveillance strategy for 2014-2020, which has been followed by the development of surveillance systems in at least 20 European countries. However, surveillance activities in individual countries have slowed during the COVID-19 pandemic as resources were diverted to the global health crisis. A renewed and strengthened focus on CDI surveillance and prevention is therefore urgently needed post COVID-19.

Characteristics and outcomes of Clostridioides difficile infection after a change in the diagnostic testing algorithm

BACKGROUND

Polymerase chain reaction (PCR) testing for the detection of C. difficile is a highly sensitive test. Some clinical laboratories have included a 2-step testing algorithm utilizing PCR plus toxin enzyme immunoassays (EIAs) to increase specificity.

OBJECTIVE

To determine the risk factors and outcomes of C. difficile PCR-positive/toxin-positive encounters compared to PCR-positive/toxin-negative encounters.

DESIGN

Retrospective study.

SETTING

A Veterans' Affairs hospital.

METHODS

A retrospective case-control study of patient encounters with a positive C. difficile test by PCR and either a toxin EIA-positive assay (ie, cases) or toxin EIA-negative assay (ie, controls). Clinically relevant exposures and risk factors were determined to assess CDI recurrence at 30 days. Available encounter stool specimens were cultured for C. difficile and were subjected to restriction endonuclease analysis (REA) strain typing.

RESULTS

Among 130 C. difficile PCR-positive patient encounters, 80 (61.5%) were toxin EIA negative and 50 (38.5%) were toxin EIA positive. Encounters that were toxin positive were more frequently treated (96.0%) compared to toxin-negative encounters (71.3%; P < .01). A multivariable logistic regression model revealed that toxin-negative encounters were less likely to suffer a recurrent CDI episode within 30 days (odds ratio [OR], 0.20, 95% confidence interval [CI], 0.05-0.83). Additionally, a higher C. difficile PCR cycle threshold predicted a lower risk of CDI recurrence at 30 days. (OR, 0.82; 95% CI, 0.68-0.98). During the study period, the REA group Y strain accounted for most toxin-negative encounters (32.5%; P = .05), whereas REA group BI strain accounted for most toxin-positive encounters (24.3%; P = .02).

CONCLUSIONS

A testing strategy of PCR plus toxin EIA helped predict recurrent CDI.

Fecal calprotectin level is nonlinearly associated with GI pathogen detection in patients with and without inflammatory bowel disease

Fecal calprotectin (FCP) is used to monitor inflammatory bowel disease (IBD) activity and can also be elevated in gastrointestinal infections. Our study's objective was to quantify the relationship between FCP levels and lab-confirmed infections in people with and without IBD. We performed a cross-sectional study at a tertiary-care center of all encounters during which FCP and gastrointestinal pathogen polymerase-chain reaction (GI PCR) panel testings were conducted. Using non-parametric tests and quantile regression, we compared the FCP levels by IBD status and pathogen detection. There were 3,347 encounters with FCP and GI PCR testings from 2,780 unique individuals between 1 August 2016 and 17 February 2022. Overall, 54.4% had IBD (n = 1,819). Pathogens were detected in 744 encounters (22.2%), and the detection rate did not differ by IBD status. Median FCP without IBD was significantly elevated when a pathogen was detected (64 vs 41 mg/kg, P = 0.0003, normal ≤50.0 mg/kg), but FCP with IBD was not significantly elevated when a pathogen was detected (299 vs 255 mg/kg, P = 0.207). In quantile regression adjusted for age and IBD, pathogen detection was only significantly associated with higher FCP in the lower two quartiles, though IBD remained significantly associated with higher FCP at all levels (P > 0.001). Pathogen detection by GI PCR is associated with elevated FCP, though this relationship is nonlinear and varies by IBD status. Our findings indicate that FCP may be an adjunct to, but not a substitute for, stool pathogen testing.

Implementation of a multidisciplinary process to improve diagnostic stewardship of hospital-onset Clostridioides difficile infections

BACKGROUND

Testing inappropriate stool samples for Clostridioides (Clostridium) difficile can lead to the identification of the patient colonized with C difficile and erroneous diagnosis of an active infection. We hypothesized that a multidisciplinary process to improve diagnostic stewardship could reduce our numbers of hospital-onset C difficile infection (HO-CDI).

METHODS

We created an algorithm describing appropriate stool specimens for polymerase chain reaction testing. The algorithm was converted into "ticket to test" checklist cards designed to accompany each specimen. Rejection of a specimen could occur via nursing staff or laboratory staff.

RESULTS

A baseline period of comparison was established from January 1, 2017 to June 30, 2017. Following implementation of all improvement strategies, a retrospective analysis was done, and the total number of HO-CDI cases in a 6-month period dropped from 57 to 32 cases. During the initial 3 months, the percentage of appropriate samples sent to the lab ranged from 41% to 65%. After the interventions were in place, the percentages improved between 71% and 91%.

CONCLUSIONS

A multidisciplinary approach led to improved diagnostic stewardship to identify true CDI cases. This, in turn, reduced the number of reported HO-CDIs, and resulted in potentially more than $1,080,000 in patient care savings.

Antimicrobial Stewardship in Immunocompromised Patients: Current State and Future Opportunities

Immunocompromised (IC) patients are high risk for complications due to a high rate of antibiotic exposure. Antimicrobial stewardship interventions targeted to IC patients can be challenging due to limited data in this population and a high risk of severe infection-related outcomes. Here, the authors review immunocompromised antimicrobial stewardship barriers, metrics, and opportunities for antimicrobial use and testing optimization. Last, the authors highlight future steps in the field.