Glutamate Dehydrogenase Antigen Research Articles

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

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. 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. 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. 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.

Derivation and internal validation of the multivariate toxigenic C. difficile diarrhea model and risk score for emergency room and hospitalized patients with diarrhea.

Many factors have been associated with the risk of toxigenic C. difficile diarrhea (TCdD). This study derived and internally validated a multivariate model for estimating the risk of TCdD in patients with diarrhea using readily available clinical factors. A random sample of 3,050 symptomatic emergency department or hospitalized patients undergoing testing for toxigenic C. difficile at a single teaching hospital between 2014 and 2018 was created. Unformed stool samples positive for both glutamate dehydrogenase antigen by enzyme immunoassay and tcdB gene by polymerase chain reaction were classified as TCdD positive. The TCdD Model was created using logistic regression and was modified to the TCdD Risk Score to facilitate its use. 8.1% of patients were TCdD positive. TCdD risk increased with abdominal pain (adjusted odds ratio 1.3; 95% CI, 1.0-1.8), previous C. difficile diarrhea (2.5, 1.1-6.1), and prior antibiotic exposure, especially when sampled in the emergency department (4.2, 2.5-7.0) versus the hospital (1.7, 1.3-2.3). TCdD risk also increased when testing occurred earlier during the hospitalization encounter, when age and white cell count increased concurrently, and with decreased eosinophil count. In internal validation, the TCdD Model had moderate discrimination (optimism-corrected C-statistic 0.65, 0.62-0.68) and good calibration (optimism-corrected Integrated Calibration Index [ICI] 0.017, 0.001-0.022). Performance decreased slightly for the TCdD Risk Score (C-statistic 0.63, 0.62-0.63; ICI 0.038, 0.004-0.038). TCdD risk can be predicted using readily available clinical risk factors with modest accuracy.

673. Sniffing Out Adherence: Evaluation of a Clostridioides difficile guideline at a Tertiary Academic Medical Center

Abstract Background Tufts Medical Center’s (TMC) Antimicrobial Stewardship Team (AMT) in collaboration with gastroenterology (GI) developed an institutional treatment algorithm to guide appropriate inpatient management of Clostridioides difficile infection (CDI). The CD treatment algorithm was revised in April 2022 to reflect updated national clinical practice guidelines and disseminated to TMC providers. Our study aimed to assess provider compliance to TMC’s CD treatment algorithm. Methods A retrospective study of adult patients hospitalized from April 15, 2022 to October 31, 2022 and tested for CD was conducted. We collected patient demographics, white blood cell count, serum creatinine (SC), length of stay, CD treatment, Infectious Diseases (ID) &amp; GI consult, occurence of severe CDI (defined as white blood cell &amp;gt; 15 K/uL or SC &amp;gt; 1.5 mg/dL), occurrence of recurrent CDI, and immunocompromised status (defined by having had organ or bone marrow transplant, receiving immunomodulatory therapy or chronic steroids). A 2-step Clostridioides difficile (CD) testing algorithm was used. For CD toxin A/B &amp; glutamate dehydrogenase antigen (GDH) indeterminate results, reflex to nucleic amplification test (NAAT) was performed only with AMT approval. Results A total of 111 inpatients had CD toxin/GDH stool testing; 70 (63%) positive and 41 (37%) indeterminate. Of patients who had an indeterminate CD toxin/GDH, none had subsequent CD NAAT testing, and none receive CDI treatment. Of the others, 81 (73%), 23 (21%), and 7 (6%) were diagnosed with non-severe, severe, and fulminant CDI, respectively. The overall adherence to the institutional CD treatment algorithm was 58% (figure 1). More patients were appropriately treated with oral vancomycin (11, 65%) compared to those who were appropriately treated with fidaxomicin (9, 24%). Guidance adherence was (3) 38% among patients who had one or more recurrent episodes of CD, and none received suggested ID or GI consultation for additional CDI treatment consideration. Conclusion Adherence to institutional CD treatment algorithm was low. This study highlights opportunities to improve prescription of first line CDI therapy, especially among patients who are at higher risk for recurrence. Disclosures Maureen Campion, PharmD, BCIDP, Shinoigi: Speaker

A-286 Performance Evaluation of Molecular Clostridium Difficile Assay using BD MaxTM System

Abstract Background Clostridium difficile (C.Diff) is a gram positive anaerobe producing Enterotoxin and Cytotoxin (toxin A and B respectively); toxin B has been reported to be essential for its virulence. It is estimated that C. Diff will cause over half a million infection yearly and one in 11 people over the age of 65 diagnosed with healthcare-associated C.Diff infection die within one month. It is the most common cause of acute diarrhea; residents in Long-Term Care Facilities (LTCF) are more prone to have C. Diff infection (CDI) because of their age, the frequent use of antibiotics, fragilities, co-morbidity, and living environment. Diagnosing CDI is based on clinical signs and symptoms as well as laboratory tests. Several tests available for diagnosing the infection which include: enzyme immunoassays, tissue culture cytotoxicity, anaerobic culture, glutamate dehydrogenase antigen and nucleic acid amplification. The BD MAX™ System is a PCR based assay that provides the sensitivity, specificity and faster turnaround. Methods The MAX™ System is an automated in vitro diagnostic test for the direct qualitative detection of the C. difficile toxin B gene (tcdB) in human liquid or soft stool specimens from patients suspected of having Clostridium difficile Infection (CDI).The test is performed directly on the specimen, utilizing real-time polymerase chain reaction (PCR) for the amplification of C. difficile toxin B gene (tcdB). The test utilizes fluorogenic sequence-specific hybridization probes for detection of the amplified DNA. The test was validated for accuracy, precision, and patient correlation to enzyme-immunoassay using Premier Toxins A &amp; B is an enzyme immunoassay for the direct detection of Clostridium difficile toxin A and toxin B in stool samples. Statistical analyses were done using Analyse-it. Results The percentage agreement for precision, reproducibility, and accuracy were 100%. We had 100% agreement for positive patients on EIA and 85% for negative patients on EIA; however, upon investigation we found the discrepancies were due to false negative EIA results. Conclusion The BD Max gave the benefit of a fully automated with high sensitivity and specificity for the presence of toxin B producing C. Diff. The faster turnaround gives the physician the ability to diagnose CDI and prevent spreading of the disease to other patients. It is very important to remember that C.diff infection can be prevented with appropriate use of antibiotics and implementing antibiotic stewardship and infection control plan to prevent and stop spreading of the infection.

Laboratory diagnosis of Clostridioides difficile infection in symptomatic patients: what can we do better?

The laboratory diagnosis of Clostridioides difficile infection (CDI) is challenging since this bacteria may be detected in healthy people and toxin production detection is not sensitive enough to be used alone. Thus, there is no single test with adequate sensitivity and specificity to be used in laboratory diagnosis. We evaluated the performance of tests used in the diagnosis of CDI in symptomatic patients with risk factors in hospitals in southern Brazil. Enzyme immunoassays (EIA) for glutamate dehydrogenase antigen (GDH) and toxins A/B, real-time polymerase chain reaction (qPCR), GeneXpert system, and a two-step algorithm comprising GDH/TOXIN EIA performed simultaneously followed by GeneXpert for outliers were evaluated. Toxigenic strain in stool culture was considered CDI positive (gold standard). Among 400 samples tested, 54 (13.5%) were positive for CDI and 346 (86.5%) were negative. The diagnosis of the two-step algorithm and qPCR had an excellent performance with an accuracy of 94.5% and 94.2%, respectively. The Youden index showed that GeneXpert as a single test (83.5%) and the two-step algorithm (82.8%) were the most effective assays. Diagnosing CDI and non-CDI diarrhea could be successfully attained by the combination of clinical data with accuracy of laboratory tests.

Detection and molecular characterization of VRE isolates in Slovakia from stool samples positive for Clostridioides difficile toxins.

The study aimed to identify colonized patients as a possible source of eventual VRE (vancomycin-resistant enterococci) infection from stool samples positive for glutamate dehydrogenase antigen, as well as for Clostridioides difficile toxins A and B. The study was carried out from 7/2020 to 9/2021. Stool samples were grown in a brain heart infusion medium with a gram-positive non-spore-forming bacteria supplement under aerobic conditions. The samples for VRE identification were grown on CHROMID® VRE agar, and the MICs for vancomycin and teicoplanin were also estimated. The presence of the vanA/vanB genes was tested using the PCR method. The total number of 113 stool samples positive for Clostridioides difficile toxins was analyzed. Of these samples, 44 isolates with VRE characters were identified. The most prevalent isolates in our set of isolates were Enterococcus faecium (27 isolates, 62%), Enterococcus faecalis (9 isolates, 21%), Enterococcus solitarius (4 isolates, 9%), Enterococcus durans (2 isolates, 4%), 1 isolate Enterococcus sulfurous (2%), and Enterococcus raffinosus (2%). In total, 26 isolates were detected in the study in the presence of vanA genes (24 isolates E. faecium, 2 isolates E. faecalis) and 18 isolates detected in the presence of vanB genes (7 isolates E. faecalis, 4 isolates E. solitarius, 3 isolates E. faecium, 2 isolates E. durans, 1 isolate E. sulfurous, and E. raffinosus). The results of this study showed the local dominance character of the vanA gene of hospital VRE isolates that were carriers of genes associated with high resistance to vancomycin, teicoplanin, and occasionally linezolid.

Clostridioides difficile infection (CDI) treatment outcomes and recurrence factor at a pediatric hospital

Background: CDI is the single most common cause of nosocomial diarrhea in both adults and children. Available data regarding treatment outcomes in hospitalized children remain limited. CDI recurrence in children has been reported in 20%–30% of cases. Consensus regarding the best testing method for CDI is lacking. The 2018 IDSA guideline recommends a multistep algorithm with detection of glutamate dehydrogenase antigen plus toxin, followed by detection of toxigenic C. difficle with nucleic acid amplification test (NAAT) if results are discordant. Methods: We included patients aged 1–26 years admitted from July 2020 through June 2021 with CDI symptoms and positive toxin or NAAT. Healthcare facility-onset CDI (HO-CDI) was defined as positive specimen collected &gt;3 days after admission. Community-onset CDI (CO-CDI) was defined as positive specimen collected ≤3 days after admission. Community-onset healthcare facility-associated CDI (CO-HCFA-CDI) was defined as positive specimen from a patient who was discharged from the facility ≤4 weeks prior. Recurrence was defined as an episode of CDI occurring within 60 days after onset of a previous infection. Results: Mean age of the 63 patients meeting inclusion criteria was 11.2 years (range, 1–21 years). Most patients (n = 37; 58.7%) were male, tested negative for C. difficile toxins (n = 39; 61.9%), and had mild-to-moderate disease (n = 61; 96.8%). Patients with immunocompromising conditions were common, including malignancy (n = 38; 60.3%), inflammatory bowel disorder (n = 8; 12.7%), and history of solid organ transplant (n = 5; 7.9%). Previously healthy without chronic medical conditions were uncommon (n = 4; 6.3%). CO-CDI was most common (n = 26; 41.3%) followed by HO-CDI (n = 23; 36.5%). Also, 34 patients (53.9%) were exposed to antibiotics within the previous 30 days, 16 (47.0%) of whom received 2 or more antibiotics. Sulfamethoxazole–trimethoprim was the most prescribed agent (13; 38%), most (12; 92.3%) as prophylaxis for Pneumocystis jirovecii pneumonia. Furthermore, 42 patients (66.7%) were receiving gastric acid suppressant agents. Laxatives were given to 14 patients (22.2%) within 72 hours of testing, despite electronic reminders. Most were treated with oral vancomycin (n = 46; 73.0%). In addition, 5 patients (7.9%) did not receive CDI treatment at the discretion of the treating physician; all were toxin negative. CDI was cured in 58 patients (92.1%) with only 5 (7.9%) experiencing recurrence infection. Patients testing positive for C. difficile toxin were more likely to experience infection recurrence compared to those with a negative toxin screen: 4 of 24 (16.7%) versus 1 of 39 (2.6%) (P = .044). Conclusions: Most patients with CDI were treated with oral vancomycin at our institution. We observed significantly lower rate of recurrence than previously reported. Toxin-positive patients experienced higher recurrence rate. Prospective studies are needed to confirm our findings.Funding: NoneDisclosures: None

Comparative Evaluation of Three Immunoassays for the Simultaneous Detection of Clostridioides difficile Glutamate Dehydrogenase and Toxin A/B.

Background: In the medical laboratory, a step-by-step workflow for Clostridioides difficile infection (CDI) detection using glutamate dehydrogenase (GDH) and toxin A/B assays for initial screening, along with a nucleic acid amplification test (NAAT), has been recommended recently. In this study, we evaluated these three immunoassays for the simultaneous detection of GDH and Clostridioides difficile (CD) toxin A/B. Methods: A total of 304 stool samples were tested for the presence of GDH antigen and CD toxin A/B using VIDAS C. difficile GDH and toxin A/B (CDAB), RIDASCREEN C. difficile GDH and toxin A/B (RIDA), and C. DIFF QUIK CHEK COMPLETE according to the manufacturers’ recommendations. As complementary reference methods for GDH and toxin A/B detection in the three immunoassays, CD cultures using ChromID C. difficile agar and the Xpert C. difficile assay, respectively, were tested. Results: All three GDH assays showed overall substantial agreement with the CD culture. All three toxin A/B assays showed overall moderate agreement with the Xpert C. difficile assay. In comparison with consensus results, VIDAS GDH and QCC GDH showed almost perfect agreement, whereas RIDA GDH showed inferior but substantial agreement. All three toxin A/B assays showed almost perfect agreement. Conclusions: Since the QCC GDH and toxin A/B assay is relatively more sensitive and specific than the other two immunoassays for discriminating toxigenic or non-toxigenic CDI, QCC is very helpful for the simultaneous identification of GDH and CD toxin A/B in the initial step of the two-round workflow for diagnosing CDI.

Health care associated Clostridioides difficile infection and colonization in patients admitted at tertiary care hospital Pakistan.

To evaluate the epidemiology of clostridioides difficile infections and colonisation in a tertiary-care setting. The cross-sectional study was conducted at the Combined Military Hospital, Rawalpindi, Pakistan, from June 1, 2017, to October 31, 2019, and comprised adult patients admitted in high-risk units of the hospital for any disease experiencing watery stools after 48 hours of hospital admission and passing more than 3 stools per day with no other recognised aetiology. Stool samples of the participants, diagnosed with antibiotic associated diarrhoea, were submitted for glutamate dehydrogenase antigen assay and clostridioides toxin A/B assay detected by enzyme-linked immunosorbent assay and clostridioides difficile toxin gene detection by polymerase chain reaction. Clostridium difficile-associated diarrhoea was diagnosed by a positive toxin assay or polymerase chain reaction. Data was analysed using SPSS25. Of the 715 subjects, 322(45%) were males and 393(55%) were females. The overall mean age was 56.64±8.57 years, and 488(68.3%) were aged <60 years, while 227(31.7%) were aged >60 years. The incidence of clostridioides difficile-associated diarrhoea was found in 10(1.4%) patients and was highest in oncology unit 3(4.3%). No positive case was detected from the high dependency unit and the surgical ward. All the10(1.4%) positive cases were on >2 antibiotics with a combination of oral vancomycin and intravenous metronidazole. Mortality rate was significantly higher in the positive cases compared to those with clostridioides difficile colonisation (p<0.05). The incidence of clostridioides difficile-associated diarrhoea was found to be low.

The impact of diagnostic stewardship interventions on Clostridiodes difficile test ordering practices and results

Clostridiodes difficile infection (CDI) is a leading cause of healthcare associated infection and is associated with increased morbidity and mortality. Diagnostic stewardship is critical in optimizing testing accuracy for CDI. Multiple algorithms have been used for testing combining toxin A/B, glutamate dehydrogenase antigen and nucleic acid amplification test (NAAT) to enhance sensitivity. This study evaluated the effectiveness of two interventions on the rates and appropriateness of Clostridiodes difficile test orders and hospital-onset (HO) CDI. All Clostridiodes difficile orders and results in the study period (1/2018–2/2021) were included. To evaluate ordering appropriateness, we reviewed the medical charts of a random subsample of 100 orders that were collected from three periods within the study: pre-intervention and following each intervention. The first intervention was a clinical decision support system (CDSS) tool guiding providers to order testing only if CDI clinical criteria were met. The second intervention eliminated automatic NAAT reflex for indeterminate results and required antimicrobial stewardship team approval. A total of 3004 orders were registered during the study period. There was a 33% reduction in the rates of Clostridiodes difficile orders by the end of the study period (p < 0.001). The rates of reportable HO-CDI were significantly reduced by 57.1% (p = 0.003). We also noted a trend of increased appropriateness of testing overtime. In conclusion, combining CDSS intervention with NAAT reflex restriction was an effective tool to reduce inappropriate Clostridiodes difficile orders and decrease the rates of reportable HO-CDI.

Description of antibiotic treatment in adults tested for Clostridioides difficile infection: a single-center case\u2013control study

BackgroundDiagnosing Clostridioides difficile infection (CDI) is complicated. There have been reports on effects of compliance with anti-C. difficile prescription guidelines on patient outcomes. However, the causes of non-adherence and their impact on outcomes have rarely been explored. Therefore, an investigation on the risk factors for non-adherence with treatment guidelines and their influence on recurrence is important.MethodsThis case–control study was conducted with patients with a positive C. difficile culture from March 2020 to April 2021. We conducted analysis based on treatment categories using factors associated with recurrent CDI as variables. Univariate and multivariable analyses were conducted to identify risk factors for non-adherence with treatment guidelines.ResultsIn total, culture positive stool samples from 172 patients were analyzed. Having positive glutamate dehydrogenase antigen (GDH Ag), negative toxin enzyme immunoassay (EIA), and positive nucleic acid amplification test (NAAT) (GDH+/toxin EIA−/NAAT +) results were associated with both under- (adjusted odds ratio [aOR] 3.49 [95% CI 1.62–7.51], p = 0.001) and over-treatment (aOR 0.17 [95% CI 0.06–0.48], p = 0.001). Patients with refractory diarrhea were over treated (aOR 2.71 [95% CI 1.02–7.20], p = 0.046). Patients with an increased risk of CDI recurrence were not over treated.ConclusionsOur results suggest that non-adherence with CDI treatment guidelines depends on the duration of symptoms and rapid EIA test results. Patients with an increased risk of recurrence were neglected.

BEZLOTOXUMAB THERAPY FOR RECURRENT CLOSTRIDIUM DIFFICILE INFECTION IN AN ULCERATIVE COLITIS PATIENT

Abstract INTRODUCTION Clostridium difficile infection (CDI) is the most common infectious cause of nosocomial diarrhea, comprising 10-20% of all cases. CDI is a significant complication for IBD patients. Not only can CDI induce IBD flare, IBD patients also experience significantly higher CDI recurrence when compared to the general population. New monoclonal antibody (mAB) therapies, such as bezlotoxumab, have improved management of recurrent CDI (rCDI). The MODIFY I/II trial included 44 patients with known IBD, 28 of which received bezlotoxumab. Among these 28 patients, there was a 27.2% absolute reduction in the incidence of rCDI. Encouraged by these results, we recently prescribed bezlotoxumab in a UC patient with rCDI and herein report our experience. CASE REPORT A 21-year-old female with a history of ulcerative colitis (UC) diagnosed in 2017 presented for treatment of rCDI. Her first episode of CDI occurred in 2019 during an active UC flare treated with steroids and infliximab induction. CDI was successfully treated with a four-week course of 125mg oral vancomycin twice daily followed by once daily for an additional four weeks. She had a recurrent episode of CDI one year after her initial infection while on vedolizumab for UC treatment. She was treated with 125mg oral vancomycin, four times daily, and tapered down by one dose over a four-month period. Two years after her initial CDI, she developed worsening non-bloody diarrhea, nausea, and anorexia with weight loss. She again tested positive for C. difficile via glutamate dehydrogenase antigen and PCR for toxin B. Fecal calprotectin was 2190 mg/g. She was treated with 14-day course fidaxomicin 200mg BID and a single infusion of bezlotoxumab 10mg/kg. Treatment for UC was not adjusted. At follow up one month later, her symptoms had resolved and fecal calprotectin normalized (17 mg/g). Six months later, she remains asymptomatic. DISCUSSION Recurrent CDI is a frequent culprit for inducing IBD flares, and is difficult to manage. Fecal transplant (FMT) is an option for rCDI, but often entails logistical challenges and risks cross-contamination of endoscopic facilities. Bezlotoxumab is an appealing option for rCDI as a single dose medication with few reported side effects in the MODIFY clinical trials. While the number of IBD patients in the MODIFY trial was small, results were promising. In our patient, bezlotoxumab quickly resolved her rCDI and IBD flare without need for alteration or escalation of her biologic therapy, and she has remained asymptomatic for six months. This case corroborates the prospect that bezlotoxumab positively affects the clinical outcomes of UC patients with rCDI compared to those on repetitive antimicrobial therapy and/or FMT without mAB therapy. Further investigation into the long-term efficacy of this therapy is merited for the IBD patient population in the real-world setting.

Clostridioides difficile Diarrhea: An Emerging Problem in a South Indian Tertiary Care Hospital.

ContextClostridioides difficile infection (CDI) is one of the most common infectious causes of hospital-acquired diarrhea. The actual burden of the disease is underestimated in India due to inadequate diagnostic methods and limited studies conducted. Aims The aim of this study was to determine the burden and risk factors of CDI among patients with hospital-acquired diarrhea. Methods and Materials Stool specimen of patients (age > 1 year) with hospital-acquired diarrhea were screened for glutamate dehydrogenase antigen and toxin using an enzyme immunoassay. If both antigen and toxin were present, it was reported as positive for toxigenic CDI. Samples positive for antigen and negative for toxin were further tested with Cepheid GeneXpert assay for detecting the toxin producing gene. Results Of 75 patients (mean age 36.07 ± 20.79, 64% males), 14 (18.67%) patients were positive for toxigenic Clostridioides difficile ( C. difficile ) and 3 (4%) patients were nontoxigenic C. difficile . Addition of GeneXpert to the testing algorithm increased the yield of toxin detection in 5/14 patients who were negative by toxin assay. On analysis of risk factors, prolonged hospital stay was found to have significant association ( p -value = 0.022). Patients with factors like intensive care unit stay, presence of diabetes mellitus as a comorbidity, and exposure to antibiotics like carbapenems and glycopeptides have been found to have a higher prevalence of CDI. Conclusions The prevalence of CDI in our population was 18.67% and the major risk factor associated was prolonged hospital stay. The addition of GeneXpert for the detection of toxin gene increased the yield from 12 to 18.68%.

Impact of Two-Step Testing Algorithm on Reducing Hospital-Onset Clostridioides difficile Infections

Clostridioides difficile infection (CDI) is one of the leading causes of hospital–onset infections. Clinically distinguishing true CDI versus colonization with C. difficile is challenging and often requires reliable and rapid molecular testing methods. At our academic center, we implemented a 2-step testing algorithm to help identify true CDI cases. The University of Mississippi Medical Center is a 700+ bed academic facility located in Jackson, Mississippi. Hospital-onset (HO) CDI was defined based on NHSN Laboratory Identified (LabID) event as the last positive C. difficile test result performed on a specimen using a multistep testing algorithm collected &gt;3 calendar days after admission to the facility. HO-CDI data were collected from all inpatient units except the NICU and newborn nursery. HO-CDI outcomes were assessed based on standardized infection ratio (SIR) data. In May 2020, we implemented a 2-step testing algorithm (Figure 1). All patients with diarrhea underwent C. difficile PCR testing. Those with positive C. difficile PCR test were reflexed to undergo enzyme immunoassay (EIA) glutamate dehydrogenase antigen (Ag) testing and toxin A and B testing. The final results were reported as colonization (C. difficile PCR+/EIA Ag+/Toxin A/B−) or true CDI case (C. difficile PCR+/EIA +/Toxin A/B +) or negative (C. difficile PCR−). All patients with colonization or true infection were placed under contact isolation precautions until diarrhea resolution for 48 hours. During the preintervention period (October 2019–April 2020), 25 HO-CDI cases were reported compared to 8 cases in the postintervention period (June 2020–December 2020). A reduction in CDI SIR occurred in the postintervention period (Q3 2020–Q4 2020, SIR 0.265) compared to preintervention period (Q4 2019–Q1 2020, SIR 0.338) (Figure 2). We successfully reduced our NHSN HO-CDI SIR below the national average after implementing a 2-step testing algorithm for CDI. The 2-step testing algorithm was useful for antimicrobial stewardship to guide appropriate CDI treatment for true cases and for infection prevention to continue isolation of infected and colonized cases to reduce the spread of C. difficile spores.Funding: NoDisclosures: None

Significance of a polymerase chain reaction method in the detection of Clostridioides difficile.

RESUMENObjetivosClostridioides difficile (CD) es la causa más frecuente de diarrea nosocomial. Se han propuesto algoritmos para mejorar el diagnóstico de la infección, basados en la realización de un método rápido que detecte glutamato deshidrogenasa (GDH) y/o toxinas A/B, seguido de una prueba confirmatoria (cultivo toxigénico, prueba de citotoxicidad, técnicas de biología molecular). Evaluamos un algoritmo diagnóstico para la detección de CD utilizando un test inmunocromatográfico y una prueba de reacción en cadena de la polimerasa (PCR).Material y métodosSe realizaron dos pasos: 1) Un enzimoinmunoensayo rápido de membrana que detecta simultáneamente GDH y toxinas de CD (C.diff QUIK CHEK complete). Las muestras positivas frente a ambos se consideraron positivas; 2) A todas las muestras que fueron positivas sólo para GDH o toxina se les realizó un ensayo de PCR en tiempo real que detecta el gen de la toxina B (tcdB) (BD MAX Cdiff). Se consideraron positivas todas las muestras PCR positivas.ResultadosSe realizaron 2.138 determinaciones. 139 fueron positivas en GDH y toxinas, 148 sólo en GDH, y 12 sólo en toxinas. De las 160 dudosas, 117 fueron positivas por PCR (107/148 GDH+ y 10/12 toxinas+).ConclusionesLa PCR ha detectado 117 positivos más (un 73,1% de las muestras dudosas). Tradicionalmente los resultados toxinas+/GDH- se consideran falsos positivos. Creemos que la detección sumada de toxinas en el inmunoensayo y del gen tcdB en una misma muestra sería indicativa de su presencia real, y el resultado negativo de la GDH podría deberse a un falso negativo.

Differences in Gut Microbiome in Hospitalized Immunocompetent vs. Immunocompromised Children, Including Those With Sickle Cell Disease.

Background: Gut microbial diversity and composition play important roles in health. This cross-sectional study was designed to test the hypothesis that hospitalized children who may be relatively immunocompromised (IC), defined as those with cancer, sickle cell disease (SCD), transplantation, or receiving immunosuppressive therapy) would have decreased microbial diversity, increased Clostridioides difficile colonization and different species composition compared to non-immunocompromised (Non-IC) children admitted to the same pediatric unit.Methods: A stool sample was obtained within 72 h of admission to a single unit at The Children's Hospital at Montefiore, Bronx, NY from March 2016 to February 2017 and the microbiome assessed by 16S rRNA sequencing. C. difficile colonization was assessed by glutamate dehydrogenase antigen and toxin polymerase chain reaction assays.Results: Stool samples were obtained from 69 IC (32 SCD, 19 cancer, 9 transplantation and 9 other) and 37 Non-IC patients. There were no significant differences in microbial alpha diversity and C. difficile colonization comparing IC vs. non-IC patients. Lower alpha diversity, however, was independently associated with the use of proton pump inhibitors or antibiotics, including prophylactic penicillin in patients with SCD. Differences in specific species abundances were observed when comparing IC vs. non-IC patients, particularly children with SCD. Non-IC patients had increased abundance of commensals associated with health including Alistipes putredinis, Alistipes ihumii, Roseburia inulinivorans, Roseburia intestinalis, and Ruminococcus albus (p < 0.005).Conclusions: Antibiotics and proton pump inhibitors, which were more commonly used in IC children, were identified as risk factors for lower microbial diversity. Non-IC patients had higher abundance of several bacterial species associated with health. Longitudinal studies are needed to determine the clinical significance of these differences in gut microbiome.

Management of bacteriological specimens of patients suffering from coronavirus disease 2019 (COVID-19)

Management of bacteriological specimens of patients suffering from coronavirus disease 2019 (COVID-19)

A study of Clostridium difficile positivity using multistep algorithm of testings in a tertiary care hospital

Clostridium difficile is an anaerobic, spore bearing bacteria can colonize hospitalized patients commonly. Toxin producing strains are an important cause of nosocomial diarrhea. Though various testing methods are available for the diagnosis of C. difficile infection (CDI) but, correct diagnosis is still a challenge for laboratories. To study the positivity of the infection by multiple testing methods available. This is an observational study. A total of 1429 freshly passed stool samples received in the Department of Microbiology from February 2019-May 2020 were included in the study. Further, the samples (1415) were tested for presence of Glutamate Dehydrogenase antigen (GDH Ag), toxin A, toxin B by an ICT (immunochromatography test) from Vittassay. A total of 48 samples were tested by GeneXpert (Cepheid) PCR (Polymerase Chain Reaction). Out of these, 14 samples were tested by PCR alone &amp;34 samples were tested by both ICT &amp; PCR. A total of 188(13.2%) samples received, from 165 patients including 94(57%) male patients &amp; 71(43%) female patients, were found positive for CDI. Out of these, 184(13%) samples were found positive for GDH Ag screening in ICT. Among, 48 PCR tested samples, 5(10.4%) were detected positive for tcdtB gene. A total of 97(6.8%) samples showed the presence of toxins. Multiple algorithm of testings is required to increase the sensitivity of the diagnosis, but high cost is a limiting factor in the developing countries.

The Great Masquerade: Identification of Clinically Relevant Clostridioides difficile Infections

Background: Despite clear guidance for appropriate testing of symptomatic patients for Clostridioides difficile testing (McDonald et al), the ideal testing methodology remains unresolved. Laboratories currently use different algorithms that incorporate enzyme immunoassay (EIA) testing for toxin, glutamate dehydrogenase (GDH) antigen, and polymerase chain reaction (PCR) testing in combination or as a single test. At UNC Hospitals, a large academic hospital with nearly 1,000 beds in the ninth most populous state in the United States, patients are currently tested by an EIA test for toxin and GDH antigen first, and discordant toxin/GDH results are referred for PCR testing. Previous studies have demonstrated that detection of toxin by EIA is a better predictor of C. difficile infection (CDI) complications (Polage et al). Methods: We investigated all patients who were tested for C. difficile from July 2018 to June 2019. Within each testing methodology and result, we assessed the percentage of patients with at least 3 loose stools documented within a 24-hour period, percentage with a severe episode based on white blood cell (WBC) counts &gt;15,000 cells/mL, or percentage with a serum creatinine level &gt;1.5 mg/dL. Fisher-type confidence intervals were calculated for each proportion. Results: Patients positive for C. difficile by the EIA method had 66.9% appropriate loose stool documentation (95% CI, 57.4%–75.5%), whereas patients with EIA-indeterminate (toxin negative, GDH positive) and positive by only PCR had 49.7% appropriate loose stool documentation (95% CI, 42.7%–56.8%). C. difficile patients that tested negative had 48.1% appropriate loose stool documentation (95% CI, 46.0–50.2%). In addition, patients positive by the EIA method had nearly double the proportion of severe disease by WBC or creatinine criteria compared to patients who were either positive by PCR or who tested negative (Table 1). Conclusions: Patients positive for C. difficile by the EIA method were statistically more likely to meet criteria for loose stool documentation. There was no statistically significant difference between patients that tested positive only by PCR or who tested negative. The percentage of patients with severe episode criteria based on WBC or creatinine was nearly doubled between those who tested positive by EIA and PCR (20% vs 10%), although this finding was not statistically significant. The percentage with severe disease (WBC or creatinine) was nearly identical among patients who were positive by PCR and who tested negative. These findings demonstrate that documentation of loose stool is a more sensitive indicator of toxin detection than either clinical parameter, reinforcing the importance of stool documentation in evaluating patients for C. difficile testing.Funding: NoneDisclosures: None

S0211 Emerging Evidence for Frequent Occurrence of Clostridioides difficile-Associated Diarrhea in Untreated Symptomatic Clostridioides difficile Carriers

INTRODUCTION: Currently, the diagnosis of Clostridioides difficile infection (CDI) is based on stool testing for the detection of C.diff glutamate dehydrogenase antigen (Ag), C.diff toxin (A or B), and toxin gene sequences (PCR, Amplified test). The sensitivity and specificity of these tests ranges between 90% and 99%. The results are interpreted as Ag (+/-) Toxin (+/-) and Amplified (+/-). Based on these results, the patients are classified as having C.diff infection, C.diff carriers or C.diff negative. The subset of patients who are Ag(+)Toxin(-) and Amplified (-) are classified as C.diff carriers. To date, there are no guidelines for management of symptomatic C.diff carriers, nor is there a longitudinal follow up of these patients in the literature. METHODS: A retrospective study was conducted for all the patients who were admitted for or developed diarrhea and who tested positive for C.diff Antigen (n = 86) between July, 2017 and June, 2018. RESULTS: Of the 86 patients, 29 were Ag(+) Toxin(+) and 35 were Ag(+) Toxin(-) Amplified(+), these group of patients were identified as having CDI and were treated. However, a subset of patients (n = 22) who were Ag(+) Toxin(-) Amplified(-) who were symptomatic, were classified as Symptomatic C.diff carriers (Table 1). The mean age of this subgroup was 59.3 years(+/- 24.2 years, SD) and it consisted of 10 males and 12 females. It is noteworthy, that 19 out of these 22 symptomatic carriers were not given any antibiotic treatment. A longitudinal follow up of this group of patients, for a period of 6-12 months revealed that 6 out of these 22 C.diff carriers went on to develop CDI and requiring multiple admissions (1–3) to the hospital.Table 1CONCLUSION: As many as 22 out of 86 patients were identified as symptomatic C.diff carriers, and the majority of these patients (86.3%) went untreated. The prevalence of the symptomatic carrier is quite significant (25.6%) in our study population. Of the untreated symptomatic C.diff carriers, six patients (27.3%) developed subsequent CDI and required readmissions to the hospital (1–3) within 6–12 months. The cost of a single hospitalization due to a single incidence of CDI is roughly $43,000. These data suggest that symptomatic C.diff carriers should be treated with antibiotics to prevent CDI and readmission to the hospital. Additional prospective clinical studies on larger group of patients with longitudinal follow up are needed for optimum guidelines for the management of this group of patients.