Toxin Enzyme Immunoassay Research Articles

Comparing rates of recurrent infection for first occurrence of Clostridioides difficile between tapered oral vancomycin and standard vancomycin: a retrospective, propensity matched cohort study.

To compare rates of Clostridioides difficile infection (CDI) recurrence following initial occurrence treated with tapered enteral vancomycin compared to standard vancomycin. Retrospective cohort study. Community health system. Adults ≥18 years of age hospitalized with positive C. difficile polymerase chain reaction or toxin enzyme immunoassay who were prescribed either standard 10-14 days of enteral vancomycin four times daily or a 12-week tapered vancomycin regimen. Retrospective propensity score pair matched cohort study. Groups were matched based on age < or ≥ 65 years and receipt of non-C. difficile antibiotics during hospitalization or within 6 months post-discharge. Recurrence rates were analyzed via logistic regression conditioned on matched pairs and reported as conditional odds ratios. The primary outcome was recurrence rates compared between standard vancomycin versus tapered vancomycin for treatment of initial CDI. The CDI recurrence rate at 6 months was 5.3% (4/75) in the taper cohort versus 28% (21/75) in the standard vancomycin cohort. The median time to CDI recurrence was 115 days versus 20 days in the taper and standard vancomycin cohorts, respectively. When adjusted for matching, patients in the taper arm were less likely to experience CDI recurrence at 6 months when compared to standard vancomycin (cOR = 0.19, 95% CI 0.07-0.56, p < 0.002). Larger prospective trials are needed to elucidate the clinical utility of tapered oral vancomycin as a treatment option to achieve sustained clinical cure in first occurrences of CDI.

High Prevalence of Laxative Use Among Those Tested for Clostridioides difficile Infection in VA Hospitals

Background: Clostridioides difficile infection (CDI) is associated with 500,000 infections and 30,000 deaths per year. Inappropriate testing and treatment of patients with asymptomatic colonization occurs frequently (between 15% and 41%). The VA CDI guidelines emphasize avoidance of CDI testing in patients with laxative use within the previous 48 hours due to the high likelihood of non-infectious diarrhea. The objective of this study was to assess laxative administration among inpatients tested for CDI in VA hospitals and identify factors associated with guideline discordance. Methods: Adults hospitalized in Illinois, Wisconsin, and Michigan VA Medical Centers from January 2019-December 2022 with a CDI test performed during the admission were included. CDI tests included Toxin B gene Polymerase Chain Reaction or Toxin Enzyme Immunoassay. Tests were defined as positive, negative, or cancelled according to the diagnostic protocols of the VA testing laboratories. Laxative use, patient demographics, admission data, and comorbidities were collected from the VA Corporate Data Warehouse. Guideline discordant testing was defined as a diagnostic test for CDI ordered within 48 hours of a recorded laxative dose. Factors associated with discordant testing were analyzed using clustered binomial logistic regression models. Analyses were completed using SAS 9.4. Results: There were 7,326 tests ordered for 4,888 patients during the study. Patients were predominantly White (61.8%), male (95.6%), and elderly (mean age=70.0 standard deviation=12.1). Most (59.0%) patients had received at least one dose of laxative in the 48 hours preceding their CDI test. Being Black (Odds Ratio (OR)=0.86 (95%Confidence Interval (95%CI) =0.76,0.98) or Hispanic (OR (95%CI) =0.62(0.48,0.82) vs White) was associated with a decreased likelihood of inappropriate testing due to recent laxative use. Being tested at a rural facility (OR (95%CI) =1.23 (1.07,1.41) vs urban), within a long-term care (LTC) unit (OR (95%CI) =1.67 (1.41,1.97) vs inpatient), or within an intensive care unit (ICU) (OR (95%CI) =1.40 (1.24,1.59)) were all associated with an increased likelihood of being inappropriately tested. Guideline discordant tests were more likely to have negative results (OR (95%CI) =1.25 (1.05,1.49)) compared to guideline concordant tests. Discussion: Laxative administration in the 48 hours preceding CDI testing was common among hospitalized Veterans and associated with a lower likelihood of positive Results: This echoes non-VA studies where laxative use was reported at 44%. An increased likelihood of guideline discordant testing in ICU and LTC settings suggests the need for greater diagnostic stewardship interventions. Additionally, further work to determine negative outcomes associated with inappropriate testing are needed.

Clinician Interpretation and Management of Discordant PCR+/Toxin- Clostridioides difficile Testing Results Post-COVID

Background: Our institution utilizes a two-step algorithm consisting of an initial polymerase chain reaction (PCR) test with positive results reflexed to an enzyme immunoassay (EIA) for toxin. Institutional guidelines implemented during the COVID-19 pandemic recommended applying clinical judgment to patients with PCR+/Toxin- (discordant) results when determining if treatment is indicated. Pre-pandemic, we found that clinicians continued CDI-directed therapy in 56% of patients following the Toxin- result. Our study aims to identify how clinicians interpret PCR+/Toxin- results and reasons for management decisions post-pandemic. Methods: At an academic medical center, we conducted a retrospective cohort study of the first 50 inpatient charts with PCR+/Toxin- results from August to October 2022. Data was abstracted from clinical, pharmacy, and microbiology databases. The primary outcome was the proportion of patients continued on CDI-directed therapy for ≥24 hours after the Toxin- result became available. Secondary outcomes included the proportion of patients prescribed a full treatment course for CDI and the reasons for continuing treatment. Results: There were 37 patients (74%) who started CDI-directed treatment after initial PCR+ Results: Of these patients, 59% (22/37) were continued on treatment for ≥24 hours after the Toxin- result (primary outcome). 77% (17/22) of these patients who met the primary outcome completed full treatment courses. Three patients were transitioned to prophylaxis dosing after the Toxin- result. The most common reason for continuing treatment after discordant results was high clinical suspicion for CDI (Figure). There were no CDI-related complications in this 50-patient cohort. In immunocompromised patients, 70% (16/23) started treatment after initial PCR+ results and 81% (13/16) met the primary outcome. In patients admitted specifically to immunocompromised inpatient services, 90% (9/10) started treatment after initial PCR+ results and 100% (9/9) met the primary outcome. Conclusion: The majority of patients started on treatment after the PCR+ result were continued on treatment following the Toxin- result, though several of these patients did not complete full treatment courses. Treatment rates were similar to our pre-pandemic baseline. When patients were continued on treatment after discordant results, clinicians cited appropriate high clinical suspicion. Notably, every patient admitted to an immunocompromised service was continued on treatment after Toxin- Results: Overall, clinicians are following institutional guidelines by applying clinical judgement when interpreting discordant Results: Further research will help identify what variables affect clinician interpretation and management practices for discordant results, which will help shape institutional guideline updates, clinician education, and additional stewardship interventions.

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

PurposeThe clinical significance of negative toxin enzyme immunoassays (EIA) for Clostridioides difficile infections (CDIs) is unclear. Our study aimed to investigate the significance of toxin EIA-negative in the diagnosis and prognosis of CDI.MethodsAll stool specimens submitted for C. difficile toxin EIA testing were cultured to isolate C. difficile. In-house PCR for tcdA, tcdB, cdtA, and cdtB genes were performed using C. difficile isolates. Stool specimens were tested with C. difficile toxins A and B using EIA kit (RIDASCREEN Clostridium difficile toxin A/B, R-Biopharm AG, Darmstadt, Germany). Characteristics and subsequent CDI episodes of toxin EIA-negative and -positive patients were compared.ResultsAmong 190 C. difficile PCR-positive patients, 83 (43.7%) were toxin EIA-negative. Multivariate analysis revealed independent associations toxin EIA-negative results and shorter hospital stays (OR = 0.98, 95% CI 0.96–0.99, p = 0.013) and less high-risk antibiotic exposure in the preceding month (OR = 0.38, 95% CI 0.16–0.94, p = 0.035). Toxin EIA-negative patients displayed a significantly lower white blood cell count rate (11.0 vs. 35.4%, p < 0.001). Among the 54 patients who were toxin EIA-negative and did not receive CDI treatment, three (5.6%) were diagnosed with CDI after 7–21 days without complication.ConclusionOur study demonstrates that toxin EIA-negative patients had milder laboratory findings and no complications, despite not receiving treatment. Prolonged hospitalisation and exposure to high-risk antibiotics could potentially serve as markers for the development of toxin EIA-positive CDI.

672. Impact of Multistep Testing Algorithm on Hospital Acquired Clostridioides difficile Infection Rates

Abstract Background Clostridioides difficile infection (CDI) is one of the leading causes of hospital-acquired (HA) infections. Clinically distinguishing true CDI versus colonization is challenging. Our center previously used a polymerase chain reaction (PCR) assay as a standalone test for diagnosing CDI. While PCR is very sensitive for diagnosing CDI, it cannot distinguish between CDI and asymptomatic colonization. A multistep testing algorithm, which consists of an initial C. difficile PCR test followed by a reflex enzyme immunoassay (EIA) for glutamate dehydrogenase (GDH) and Toxin A/B testing, was implemented in our institution. We conducted this study to determine the rates of HA-CDI and C. difficile colonization based on laboratory results. Methods This retrospective observational study was conducted at Allegheny General Hospital (Pittsburgh, PA, US). Patients with a positive C. difficile PCR assay at day 3 or later from admission date were included for analysis. The pre-intervention period was from August 2021 to February 2022 and post-intervention period was from August 2022 to February 2023. Before the intervention, results for C. difficile testing were reported as PCR positive (PCR+) or negative (PCR-). On July 2022, a multistep testing algorithm was implemented with an initial C. difficile PCR assay; if results were positive, a reflex EIA for GDH and Toxin A/B testing was performed and resulted as follows: Figure 1. The HA-CDI rates before and after implementation of a multistep testing algorithm were compared. Results A total of 112 unique patients were included. HA-CDI in the post intervention period decreased by 53% after the intervention (N=57 [pre-intervention] versus N=26 [post-intervention]; P &amp;lt; 0.001). During the post-intervention period, there were 55 PCR+ C. difficile assays, of which 29 (53%) were resulted as "indeterminate, likely C. difficile colonization." Of the 29 indeterminate results, 23 (79%) still received CDI therapy. Conclusion Our study demonstrated that a multistep C. difficile testing algorithm significantly reduced the rates of HA-CDI in our institution. We found that the majority of patients still received CDI therapy despite having a negative EIA toxin result. We plan to analyze the clinical impact of this multistep testing algorithm in a follow-up study. Disclosures Thomas L. Walsh, MD, Accelerate Diagnostics: Advisor/Consultant

136. Impact of a Tele-Stewardship and Tele-Infection Prevention Program on Hospital-Onset Clostridioides Difficile Rates in a Community Three-Hospital Health System

Abstract Background Clostridioides difficile infection (CDI) is a common hospital-acquired infection (HAI) that can be difficult to diagnose accurately given the numerous test modalities with differing performance characteristics. Inaccurate diagnosis of CDI can negatively affect patient care decisions as well as reimbursement rates. Community and rural hospitals (CARH) may lack specialized personnel or knowledge to implement diagnostic best practices, but telehealth solutions like tele-infection prevention (TIP) and tele-antimicrobial stewardship (TASP) can provide specialist support for CARHs to optimize diagnostic pathways, improve accuracy, and reduce unnecessary treatment. Methods In June 2021 under the guidance of TIP and TASP recommendations, C. difficile testing was transitioned from a 1-step nucleic acid amplification test (NAAT)-only algorithm to a 2-step algorithm that included NAAT and toxin enzyme immunoassay (EIA) testing. A 6-month pre- and post-implementation assessment was conducted to assess the impacts of this change in hospital-onset CDI (HO-CDI) case rate. Additionally, total C. difficile (community- and hospital-onset CDI) rates per 1000 patient days (PD) and consumption of CDI therapeutics were assessed. For statistical analysis, Wilcoxon ranked-sum test to assess changes in CDI rates. Estimated annualized cost-savings for therapeutics were calculated based on institutional purchasing costs. Results Following implementation, a 35.9% reduction in HO-CDI was observed (pre 0.96 cases/1000PD vs. 0.61 cases/1000PD; p = 0.054). A 10.2% reduction was observed in total CDI (pre 3.66 cases/1000PD vs. 3.28 cases/1000PD; p = 0.37). Additionally, a 30.6% reduction was observed in consumption of CDI therapeutics (20.1 doses/1000PD vs. 14.0 doses/1000PD) resulting in an annualized cost-savings of approximately $9200. Conclusion Our TIP and TASP advised a community three-hospital health system on optimal diagnostics resulting in a change in their algorithm. Following this, considerable reductions were observed in HO-CDI, total CDI, consumption of CDI therapeutics, and the associated costs of care. Disclosures Erin K. McCreary, PharmD, Abbvie: Advisor/Consultant|Ferring: Advisor/Consultant|GSK: Honoraria|La Jolla (Entasis): Advisor/Consultant|LabSimply: Advisor/Consultant|Merck: Advisor/Consultant|Shionogi: Advisor/Consultant|Shionogi: Honoraria

Prevalence of diagnostically-discrepant Clostridioides difficile clinical specimens: insights from longitudinal surveillance

BackgroundClostridioides difficile Infection (CDI) is a healthcare-associated diarrheal disease prevalent worldwide. A common diagnostic algorithm relies on a two-step protocol that employs stool enzyme immunoassays (EIAs) to detect the pathogen, and its toxins, respectively. Active CDI is deemed less likely when the Toxin EIA result is negative, even if the pathogen-specific EIA is positive for C. difficile. We recently reported, however, that low-toxin-producing C. difficile strains recovered from Toxin-negative (‘discrepant’) clinical stool specimens can be fully pathogenic, and cause lethality in a rodent CDI model. To document frequency of discrepant CDI specimens, and evaluate C. difficile strain diversity, we performed longitudinal surveillance at a Southern Arizona tertiary-care hospital.MethodsDiarrheic stool specimens from patients with clinical suspicion of CDI were obtained over an eight-year period (2015–2022) from all inpatient and outpatient Units of a &amp;gt; 600-bed Medical Center in Southern Arizona. Clinical laboratory EIA testing identified C. difficile-containing specimens, and classified them as Toxin-positive or Toxin-negative. C. difficile isolates recovered from the stool specimens were DNA fingerprinted using an international phylogenetic lineage assignment system (“ribotyping”). For select isolates, toxin abundance in stationary phase supernatants of pure cultures was quantified via EIA.ResultsOf 8,910 diarrheic specimens that underwent diagnostic testing, 1733 (19.4%) harbored C. difficile. Our major findings were that: (1) C. difficile prevalence and phylogenetic diversity was stable over the 8-year period; (2) toxigenic C. difficile was recovered from 69% of clinically Tox-neg (‘discrepant’) specimens; (3) the six most prevalent USA ribotypes were recovered in significant proportions (&amp;gt;60%) from Tox-neg specimens; and (4) toxin–producing C. difficile recovered from discrepant specimens produced less toxin than strains of the same ribotype isolated from non-discrepant specimens.ConclusionOur study highlights the dominance of Toxin EIA-negative CDI specimens in a clinical setting and the high frequency of known virulent ribotypes in these specimens. Therefore, a careful reevaluation of the clinical relevance of diagnostically-discrepant specimens particularly in the context of missed CDI diagnoses and C. difficile persistence, is warranted.

Improving Pediatric Clostridioides difficile Testing Practices: Implementation of a 2-Tier Diagnostic Pathway

Introduction: Clostridioides difficile (C. difficile) is a significant concern for children, especially for those who are hospitalized or who have underlying medical conditions. Diagnosis of C. difficile infection (CDI) in these patients can be challenging due to asymptomatic colonization. Inappropriate testing and non-adherence to laboratory testing guidelines can result in increased false-positive rates precipitating unnecessary isolation precautions and antibiotic treatment for these patients. &#x0D; &#x0D; Methods: This retrospective cohort study aimed to evaluate the effectiveness of a new diagnostic pathway for C. difficile testing that was implemented in two pediatric hospitals. The study design collected data for two years, one year before and one year after pathway implementation. The study highlighted the importance of appropriate testing and the need for interventions to improve testing practices in pediatric patients. A 2-tier testing algorithm was implemented, consisting of polymerase chain reaction (PCR) for the presence or absence of the toxin B gene and an enzyme immunoassay for toxin A/B production. The best practice advisory was used to determine when C. difficile testing should not be performed. The chi-square test and Fisher's Exact Test analyzed the data using SPSS version 29.&#x0D; &#x0D; Results: The study found a significant association between the implementation of the C. difficile testing pathway and the test positivity rates for both inpatient and emergency department (ED) patients at both hospitals. Out of 159,434 Hospital A inpatients, 71 had positive C. difficile test results, and out of 11,109 Hospital B inpatients, nine had positive test results. Similarly, out of 121,951 Hospital A ED patients, eight had positive test results, and out of 67,999 Hospital B ED patients, 16 had positive test results. The study found a statistically significant association between the pre and post pathway implementation years for both hospitals (p&lt;0.001 for Hospital B inpatient and ED, p=0.033 for Hospital A inpatient, and p=0.004 for Hospital A ED).&#x0D; &#x0D; Conclusion: Adherence to laboratory testing guidelines, appropriate testing based on factors such as the patient's age, underlying health conditions, recent antibiotic use, and the presence of other infections or illnesses can reduce unnecessary testing and false-positive rates. False-positive results can occur in pediatric patients due to the high rate of asymptomatic colonization, making it essential to use a combination of clinical symptoms, history, and appropriate diagnostic testing to minimize the risk of misdiagnosis.

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

Polymerase chain reaction (PCR) testing for the detection of C. difficile is a highly sensitive test. Some clinical laboratories have included a 2-step testing algorithm utilizing PCR plus toxin enzyme immunoassays (EIAs) to increase specificity. To determine the risk factors and outcomes of C. difficile PCR-positive/toxin-positive encounters compared to PCR-positive/toxin-negative encounters. Retrospective study. A Veterans' Affairs hospital. A retrospective case-control study of patient encounters with a positive C. difficile test by PCR and either a toxin EIA-positive assay (ie, cases) or toxin EIA-negative assay (ie, controls). Clinically relevant exposures and risk factors were determined to assess CDI recurrence at 30 days. Available encounter stool specimens were cultured for C. difficile and were subjected to restriction endonuclease analysis (REA) strain typing. Among 130 C. difficile PCR-positive patient encounters, 80 (61.5%) were toxin EIA negative and 50 (38.5%) were toxin EIA positive. Encounters that were toxin positive were more frequently treated (96.0%) compared to toxin-negative encounters (71.3%; P < .01). A multivariable logistic regression model revealed that toxin-negative encounters were less likely to suffer a recurrent CDI episode within 30 days (odds ratio [OR], 0.20, 95% confidence interval [CI], 0.05-0.83). Additionally, a higher C. difficile PCR cycle threshold predicted a lower risk of CDI recurrence at 30 days. (OR, 0.82; 95% CI, 0.68-0.98). During the study period, the REA group Y strain accounted for most toxin-negative encounters (32.5%; P = .05), whereas REA group BI strain accounted for most toxin-positive encounters (24.3%; P = .02). A testing strategy of PCR plus toxin EIA helped predict recurrent CDI.

Clostridioides difficile PCR Tcdb Cycle Threshold predicts toxin EIA positivity but not severity of infection

BackgroundDiagnosis of Clostridioides difficile Infection (CDI) entails compatible clinical presentation and laboratory findings. We evaluated real-time polymerase chain reaction (qPCR) cycle threshold (CT) as a predictor for disease severity and TcdB enzyme immunoassay (EIA) results. MethodsInpatients or emergency department patients who tested positive for tcdB gene by PCR were evaluated. Patients’ stools underwent testing for GDH and TcdA/B by EIA. Medical health records were reviewed for demographic, clinical presentation, laboratory, treatment and outcome data. Severity of CDI was calculated using various severity score indexes. ResultsThe median CT of cases was 32.05 ± 5.45. The optimal cut-off for predicting toxin EIA positivity and severe CDI based on chart review was 32.6 and 29.8, respectively, with the area under the receiver operator characteristics curve (AUC) of 0.74 and 0.60 respectively. ConclusionCT value was an acceptable predictor for EIA toxin but less so for clinical severity. Our study potentially supports a diagnostic algorithm including CT value to reduce the number of EIA toxin assays performed.

Safety and Tolerability of SER-109 as an Investigational Microbiome Therapeutic in Adults With Recurrent Clostridioides difficile Infection

A safe and effective treatment for recurrent Clostridioides difficile infection (CDI) is urgently needed. Antibiotics kill toxin-producing bacteria but do not repair the disrupted microbiome, which promotes spore germination and infection recurrence. To evaluate the safety and rate of CDI recurrence after administration of investigational microbiome therapeutic SER-109 through 24 weeks. This phase 3, single-arm, open-label trial (ECOSPOR IV) was conducted at 72 US and Canadian outpatient sites from October 2017 to April 2022. Adults aged 18 years or older with recurrent CDI were enrolled in 2 cohorts: (1) rollover patients from the ECOSPOR III trial who had CDI recurrence diagnosed by toxin enzyme immunoassay (EIA) and (2) patients with at least 1 CDI recurrence (diagnosed by polymerase chain reaction [PCR] or toxin EIA), inclusive of their acute infection at study entry. SER-109 given orally as 4 capsules daily for 3 days following symptom resolution after antibiotic treatment for CDI. The main outcomes were safety, measured as the rate of treatment-emergent adverse events (TEAEs) in all patients receiving any amount of SER-109, and cumulative rates of recurrent CDI (toxin-positive diarrhea requiring treatment) through week 24 in the intent-to-treat population. Of 351 patients screened, 263 were enrolled (180 [68.4%] female; mean [SD] age, 64.0 [15.7] years); 29 were in cohort 1 and 234 in cohort 2. Seventy-seven patients (29.3%) were enrolled with their first CDI recurrence. Overall, 141 patients (53.6%) had TEAEs, which were mostly mild to moderate and gastrointestinal. There were 8 deaths (3.0%) and 33 patients (12.5%) with serious TEAEs; none were considered treatment related by the investigators. Overall, 23 patients (8.7%; 95% CI, 5.6%-12.8%) had recurrent CDI at week 8 (4 of 29 [13.8%; 95% CI, 3.9%-31.7%] in cohort 1 and 19 of 234 [8.1%; 95% CI, 5.0%-12.4%] in cohort 2), and recurrent CDI rates remained low through 24 weeks (36 patients [13.7%; 95% CI, 9.8%-18.4%]). At week 8, recurrent CDI rates in patients with a first recurrence were similarly low (5 of 77 [6.5%; 95% CI, 2.1%-14.5%]) as in patients with 2 or more recurrences (18 of 186 [9.7%; 95% CI, 5.8%-14.9%]). Analyses by select baseline characteristics showed consistently low recurrent CDI rates in patients younger than 65 years vs 65 years or older (5 of 126 [4.0%; 95% CI, 1.3%-9.0%] vs 18 of 137 [13.1%; 95% CI, 8.0%-20.0%]) and patients enrolled based on positive PCR results (3 of 69 [4.3%; 95% CI, 0.9%-12.2%]) vs those with positive toxin EIA results (20 of 192 [10.4%; 95% CI, 6.5%-15.6%]). In this trial, oral SER-109 was well tolerated in a patient population with recurrent CDI and prevalent comorbidities. The rate of recurrent CDI was low regardless of the number of prior recurrences, demographics, or diagnostic approach, supporting the beneficial impact of SER-109 for patients with CDI. ClinicalTrials.gov identifier: NCT03183141.

924. Reducing Rates of Hospital Acquired Clostridium Difficile Infection by Switching to Two-Step Testing

Abstract Background Clostridium difficile infection (CDI) tests have various degrees of sensitivity, making diagnosis challenging. Polymerase chain reaction (PCR) positive tests in colonized patients can impact rates of hospital-acquired CDI (HACDI). A negative toxin A/B enzyme immunoassay (EIA) as a second step can help determine colonization but is not as sensitive. We aimed to study the impact of a two-step testing strategy on rates of HACDI and CDI treatment outcomes. Methods Two-step testing consisted of C. difficle DNA PCR, which if positive, was followed by toxin A/B EIA (Figure 1). We conducted a retrospective study in a 359-bed hospital from March 2020 to July 2021. Patients with positive PCR and negative EIA results were included and further classified based on CDI treatment status. The primary outcome was the number of HACDI cases avoided. Secondary outcomes included location at the time of testing, symptoms, leukocytosis, discharge disposition and readmission. Results Ninety-six patients were included. Sixty-five patients (68%) were treated while 31 (32%) were not. HACDI was avoided in 18 cases (18.8%). There were more HACDI avoided in the non-treated group compared to the treated group (32.3% vs 12.3%; p=0.026). Most non-treated patients were tested on medical-surgical units (77.4%), whereas 49.2 % of the treated patients were tested in more acute areas such as emergency or intensive care. Treated patients were more likely to have leukocytosis and/or fever (66.2%) compared to non-treated patients (29%; p= 0.0009), while there was no difference in abdominal pain, diarrhea, bloody stool, or constipation (Table 1). Most patients had an abdominal CT scan (70.8%). Of those that had a CT, colitis was found in 48.5%. Patients in the treated group were more likely to have had a CT completed that showed colitis vs the non-treated patients (43.1% vs 16.1%; p&amp;lt; 0.011). Finally, compared to the non-treated patients, treatment did not affect home disposition on discharge or 30-day readmission rate (80% vs 71%, P=0.436) and (25 % vs 29%, P= 0.63) respectively. Symptoms Associated with C. difficile infection. Schematic of C. difficile test interpretation. Conclusion CDI two-step testing led to decreased HACDI rates without affecting discharge disposition or readmission rates in patients with PCR positive and toxin EIA negative results regardless of treatment status. Disclosures All Authors: No reported disclosures.

1665. Potential underreporting of treated patients using a Clostridioides difficile testing algorithm that screens with a nucleic acid amplification test

Abstract Background U.S. laboratories are increasingly using a two-step algorithm to diagnose Clostridioides difficile infection (CDI) that starts with a nucleic acid amplification test (NAAT), and if positive, reflexes to a toxin enzyme immunoassay. Here only a NAAT+/toxin+ result is reported to the Centers for Disease Control and Prevention’s (CDC) National Healthcare Safety Network (NHSN) as a CDI laboratory-identified (LabID) event, but limited data suggest that NAAT+/toxin- results may also be considered CDI by clinicians. To explore this discrepancy, we compared the characteristics and treatment of NAAT+/toxin- and NAAT+/toxin+ patients. Methods CDC’s Emerging Infections Program (EIP) conducts population-based CDI surveillance. A case was defined as a positive C. difficile test in a person aged ≥1 year with no positive tests in the prior 8 weeks. We included cases detected by this two-step algorithm in 5 EIP sites during 2018–2020 that underwent a full chart review. Multivariable logistic regression models adjusting for age, sex, race, comorbidities, epidemiologic classification, and CDI therapy were used to compare CDI-related complications (i.e., toxic megacolon, ileus, colectomy, or intensive-care unit stay) and recurrence between the two groups. Results Of 1250 NAAT+ cases, 897 (72%) were toxin- and 353 (28%) were toxin+. Lower percentages of toxin- versus toxin+ cases were aged ≥65 years (42% vs 58%; P&amp;lt; 0.0001), had diarrhea (779/831 [94%] vs 329/338 [97%]; P=0.01), or had white blood cell counts ≥15,000 cells/μL (183/811 [23%] vs 132/321 [42%]; P&amp;lt; 0.0001). CDI therapy was given to 683/882 (77%) toxin- versus 338/349 (97%) toxin+ cases (P&amp;lt; 0.0001). In multivariable analysis, toxin- status was protective for recurrence (adjusted odds ratio [aOR], 0.49; 95% confidence interval [CI], 0.32–0.74) but not for CDI-related complications (aOR, 1.00; 95% CI, 0.64–1.56). Conclusion NAAT+/toxin- cases were less likely to have recurrence but were as likely to have CDI-related complications as NAAT+/toxin+ cases. More than twice as many potentially unreported NAAT+/toxin- cases were treated than the number of reported NAAT+/toxin+ treated cases. Use of this two-step algorithm likely results in underreporting of treated CDI cases to NHSN. Disclosures Scott Fridkin, MD, Pfizer: Grant/Research Support Dale N. Gerding, MD, Destiny Pharma plc.: Advisor/Consultant.

180. Impact of a two-step diagnostic bundle on hospital-onset Clostridioides difficile infection rates and treatment across a large health system.

Abstract Background Distinguishing true Clostridioides difficile Infection (CDI) from colonization is a challenge, with nearly 20% of hospitalized adults being carriers of C. difficile. Polymerase chain reaction (PCR) testing alone is not able to distinguish colonization from infection, leading to over-diagnosis and unnecessary treatment. Despite interventions including pre-approval by antimicrobial stewardship programs (ASP), reportable hospital-onset CDI (HO-CDI) rates across our health system remained high. In 2021, we implemented a C. difficile PCR with reflex toxin enzyme immunoassay (EIA) testing strategy to improve diagnostic accuracy and treatment outcomes. The purpose of this study was to evaluate the impact of this two-step testing algorithm bundled with education, ASP support and order set changes on HO-CDI rates and C. difficile treatment across our health system. Methods PCR with EIA testing algorithm was implemented between May and August 2021 across seven hospitals within the Northwestern Medicine Health System. Multifaceted education was delivered to leadership and clinicians in person and electronically to. ASP performed daily diagnostic prospective audit and management support. Clinical decision support (CDS) was incorporated into order sets to promote diagnostic stewardship (Table 1, Figure 1). Standardization of analyst-developed tracking reports allowed for longitudinal monitoring across the system and at each facility, including unit- and patient-level data. Figure 1C. Difficile Testing Algorithm PCR/Reflex Toxin EIA Results The HO-CDI standardized infection ratio (SIR) reduced significantly from 0.8 to 0.57 p&amp;lt; 0.001), and reportable HO-CDI cases reduced by 238 cases across the health system between May 2021 and March 2022. 6043 samples were tested, of which 282 (4.7%) were confirmed CDI cases (PCR+/toxin+) and 687 (11%) were non-CDI cases (PCR+/toxin-), of which 438 (67%) received CDI treatment. (Figure 2 and 3). Figure 3 Actual versus avoided HO C. difficile cases. Conclusion The two-step CDI diagnostic and treatment bundle significantly reduced the SIR of HO-CDI. Although treatment of colonized patients remained high, a large number of patients safely avoided CDI treatment. Testing and education bundles can help advance antimicrobial and diagnostic stewardship by improving detection, treatment, and tracking of CDI. Disclosures Asra Salim, MPH, CPH, FAPIC, IRhythym Technologies Inc: Stocks/Bonds.

Prevalence and Seasonality of Clostridiodes difficile over 12Years at a Tertiary Hospital in Brazil.

Clostridioides difficile is the main pathogen responsible for antibiotic-associated diarrhea in adults. Besides its challenging diagnosis, C. difficile infection (CDI) causes substantial morbidity and mortality. Commercially, there are assays with different targets and performances in sensitivity and specificity. The objectives of this study were to: (1) evaluate the prevalence and seasonal variability of CDI rates at a tertiary hospital in southern Brazil over 12years and (2) determine the impact of using a two-step algorithm test in the laboratory diagnosis. Between January 2007 and May 2019, fecal samples from 2275 patients were analyzed in a cross-sectional study. Four commercial tests were adopted for the diagnosis of CDI, the immunochromatographic test for toxin A from 2007 to 2010; the enzyme-linked immunosorbent assay method for toxins A and B from 2011 to March 2017; and the rapid enzyme immunoassay (EIA) for GDH and toxins A and B, associated with a Polymerase Chain Reaction (PCR) for the toxin B gene from June 2017 to 2019. The annual prevalence was 8.7% from 2007 to March 2017, increasing between June 2017 and 2019 to 14.7% when the C. diff Quik Chek Complete + GeneXpert C. difficile (two-step algorithm) test was adopted. The number of samples (691) and percentage of CDI cases (10.5%) were higher in winter, but the difference has no statistical significance (P > 0.05). An accurate diagnosis and adequate knowledge of the local seasonality of CDI allow the effective implementation of prevention and control strategies for nosocomial CDI, in addition to effective treatment for patients.

Clinical Outcomes of Treated and Untreated C. difficile PCR-Positive/Toxin-Negative Adult Hospitalized Patients: a Quasi-Experimental Noninferiority Study.

Clostridioides difficile infection (CDI) is routinely diagnosed by PCR, with or without toxin enzyme immunoassay testing. The role of therapy for positive PCR and negative toxin remains unclear. The objective of this study was to determine whether clinical outcomes of PCR+/cycle threshold-based toxin (CT-toxin)- individuals vary by result reporting and treatment strategy. We performed a quasiexperimental noninferiority study comparing clinical outcomes of PCR+/CT-toxin- individuals by reporting PCR result only (most patients treated) with reporting CT-toxin result only (most patients untreated) in a single-center, tertiary academic hospital. The primary outcome was symptomatic PCR+/CT-toxin+ conversion at 8 weeks. Secondary outcomes included 7-day diarrhea resolution, hospital length of stay, and 30-day all-cause mortality. A total of 663 PCR+/CT-toxin- test results were analyzed from 632 individuals with a median age of 61 years (interquartile range [IQR], 44 to 72) and 50.4% immunocompromised. Individuals in the preintervention group were more likely to have received CDI therapy than those in the intervention group (91.5 versus 15.1%; P < 0.001). Symptomatic toxin conversion at 8 weeks and hospital length of stay failed to establish the predefined thresholds for noninferiority. Lack of diarrhea resolution at 7 days and 30-day all-cause mortality was similar and established noninferiority (20.0 versus 13.7%; adjusted odds ratio [aOR], 0.57; 90% confidence interval [CI], 0.32 to 1.01; P = 0.1; and 8.6 versus 6.5%; aOR, 0.46; 90% CI, 0.20 to 1.04; P = 0.12). These data support the safety of withholding antibiotics for selected hospitalized individuals with suspected CDI but negative toxin.

Impact of the Introduction of a Two-Step Laboratory Diagnostic Algorithm in the Incidence and Earlier Diagnosis of Clostridioides difficile Infection.

Our aim was to determine changes in the incidence of CD infection (CDI) following the introduction of a two-step diagnostic algorithm and to analyze CDI cases diagnosed in the study period. We retrospectively studied CDI (January 2009 to July 2018) in adults diagnosed by toxin enzyme immunoassay (EIA) (2009–2012) or toxin-EIA + polymerase chain reaction (PCR) algorithm (2013 onwards). A total of 443 patients with a first episode of CDI were included, 297 (67.1%) toxin-EIA-positive and 146 (32.9%) toxin-EIA-negative/PCR-positive were only identified through the two-step algorithm including the PCR test. The incidence of CDI increased from 0.9 to 4.7/10,000 patient-days (p < 0.01) and 146 (32.9%) toxin-negative CDI were diagnosed. Testing rate increased from 24.4 to 59.5/10,000 patient-days (p < 0.01) and the percentage of positive stools rose from 3.9% to 12.5% (p < 0.01). CD toxin-positive patients had a higher frequency of severe presentation and a lower rate of immunosuppressive drugs and inflammatory bowel disease. Mortality (16.3%) was significantly higher in patients with hematological neoplasm, intensive care unit admission and complicated disease. Recurrences (14.9%) were significantly higher with proton pump inhibitor exposure. The two-step diagnostic algorithm facilitates earlier diagnosis, potentially impacting patient outcomes and nosocomial spread. CD-toxin-positive patients had a more severe clinical presentation, probably due to increased CD bacterial load with higher toxin concentration. This early and easy marker should alert clinicians of potentially more severe outcomes.

Identification of Clostridium innocuum hypothetical protein that is cross-reactive with C. difficile anti-toxin antibodies

ObjectivesPreviously considered solely an opportunistic pathogen, Clostridium innocuum (CI) was recently reported in Taiwan to be an emerging cause of antibiotic-associated diarrhea and clinically indistinguishable from Clostridioides difficile (CD) infection. We previously identified CI culture supernatant being cross-reactive with commercial CD toxin enzyme immunoassays. We aimed to identify and characterize the cross-reacting protein and determine whether it functioned as a human toxin. MethodsWe performed western blots using CI culture supernatants and CD anti-toxin antibodies and identified interacting bands. We identified protein(s) using tandem mass spectrometry and evaluated them by cytotoxicity assays. ResultsCI, but not CD, was isolated from stool of 12 children and adults with diarrhea. Culture supernatant from 6/12 CI isolates, and an ATCC reference strain, tested positive for CD toxins (total 7/13 isolates) by commercial EIA. Using two of these isolates, we identified two ∼40 kDa hypothetical proteins, CI_01447 and CI_01448, and confirmed cross-reactivity with CD anti-toxin antibodies by enzyme immunoassay and Western blot. Whole-genome sequencing confirmed all 13 isolates contained both genes, which were highly conserved. We observed no cytopathic or cytotoxic effects to HeLa cells when treated with these proteins. We identified amino acid sequence similarity to the NlpC/P60 family of proteins. ConclusionsOur findings do not suggest CI proteins CI_01448 and CI_01447, which cross-react with antibodies against CD toxins A and B, are toxic to HeLa cells. Further studies are needed to determine the function of these cross-reacting proteins and the potential virulence factors that could be responsible for CI diarrheal disease.

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.

Outcomes in patients with inflammatory bowel disease and acute gastrointestinal symptoms who test indeterminate for Clostridioides difficile.

BackgroundInflammatory bowel disease (IBD) and Clostridioides difficile infection (CDI) can present with similar symptoms. The current preferred method for diagnosing CDI is the nucleic acid amplification test (NAAT) for C. difficile in stool, followed by reflex toxin enzyme immunoassay (EIA) when NAAT is positive. The clinical significance of NAAT(+)/EIA(-) in the IBD population is uncertain.MethodsThis retrospective cohort included IBD patients who presented with acute onset of gastrointestinal symptoms and a C. difficile NAAT(+) test. The primary outcome was C. difficile recurrence within 12 months. Other outcomes examined included hospital admissions within 30 days of CDI, change of IBD maintenance therapy within 90 days of CDI, and complications such as bowel resection or death.ResultsA total of 71 patients were included. Eighty-four percent of the tests were EIA(-) and among the EIA(-) 88% were treated with antibiotics. Outcomes between EIA(+) and EIA(-) were not significantly different in terms of recurrences, admissions, changes to IBD medications or complications. Outcomes were also similar when comparing those who received antibiotic therapy to those who did not.ConclusionsOur cohort did not demonstrate a significant difference in outcomes between EIA(+) and EIA(-) C. difficile patients. Treatment for EIA(-) patients did not improve outcomes. Even though there may be a role for antibiotic therapy in IBD patients who test NAAT(+)/EIA(-) for C. difficile, further studies will be needed to identify that subpopulation.