Validation of SeptiCyte RAPID to Discriminate Sepsis from Non-Infectious Systemic Inflammation

(1) Background: SeptiCyte RAPID is a molecular test for discriminating sepsis from non-infectious systemic inflammation, and for estimating sepsis probabilities. The objective of this study was the clinical validation of SeptiCyte RAPID, based on testing retrospectively banked and prospectively collected patient samples. (2) Methods: The cartridge-based SeptiCyte RAPID test accepts a PAXgene blood RNA sample and provides sample-to-answer processing in ~1 h. The test output (SeptiScore, range 0-15) falls into four interpretation bands, with higher scores indicating higher probabilities of sepsis. Retrospective (N = 356) and prospective (N = 63) samples were tested from adult patients in ICU who either had the systemic inflammatory response syndrome (SIRS), or were suspected of having/diagnosed with sepsis. Patients were clinically evaluated by a panel of three expert physicians blinded to the SeptiCyte test results. Results were interpreted under either the Sepsis-2 or Sepsis-3 framework. (3) Results: Under the Sepsis-2 framework, SeptiCyte RAPID performance for the combined retrospective and prospective cohorts had Areas Under the ROC Curve (AUCs) ranging from 0.82 to 0.85, a negative predictive value of 0.91 (sensitivity 0.94) for SeptiScore Band 1 (score range 0.1-5.0; lowest risk of sepsis), and a positive predictive value of 0.81 (specificity 0.90) for SeptiScore Band 4 (score range 7.4-15; highest risk of sepsis). Performance estimates for the prospective cohort ranged from AUC 0.86-0.95. For physician-adjudicated sepsis cases that were blood culture (+) or blood, urine culture (+)(+), 43/48 (90%) of SeptiCyte scores fell in Bands 3 or 4. In multivariable analysis with up to 14 additional clinical variables, SeptiScore was the most important variable for sepsis diagnosis. A comparable performance was obtained for the majority of patients reanalyzed under the Sepsis-3 definition, although a subgroup of 16 patients was identified that was called septic under Sepsis-2 but not under Sepsis-3. (4) Conclusions: This study validates SeptiCyte RAPID for estimating sepsis probability, under both the Sepsis-2 and Sepsis-3 frameworks, for hospitalized patients on their first day of ICU admission.

Syndromic Panel Testing Among Patients With Infectious Diarrhea: The Challenge of Interpreting Clostridioides difficile Positivity on a Multiplex Molecular Panel

Background

Including Clostridioides difficile (CD) in gastrointestinal multiplex molecular panels (GIPCR) presents a diagnostic challenge. Incidental detection by polymerase chain reaction (PCR) without consideration of pretest probability (PTP) may inadvertently delay diagnoses of other treatable causes of diarrhea and lead to prescription of unnecessary antibiotics.

Methods

We conducted a retrospective study to determine the frequency at which clinicians characterize PTP and disease severity in adult patients who test positive for CD by GIPCR. We organized subjects into cohorts based on the status of their CD PCR, glutamate dehydrogenase enzyme immunoassay (GDH), and toxin A/B detection, as well as by high, moderate, or low CD PTP. We used multivariable regression models to describe predictors of toxin positivity.

Results

We identified 483 patients with positive CD PCR targets. Only 22% were positive for both GDH and CD toxin. Among patients with a low PTP for CDI, 11% demonstrated a positive CD toxin result compared to 63% of patients with a high PTP. A low clinician PTP for CD infection (CDI) correlated with a negative CD toxin result compared to cases of moderate-to-high PTP for CDI (odds ratio, 0.19 [95% confidence interval, .10-.36]). Up to 64% of patients with negative GDH and CD toxin received CD treatment. Only receipt of prior antibiotics, fever, and a moderate-to-high clinician PTP were statistically significant predictors of toxin positivity.

Conclusions

Patients with a positive CD PCR were likely to receive treatment regardless of PTP or CD toxin results. We recommend that CD positivity on GIPCR be interpreted with caution, particularly in the setting of a low PTP.

An Algorithm Addressing the Problem of Overdiagnoses of Clostridioides difficile Infections in Hematopoietic Stem-Cell Transplant Recipients: Effects on CDI Rates and Patient Outcomes

BACKGROUND

Diarrhea of other causes and Clostridioides difficile colonization are common in patients hospitalized for hematopoietic stem-cell transplants (HSCT). It has been well recognized that these issues tend to decrease the specificity of stool testing for C. difficile infection (CDI). The best way to address this problem is uncertain.

OBJECTIVE

In September 2018, we initiated a project with the goal of addressing the apparent problem of overdiagnosis of CDIs in our HSCT population. Using the quality improvement tool Model for Improvement we introduced a C. difficile stool testing and CDI diagnosis algorithm with the aim of decreasing unnecessary inpatient CDI diagnoses and treatments. In this study we examine the effects of the algorithm.

STUDY DESIGN

We reviewed all HSCT admissions for the 2 years before the algorithm introduction and the 3 years following recording all stool submissions for C. difficile determination and CDI. At the close of the study, we recruited our advanced practice providers (APPs) to review all CDI following algorithm initiation and provide feedback on the ease of use of the algorithm and potential improvements to the overall process.

RESULTS

Stool submissions for C. difficile determination decreased from 38.0 to 20.6/1000 inpatient days (p=<0.001) and CDI from 5.5 to 2.4/1000 days (p=0.007). Patients admitted for a first allogeneic-HSCT, a first autologous-HSCT, or an HSCT readmission showed similar proportionate reductions. No detrimental effects on length of stay, overall survival, progression free survival, rates of readmission following transplant, incidence of acute graft vs. host disease, or incidence of recurrent CDI were noted following algorithm introduction. A strategy of education, monitoring/feedback, and ease of algorithm access proved effective in inducing provider compliance. APPs rated the algorithm high on ease of use.

CONCLUSIONS

Use of an algorithm defining criteria for C. difficile testing, diagnosis, and treatment was associated with significantly decreased CDI diagnoses on a HSCT inpatient unit without apparent adverse effects.

Extended spectrum cephalosporin resistant enterobacteriaceae carriage and infection in patients admitted with newly-diagnosed acute leukemia

BACKGROUND

Current information is limited on the incidence, risk factors, and consequences of extended-spectrum cephalosporin resistant Enterobacteriaceae (ESCRE) carriage in patients undergoing therapy for newly-diagnosed acute leukemia.

METHODS

We monitored 300 consecutive patients who submitted a first stool within the first week of initial hospitalization for initial and hospital acquired ESCRE carriage. Selected available isolates underwent DNA sequencing for determination of strain typing and resistance genes.

RESULTS

19 (6%) patients had ESCRE in their initial stool, and there was continued risk for new acquisition throughout their multiple hospitalizations. Patients with AML had more acquired carriage during their initial hospitalization. Increased hospitalizations and male sex were risk factors for detected acquired ESCRE carriage. ESCRE stool carriage was predictive for ESCRE BSI but not for overall survival. Sequencing revealed that E. coli ESCRE isolates contained primarily ESBL, while Enterobacter spp. and Citrobacter spp. showed primarily AmpC genes. The antibiotic sensitivity patterns for ESCRE BSI isolates reflected these genome findings.

DISCUSSION/CONCLUSIONS

ESCRE carriage is common in patients with acute leukemia undergoing repeated hospitalizations and increases the risk for ESCRE BSI. ESCRE genera express differing resistance genes which may be predictive for empiric antibiotic efficacy.

1221. Stenotrophomonas maltophilia Outbreak Associated with Sink Drains in an Intensive Care Unit

Background

Stenotrophomonas maltophilia (SMA) is an opportunistic pathogen that causes significant morbidity and mortality and has been associated with outbreaks in various hospital environments. We describe an outbreak of SMA in our intensive care unit (ICU) and highlight the sink drain as the probable source of SMA.

Methods

Clinical surveillance for hospital-acquired infections due to SMA was instituted in December of 2017, when a cluster of cases was identified in our ICU. We first performed an environmental survey in random sites in our ICU rooms: high-touch surfaces, drains in handwashing sinks, clean water, enteral feeding, and ice machines. SMA was only found in the sink drain. We then performed an environmental survey focused on sink drains and the surrounding areas. We identified rooms where patients positive for SMA were previously hospitalized. Sampling sites were standardized for all rooms: bed rail, sink drain, splash zone, and air near sinks. Bed rails were swabbed with sponge-swabs and sink drains with flocked swabs with liquid Amies transport media. Swab samples were cultured in broth and solid media. Splash zone samples were collected using MacConkey agar plates left for four hours immediately adjacent and at one foot from the sink. Air samples were also collected for 10 minutes onto MacConkey agar plates using EMD Millipore MAS-100 NT impactor air sampler. All media was incubated aerobically at 35-37°C. Identification of all isolated gram-negative organisms was performed using MALDI-TOF MS.

Results

Five rooms were surveyed (Table 1). All rooms were found to have medical supplies within the splash zone. 100% (5/5) of sink drain samples had SMA recovered in culture, compared to 10% (1/10) of splash zone samples, 20% (1/5) of air samples, and 20% (1/5) of bed rails. In addition, we isolated other gram-negative organisms. We repeated the environmental survey after placing a sink drain cover in rooms found to have SMA in areas other than the drain. In the follow-up survey, we found no growth in cultures except for air samples (Table 2).

Conclusion

Sink drains pose a risk for SMA, possibly via contamination of medical supplies near sinks. Further investigation, including sequencing of environmental and clinical isolates, is needed to understand the mode of transmission.

Disclosures

All Authors: No reported disclosures.

Cerebrospinal Fluid Pterins, Pterin-Dependent Neurotransmitters, and Mortality in Pediatric Cerebral Malaria

BACKGROUND

Cerebral malaria (CM) pathogenesis remains incompletely understood. Having shown low systemic levels of tetrahydrobiopterin (BH4), an enzymatic cofactor for neurotransmitter synthesis, we hypothesized that BH4 and BH4-dependent neurotransmitters would likewise be low in cerebrospinal fluid (CSF) in CM.

METHODS

We prospectively enrolled Tanzanian children with CM and children with nonmalaria central nervous system conditions (NMCs). We measured CSF levels of BH4, neopterin, and BH4-dependent neurotransmitter metabolites, 3-O-methyldopa, homovanillic acid, and 5-hydroxyindoleacetate, and we derived age-adjusted z-scores using published reference ranges.

RESULTS

Cerebrospinal fluid BH4 was elevated in CM (n = 49) compared with NMC (n = 51) (z-score 0.75 vs -0.08; P < .001). Neopterin was increased in CM (z-score 4.05 vs 0.09; P < .001), and a cutoff at the upper limit of normal (60 nmol/L) was 100% sensitive for CM. Neurotransmitter metabolite levels were overall preserved. A higher CSF BH4/BH2 ratio was associated with increased odds of survival (odds ratio, 2.94; 95% confidence interval, 1.03-8.33; P = .043).

CONCLUSION

Despite low systemic BH4, CSF BH4 was elevated and associated with increased odds of survival in CM. Coma in malaria is not explained by deficiency of BH4-dependent neurotransmitters. Elevated CSF neopterin was 100% sensitive for CM diagnosis and warrants further assessment of its clinical utility for ruling out CM in malaria-endemic areas.

No Implementation Without Representation: Real-Time Pharmacist Intervention Optimizes Rapid Diagnostic Tests for Bacteremia at a Small Community Hospital

Background: Rapid diagnostic tests (RDTs) for bacteremia allow for early antimicrobial therapy modification based on organism and resistance gene identification. Studies suggest patient outcomes are optimized when infectious disease (ID)-trained antimicrobial stewardship personnel intervene on RDT results. However, data are limited regarding RDT implementation at small community hospitals, which often lack access to on-site ID clinicians. Methods: This study evaluated the impact of RDTs with and without real-time pharmacist intervention (RTPI) at a small community hospital with local pharmacist training and asynchronous support from a remote ID Telehealth pharmacist. Time to targeted therapy (TTT) in patients with bacteremia was compared retrospectively across 3 different time periods: a control without RDT, RDT-only, and RDT with RTPI. Results: Median TTT was significantly faster in both the RDT with RTPI and RDT-only groups compared with the control group (2 vs 25 vs 51 hours respectively; P < .001). TTT was numerically faster for RDT with RTPI compared with RDT-only but did not reach statistical significance ( P = .078). Median time to any de-escalation was significantly shorter for RDT with RTPI compared with both RDT-only (14 vs 33 hours; P = .012) and the control group (14 vs 45 hours; P < .001). Median length of stay was also significantly shorter in both RDT groups compared with the control group (4.0 vs 4.1 vs 5.5 hours; P = .013). Conclusion: This study supports RDT use for bacteremia in a small community hospital with ID Telehealth support, suggesting additional benefit with RTPI.

Evaluation of potential COVID-19 recurrence in patients with late repeat positive SARS-CoV-2 testing

BACKGROUND

SARS-CoV-2 reinfection and reactivation has mostly been described in case reports. We therefore investigated the epidemiology of recurrent COVID-19 SARS-CoV-2.

METHODS

Among patients testing positive for SARS-CoV-2 between March 11 and July 31, 2020 within an integrated healthcare system, we identified patients with a recurrent positive SARS-CoV-2 reverse transcription polymerase chain reaction (RT-PCR) assay ≥60 days after an initial positive test. To assign an overall likelihood of COVID-19 recurrence, we combined quantitative data from initial and recurrent positive RT-PCR cycle thresholds-a value inversely correlated with viral RNA burden- with a clinical recurrence likelihood assigned based on independent, standardized case review by two physicians. "Probable" or "possible" recurrence by clinical assessment was confirmed as the final recurrence likelihood only if a cycle threshold value obtained ≥60 days after initial testing was lower than its preceding cycle threshold or if the patient had an interval negative RT-PCR.

RESULTS

Among 23,176 patients testing positive for SARS-CoV-2, 1,301 (5.6%) had at least one additional SARS-CoV-2 RT-PCRs assay ≥60 days later. Of 122 testing positive, 114 had sufficient data for evaluation. The median interval to the recurrent positive RT-PCR was 85.5 (IQR 74-107) days. After combining clinical and RT-PCR cycle threshold data, four patients (3.5%) met criteria for probable COVID-19 recurrence. All four exhibited symptoms at recurrence and three required a higher level of medical care compared to their initial diagnosis. After including six additional patients (5.3%) with possible recurrence, recurrence incidence was 4.3 (95% CI 2.1-7.9) cases per 10,000 COVID-19 patients.

CONCLUSIONS

Only 0.04% of all COVID-19 patients in our health system experienced probable or possible recurrence; 90% of repeat positive SARS-CoV-2 RT-PCRs were not consistent with true recurrence. Our pragmatic approach combining clinical and quantitative RT-PCR data could aid assessment of COVID-19 reinfection or reactivation by clinicians and public health personnel.

Antimicrobial Stewardship in a Hematological Malignancy Unit: Carbapenem Reduction and Decreased Vancomycin-Resistant Enterococcus Infection

BACKGROUND

Antibiotic stewardship is challenging in hematological malignancy patients.

METHODS

We performed a quasiexperimental implementation study of 2 antimicrobial stewardship interventions in a hematological malignancy unit: monthly antibiotic cycling for febrile neutropenia that included cefepime (± metronidazole) and piperacillin-tazobactam and a clinical prediction rule to guide anti-vancomycin-resistant Enterococcus faecium (VRE) therapy. We used interrupted time-series analysis to compare antibiotic use and logistic regression in order to adjust observed unit-level changes in resistant infections by background community rates.

RESULTS

A total of 2434 admissions spanning 3 years pre- and 2 years postimplementation were included. Unadjusted carbapenem and daptomycin use decreased significantly. In interrupted time-series analysis, carbapenem use decreased by -230 days of therapy (DOT)/1000 patient-days (95% confidence interval [CI], -290 to -180; P < .001). Both VRE colonization (odds ratio [OR], 0.64; 95% CI, 0.51 to 0.81; P < .001) and infection (OR, 0.41; 95% CI, 0.2 to 0.9; P = .02) decreased after implementation. This shift may have had a greater effect on daptomycin prescribing (-160 DOT/1000 patient-days; 95% CI, -200 to -120; P < .001) than did the VRE clinical prediction score (-30 DOT/1000 patient-days; 95% CI, -50 to 0; P = .08). Also, 46.2% of Pseudomonas aeruginosa isolates were carbapenem-resistant preimplementation compared with 25.0% postimplementation (P = .32). Unit-level changes in methicillin-resistant Staphylococcus aureus and extended-spectrum beta lactamase (ESBL) incidence were explained by background community-level trends, while changes in AmpC ESBL and VRE appeared to be independent. The program was not associated with increased mortality.

CONCLUSIONS

An antibiotic cycling-based strategy for febrile neutropenia effectively reduced carbapenem use, which may have resulted in decreased VRE colonization and infection and perhaps, in turn, decreased daptomycin prescribing.

Clinical evaluation of the acuitas® AMR gene panel for rapid detection of bacteria and genotypic antibiotic resistance determinants

Urinary tract infections are leading causes of hospital admissions. Accurate and timely diagnosis is important due to increasing morbidity and mortality from antimicrobial resistance. We evaluated a polymerase chain reaction test (Acuitas AMR Gene Panel with the Acuitas Lighthouse Software) for detection of 5 common uropathogens (Escherichia coli, Klebsiella pneumoniae, Proteus mirabilis, Pseudomonas aeruginosa, Enterococcus faecalis) and antibiotic resistance genes directly from urine for prediction of phenotypic resistance. Overall percent agreement was 97% for semiquantitative detection of uropathogens versus urine culture using a cut-off of 10⁴ colony forming units per mL urine. Overall accuracy was 91% to 93% for genotypic prediction of common antibiotic resistance harbored by E. coli, K. pneumoniae, and P. mirabilis.

Are Clostridioides difficile infections being overdiagnosed in hematopoietic stem cell transplant recipients?

BACKGROUND

Because both diarrhea due to other causes and gastrointestinal colonization with toxigenic Clostridioides difficile are common in HSCT, there is a possibility of false-positive diagnoses of C difficile infections (CDI).

METHODS

We estimated the probability of a patient being colonized by toxigenic C difficile by testing non-diarrheal surveillance stools from 223 HSCT recipients and the probability that a specimen submitted for C difficile testing was not CDI by determining the number of clinical tests that returned negative from this cohort. The number of expected false-positive CDI was estimated using these probabilities and compared with observed clinical test results.

RESULTS

The expected false-positive and the observed numbers of positive clinical results were similar. The 20 patients diagnosed with CDI were also similar to 142 patients with diarrhea and C difficile-negative stools in number of stools on day of testing, associated symptoms, and the recorded number of days to formed stools. C difficile colonization was most commonly detected during the first week and CDI during the second. Retrospective analysis of 837 patients showed that 18 stools were submitted for each diagnosis of CDI. Ribotyping of the surveillance samples showed 17 ribotypes.

CONCLUSIONS

Although several assumptions could impact the accuracy of our false-positive CDI estimates, it appears that many HSCT recipients diagnosed with CDI may actually represent colonized status and an alternative cause of diarrhea. Diagnostic stewardship, including limiting CDI diagnoses to patients with positive toxin and restricting stool submissions to patients with more severe symptoms, may decrease the number of false-positive diagnoses.

Repurposing an Old Drug for a New Epidemic: Ursodeoxycholic Acid to Prevent Recurrent Clostridioides difficile Infection

Recurrent Clostridioides difficile infection (rCDI) may be mediated in part by secondary bile acids. Here we report salvage therapy with ursodeoxycholic acid (UDCA) to prevent rCDI in 16 high-risk patients. Patients on UDCA had a low observed recurrence rate (12.5%). Controlled trials are needed to confirm these observations.

Clostridioides difficile colonization and infection in patients admitted for a first autologous transplantation: Incidence, risk factors, and patient outcomes

BACKGROUND

More data are needed regarding the incidence, risk factors, and outcomes for Clostridioides difficile infection (CDI) and colonization in patients undergoing an autologous hematopoietic stem cell transplantation (AHSCT).

METHODS

We studied 472 consecutive patients admitted for a first AHSCT and conducted a prospective C difficile stool surveillance and ribotyping analysis in a subset of 94 patients.

RESULTS

Clostridioides difficile infection was diagnosed in 7% of patients for an incidence of 3.4 CDI/1000 inpatient days, recurrent/reinfection CDI was rare. CDI was increased in patients who were colonized on admission, had required a recent pre-admission inpatient stay for fever and/or serious infection, or received empiric therapy with a carbapenem or extended-spectrum penicillin. CDI was associated with a longer length of stay and higher hospital costs. Twelve of 94 patients (13%) were found to have colonization on admission; CDI was diagnosed in 27% of these vs 1% in those with initial negative stools. Colonization in the hospital for those negative on admission was infrequent. C difficile ribotyping showed a predominance of 014/020.

CONCLUSIONS

Clostridioides difficile infection is a significant infection in patients receiving a first AHSCT. The risk factors identified may be useful in designing preventive interventions.

2352. Clinician Assessment of Pretest Probability for Clostridioides difficile Infection and Disease Severity While Using Multiplex, Syndromic Molecular Panel in Patients Presenting with Diarrhea

Background

The role of nucleic acid amplification tests (NAAT) for diagnosing Clostridioides difficile (CD) infection remains controversial. Adding CD to multiplex molecular panels (GIPCR) that detects multiple GI pathogens of community origin, has the potential to introduce confusion leading to delayed diagnosis and unnecessary antibiotic use especially if pretest probability is not considered.

Methods

We conducted a retrospective study to determine the frequency at which clinicians characterize pretest probability and disease severity in adult patients with diarrhea who tested positive for CD by GIPCR (BioFire, Inc.) from July 1, 2017 to October 16, 2018. We excluded immunocompromised patients. Routine testing includes reflex to GDH and toxin A/B detection when GIPCR is positive for CD. Charts were reviewed and clinical suspicion (PTP) was assigned as high, medium, low, or not done. Disease severity was classified as mild, moderate and severe. Exposure to systemic antibiotic within 90 days prior to testing and stool frequency was also captured.

Results

In total, 447 patients were included in the analysis: 110 (24.6%) were positive for both GDH and Toxin (G+/T+), 158 (35.3%) were G+/T−, 179 (40%) were G−/T−, and 149 (33%) were not classified. Toxin positivity was highest in the setting of high PTP (67%) (figure). In contrast, toxin was negative in most cases when suspicion for CDI was low or not characterized (81%). For medium suspicion, only 36% were T+. Antibiotic exposure prior to testing was observed in 203 (45%) of the cases. More G+/T+ patients received antibiotics (63%) before testing and 66% of G−/T− did not receive antecedent antibiotics. Clinicians did not characterize frequency of diarrhea in 261 (58%) of the patients tested and 95% of cases did not undergo severity classification. When documented, 24% of tested patients had < 3 diarrheal episodes/day (Table 1). Most cases where multiple pathogens were detected were T− (84.5%) and G−/T− (44%) (Table 2).

Conclusion

Overall, characterization of diarrheal illness was poor and PTP was frequently omitted. A large proportion of GIPCR results positive for CD (40%) were negative for both GDH and Toxin. CD results in molecular testing with syndromic panels should be interpreted with caution.

Disclosures

All authors: No reported disclosures.

511. MDRO Carriage in Patients in Two ICUs and Prevalence of Environmental Surface and Healthcare Worker Hand Contamination

Background

Determining MDRO (multidrug-resistant organism) transmission routes in intensive care units (ICUs) can be complex and require the evaluation of multiple potential MDRO sources, including patients, the environment, and healthcare worker (HCW) hands. The objective of this study was to determine MDRO carriage in patients in two separate ICUs, and simultaneous environmental and HCW hand contamination from associated rooms.

Methods

Patient (P), environmental (E), and HCW hand (H) samples were collected from hospital A (1183 H, 1253 E, 729 P) and hospital B (699 H, 1372 E, 437 P) over approximately 5 weeks in each unit. Environmental and HCW hand samples were collected using a cellulose sponge. HCW hand samples were collected prior to any hand hygiene. Patient samples were collected from the axilla, groin, and perianal areas with a flocked swab with patient consent. All samples were tested semi-quantitatively for Clostridium difficile (Cdiff), vancomycin-resistant enterococci (VRE), and cefotaxime-resistant Enterobacteriaceae (Cef-R-Ent) by selective culture. Cdiff isolates representative of each P/E/H cluster were tested for Cdiff toxin testing by PCR.

Results

Cdiff, VRE, and Cef-R-Ent were detected in patients, patient rooms, and on HCW hands in both facilities (Table 1). Cdiff was more prevalent in Facility A, while Cef-R-Ent was more prevalent in Facility B. The prevalence of VRE was minimal in both facilities. Cdiff toxin gene testing revealed that 17% of the Cdiff isolate clusters tested positive for toxin genes. In Facility A, the prevalence of a given MDRO was similar regardless of sample type, but was more widely varied between sample types in Facility B. Prevalence of MDROs on HCW hands and in the environment was typically higher in Facility A compared with Facility B. Individual patient positives were frequently linked to positive HCW hand and environmental cultures.

Conclusion

We discovered a low prevalence of all MDROs in both facilities, with most positive cultures associated with patients who were not on MDRO precautions. HCW hand and environmental MDRO prevalence was generally similar for each MDRO, regardless of patient prevalence, supporting previously reported links on HCW hand contamination and hospital room surfaces.

Disclosures

All authors: No reported disclosures.

Validation of a Host Response Assay, SeptiCyte LAB, for Discriminating Sepsis from Systemic Inflammatory Response Syndrome in the ICU

RATIONALE

A molecular test to distinguish between sepsis and systemic inflammation of noninfectious etiology could potentially have clinical utility.

OBJECTIVES

This study evaluated the diagnostic performance of a molecular host response assay (SeptiCyte LAB) designed to distinguish between sepsis and noninfectious systemic inflammation in critically ill adults.

METHODS

The study employed a prospective, observational, noninterventional design and recruited a heterogeneous cohort of adult critical care patients from seven sites in the United States (n = 249). An additional group of 198 patients, recruited in the large MARS (Molecular Diagnosis and Risk Stratification of Sepsis) consortium trial in the Netherlands ( www.clinicaltrials.gov identifier NCT01905033), was also tested and analyzed, making a grand total of 447 patients in our study. The performance of SeptiCyte LAB was compared with retrospective physician diagnosis by a panel of three experts.

MEASUREMENTS AND MAIN RESULTS

In receiver operating characteristic curve analysis, SeptiCyte LAB had an estimated area under the curve of 0.82-0.89 for discriminating sepsis from noninfectious systemic inflammation. The relative likelihood of sepsis versus noninfectious systemic inflammation was found to increase with increasing test score (range, 0-10). In a forward logistic regression analysis, the diagnostic performance of the assay was improved only marginally when used in combination with other clinical and laboratory variables, including procalcitonin. The performance of the assay was not significantly affected by demographic variables, including age, sex, or race/ethnicity.

CONCLUSIONS

SeptiCyte LAB appears to be a promising diagnostic tool to complement physician assessment of infection likelihood in critically ill adult patients with systemic inflammation. Clinical trial registered with www.clinicaltrials.gov (NCT01905033 and NCT02127502).

Clostridioides difficile colonization and infection in patients with newly diagnosed acute leukemia: Incidence, risk factors, and patient outcomes

BACKGROUND

The frequency, risk factors, and outcomes for Clostridioides difficile infection (CDI) in patients with newly diagnosed acute leukemia (AL) admitted for induction therapy are unclear.

METHODS

We studied 509 consecutive patients with AL admitted between 2006 and 2017 and conducted a prospective C difficile surveillance and ribotyping analysis in a subset of these.

RESULTS

The incidence of CDI was 2.2/1,000 inpatient days during induction, and CDI was rare after discharge. CDI was highest in patients with acute myelogenous leukemia. A hospitalization shortly before admission and administration of a greater number of antibiotics increased the risk for CDI. No single class of antibiotics conveyed an increased risk. All cases were successfully treated, and CDI was not associated with an increase in length of stay, costs, or mortality. In a subgroup analysis, 16% of patients with acute myelogenous leukemia and 4% with other leukemia types were colonized on admission. Colonization was associated with a higher risk of CDI. Ribotyping of available isolates showed 27 different strain types with 014/020 and 027 being the most frequent.

CONCLUSIONS

The number of antibiotics administered are a major risk factor for CDI in patients with AL. However, CDI appears to have minimal clinical impact in this population.

Physician agreement on the diagnosis of sepsis in the intensive care unit: estimation of concordance and analysis of underlying factors in a multicenter cohort

Background

Differentiating sepsis from the systemic inflammatory response syndrome (SIRS) in critical care patients is challenging, especially before serious organ damage is evident, and with variable clinical presentations of patients and variable training and experience of attending physicians. Our objective was to describe and quantify physician agreement in diagnosing SIRS or sepsis in critical care patients as a function of available clinical information, infection site, and hospital setting.

Methods

We conducted a post hoc analysis of previously collected data from a prospective, observational trial (N = 249 subjects) in intensive care units at seven US hospitals, in which physicians at different stages of patient care were asked to make diagnostic calls of either SIRS, sepsis, or indeterminate, based on varying amounts of available clinical information (clinicaltrials.gov identifier: NCT02127502). The overall percent agreement and the free-marginal, inter-observer agreement statistic kappa (κ_free) were used to quantify agreement between evaluators (attending physicians, site investigators, external expert panelists). Logistic regression and machine learning techniques were used to search for significant variables that could explain heterogeneity within the indeterminate and SIRS patient subgroups.

Results

Free-marginal kappa decreased between the initial impression of the attending physician and (1) the initial impression of the site investigator (κ_free 0.68), (2) the consensus discharge diagnosis of the site investigators (κ_free 0.62), and (3) the consensus diagnosis of the external expert panel (κ_free 0.58). In contrast, agreement was greatest between the consensus discharge impression of site investigators and the consensus diagnosis of the external expert panel (κ_free 0.79). When stratified by infection site, κ_free for agreement between initial and later diagnoses had a mean value + 0.24 (range − 0.29 to + 0.39) for respiratory infections, compared to + 0.70 (range + 0.42 to + 0.88) for abdominal + urinary + other infections. Bioinformatics analysis failed to clearly resolve the indeterminate diagnoses and also failed to explain why 60% of SIRS patients were treated with antibiotics.

Conclusions

Considerable uncertainty surrounds the differential clinical diagnosis of sepsis vs. SIRS, especially before organ damage has become highly evident, and for patients presenting with respiratory clinical signs. Our findings underscore the need to provide physicians with accurate, timely diagnostic information in evaluating possible sepsis.

Electronic supplementary material

The online version of this article (10.1186/s40560-019-0368-2) contains supplementary material, which is available to authorized users.

1197. Microbiological Surveillance of Duodenoscopes Before and After High-Level Disinfection Following Endoscopic Retrograde Cholangiopancreatography (ERCP)

Background

Transmission of antibiotic-resistant bacteria during endoscopic retrograde cholangiopancreatography (ERCP) has been linked to the complex design of the duodenoscope (scope) elevator channel and cantilever. We implemented a scope culturing program to monitor the efficacy of disinfection and to identify frequency of pre-disinfection exposure to antibiotic-resistant bacteria.

Methods

Facilities performing ERCPs within the Intermountain Healthcare system voluntarily submit scope cultures to the Infectious Diseases Epidemiology Laboratory. Cultures are collected at designated intervals based on procedure volumes at each site. Samples are submitted by endoscopy techs trained to collect flush and swab samples of the distal end of the scope using a previously described method before (PRE) and after (POST) high-level disinfection. Selective media is used to screen for Gram-negative bacilli-resistant to third-generation cephalosporins (ESBL) and vancomycin-resistant Enterococcus (VRE).

Results

Between March 7, 2016 and April 18, 2018, 1,255 scope samples from 10 facilities were cultured (533 PRE samples and 722 POST samples). 483 (90.6%) PRE samples were positive, with 75 (15.5%) screening positive for an antibiotic-resistant organism (60 ESBL and 15 VRE). 19 (2.6%) POST samples were positive, with 4 (21.1%) screening positive for ESBL. One of the four ESBL positive POST samples had a corresponding PRE sample for comparison; E. coli and Klebsiella variicola were isolated in both indicating residual contamination. Two of the ESBL-positive POST cultures did not have corresponding PRE samples and one had a PRE culture negative for ESBL. No POST samples contained VRE. Endoscopy personnel were contacted for each positive POST culture and endoscopy reprocessing practices were reviewed. Additionally, scopes were quarantined, reprocessed and re-cultured. Scopes were returned to use once POST cultures were negative.

Conclusion

Contamination of scopes with antibiotic-resistant bacteria during ERCP is common. High-level disinfection is effective at reducing bacterial burden but is imperfect. Routine surveillance for post-reprocessing bacterial colonization has been helpful to minimize patient exposure and to maintain focus on the importance of reprocessing.

Disclosures

All authors: No reported disclosures.

Fecal Host Transcriptomics for Non-Invasive Human Mucosal Immune Profiling: Proof of Concept in Clostridium Difficile Infection

Background:

Host factors play an important role in pathogenesis and disease outcome in Clostridium difficile infection (CDI), and characterization of these responses could uncover potential host biomarkers to complement existing microbe-based diagnostics.

Methods:

We extracted RNA from fecal samples of patients with CDI and profiled human mRNA using amplicon-based next-generation sequencing (NGS). We compared the fecal host mRNA transcript expression profiles of patients with CDI to controls with non-CDI diarrhea.

Results:

We found that the ratio of human actin gamma 1 (ACTG1) to 16S ribosomal RNA (rRNA) was highly correlated with NGS quality as measured by percentage of reads on target. Patients with CDI could be differentiated from those with non-CDI diarrhea based on their fecal mRNA expression profiles using principal component analysis. Among the most differentially expressed genes were ones related to immune response (IL23A, IL34) and actin-cytoskeleton function (TNNT1, MYL4, SMTN, MYBPC3, all adjusted P-values < 1 x 10^-3).

Conclusions:

In this proof-of-concept study, we used host fecal transcriptomics for non-invasive profiling of the mucosal immune response in CDI. We identified differentially expressed genes with biological plausibility based on animal and cell culture models. This demonstrates the potential of fecal transcriptomics to uncover host-based biomarkers for enteric infections.

Impact of Implementing Antibiotic Stewardship Programs in 15 Small Hospitals: A Cluster-Randomized Intervention

Background

Studies on the implementation of antibiotic stewardship programs (ASPs) in small hospitals are limited. Accreditation organizations now require all hospitals to have ASPs.

Methods

The objective of this cluster-randomized intervention was to assess the effectiveness of implementing ASPs in Intermountain Healthcare's 15 small hospitals. Each hospital was randomized to 1 of 3 ASPs of escalating intensity. Program 1 hospitals were provided basic antibiotic stewardship education and tools, access to an infectious disease hotline, and antibiotic utilization data. Program 2 hospitals received those interventions plus advanced education, audit and feedback for select antibiotics, and locally controlled antibiotic restrictions. Program 3 hospitals received program 2 interventions plus audit and feedback on the majority of antibiotics, and an infectious diseases-trained clinician approved restricted antibiotics and reviewed microbiology results. Changes in total and broad-spectrum antibiotic use within programs (intervention versus baseline) and the difference between programs in the magnitude of change in antibiotic use (eg, program 3 vs 1) were evaluated with mixed models.

Results

Program 3 hospitals showed reductions in total (rate ratio, 0.89; confidence interval, .80-.99) and broad-spectrum (0.76; .63-.91) antibiotic use when the intervention period was compared with the baseline period. Program 1 and 2 hospitals did not experience a reduction in antibiotic use. Comparison of the magnitude of effects between programs showed a similar trend favoring program 3, but this was not statistically significant.

Conclusions

Only the most intensive ASP intervention was associated with reduction in total and broad-spectrum antibiotic use when compared with baseline.

Clinical Trials Registration

NCT03245879.

Implementation of a Centralized Infectious Diseases Telehealth (IDt) Service for 16 Small Community Hospitals

Background

The majority of U.S. small community hospitals (SCHs) lack access to infectious diseases (ID) subspecialists. Telehealth can extend ID expertise to such facilities. We describe lessons learned from implementing a new IDt program for 16 SCHs in the Intermountain Healthcare system in Utah and Idaho.

Methods

From October 1, 2016 to April 30, 2017, we implemented an IDt service comprised of: a 24-hour ID physician advice line; an inpatient ID consult service that provided chart review and documentation (e-consults) and daytime telemedicine consultation (TC) using encrypted, HIPAA-compliant, synchronous, 2-way audio-video connection; and an ID pharmacist-led antibiotic stewardship program. The IDt service included a medical director, operations officer, ID pharmacist, analyst, and rotating ID physicians, and was implemented in a step-wise manner at 16 SCHs. IDt requests were received through a dedicated phone line with duplicate transcription to a monitored email inbox or generated from daily antibiotic stewardship rounds.

Results

The physician advice line was operational for all 16 SCHs on October 1, 2016. 312 advice-only calls were fielded (92 per 1000 hospital-days covered) through April 30, 2017. Common infections requiring phone advice included: bloodstream (16%), genitourinary (13%), and musculoskeletal (12%). E-consult and TC services were operational at 11 SCHs by April 30, 2017 (hospital-days covered: 1074). The IDt service completed 104 eConsults, 163 TCs, and 1198 stewardship reviews. Mean time [minutes (range)] spent per case was 16 (5–30) for eConsults and 55 (30–120) for TCs [on-camera time: 25 (12–46)]. Common infections requiring e-consult or TC were: bloodstream (45%), musculoskeletal (16%), and skin/soft tissue (11%). 22 patients (14%) seen by TC were surveyed: 100% felt the service improved their care and was necessary at their SCH. 97% of surveyed SCH staff felt the IDt service improved patient care and 90% felt it was a necessary service (32% response from 98 providers, nurses, pharmacists).

Conclusion

A new IDt service was well utilized and received by SCH staff and patients, with bloodstream infections being the most common reason for consultation. Future steps include evaluation of the IDt effect on clinical outcomes, financial metrics, and staff education on common ID conditions.

Disclosures

All authors: No reported disclosures.

Risk Factors for Community Acquired Extended-Spectrum Β-lactamase (ESBL) Producing Enterobacteriaceae Urinary Tract Infections (UTIs)

Background

Community-acquired extended-spectrum β-lactamase (ESBL) producing Enterobacteriaceae infections pose unique treatment challenges. Identifying risk factors associated with ESBL Enterobacteriaceae infections outside of prior colonization is important for empiric management in an era of antimicrobial stewardship.

Methods

We randomly selected 251 adult inpatients admitted to an Intermountain healthcare facility in Utah with an ESBL Enterobacteriaceae urinary tract infection (UTI) between January 1, 2001 and January 1, 2016. 1:1 matched controls had UTI at admission with Enterobacteriaceae but did not produce ESBL. UTI at admission was defined as urine culture positive for > 100,000 colony forming units per milliliter (cfu/mL) of Enterobacteriaceae and positive symptoms within 7 days prior or 2 days after admission. Repeated UTI was defined as more than 3 episodes of UTI within 12 months preceding index hospitalization. Cases with prior history of ESBL Enterobacteriaceae UTIs or another hospitalization three months preceding the index admission were excluded. Univariate and multiple logistic regression techniques were used to identify the risk factors associated with first episode of ESBL Enterobacteriaceae UTI at the time of hospitalization.

Results

In univariate analysis, history of repeated UTIs, neurogenic bladder, presence of a urinary catheter at time of admission, and prior exposure to outpatient antibiotics within past one month were found to be significantly associated with ESBL Enterobacteriaceae UTIs. When controlling for age differences, severity of illness and co-morbid conditions, history of repeated UTIs (adjusted odds ratio (AOR) 6.76, 95% confidence interval (CI) 3.60–13.41), presence of a urinary catheter at admission (AOR 2.75, 95% CI 1.25 – 6.24) and prior antibiotic exposure (AOR: 8.50, 95% CI: 3.09 – 30.13) remained significantly associated with development of new ESBL Enterobacteriaceae UTIs.

Conclusion

Patients in the community with urinary catheters, history of recurrent UTIs, or recent antimicrobial use can develop de novo ESBL Enterobacteriaceae UTIs.

Disclosures

All authors: No reported disclosures.

Room contamination, patient colonization pressure, and the risk of vancomycin-resistant Enterococcus colonization on a unit dedicated to the treatment of hematologic malignancies and hematopoietic stem cell transplantation

BACKGROUND

Contaminated surfaces and colonization pressure are risk factors for vancomycin-resistant Enterococcus (VRE) colonization in intensive care units (ICUs). Whether these apply to modern units dedicated to the care of hematologic malignancies and hematopoietic stem cell transplant (HSCT) procedures is unknown.

METHODS

We reviewed the records of 780 consecutive admissions for acute leukemia, autologous HSCT, or allogeneic HSCT in which the patient was at risk for hospital-acquired VRE and underwent weekly surveillance. We also obtained staff and room cultures, observed staff behavior, and performed VRE molecular strain typing on selected isolates.

RESULTS

The overall rate of VRE colonization was 11.4 cases/1,000 patient days. Cultures of room surfaces revealed VRE isolates in 10% of terminally cleaned rooms. A prior VRE-colonized room occupant did not increase risk, and paired isolates from 20 patients and prior occupants were indistinguishable on molecular typing in only 1 pair. VRE colonization pressure was significantly associated with acquisition. Cultures of unit personnel and shared equipment were negative except for weighing scales. Observation of unit clinical personnel showed high compliance for hand sanitation and but less so for gowns. Conversely, ancillary staff showed poor compliance.

CONCLUSIONS

Transmission of VRE from room surfaces seems to be an infrequent event. Encouraging adherence to surveillance, disinfection, and contact isolation protocols may decrease VRE colonization rates.

The clinical impact of vancomycin-resistant Enterococcus colonization and bloodstream infection in patients undergoing autologous transplantation

BACKGROUND

Although several studies have documented adverse outcomes for vancomycin-resistant Enterococcus (VRE) colonization and infection in allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients, data are inadequate for patients undergoing autologous (auto-)HSCT.

METHODS

We conducted a retrospective cohort study of 300 consecutive patients receiving an auto-HSCT between 2006 and 2014. Patients had stool cultures for VRE on admission and weekly during hospitalization.

RESULTS

Thirty-six percent of patients had VRE gastrointestinal (GI) colonization and 3% developed a VRE bloodstream infection (BSI), all of whom were colonized. VRE strain typing of BSI isolates showed that some patients shared identical patterns. Rates of colonization and BSI in colonized patients were similar to simultaneous patients undergoing allo-HSCT, except that the latter had a higher rate of colonization at admission. A diagnosis of lymphoma was associated with an increased risk of colonization. VRE BSI was associated with longer lengths of stay and possibly higher costs, but no decrease in overall survival, and colonized patients had no VRE infections during the year following discharge. Repeat stool cultures in patients subsequently undergoing allo-HSCT suggested that most, if not all, VRE-positive auto-HSCT patients lose their detectable GI colonization within a few months of discharge.

CONCLUSION

VRE colonization is frequent but carries a low risk for infection in patients undergoing auto-HSCT. However, these patients can serve as reservoirs for transmission to higher risk patients. Moreover, patients may remain colonized if proceeding to an allo-HSCT shortly after auto-HSCT, potentially increasing the risk of the allogeneic procedure.

Impaired systemic tetrahydrobiopterin bioavailability and increased oxidized biopterins in pediatric falciparum malaria: association with disease severity

Decreased bioavailability of nitric oxide (NO) is a major contributor to the pathophysiology of severe falciparum malaria. Tetrahydrobiopterin (BH4) is an enzyme cofactor required for NO synthesis from L-arginine. We hypothesized that systemic levels of BH₄ would be decreased in children with cerebral malaria, contributing to low NO bioavailability. In an observational study in Tanzania, we measured urine levels of biopterin in its various redox states (fully reduced [BH₄] and the oxidized metabolites, dihydrobiopterin [BH₂] and biopterin [B₀]) in children with uncomplicated malaria (UM, n = 55), cerebral malaria (CM, n = 45), non-malaria central nervous system conditions (NMC, n = 48), and in 111 healthy controls (HC). Median urine BH4 concentration in CM (1.10 [IQR:0.55-2.18] μmol/mmol creatinine) was significantly lower compared to each of the other three groups - UM (2.10 [IQR:1.32-3.14];p<0.001), NMC (1.52 [IQR:1.01-2.71];p = 0.002), and HC (1.60 [IQR:1.15-2.23];p = 0.005). Oxidized biopterins were increased, and the BH4:BH2 ratio markedly decreased in CM. In a multivariate logistic regression model, each Log10-unit decrease in urine BH4 was independently associated with a 3.85-fold (95% CI:1.89-7.61) increase in odds of CM (p<0.001). Low systemic BH4 levels and increased oxidized biopterins contribute to the low NO bioavailability observed in CM. Adjunctive therapy to regenerate BH4 may have a role in improving NO bioavailability and microvascular perfusion in severe falciparum malaria.

Plasma Plasmodium falciparum histidine-rich protein-2 concentrations are associated with malaria severity and mortality in Tanzanian children

Plasma Plasmodium falciparum histidine-rich protein-2 (PfHRP-2) concentrations, a measure of parasite biomass, have been correlated with malaria severity in adults, but not yet in children. We measured plasma PfHRP-2 in Tanzanian children with uncomplicated (n = 61) and cerebral malaria (n = 45; 7 deaths). Median plasma PfHRP-2 concentrations were higher in cerebral malaria (1008 [IQR 342–2572] ng/mL) than in uncomplicated malaria (465 [IQR 36–1426] ng/mL; p = 0.017). In cerebral malaria, natural log plasma PfHRP-2 was associated with coma depth (r = −0.42; p = 0.006) and mortality (OR: 3.0 [95% CI 1.03–8.76]; p = 0.04). In this relatively small cohort study in a mesoendemic transmission area of Africa, plasma PfHRP-2 was associated with pediatric malaria severity and mortality. Further studies among children in areas of Africa with higher malaria transmission and among children with different clinical manifestations of severe malaria will help determine the wider utility of quantitative PfHRP-2 as a measure of parasite biomass and prognosis in sub-Saharan Africa.

Increased asymmetric dimethylarginine in severe falciparum malaria: association with impaired nitric oxide bioavailability and fatal outcome

Asymmetrical dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide synthase (NOS), is a predictor of mortality in critical illness. Severe malaria (SM) is associated with decreased NO bioavailability, but the contribution of ADMA to the pathogenesis of impaired NO bioavailability and adverse outcomes in malaria is unknown. In adults with and without falciparum malaria, we tested the hypotheses that plasma ADMA would be: 1) increased in proportion to disease severity, 2) associated with impaired vascular and pulmonary NO bioavailability and 3) independently associated with increased mortality. We assessed plasma dimethylarginines, exhaled NO concentrations and endothelial function in 49 patients with SM, 78 with moderately severe malaria (MSM) and 19 healthy controls (HC). Repeat ADMA and endothelial function measurements were performed in patients with SM. Multivariable regression was used to assess the effect of ADMA on mortality and NO bioavailability. Plasma ADMA was increased in SM patients (0.85 µM; 95% CI 0.74–0.96) compared to those with MSM (0.54 µM; 95%CI 0.5–0.56) and HCs (0.64 µM; 95%CI 0.58–0.70; p<0.001). ADMA was an independent predictor of mortality in SM patients with each micromolar elevation increasing the odds of death 18 fold (95% CI 2.0–181; p = 0.01). ADMA was independently associated with decreased exhaled NO (r_s = −0.31) and endothelial function (r_s = −0.32) in all malaria patients, and with reduced exhaled NO (r_s = −0.72) in those with SM. ADMA is increased in SM and associated with decreased vascular and pulmonary NO bioavailability. Inhibition of NOS by ADMA may contribute to increased mortality in severe malaria.

Severe falciparum malaria is associated with impaired microvascular perfusion, lung injury and decreased bioavailability of nitric oxide (NO), but the causes of these processes are not fully understood. Asymmetrical dimethylarginine (ADMA), a competitive endogenous inhibitor of nitric oxide synthase (NOS), is an independent predictor of mortality in other critical illnesses, and can impair vascular function in chronic disease. ADMA can be produced by both the host and malaria parasites. The major novel findings of this study in malaria are that ADMA is an independent predictor of death in falciparum malaria, and is associated with decreased availability of nitric oxide in at least two organ systems affected by malaria parasites, the lining of blood vessels and the lungs. This study contributes to knowledge of regulation and availability of pulmonary and endothelial NO in critical illness and identifies pathogenic processes which may contribute to death in severe malaria. Therapies which increase the availability of NO or which reduce ADMA levels may have potential for adjunctive therapy of severe malaria.

Relationship of cell-free hemoglobin to impaired endothelial nitric oxide bioavailability and perfusion in severe falciparum malaria

BACKGROUND

Hemolysis causes anemia in falciparum malaria, but its contribution to microvascular pathology in severe malaria (SM) is not well characterized. In other hemolytic diseases, release of cell-free hemoglobin causes nitric oxide (NO) quenching, endothelial activation, and vascular complications. We examined the relationship of plasma hemoglobin and myoglobin to endothelial dysfunction and disease severity in malaria.

METHODS

Cell-free hemoglobin (a potent NO quencher), reactive hyperemia peripheral arterial tonometry (RH-PAT) (a measure of endothelial NO bioavailability), and measures of perfusion and endothelial activation were quantified in adults with moderately severe (n = 78) or severe (n = 49) malaria and control subjects (n = 16) from Papua, Indonesia.

RESULTS

Cell-free hemoglobin concentrations in patients with SM (median, 5.4 micromol/L; interquartile range [IQR], 3.2-7.4 micromol/L) were significantly higher than in those with moderately severe malaria (2.6 micromol/L; IQR, 1.3-4.5 micromol/L) or controls (1.2 micromol/L; IQR, 0.9-2.4 micromol/L; P < .001). Multivariable regression analysis revealed that cell-free hemoglobin remained inversely associated with RH-PAT, and in patients with SM, there was a significant longitudinal association between improvement in RH-PAT index and decreasing levels of cell-free hemoglobin (P = .047). Cell-free hemoglobin levels were also independently associated with lactate, endothelial activation, and proinflammatory cytokinemia.

CONCLUSIONS

Hemolysis in falciparum malaria results in NO quenching by cell-free hemoglobin, and may exacerbate endothelial dysfunction, adhesion receptor expression and impaired tissue perfusion. Treatments that increase NO bioavailability may have potential as adjunctive therapies in SM.

Recovery of endothelial function in severe falciparum malaria: relationship with improvement in plasma L-arginine and blood lactate concentrations

BACKGROUND

Severe malaria is characterized by microvascular obstruction, endothelial dysfunction, and reduced levels of L-arginine and nitric oxide (NO). L-Arginine infusion improves endothelial function in moderately severe malaria. Neither the longitudinal course of endothelial dysfunction nor factors associated with recovery have been characterized in severe malaria.

METHODS

Endothelial function was measured longitudinally in adults with severe malaria (n = 49) or moderately severe malaria (n = 48) in Indonesia, using reactive hyperemia peripheral arterial tonometry (RH-PAT). In a mixed-effects model, changes in RH-PAT index values in patients with severe malaria were related to changes in parasitemia, lactate, acidosis, and plasma L-arginine concentrations.

RESULTS

Among patients with severe malaria, the proportion with endothelial dysfunction fell from 94% (46/49 patients) to 14% (6/42 patients) before discharge or death (P < .001). In severe malaria, the median time to normal endothelial function was 49 h (interquartile range, 20-70 h) after the start of antimalarial therapy. The mean increase in L-arginine concentrations in patients with severe malaria was 11 micromol/L/24 h (95% confidence interval [CI], 9-13 micromol/L/24 h), from a baseline of 49 micromol/L (95% CI, 37-45 micromol/L). Improvement of endothelial function in patients with severe malaria correlated with increasing levels of L-arginine (r = 0.56; P = .008) and decreasing levels of lactate (r = -0.44; P = .001).

CONCLUSIONS

Recovery of endothelial function in severe malaria is associated with recovery from hypoargininemia and lactic acidosis. Agents that can improve endothelial NO production and endothelial function, such as L-arginine, may have potential as adjunctive therapy early during the course of severe malaria.

Arginine, nitric oxide, carbon monoxide, and endothelial function in severe malaria

PURPOSE OF REVIEW

Parasiticidal therapy of severe falciparum malaria improves outcome, but up to 30% of these patients die despite best therapy. Nitric oxide is protective against severe disease, and both nitric oxide and arginine (the substrate for nitric oxide synthase) are low in clinical malaria. Parasitized red blood cell interactions with endothelium are important in the pathophysiology of malaria. This review describes new information regarding nitric oxide, arginine, carbon monoxide, and endothelial function in malaria.

RECENT FINDINGS

Low arginine, low nitric oxide production, and endothelial dysfunction are common in severe malaria. The degree of hypoargininemia and endothelial dysfunction (measured by reactive hyperemia-peripheral artery tonometry) is proportional to parasite burden and severity of illness. Plasma arginase (an enzyme that catabolizes arginine) is elevated in severe malaria. Administering arginine intravenously reverses hypoargininemia and endothelial dysfunction. The cause(s) of hypoargininemia in malaria is unknown. Carbon monoxide (which shares certain functional properties with nitric oxide) protects against cerebral malaria in mice.

SUMMARY

Replenishment of arginine and restoration of nitric oxide production in clinical malaria should diminish parasitized red blood cells adherence to endothelium and reduce the sequelae of these interactions (e.g. cerebral malaria). Arginine therapy given in addition to conventional antimalaria treatment may prove to be beneficial in severe malaria.

Safety profile of L-arginine infusion in moderately severe falciparum malaria

BACKGROUND

L-arginine infusion improves endothelial function in malaria but its safety profile has not been described in detail. We assessed clinical symptoms, hemodynamic status and biochemical parameters before and after a single L-arginine infusion in adults with moderately severe malaria.

METHODOLOGY AND FINDINGS

In an ascending dose study, adjunctive intravenous L-arginine hydrochloride was infused over 30 minutes in doses of 3 g, 6 g and 12 g to three separate groups of 10 adults hospitalized with moderately severe Plasmodium falciparum malaria in addition to standard quinine therapy. Symptoms, vital signs and selected biochemical measurements were assessed before, during, and for 24 hours after infusion. No new or worsening symptoms developed apart from mild discomfort at the intravenous cannula site in two patients. There was a dose-response relationship between increasing mg/kg dose and the maximum decrease in systolic (rho = 0.463; Spearman's, p = 0.02) and diastolic blood pressure (r = 0.42; Pearson's, p = 0.02), and with the maximum increment in blood potassium (r = 0.70, p<0.001) and maximum decrement in bicarbonate concentrations (r = 0.53, p = 0.003) and pH (r = 0.48, p = 0.007). At the highest dose (12 g), changes in blood pressure and electrolytes were not clinically significant, with a mean maximum decrease in mean arterial blood pressure of 6 mmHg (range: 0-11; p<0.001), mean maximal increase in potassium of 0.5 mmol/L (range 0.2-0.7 mmol/L; p<0.001), and mean maximal decrease in bicarbonate of 3 mEq/L (range 1-7; p<0.01) without a significant change in pH. There was no significant dose-response relationship with blood phosphate, lactate, anion gap and glucose concentrations. All patients had an uncomplicated clinical recovery.

CONCLUSIONS/SIGNIFICANCE

Infusion of up to 12 g of intravenous L-arginine hydrochloride over 30 minutes is well tolerated in adults with moderately severe malaria, with no clinically important changes in hemodynamic or biochemical status. Trials of adjunctive L-arginine can be extended to phase 2 studies in severe malaria.

TRIAL REGISTRATION

ClinicalTrials.gov NCT00147368.

Impaired nitric oxide bioavailability and L-arginine reversible endothelial dysfunction in adults with falciparum malaria

Severe falciparum malaria (SM) is associated with tissue ischemia related to cytoadherence of parasitized erythrocytes to microvascular endothelium and reduced levels of NO and its precursor, l-arginine. Endothelial function has not been characterized in SM but can be improved by l-arginine in cardiovascular disease. In an observational study in Indonesia, we measured endothelial function using reactive hyperemia-peripheral arterial tonometry (RH-PAT) in 51 adults with SM, 48 patients with moderately severe falciparum malaria (MSM), and 48 controls. The mean RH-PAT index was lower in SM (1.41; 95% confidence interval [CI] = 1.33-1.47) than in MSM (1.82; 95% CI = 1.7-2.02) and controls (1.93; 95% CI = 1.8-2.06; P < 0.0001). Endothelial dysfunction was associated with elevated blood lactate and measures of hemolysis. Exhaled NO was also lower in SM relative to MSM and controls. In an ascending dose study of intravenous l-arginine in 30 more patients with MSM, l-arginine increased the RH-PAT index by 19% (95% CI = 6-34; P = 0.006) and exhaled NO by 55% (95% CI = 32-73; P < 0.0001) without important side effects. Hypoargininemia and hemolysis likely reduce NO bioavailability. Endothelial dysfunction in malaria is nearly universal in severe disease, is reversible with l-arginine, and likely contributes to its pathogenesis. Clinical trials in SM of adjunctive agents to improve endothelial NO bioavailability, including l-arginine, are warranted.

Elevated plasma phenylalanine in severe malaria and implications for pathophysiology of neurological complications

Cerebral malaria is associated with decreased production of nitric oxide and decreased levels of its precursor, l-arginine. Abnormal amino acid metabolism may thus be an important factor in malaria pathogenesis. We sought to determine if other amino acid abnormalities are associated with disease severity in falciparum malaria. Subjects were enrolled in Dar es Salaam, Tanzania (children) (n = 126), and Papua, Indonesia (adults) (n = 156), in two separate studies. Plasma samples were collected from subjects with WHO-defined cerebral malaria (children), all forms of severe malaria (adults), and uncomplicated malaria (children and adults). Healthy children and adults without fever or illness served as controls. Plasma amino acids were measured using reverse-phase high-performance liquid chromatography with fluorescence detection. Several plasma amino acids were significantly lower in the clinical malaria groups than in healthy controls. Despite the differences, phenylalanine was the only amino acid with mean levels outside the normal range (40 to 84 microM) and was markedly elevated in children with cerebral malaria (median [95% confidence interval], 163 [134 to 193] microM; P < 0.0001) and adults with all forms of severe malaria (median [95% confidence interval], 129 [111 to 155] microM; P < 0.0001). In adults who survived severe malaria, phenylalanine levels returned to normal, with clinical improvement (P = 0.0002). Maintenance of plasma phenylalanine homeostasis is disrupted in severe malaria, leading to significant hyperphenylalaninemia. This is likely a result of an acquired abnormality in the function of the liver enzyme phenylalanine hydroxylase. Determination of the mechanism of this abnormality may contribute to the understanding of neurological complications in malaria.

Low plasma arginine concentrations in children with cerebral malaria and decreased nitric oxide production

Nitric oxide (NO) production and mononuclear cell NO synthase 2 (NOS2) expression are high in healthy Tanzanian children but low in those with cerebral malaria. Factors that downregulate NOS2 also diminish factors involved in cellular uptake and biosynthesis of L-arginine, the substrate for NO synthesis. We therefore postulated that L-arginine concentrations would be low in individuals with cerebral malaria. We measured concentrations of L-arginine in cryopreserved plasma samples from Tanzanian children with and without malaria. L-arginine concentrations were low in individuals with cerebral malaria (mean 46 micromol/L, SD 14), intermediate in those with uncomplicated malaria (70 micromol/L, 20), and within the normal range in healthy controls (122 micromol/L, 22; p<0.0001). Analysis by logistic regression showed that hypoargininaemia was significantly associated with cerebral malaria case-fatality. Hypoargininaemia may contribute to limited NO production in children with cerebral malaria and to severe disease.