Comparison of nine commercially available Clostridium difficile toxin detection assays, a real-time PCR assay for C. difficile tcdB, and a glutamate dehydrogenase detection assay to cytotoxin testing and cytotoxigenic culture methods

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

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

Comparison of the STANDARD M10 C. difficile, Xpert C. difficile, and BD MAX Cdiff assays as confirmatory tests in a two-step algorithm for diagnosing Clostridioides difficile infection

Current guidelines recommend a two-step algorithm rather than relying solely on a single test for diagnosing Clostridioides difficile infection. This algorithm starts with enzyme immunoassay (EIA) for detecting glutamate dehydrogenase (GDH) and toxins A/B, followed by nucleic acid amplification test (NAAT) for GDH-positive but toxin-negative cases. This study compared the performance of three commercial NAATs: the STANDARD M10 C. difficile, Xpert C. difficile, and BD MAX Cdiff assays, utilized as confirmatory testing of the two-step algorithm. Two hundred archived stool specimens, previously tested GDH-positive but toxin-negative by EIA, were analyzed in parallel with these NAATs and toxigenic culture, which served as the reference standard. Sensitivity, specificity, positive predictive value, and negative predictive value were 89.1%, 92.6%, 94.6%, and 85.2%, respectively, for the M10 assay; 95.8%, 86.4%, 91.2%, and 93.3%, respectively, for the Xpert assay; and 89.8%, 91.4%, 93.8%, and 86.0%, respectively, for the BD MAX assay. The rates of invalid results were 1.0%, 0.5%, and 1.0% for the M10, Xpert, and BD MAX assays, respectively. In conclusion, the M10 assay is a reliable diagnostic tool, performing comparably to the Xpert and BD MAX assays when used as confirmatory testing in the two-step algorithm.IMPORTANCEWhile numerous studies have assessed nucleic acid amplification tests (NAATs) as stand-alone tests for diagnosing Clostridioides difficile infection, limited research has compared their performance as confirmatory tests in a two-step algorithm. This study evaluated the performance of three commercial NAATs (M10, Xpert, and BD MAX assays) using 200 archived stool specimens initially tested as glutamate dehydrogenase (GDH)-positive but toxin-negative by GDH/toxin A/B enzyme immunoassay, the first step in the two-step algorithm. All three assays demonstrated high sensitivity (89.1% to 95.8%) and specificity (86.4% to 92.6%), with low rates of invalid results (≤1%). Our findings suggest that the M10 assay performs comparably to the Xpert and BD MAX assays when used as confirmatory testing in the two-step algorithm. Offering similar performance and turnaround time to these widely used assays at a slightly lower cost, the M10 assay serves as a practical alternative in this setting.

Diagnosis of Clostridioides difficile infection and impact of testing

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

Comparative evaluation of the STANDARD M10 and Xpert C. difficile assays for detection of toxigenic Clostridioides difficile in stool specimens

This study compared the performance of two commercial molecular assays, the STANDARD M10 Clostridioides difficile assay (M10) and the Xpert C. difficile assay (Xpert), for detecting toxigenic C. difficile in stool specimens. A total of 487 consecutive stool specimens submitted for routine C. difficile testing between June and November 2023 were included. Following routine testing using C. DIFF QUIK CHEK COMPLETE (QCC), M10 and Xpert were tested in parallel, alongside toxigenic culture (reference standard). Additionally, two-step algorithms, using QCC on the first step and either M10 or Xpert on the second step, were assessed. Both M10 and Xpert demonstrated a sensitivity and negative predictive value (NPV) of 100%. M10 exhibited significantly higher specificity and positive predictive value (PPV; 91.9% and 64.2%, respectively) than Xpert (90.3% and 59.8%, respectively). Both two-step algorithms showed a sensitivity and NPV of 98.4% and 99.8%, respectively. The specificity and PPV of the two-step algorithm using M10 (95.2% and 75.0%, respectively) were slightly higher than those of the one using Xpert (94.8% and 73.2%, respectively), without statistical significance. Receiver operating characteristic curve analysis, assessing the predictive ability of cycle threshold (Ct) values for the detection of free toxin, exhibited an area under the curve of 0.825 for M10 and 0.843 for Xpert. This indicates the utility of Ct values as predictors for the detection of free toxin in both assays. In conclusion, M10 proves to be an effective diagnostic tool with performance comparable to Xpert, whether utilized independently or as part of a two-step algorithm.

Early Economic Modeling to Inform a Target Product Profile: A Case Study of a Novel Rapid Test for Clostridioides difficile Infection

Background. Target product profiles (TPPs) specify the essential properties tests must have to be able to address an unmet clinical need. Aim. To explore how early economic modeling can help to define TPP specifications based on cost-effectiveness considerations using the example of a new rapid diagnostic for Clostridioides difficile infection (CDI), a contagious health care-associated infection causing potentially fatal diarrhea. Methods. A resource-constrained simulation model was developed to compare a hypothetical test for CDI with current practice (i.e., test with glutamate dehydrogenase enzyme immunoassay first; if positive, test with polymerase chain reaction and cytotoxicity assay) for adult individuals with suspected CDI at the Leeds Teaching Hospital National Health System (NHS) Trust in the United Kingdom. Parameters are taken from UK-based observational data collected between 2018 and 2021, published literature, and expert opinion. A methodological framework was developed 1) to derive minimum diagnostic sensitivity and specificity and maximum price for different test turnaround-time values based on cost-effectiveness considerations from the health care perspective using the National Institute of Health Care Excellence willingness-to-pay threshold of £20,000 per quality-adjusted life-years and 2) to test their robustness using a series of sensitivity analyses. Results. A new rapid test for CDI with a 15-min turnaround time would require a minimum diagnostic sensitivity and specificity both equal to 96% and a maximum price of £44 to maintain cost-effectiveness compared with standard of care. Conclusions. This study provides a framework to inform the essential test properties based on cost-effectiveness considerations and to isolate the most influential model parameters and scenarios via a series of sensitivity analyses. These specifications, in turn, could be used to inform future TPPs for tests.

Highlights

Target product profiles (TPPs) for new medical tests provide test developers with performance benchmarks and technical requirements for new tests. Early economic evaluation has already been used to identify acceptable ranges for certain performance requirements for new tests. Currently, however, early economic evaluation methods are yet to be used in the context of TPP development, and there is no guidance as to how this could and should be done.A de novo approach was developed to identify the minimum performance requirements and maximum costs for new tests, based on cost-effectiveness considerations, while also isolating most influential parameters. The added value of this framework lies in structuring early economic evaluation methods as a means of informing transparent, evidence-based minimum TPP performance specifications while also accounting as much as possible for the (inevitable) uncertainty surrounding the minimum performance requirements.This study represents the first application of early economic modeling as a means of deriving the minimum performance specifications for a novel point-of-care test for Clostridioides difficile infection as set out in a future TPP.

Infectious complications in patients with inflammatory bowel disease in Asia: the results of a multinational web-based survey in the 8th Asian Organization for Crohn's and Colitis meeting

BACKGROUND/AIMS

Infectious complications are major concerns when treating patients with inflammatory bowel disease (IBD). This study evaluated clinical differences across countries/regions in the management of infectious diseases in patients with IBD.

METHODS

A multinational online questionnaire survey was administered to participants at the 8th meeting of the Asian Organization for Crohn's and Colitis. The questionnaire included questions regarding surveillance, diagnosis, management, and prevention of infection in patients with IBD.

RESULTS

A total of 384 physicians responded to the questionnaire. The majority of Korean (n=70, 63.6%) and Chinese (n=51, 51.5%) physicians preferred vancomycin to metronidazole in the treatment of Clostridium difficile infection, whereas more than half of the Japanese physicians (n=62, 66.7%) preferred metronidazole. Physicians in Korea (n=88, 80.0%) and China (n=46, 46.5%) preferred a 3-month course of isoniazid and rifampin to treat latent tuberculosis infection, whereas most physicians in Japan (n=71, 76.3%) favored a 9-month course of isoniazid. Most Korean physicians (n=89, 80.9%) recommended hepatitis B virus (HBV) vaccination in patients lacking HBV surface antigen, whereas more than half of Japanese physicians (n=53, 57.0%) did not consider vaccination.

CONCLUSIONS

Differences in the diagnosis, prevention, and management of infections in patients with IBD across countries/regions reflect different prevalence rates of infectious diseases. This survey may broaden understanding of the real-world clinical settings across Asian countries/regions and provide information for establishing practical guidelines to manage patients with IBD.

Understanding the Factors Affecting Travel Avoidance behavior During the COVID-19 Pandemic: Findings From a Mixed Method Approach

Pandemics are affecting tourism in many ways, and have had a major effect on international travel, the hospitality industry and tourism demand. Grounded in the protective action decision model and complexity theory, this study seeks to develop a model to explain the conditions that have led to travel avoidance in the UK in the context of the COVID-19 pandemic. To test our proposed model, we used a fuzzy-set qualitative comparative analysis of data gathered from 1,290 travelers, with semi-structured interviews conducted to confirm the configurations identified by the model. The findings indicate that effective pandemic information, effective risk communication, supplies, trust in government and trust in the media are necessary to combat travel avoidance, but the refutation of rumor and trust among traveler is not necessary to foster travel avoidance. Furthermore, qualitative follow-up interviews were conducted to obtain deeper insights into the discovered configurations and develop effective pathways to travel avoidance.

Overview of current detection methods and microRNA potential in Clostridioides difficile infection screening

Clostridioides difficile (formerly called Clostridium difficile, C. difficile) infection (CDI) is listed as an urgent threat on the 2019 antibiotic resistance threats report in the United States by the Centers for Disease Control and Prevention. Early detection and appropriate disease management appear to be essential. Meanwhile, although the majority of cases are hospital-acquired CDI, community-acquired CDI cases are also on the rise, and this vulnerability is not limited to immunocompromised patients. Gastrointestinal treatments and/or gastrointestinal tract surgeries may be required for patients diagnosed with digestive diseases. Such treatments could suppress or interfere with the patient’s immune system and disrupt gut flora homeostasis, creating a suitable microecosystem for C. difficile overgrowth. Currently, stool-based non-invasive screening is the first-line approach to CDI diagnosis, but the accuracy is varied due to different clinical microbiology detection methods; therefore, improving reliability is clearly required. In this review, we briefly summarised the life cycle and toxicity of C. difficile, and we examined existing diagnostic approaches with an emphasis on novel biomarkers such as microRNAs. These biomarkers can be easily detected through non-invasive liquid biopsy and can yield crucial information about ongoing pathological phenomena, particularly in CDI.

Rapid-format recombinant antibody-based methods for the diagnosis of Clostridioides difficile infection: Recent advances and perspectives

Clostridioides difficile, the most common cause of nosocomial diarrhea, has been continuously reported as a worldwide problem in healthcare settings. Additionally, the emergence of hypervirulent strains of C. difficile has always been a critical concern and led to continuous efforts to develop more accurate diagnostic methods for detection of this recalcitrant pathogen. Currently, the diagnosis of C. difficile infection (CDI) is based on clinical manifestations and laboratory tests for detecting the bacterium and/or its toxins, which exhibit varied sensitivity and specificity. In this regard, development of rapid diagnostic techniques based on antibodies has demonstrated promising results in both research and clinical environments. Recently, application of recombinant antibody (rAb) technologies like phage display has provided a faster and more cost-effective approach for antibody production. The application of rAbs for developing ultrasensitive diagnostic tools ranging from immunoassays to immunosensors, has allowed the researchers to introduce new platforms with high sensitivity and specificity. Additionally, DNA encoding antibodies are directly accessible in these approaches, which enables the application of antibody engineering to increase their sensitivity and specificity. Here, we review the latest studies about the antibody-based ultrasensitive diagnostic platforms for detection of C. difficile bacteria, with an emphasis on rAb technologies.

Glutamate Oxidase-Integrated Biomimetic Metal-Organic Framework Hybrids as Cascade Nanozymes for Ultrasensitive Glutamate Detection

The hybrid coupling of biocatalysts and chemical catalysts plays a vital role in the fields of catalysis, sensing, and medical treatment due to the integrated advantages in the high activity of natural enzymes and the excellent stability of nanozymes. Herein, a new nanozyme/natural enzyme hybrid biosensor was established for ultrasensitive glutamate detection. The MIL-88B(Fe)-NH₂ material with remarkable peroxidase mimic activity and stability was used as a nanozyme and carrier for immobilizing glutamate oxidase (GLOX) through Schiff base reaction to construct a chem-enzyme cascade detector (MIL-88B(Fe)-NH₂@GLOX). The resultant MIL-88B(Fe)-NH₂@GLOX exhibited a wide linear range (1-100 μM), with a low detection limit of 2.5 μM for glutamate detection. Furthermore, the MIL-88B(Fe)-NH₂@GLOX displayed excellent reusability and storage stability. After repeated seven cycles, MIL-88B(Fe)-NH₂-GLOX (GLOX was adsorbed on MIL-88B(Fe)-NH₂) lost most of its activity, whereas MIL-88B(Fe)-NH₂@GLOX still retained 69% of its initial activity. Meanwhile, MIL-88B(Fe)-NH₂@GLOX maintained 60% of its initial activity after storage for 90 days, while free GLOX only retained 30% of its initial activity. This strategy of integrating MOF mimics and natural enzymes for cascade catalysis makes it possible to design an efficient and stable chemo-enzyme composite catalysts, which are promising for applications in biosensing and biomimetic catalysis.

Identification of novel, cryptic Clostridioides species isolates from environmental samples collected from diverse geographical locations

Clostridioides difficile is a pathogen often associated with hospital-acquired infection or antimicrobial-induced disease; however, increasing evidence indicates infections can result from community or environmental sources. Most genomic sequencing of C. difficile has focused on clinical strains, although evidence is growing that C. difficile spores are widespread in soil and water in the environment. In this study, we sequenced 38 genomes collected from soil and water isolates in Flagstaff (AZ, USA) and Slovenia in an effort targeted towards environmental surveillance of C. difficile. At the average nucleotide identity (ANI) level, the genomes were divergent to C. difficile at a threshold consistent with different species. A phylogenetic analysis of these divergent genomes together with Clostridioides genomes available in public repositories confirmed the presence of three previously described, cryptic Clostridioides species and added two additional clades. One of the cryptic species (C-III) was almost entirely composed of Arizona and Slovenia genomes, and contained distinct sub-groups from each region (evidenced by SNP and gene-content differences). A comparative genomics analysis identified multiple unique coding sequences per clade, which can serve as markers for subsequent environmental surveys of these cryptic species. Homologues to the C. difficile toxin genes, tcdA and tcdB, were found in cryptic species genomes, although they were not part of the typical pathogenicity locus observed in C. difficile, and in silico PCR suggested that some would not amplify with widely used PCR diagnostic tests. We also identified gene homologues in the binary toxin cluster, including some present on phage and, for what is believed to be the first time, on a plasmid. All isolates were obtained from environmental samples, so the function and disease potential of these toxin homologues is currently unknown. Enzymatic profiles of a subset of cryptic isolates (n=5) demonstrated differences, suggesting that these isolates contain substantial metabolic diversity. Antimicrobial resistance (AMR) was observed across a subset of isolates (n=4), suggesting that AMR mechanisms are intrinsic to the genus, perhaps originating from a shared environmental origin. This study greatly expands our understanding of the genomic diversity of Clostridioides. These results have implications for C. difficile One Health research, for more sensitive C. difficile diagnostics, as well as for understanding the evolutionary history of C. difficile and the development of pathogenesis.

Development and clinical validation of an automated cell cytotoxicity neutralization assay for detecting Clostridioides difficile toxins in clinically relevant stools samples

OBJECTIVES

To improve the diagnostic accuracy of Clostridioides difficile infection, current U.S. and E.U. guidelines recommend multistep testing that detects the presence of C. difficile and toxin in clinically relevant stool samples to confirm active disease. An accepted gold standard to detect C. difficile toxins is the cell cytotoxicity neutralization assay (CCNA). Although highly sensitive, the traditional CCNA has limitations. One such limitation is the subjective interpretation of an analyst to recognize cytopathic effects in cultured cells exposed to a fecal sample containing toxin. To overcome this limitation, an automated CCNA was developed that replaces most human pipetting steps with robotics and incorporates CellTiterGlo® for a semi-quantitative, non-subjective measure of cell viability instead of microscopy.

METHODS

To determine sample positivity and control for non-specific cytopathic effects, two thresholds were defined and validated by evaluating the sample with/without antitoxin antisera (sample-antitoxin/sample + antitoxin): 1) a >70% cell viability threshold was validated with samples containing anti-toxin, and 2) a >1.2-fold difference cut-off where sample results above the cut-off are considered positive.

RESULTS

Assay validation demonstrated excellent accuracy, precision, and sample linearity with an LOD of 126.9 pg/mL toxin-B in stool. The positivity cut-offs were clinically validated by comparing 322 diarrheal stool sample results with those run in a predicate, microscopic readout-based CCNA. The automated CCNA demonstrated 96% sensitivity and 100% specificity compared with the predicate CCNA.

CONCLUSIONS

Overall, the automated CCNA provides a specific, sensitive, and reproducible tool to support determination of CDI epidemiology or the efficacy of interventions such as vaccines.

A cost of illness comparison for toxigenic Clostridioides difficile diagnosis algorithms in developing countries

BACKGROUND

Availability of several commercial tests with different Clostridioides difficile targets contributes to uncertainty and controversies around the optimal diagnostic algorithm. While numerous studies have estimated the financial impact of C. difficile infection, models to guide testing strategies decisions in developing countries, where economic value significantly impacts clinical practice, are currently not available.

AIM

To determine the cost of illness of different C. difficile infection (CDI) diagnostic strategies in developing countries.

METHODS

Cost-comparison analysis was performed to compare eleven different algorithms of CDI diagnosis. The basis of calculation was a hypothetical cohort of 1000 adult inpatients suspected of CDI. We analyzed turnaround time of test results (i.e., time from taking sample to results emission), test performance (i.e., sensitivity and specificity) and testing costs. Patients were divided in true positive, false positive, true negative and false negative in order to integrate test performance and economics effects. Additional medical costs were calculated: costs of hygiene, medication, length of stay and intensive care unit costs, based on a Brazilian University Hospital costs. CDI prevalence was considered 22.64%.

FINDINGS

From laboratory-assisted tests, simultaneous glutamate dehydrogenase (GDH) and toxin A/B rapid immunoassay arbitrated by nucleic acid amplification test (NAAT) presented the lowest cost of illness (450,038.70 USD), whereas standalone NAAT had the highest (523,709.55 USD). Empirical diagnosis only presented the highest overall cost (809,605.44 USD).

CONCLUSION

The two-step algorithm with simultaneous GDH and toxin A/B rapid immunoassay arbitrated by NAAT seems to be the best strategy for CDI diagnosis in developing countries.

SER-109, an Investigational Microbiome Drug to Reduce Recurrence After Clostridioides difficile Infection: Lessons Learned From a Phase 2 Trial

BACKGROUND

Recurrent Clostridioides difficile infection (rCDI) is associated with loss of microbial diversity and microbe-derived secondary bile acids, which inhibit C. difficile germination and growth. SER-109, an investigational microbiome drug of donor-derived, purified spores, reduced recurrence in a dose-ranging, phase (P) 1 study in subjects with multiple rCDIs.

METHODS

In a P2 double-blind trial, subjects with clinical resolution on standard-of-care antibiotics were stratified by age (< or ≥65 years) and randomized 2:1 to single-dose SER-109 or placebo. Subjects were diagnosed at study entry by PCR or toxin testing. Safety, C. difficile-positive diarrhea through week 8, SER-109 engraftment, and bile acid changes were assessed.

RESULTS

89 subjects enrolled (67% female; 80.9% diagnosed by PCR). rCDI rates were lower in the SER-109 arm than placebo (44.1% vs 53.3%) but did not meet statistical significance. In a preplanned analysis, rates were reduced among subjects ≥65 years (45.2% vs 80%, respectively; RR, 1.77; 95% CI, 1.11-2.81), while the <65 group showed no benefit. Early engraftment of SER-109 was associated with nonrecurrence (P < .05) and increased secondary bile acid concentrations (P < .0001). Whole-metagenomic sequencing from this study and the P1 study revealed previously unappreciated dose-dependent engraftment kinetics and confirmed an association between early engraftment and nonrecurrence. Engraftment kinetics suggest that P2 dosing was suboptimal. Adverse events were generally mild to moderate in severity.

CONCLUSIONS

Early SER-109 engraftment was associated with reduced CDI recurrence and favorable safety was observed. A higher dose of SER-109 and requirements for toxin testing were implemented in the current P3 trial.

CLINICAL TRIALS REGISTRATION

NCT02437487, https://clinicaltrials.gov/ct2/show/NCT02437487?term=SER-109&draw= 2&rank=4.

New Developments in PCR-Based Diagnostics for Bacterial Pathogens Causing Gastrointestinal Infections-A Narrative Mini-Review on Challenges in the Tropics

The application of modern PCR approaches for the diagnosis of bacterial gastrointestinal pathogens is on the rise due to their rapidly available results combined with high sensitivity. While multiple studies describe the ongoing implementation of this technique for routine diagnostic purposes in laboratories in Western industrialized countries, reports on successful and also sustainable respective approaches in resource-poor tropical settings are still scarce. In order to shed light on potential reasons for this marked discrepancy, this narrative review summarizes identified challenges for the application of diagnostic PCR targeting bacterial gastrointestinal pathogens from stool samples in the tropics. The identified and discussed issues comprise the lack of generally accepted definitions for (1) minimum standards regarding sample acquisition, storage and transport time for diagnostic PCR analyses in the tropics, (2) nucleic acid extraction standards allowing an optimum detection of all types of pathogens which may be responsible for gastroenteritis in the tropics, (3) validation standards to ensure comparable quality of applied diagnostic assays, and (4) cut-offs for a reliable discrimination of infection and mere colonization in areas where semi-immunity due to repeated exposition associated with poor hygiene conditions has to be expected. Further implementation research is needed to solve those issues.

Usefulness of Fecal Calprotectin in the Management of Patients with Toxigenic Clostridioides difficile

The availability of highly sensitive molecular tests for the detection of Clostridioides difficile in feces leads to overtreatment of patients who are probably only colonized. In this prospective study, the usefulness of fecal calprotectin (fCP) is evaluated in a cohort of patients with detection of toxigenic C. difficile in feces. Patients were classified by an infectious diseases consultant blinded to fCP results into three groups-group I, presumed Clostridioides difficile infection (CDI); group II, doubtful but treated CDI; and group III, presumed C. difficile colonization or self-limited CDI not needing treatment. One hundred and thirty-four patients were included. The median fCP concentrations were 410 (138-815) μg/g in group I, 188 (57-524) μg/g in group II, and 51 (26-97) μg/g in group III (26 cases); p < 0.05 for all comparisons. In forty-five out of 134 cases (33.5%), the fCP concentrations were below 100 µg/g. In conclusion, fCP is low in most patients who do not need treatment against C. difficile, and should be investigated as a potentially useful test in the management of patients with detected toxigenic C. difficile.

Two-step Testing for Clostridioides Difficile is Inadequate in Differentiating Infection From Colonization in Children

OBJECTIVES

Recent Infectious Disease Society of America guidelines recommend multistep testing algorithms to diagnose Clostridioides difficile infection (CDI), including a combination of nucleic acid amplification-based testing (NAAT) and toxin enzyme immunoassay (EIA). The use of these algorithms in children, including the ability to differentiate between C. difficile colonization and CDI, however, has not been evaluated.

METHODS

We prospectively enrolled asymptomatic pediatric patients with cancer, cystic fibrosis (CF), or inflammatory bowel disease (IBD) and obtained a stool sample for NAAT testing. If positive by NAAT (colonized), EIA was performed. In addition, children with symptomatic CDI who tested positive by NAAT via the clinical laboratory were enrolled, and EIA was performed on residual stool. A functional cell cytotoxicity neutralization assay (CCNA) was also applied to stool samples from both the colonized and symptomatic cohorts.

RESULTS

Of the 225 asymptomatic children enrolled in the study, 47 (21%) were colonized with C. difficile including 9/59 (15.5%) with cancer, 30/92 (32.6%) with CF, and 8/74 (10.8%) with IBD. An additional 41 children with symptomatic CDI were enrolled. When symptomatic and colonized children were compared, neither EIA positivity (44% vs 26%, P = 0.07) nor CCNA positivity (49% vs 45%, P = 0.70) differed significantly or were able to predict disease severity in the symptomatic cohort.

CONCLUSIONS

Use of a multistep testing algorithm with NAAT followed by EIA failed to differentiate symptomatic CDI from asymptomatic colonization in our pediatric cohort. As multistep algorithms are moved into clinical care, the pediatric provider will need to be aware of their limitations.

A history of Clostridioides difficile infection portends infection recurrence and worse outcomes after stoma reversal

BACKGROUND

Clostridioides difficile infection is reported to occur after 2.2% of colorectal operations and is associated with longer length of hospital stay, greater overall healthcare cost, and significant morbidity and mortality. The incidence of Clostridioides difficile infection is greatest after elective stoma reversal. The purpose of this study was to evaluate the effect of prior Clostridioides difficile infection on patients undergoing stoma reversal. We hypothesized that patients with a history of Clostridioides difficile infection who underwent stoma reversal will be at an increased risk of postoperative Clostridioides difficile infection compared with patients without a history of Clostridioides difficile infection.

METHODS

This was an observational cohort study of patients undergoing elective stoma reversal surgery by colorectal surgeons at a single academic institution during a 10-year period. A prospectively maintained institutional database was queried to identify 454 patients who underwent stoma reversal surgery between January 1, 2007 and December 31, 2017. The primary outcomes were Clostridioides difficile infection after stoma reversal and time to Clostridioides difficile infection after bowel refunctionalization. Secondary outcomes included postoperative complications, length of hospital stay, discharge destination, and 30-day readmission rate. Univariate and multivariable logistic regression analyses were conducted to identify factors associated with Clostridioides difficile infection after stoma reversal.

RESULTS

A total of 445 patients were identified who underwent elective stoma reversal, 42 of whom had a history of Clostridioides difficile infection before the stoma reversal. There were no significant differences in patient age, number of days diverted, or use of perioperative antibiotics between patients with and without a history of Clostridioides difficile infection. The incidence of postreversal Clostridioides difficile infection was 23.4% in patients with a history of Clostridioides difficile infection compared with 9.6% in patients with no Clostridioides difficile infection history (P = .004); however, time to Clostridioides difficile infection after reversal did not differ. History of Clostridioides difficile infection was also associated with greater risk of postoperative complications (26.2% vs 9.4%, P < .01), increased length of stay (3 vs 5 days postoperatively, P < .01), increased likelihood of discharge to a skilled-care facility (11.9% vs 6.2%, P < .01), and readmission (13.7 vs 31.0%, P < .01) within 30 days. In a multivariable logistic regression model, history of Clostridioides difficile infection, increased length of hospital stay, and discharge to a skilled facility were associated with increased risk of Clostridioides difficile infection after reversal, while proton pump inhibitors use was associated with decreased risk of Clostridioides difficile infection.

CONCLUSION

Patients with a prior history of Clostridioides difficile infection who underwent stoma reversal exhibited higher rates of postoperative Clostridioides difficile infection and were at greater risk of postoperative complications, discharge to a skilled facility, and 30-day readmission. Furthermore, research into interventions aimed at improving outcomes in this unique, high-risk population is needed.

Clostridioides difficile laboratory diagnostic techniques: a comparative approach of rapid and molecular methods

Clostridioides difficile infection is a public health problem because of it is easily spread; with harmful consequences, it is essential to reduce hospital costs and prevent its dissemination by having a precise diagnosis. The gold standard for its diagnosis is polymerase chain reaction (PCR); however, the technique is not available for all laboratories due to the high cost. New approaches using non-molecular tests to detect C. difficile and toxin A/B production has been proposed to improve cost benefits. The objective of this study is to compare molecular methods (PCR) and rapid methods (immunochromatographic test and enzymatic immunoassay). A series of tests comprising these diagnostic techniques was performed with 50 patients with a clinical diagnosis for Clostridioides difficile on GeneXpert® devices test; a calculation of the sensitivity was executed, followed by a comparison of the efficiency of all techniques. Greater sensitivity was observed in the PCR-based methods (BD MAX™ and BioFire FilmArray®) and the GDH-based assays (RIDASCREEN® and Alere Techlab®). The proposed algorithm represents minor monetary disadvantages but a significant temporal optimization of 10%. Future studies concerning both positive and negative results could be advantageous because of the possibility of calculating more method concordance indexes, such as the specificity and Kappa index, in addition to being able to indicate a monetary profit if the proposed algorithm was applied due to the nonproceeding PCR cases.

A critical review: Recent advances in "digital" biomolecule detection with single copy sensitivity

Detection of a single biomolecule, ranging from nucleic acids, proteins, viruses to bacteria, is of paramount importance in various fields including biology, environment, food and agriculture industry, public health, and medicine. With the understanding of the biological functions of these biomolecules (or bioparticles) and their impacts on public health, environmental pollution, and food safety, advanced detection techniques are unprecedentedly demanded for their early and/or sensitive detection. In this critical review, a series of elegant research about digital detection of biomolecules with potential single copy sensitivity is reviewed and summarized with the focus on the design principle and the innovation of how to accomplish the “digital” detection concept. Starting with a brief introduction on the importance of digital detection, recent advances in “digital” biomolecule detection with single copy sensitivity are grouped and discussed based on the difference of signal reporting systems, including surrogate signal development for “digital” detection, direct visualization for “digital” detection, and nucleic acid amplification enabled “digital” detection. Interdisciplinary combination and integration of different cutting-edge techniques are also discussed with details. The review is closed with the conclusion and future trends.

Frequency of toxin genes and antibiotic resistance pattern of Clostridioides difficile isolates in diarrheal samples among hospitalized patients in Hamadan, Iran

AIM

This study was designed to investigate the prevalence of Clostridioides difficile, its toxin-producing genes, and antibiotic resistance patterns in diarrheal samples from hospitalized patients in Hamadan, Iran.

BACKGROUND

Today, concerns over Clostridioides difficile infection (CDI) have significantly increased due to reduced susceptibility to antibiotics used for CDI treatment. Toxins produced by C. difficile strains are associated with disease severity and outcome.

METHODS

In this cross-sectional study, a total of 130 diarrheal samples of patients admitted to different wards of three hospitals in Hamadan from November 2018 to September 2019 were collected. C. difficile isolates were identified by culture on CCFA and PCR (Polymerase chain reaction). The presence of toxin-encoding genes (tcdA and tcdB) and binary toxin genes (cdtA and cdtB) was analyzed by PCR. Resistance of the isolates to metronidazole, vancomycin and clindamycin antibiotics was determined using agar dilution method.

RESULTS

Out of 130 diarrheal samples from hospitalized patients, 16 (12.3%) C. difficile isolates were obtained. PCR results were positive for two toxin-producing genes, tcdA and tcdB, in all (100%) C. difficile isolates, and the binary toxin genes cdtA and cdtB were detected in 6 (37.5%) and 8 (50%) isolates, respectively. The results of antibiotic susceptibility testing showed resistance to metronidazole, vancomycin, and clindamycin in 3 (18.7%), 3 (18.7%), and 2 (12.5%) isolates, respectively, and all isolates were resistant to rifampicin.

CONCLUSION

The results of this study showed toxigenic C. difficile with tcdA ⁺ /tcdB ⁺ profile is a major cause of nosocomial diarrhea in Hamadan, and clinical laboratories should routinely perform C. difficile diagnostic testing on diarrheal specimens of hospitalized patients. Resistance to conventional antibiotic therapy against C. difficile should be considered as a warning to prevent irrational administration of antibiotics.

Critical Care Management of the Patient with Clostridioides difficile

OBJECTIVES

To review published clinical evidence on management of Clostridioides difficile infection in critically ill patients.

DATA SOURCES

We obtained relevant studies from a PubMed literature review and bibliographies of reviewed articles.

STUDY SELECTION

We selected English-language studies addressing aspects of C. difficile infection relevant to critical care clinicians including epidemiology, risk factors, diagnosis, treatment, and prevention, with a focus on high-quality clinical evidence.

DATA EXTRACTION

We reviewed potentially relevant studies and abstracted information on study design, methods, patient selection, and results of relevant studies. This is a synthetic (i.e., not systematic) review.

DATA SYNTHESIS

C. difficile infection is the most common healthcare-associated infection in the United States. Antibiotics are the most significant C. difficile infection risk factor, and among antibiotics, cephalosporins, clindamycin, carbapenems, fluoroquinolones, and piperacillin-tazobactam confer the highest risk. Age, diabetes mellitus, inflammatory bowel disease, and end-stage renal disease are risk factors for C. difficile infection development and mortality. C. difficile infection diagnosis is based on testing appropriately selected patients with diarrhea or on clinical suspicion for patients with ileus. Patients with fulminant disease (C. difficile infection with hypotension, shock, ileus, or megacolon) should be treated with oral vancomycin and IV metronidazole, as well as rectal vancomycin in case of ileus. Patients who do not respond to initial therapy should be considered for fecal microbiota transplant or surgery. Proper infection prevention practices decrease C. difficile infection risk.

CONCLUSIONS

Strong clinical evidence supports limiting antibiotics when possible to decrease C. difficile infection risk. For patients with fulminant C. difficile infection, oral vancomycin reduces mortality, and adjunctive therapies (including IV metronidazole) and interventions (including fecal microbiota transplant) may benefit select patients. Several important questions remain regarding fulminant C. difficile infection management, including which patients benefit from fecal microbiota transplant or surgery.

Comparison of two commercial and one in-house real-time PCR assays for the diagnosis of bacterial gastroenteritis

Introduction

The aim of the study was a comparative evaluation of in-house real-time PCR and commercial real-time PCR (Fast Track Diagnostics (FTD), ampliCube/Mikrogen) targeting enteropathogenic bacteria from stool in preparation of Regulation (EU) 2017/746 on in vitro diagnostic medical devices.

Methods

Both 241 stool samples from patients and 100 samples from German laboratory control schemes (“Ringversuche”) were used to comparatively assess in-house real-time PCR, the FTD bacterial gastroenteritis kit, and the ampliCube gastrointestinal bacterial panels 1&2 either with the in-house PCRs as gold standard and as a test comparison without gold standard applying latent class analysis. Sensitivity, specificity, intra- and inter-assay variation and Cohen’s kappa were assessed.

Results

In comparison with the gold standard, sensitivity was 75–100% for strongly positive samples, 20–100% for weakly positive samples, and specificity ranged from 96 to 100%. Latent class analysis suggested that sensitivity ranges from 81.2 to 100% and specificity from 58.5 to 100%. Cohen’s kappa varied between moderate and nearly perfect agreement, intra- and inter-assay variation was 1–3 to 1–4 Ct values.

Conclusion

Acceptable agreement and performance characteristics suggested replaceability of the in-house PCR assays by the commercial approaches.

Advantages of Lateral Flow Assays Based on Fluorescent Submicrospheres and Quantum Dots for Clostridium difficile Toxin B Detection

Clostridium difficile colitis is caused by a cytotoxin produced by the anaerobic bacteria C. difficile in the epithelial cells of the large intestine, particularly C. difficile toxin B (TcdB). However, the sensitivity of currently utilized C. difficile endotoxin determination methods has been called into question, and, therefore, more accurate and convenient detection methods are needed. Our study is the first to systematically compare fluorescent submicrosphere-based and quantum-dot nanobead-based lateral fluidity measurement methods (FMs-LFA and QDNBs-LFA) with toxin B quantification in fecal samples via sandwich analysis. The limits of detection (LOD) of FMs-LFA and QDNBs-LFA in the fecal samples were 0.483 and 0.297 ng/mL, respectively. TcdB analyses of the fecal samples indicated that the results of QDNBs-LFA and FMs-LFA were consistent with those of a commercial enzyme-linked immunosorbent assay (ELISA) test kit. The sensitivity of QDNBs-LFA was highly correlated with clinical diagnoses. Therefore, quantum dot nanobeads (QDNBs) are deemed highly suitable for lateral fluidity analyses, which would facilitate the implementation of portable and rapid on-the-spot applications, such as food hygiene and safety tests and onsite medical testing.

A 2-step algorithm combining glutamate dehydrogenase and nucleic acid amplification tests for the detection of Clostridioides difficile in stool specimens

The optimized diagnosis algorithm of Clostridioides difficile infection (CDI) is worldwide concerns. The purpose of this study was to assess the toxigenic C. difficile test performance and propose an optimal laboratory workflow for the diagnosis of CDI in mild virulent epidemic areas. Diarrhea samples collected from patients were analyzed by glutamate dehydrogenase (GDH), toxin AB (CDAB), and nucleic acid amplification test (NAAT). We assessed the performance of GDH, the GDH-CDAB algorithm, and the GDH-NAAT algorithm using toxigenic culture (TC) as a reference method. In this study, 186 diarrhea samples were collected. The numbers of TC-positive and TC-negative samples were 39 and 147, respectively. The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and kappa of the GDH assay were 100%, 80.3%, 57.4%, 100%, and 0.63; of the GDH-CDAB algorithm were 48.7%, 97.3%, 82.6%, 87.7%, and 0.54; and of the GDH-NAAT algorithm were 74.4%, 100%, 100%, 93.6%, and 0.82, respectively. The GDH-NAAT algorithm has great concordance with TC in detecting toxigenic C. difficile (kappa = 0.82), while the sensitivity of the GDH-CDAB algorithm was too low to meet the demand of CDI diagnosis clinically. GDH-NAAT algorithm is recommended for the detection of toxigenic C. difficile with high specificity, increased sensitivity, and cost-effective.

Immunochromatographic test and ELISA for the detection of glutamate dehydrogenase (GDH) and A/B toxins as an alternative for the diagnosis of Clostridioides (Clostridium) difficile-associated diarrhea in foals and neonatal piglets

Considering the lack of studies evaluating the performance of commercially available methods for diagnosis of Clostridioides (Clostridium) difficile infection (CDI) in animals, the present study aimed to assess an immunochromatographic test for detection of glutamate dehydrogenase (GDH) and A/B toxins of C. difficile, also evaluated by an ELISA kit, in foals and neonatal piglets. Intestinal contents of 47 piglets and feces of 35 foals were tested to GDH antigen and A/B toxins in a lateral flow method (Ecodiagnostica, Brazil). Also, these samples were submitted to A/B toxin detection by an ELISA kit (C. difficile Tox A/B II, Techlab Inc., USA), using the toxigenic culture (TC) as the reference method. The GDH component of the lateral flow test showed sensitivity and negative predictive value (NPV) of 100% and a high specificity in samples of piglets (82.61%) and foals (100%). Detection of A/B toxins using the lateral flow test and the ELISA resulted in a specificity of 100% in samples of both species. On the other hand, the sensibility ranged from 54.2 to 90% for the ELISA and from 12.5 to 60% for the lateral flow test for piglets' and foals' samples, respectively. In conclusion, the present work suggests that the lateral flow test for GDH detection could be a useful method for diagnosing CDI in these species. On the other hand, the low sensitivity of the lateral flow test for A/B toxins might compromise its utility in piglets.

Rapid and fully-automated detection of Clostridium difficile Toxin B via magnetic-particle-based chemiluminescent immunoassay

Clostridium difficile colitis is caused by a cytotoxin produced by the anaerobic bacteria C. difficile on the epithelial cells of the large intestine, particularly C. difficile toxin B (Tcd B). Current C. difficile toxin assays have proven to be insensitive and have thus been ruled out from diagnostic purposes. Therefore, Tcd B detection via sandwich-type chemiluminescent immunoassay was proposed as a straightforward approach with potential diagnostic applicability. Here, two high-affinity anti-Tcd B monoclonal antibodies were successfully identified and implemented in a fully-automated magnetic-particle-based chemiluminescent immunoassay (CLEIA). In this test, toxin B was sandwiched between the anti-toxin B antibody-coated magnetic particles and alkaline phosphate-labeled anti-toxin B antibodies. Compared with traditional techniques, the proposed immunoassay demonstrated high sensitivity for toxin B identification and was further optimized to achieve a linear response ranging from 0.12 to 150 ng/mL with a limit of detection (LOD) of 0.47 ng/mL. Importantly, the entire process could be completed in less than 30 minutes. The proposed assay was used to detect toxin B in 104 randomly-selected human stool samples and delivered similar results to those of a commercial ELISA kit, highlighting its great potential for rapid and efficient toxin B determination in human stool specimens.

The Effect of Clostridioides difficile Diagnostic Stewardship Interventions on the Diagnosis of Hospital-Onset Clostridioides difficile Infections

BACKGROUND

Public reporting of Clostridioides difficile infection (CDI) using laboratory-identified events has led some institutions to revert from molecular-based tests to less sensitive testing modalities. At one academic medical center, researchers chose to use nucleic acid amplification test alone in CDI diagnosis with institutional protocols aimed at diagnostic stewardship.

METHODS

A single-center, quasi-experimental study was conducted to introduce and analyze the effects of various diagnostic stewardship interventions. In April 2017 an order report was created to inform providers of patients' recent bowel movements, laxative use, and prior Clostridioides difficile (CD) testing (Intervention 1). In November 2017 nursing staff were empowered to not send nondiarrheal stools for testing (Intervention 2). In February 2019, an interruptive alert was implemented to prevent testing that was not indicated (Intervention 3). CD testing rates and healthcare facility-onset CDI (HO-CDI) rates were compared before and after the interventions using one-way analysis of variance (ANOVA).

RESULTS

At baseline, testing for CD after 3 days of admission was performed at mean ± standard deviation of 15.9 ± 1.7 tests/1,000 patient-days. After Intervention 1, it decreased to 12.1 ± 1.1 tests. This further decreased to 10.6 ± 0.8 after Intervention 2 and to 8.1 ± 0.1 after Intervention 3 (p < 0.001). HO-CDI cases per 10,000 patient-days declined from 12.7 ± 1.4 cases at baseline to 10.7 ± 1.2 after Intervention 1, to 8.7 ± 2.4 after Intervention 2, and to 5.8 ± 0.2 after Intervention 3 (p = 0.03).

CONCLUSION

A multidisciplinary approach optimizing electronic health record support tools and leveraging nursing education can reduce both testing and HO-CDI rates while using the most sensitive testing modality.

Sequential introduction of a multistep testing algorithm and nucleic acid amplification testing leading to an increase in Clostridioides difficile detection and a trend toward increased strain diversity

BACKGROUND

Most clinical microbiology laboratories have replaced toxin immunoassay (EIA) alone with multistep testing (MST) protocols or nucleic acid amplification testing (NAAT) alone for the detection of C. difficile.

OBJECTIVE

Study the effect of changing testing strategies on C. difficile detection and strain diversity.

DESIGN

Retrospective study.

SETTING

A Veterans' Affairs hospital.

METHODS

Initially, toxin EIA testing was replaced by an MST approach utilizing a glutamate dehydrogenase (GDH) and toxin EIA followed by tcdB NAAT for discordant results. After 18 months, MST was replaced by a NAAT-only strategy. Available patient stool specimens were cultured for C. difficile. Restriction endonuclease analysis (REA) strain typing and quantitative in vitro toxin testing were performed on recovered isolates.

RESULTS

Before MST (toxin EIA), 79 of 708 specimens (11%) were positive, and after MST (MST-A), 121 of 517 specimens (23%) were positive (P < .0001). Prior to NAAT-only testing (MST-B), 80 of the 490 specimens (16%) were positive by MST, and after NAAT-only testing was implemented, 67 of the 368 specimens (18%) were positive (P = nonsignificant). After replacing toxin EIA testing, REA strain group diversity increased (8, 13, 13, and 10 REA groups in the toxin EIA, MST-A, MST-B, and NAAT-only periods, respectively) and in vitro toxin concentration decreased. The average log10 toxin concentration of the isolates were 2.08, 1.88, 1.20 and 1.55 ng/mL for the same periods, respectively.

CONCLUSIONS

MST and NAAT had similar detection rates for C. difficile. Compared to toxin testing alone, they detected increased diversity of C. difficile strains, many of which were low toxin producing.

The impact of changing reflexive to clinician-ordered Clostridioides difficile polymerase chain reaction (PCR) testing for indeterminate cases: Cost savings without associated adverse events

OBJECTIVE

To evaluate changing Clostridioides difficile infection (CDI) testing among inpatients with indeterminate enzyme immunoassay (EIA) results (antigen+/toxin-) from reflexive polymerase chain reaction (PCR) testing to clinician-ordered PCR testing.

DESIGN

Multicenter, before-and-after, quasi-experimental study.

SETTING

Four large urban tertiary-care hospitals.

METHODS

We evaluated two 6-month periods before and after an intervention. The primary study outcome was the change in the number of CDI diagnoses between periods. Secondary outcomes included the number of PCR tests performed, adverse events, and healthcare cost savings.

RESULTS

In total, 500 EIA-indeterminate C. difficile test results were evaluated: 281 before the intervention and 219 thereafter. CDI was diagnosed by PCR among EIA-indeterminate cases in 182 in the preintervention period versus 94 patients in the postintervention period (48% reduction; P < .01). PCR testing was performed in 99.6% of indeterminate cases (280 of 281; 1 not performed due to an inhibitor) in the preintervention period versus 66% (144 of 219) in the postintervention period (34% reduction; P < .01). We observed no differences between study periods in 30-day all-cause (P = .96), GI-related (P = .93), or C. difficile (P = .47) readmissions, nor in 30-day C. difficile infections (P > .99). No patient without a PCR test in the postintervention period and not treated was later diagnosed with CDI. Each reflexive PCR test not performed led to a cost savings of $4,498 per patient.

CONCLUSIONS

Applying diagnostic stewardship to C. difficile PCR testing in the inpatient setting led to significant reductions in both testing and cases. Changing the C. difficile PCR testing algorithm for EIA-indeterminate cases from reflexive to clinician-required ordering resulted in valuable cost savings without associated adverse events.

The reference method influence on the sensitivity of the Clostridium difficile enzyme immunoassays: A meta analysis

The use of enzyme immunoassays to screen for toxins A and B produced by Clostridium difficile is a common procedure in algorithms designed for its detection. Moreover, the absence of a unique test capable of providing reliable results at low cost motivates a great discussion about which algorithm is the best. Thus, several studies have evaluated the performance of these enzyme immunoassays. However, all fail to provide sufficient explanations for the different behaviours observed in different studies that evaluate the same index test against a common reference method. Our main goal was to find out which factors affect the sensitivity of these assays, since the specificity is very close to 1. In this research, we verified that sensitivity increases with the prevalence rate and with the proportion of reported cases of onset diarrhea. Therefore, its use is advisable for high prevalence rates (e.g. in an epidemic setting). As far as reference methods are concerned, nucleic acid amplification tests can be used as a reference method, with a performance similar to the well-accepted toxigenic culture. The method chosen for toxigenicity screening in a toxigenic culture also seems to affect the evaluation performance of tests and should be better studied in the future.

Recommendations for the diagnosis and treatment of Clostridioides difficile infection: An official clinical practice guideline of the Spanish Society of Chemotherapy (SEQ), Spanish Society of Internal Medicine (SEMI) and the working group of Postoperative Infection of the Spanish Society of Anesthesia and Reanimation (SEDAR)

This document gathers the opinion of a multidisciplinary forum of experts on different aspects of the diagnosis and treatment of Clostridioides difficile infection (CDI) in Spain. It has been structured around a series of questions that the attendees considered relevant and in which a consensus opinion was reached. The main messages were as follows: CDI should be suspected in patients older than 2 years of age in the presence of diarrhea, paralytic ileus and unexplained leukocytosis, even in the absence of classical risk factors. With a few exceptions, a single stool sample is sufficient for diagnosis, which can be sent to the laboratory with or without transportation media for enteropathogenic bacteria. In the absence of diarrhoea, rectal swabs may be valid. The microbiology laboratory should include C. difficile among the pathogens routinely searched in patients with diarrhoea. Laboratory tests in different order and sequence schemes include GDH detection, presence of toxins, molecular tests and toxigenic culture. Immediate determination of sensitivity to drugs such as vancomycin, metronidazole or fidaxomycin is not required. The evolution of toxin persistence is not a suitable test for follow up. Laboratory diagnosis of CDI should be rapid and results reported and interpreted to clinicians immediately. In addition to the basic support of all diarrheic episodes, CDI treatment requires the suppression of antiperistaltic agents, proton pump inhibitors and antibiotics, where possible. Oral vancomycin and fidaxomycin are the antibacterials of choice in treatment, intravenous metronidazole being restricted for patients in whom the presence of the above drugs in the intestinal lumen cannot be assured. Fecal material transplantation is the treatment of choice for patients with multiple recurrences but uncertainties persist regarding its standardization and safety. Bezlotoxumab is a monoclonal antibody to C. difficile toxin B that should be administered to patients at high risk of recurrence. Surgery is becoming less and less necessary and prevention with vaccines is under research. Probiotics have so far not been shown to be therapeutically or preventively effective. The therapeutic strategy should be based, rather than on the number of episodes, on the severity of the episodes and on their potential to recur. Some data point to the efficacy of oral vancomycin prophylaxis in patients who reccur CDI when systemic antibiotics are required again.

Clostridium Difficile Infection in Inflammatory Bowel Disease Patients

BACKGROUND

The rising incidence of Clostridium difficile infection (CDI) in the general population has been recognized by health care organizations worldwide. The emergence of hypervirulent strains has made CDI more challenging to understand and treat. Inflammatory bowel disease (IBD) patients are at higher risk of infection, including CDI.

OBJECTIVE

A diagnostic approach for recurrent CDI has yet to be validated, particularly for IBD patients. Enzyme immunoassay (EIA) for toxins A and B, as well as glutamate dehydrogenase EIA, are both rapid testing options for the identification of CDI. Without a high index of suspicion, it is challenging to initially differentiate CDI from an IBD flare based on clinical evaluation alone.

METHODS

Here, we provide an up-to-date review on CDI in IBD patients. When caring for an IBD patient with suspected CDI, it is appropriate to empirically treat the presumed infection while awaiting further test results.

RESULTS

Treatment with vancomycin or fidaxomicin, but not oral metronidazole, has been advocated by an expert review from the clinical practice update committee of the American Gastroenterology Association. Recurrent CDI is more common in IBD patients compared to non-IBD patients (32% versus 24%), thus more aggressive treatment is recommended for IBD patients along with early consideration of fecal microbiota transplant.

CONCLUSION

Although the use of infliximab during CDI has been debated, clinical experience exists supporting its use in an IBD flare, even with active CDI when needed.

In Vitro Selection of a DNA Aptamer Targeting Degraded Protein Fragments for Biosensing

Protein biomarkers often exist as degradation fragments in biological samples, and affinity agents derived using a purified protein may not recognize them, limiting their value for clinical diagnosis. Herein, we present a method to overcome this issue, by selecting aptamers against a degraded form of the toxin B protein, which is a marker for diagnosing toxigenic Clostridium difficile infections. This approach has led to isolation of a DNA aptamer that recognizes degraded toxin B, fresh toxin B, and toxin B spiked into human stool samples. DNA aptamers selected using intact recombinant toxin B failed to recognize degraded toxin B, which is the form present in stored stool samples. Using this new aptamer, we produced a simple paper-based analytical device for colorimetric detection of toxin B in stool samples, or in the NAP1 strain of Clostridium difficile. The combined aptamer-selection and paper-sensing strategy can expand the practical utility of DNA aptamers in clinical diagnosis.

Guidelines for Clostridium difficile infection in adults

Clostridium difficile infection (CDI) has become a serious medical and epidemiological problem, especially in well developed countries. There has been evident increase in incidence and severity of CDI. Prevention, proper diagnosis and effective treatment are necessary to reduce the risk for the patients, deplete the spreading of infection and diminish the probability of recurrent infection. Antibiotics are the fundamental treatment of CDI. In patients who had recurrent CDI fecal microbiota transplantation seems to be promising and efficient strategy. These guidelines systematize existing data and include recent changes implemented in the management of CDI.

The Role of Diagnostic Stewardship in Clostridioides difficile Testing: Challenges and Opportunities

PURPOSE OF REVIEW

Accurate and timely diagnosis of Clostridioides difficile infection (CDI) is imperative to prevent C. difficile transmission and reduce morbidity and mortality due to CDI, but CDI laboratory diagnostics are complex. The purpose of this article is to review the role of laboratory tests in the diagnosis of CDI, and the role of diagnostic stewardship in optimization of C. difficile testing.

RECENT FINDINGS

Results from C. difficile diagnostic tests should be interpreted with an understanding of the strengths and limitations inherent in each testing approach. Use of highly sensitive molecular diagnostic tests without accounting for clinical signs and symptoms may lead to over-diagnosis of CDI and increased facility CDI rates. Current guidelines recommend a two-step, algorithmic approach for testing. Diagnostic stewardship interventions, such as education, order sets, order search menus, reflex orders, hard and soft stop alerts, electronic references, feedback and benchmarking, decision algorithms, and predictive analytics may help improve use of C. difficile laboratory tests and CDI diagnosis. The diagnostic stewardship approaches with the highest reported success rates include computerized clinical decision support (CCDS) interventions, face-to-face feedback, and real-time evaluations.

SUMMARY

CDI is a clinical diagnosis supported by laboratory findings. Together, clinical evaluation combined with diagnostic stewardship can optimize the accurate diagnosis of CDI.

Laboratory Tests for the Diagnosis of Clostridium difficile

Clostridium (reclassified as " Clostridioides ") difficile is an anaerobic, gram-positive bacterium that causes significant disease through elaboration of two potent toxins in patients whose normal gut microbiota has been altered through antimicrobial or chemotherapeutic agents (dysbiosis). The optimum method of laboratory diagnosis is still somewhat controversial. Recent practice guidelines published by professional societies recommend a two-step approach beginning with a test for glutamate dehydrogenase (GDH), followed by a toxin test and/or a nucleic acid test. Alternatively, in institutions where established clinical algorithms guide testing, a nucleic acid test alone is acceptable. Nucleic acid tests are the methods of choice in approximately 50% of laboratories in the United States. These tests are considered as the most sensitive methods for detection of C. difficile in stool and are the least specific. Because of the lower specificity with nucleic acid tests, some clinicians believe that toxin enzyme immunoassays are better predictors of disease, despite their known poor performance in certain patient populations. This review will discuss the advantages and disadvantages of the currently available test methods for the diagnosis of C. difficile with a brief mention of some novel assays that are currently in clinical trials.

Rapid diagnostic tests for infectious diseases in the emergency department

Background

Rapid diagnostic tests (RDTs) for infectious diseases, with a turnaround time of less than 2 hours, are promising tools that could improve patient care, antimicrobial stewardship and infection prevention in the emergency department (ED) setting. Numerous RDTs have been developed, although not necessarily for the ED environment. Their successful implementation in the ED relies on their performance and impact on patient management.

Objectives

The aim of this narrative review was to provide an overview of currently available RDTs for infectious diseases in the ED.

Sources

PubMed was searched through August 2019 for available studies on RDTs for infectious diseases. Inclusion criteria included: commercial tests approved by the US Food and Drug Administration (FDA) or Conformité Européenne (CE) in vitro diagnostic devices with data on clinical samples, ability to run on fully automated systems and result delivery within 2 hours.

Content

A nonexhaustive list of representative commercially available FDA- or CE-approved assays was categorized by clinical syndrome: pharyngitis and upper respiratory tract infection, lower respiratory tract infection, gastrointestinal infection, meningitis and encephalitis, fever in returning travellers and sexually transmitted infection, including HIV. The performance of tests was described on the basis of clinical validation studies. Further, their impact on clinical outcomes and anti-infective use was discussed with a focus on ED-based studies.

Implications

Clinicians should be familiar with the distinctive features of each RDT and individual performance characteristics for each target. Their integration into ED work flow should be preplanned considering local constraints of given settings. Additional clinical studies are needed to further evaluate their clinical effectiveness and cost-effectiveness.

Comparative Study of Clostridium difficile Clinical Detection Methods in Patients with Diarrhoea

Objectives

The aim of this study was to evaluate the clinical application of three methods for detecting Clostridium difficile in fecal samples.

Methods

One hundred and fifty fecal specimens were collected and tested for C. difficile using three methods: (1) the toxigenic culture (TC); (2) the VIDAS enzyme immunoassay (EIA): the VIDAS glutamate dehydrogenase (GDH) assay and toxin A/B assay were used to detect GDH antigen and A/B toxin; and (3) the GeneXpert PCR assay. The toxigenic culture was used as a reference to evaluate the performance of the VIDAS EIA and the GeneXpert PCR assay.

Results

Of 150 specimens, 26 carried both A and B toxin genes, and none of the samples were positive for the binary toxin gene. Toxin-producing C. difficile using three methods: (1) the toxigenic culture (TC); (2) the VIDAS enzyme immunoassay (EIA): the VIDAS glutamate dehydrogenase (GDH) assay and toxin A/B assay were used to detect GDH antigen and A/B toxin; and (3) the GeneXpert PCR assay. The toxigenic culture was used as a reference to evaluate the performance of the VIDAS EIA and the GeneXpert PCR assay. C. difficile using three methods: (1) the toxigenic culture (TC); (2) the VIDAS enzyme immunoassay (EIA): the VIDAS glutamate dehydrogenase (GDH) assay and toxin A/B assay were used to detect GDH antigen and A/B toxin; and (3) the GeneXpert PCR assay. The toxigenic culture was used as a reference to evaluate the performance of the VIDAS EIA and the GeneXpert PCR assay.

Conclusion

The VIDAS GDH assay is useful for initial screening of C. difficile using three methods: (1) the toxigenic culture (TC); (2) the VIDAS enzyme immunoassay (EIA): the VIDAS glutamate dehydrogenase (GDH) assay and toxin A/B assay were used to detect GDH antigen and A/B toxin; and (3) the GeneXpert PCR assay. The toxigenic culture was used as a reference to evaluate the performance of the VIDAS EIA and the GeneXpert PCR assay.

Clostridioides difficile incidence related to in-hospital cephalosporin use: a tale of two highly comparable hospitals

Background

Antibiotic treatment is a well-known risk factor for healthcare facility-associated Clostridioides (Clostridium) difficile infection (HCF-CDI). Antibiotic stewardship programmes (ASPs) targeting high-risk antibiotics have been shown to decrease HCF-CDI incidence. HCF-CDI incidence is high in Nordic countries despite relatively low antibiotic use in hospital.

Objectives

To determine if HCF-CDI incidence was modified by a hospital ASP that restricted cephalosporin use.

Methods

The effects of an ASP on HCF-CDI incidence were evaluated in a two-centre setting using a retrospective design. We exploited a strategy of both individual case ascertainment based on chart reviews and aggregated data from the hospitals. Cases were attributed to the antibiotics given prior to disease onset, in proportion to the number of DDDs used. Three periods were studied: 2007 (before the ASP), 2012 and 2015.

Results

At the ASP hospital, cephalosporin use decreased by 87% and the number of HCF-CDI/1000 hospital admissions decreased significantly from 2.25 (2007) to 1.16 (2015) (P = 0.0014). The corresponding results at the non-ASP hospital showed a non-significant increase from 2.09 to 2.38. A high number of cases could be attributed to cephalosporins at both hospitals. The increased use of other broad-spectrum antibiotics, e.g. piperacillin/tazobactam, at the ASP hospital was not associated with offsetting increases in attributable HCF-CDI cases.

Conclusions

Decreased use of cephalosporins is an effective strategy to decrease HCF-CDI incidence over time in a setting with high incidence and low antibiotic use.

Detection of toxigenic Clostridium difficile colonization in patients admitted to the hospital for chemotherapy or haematopoietic cell transplantation

Increasing evidence suggests that asymptomatic carriers are an important source of healthcare-associated Clostridium difficile infection. However, it is not known which test for the detection of C. difficile colonization is most sensitive in patients with haematological malignancies. We performed a prospective cohort study of 101 patients with haematological malignancies who had been admitted to the hospital for scheduled chemotherapy or haematopoietic cell transplantation. Each patient provided a formed stool sample. We compared the performance of five different commercially available assays, using toxigenic culture as the reference method. The prevalence of toxigenic C. difficile colonization as determined by toxigenic culture was 14/101 (14 %). The Cepheid Xpert PCR C. difficile/Epi was the most sensitive test for the detection of toxigenic C. difficile colonization, with 93 % sensitivity and 99 % negative predictive value. Our findings suggest that the Xpert PCR C. difficile/Epi could be used to rule out toxigenic C. difficile colonization in this population.

South African Society of Clinical Microbiology Clostridioides difficile infection diagnosis, management and infection prevention and control guideline

Clostridioides difficile infection (CDI) is a problem in both developed and developing countries and is a common hospital-acquired infection. This guideline provides evidence-based practical recommendations for South Africa and other developing countries. The scope of the guideline includes CDI diagnostic approaches; adult, paediatric and special populations treatment options; and surveillance and infection prevention and control recommendations.

Analysis of Routine and Integrative Data from Clostridioides difficile Infection Diagnosis and the Consequent Observations

Background:

Clostridioides difficileInfection (CDI) is an acute disease that needs a fast proper treatment. Unfortunately, the diagnosis, and above all the understanding of the results, remain arduous.

Objective:

This study analyzed routine and integrative results of all fecal samples from patients over time. Our aim was to understand the dynamics of CDI infection and the meaning of “difficult to interpret” results, to make physicians better understand the various tools they can use.

Methods:

We evaluated routine results obtained from 815 diarrheal stools with Enzyme Immunoassay (EIA) that detectsC. difficileGlutamate Dehydrogenase (GDH) antigen and toxin B. We also reanalyzed a part of samples using integrative tests: a Real-time polymerase chain reaction (RT-PCR) forC. difficiletoxin B gene (tcdB) and the automated immunoassay VIDASC. difficilesystem for GDH and toxins A/B.

Results:

EIA GDH positivity increased through multiple testing over time, with aPvalue <0.001, depicting a sort of bacterial growth curve. Eighty-five percent of GDH positive/toxin B negative,i.e., discrepant, samples PCR weretcdBpositive, 61.5% of discrepanttcdBpositive samples were VIDAS toxins A/B positive, and 44.4% of GDH EIA negative stools were VIDAS GDH positive.

Conclusion:

The results confirmed the low sensitivity of the EIA system forC. difficileGDH and toxins, questioned the use of the latter for concluding any CDI diagnostic algorithm, and led us to indicate the algorithm beginning with tcdB molecular research, and continuing in positive cases with VIDAS CD GDH method, as the most effective for CDI.

The diagnostic performance and accuracy of 3 molecular assays for the detection of Clostridium difficile in stool samples, compared with the Xpert® C. difficile assay

This research compares the performance and diagnostic accuracy of three molecular tests for the detection of Clostridium difficile in stool samples, with the Xpert® C. difficile assay. Fifty-nine positive and twenty-five stool negative samples were analyzed by the BDmax™ Cdiff, the Simplexa C. difficile Direct, and the GenomEra™ C. difficile, and compared with the Xpert® C. difficile routinely used in our laboratory. The highest sensitivity was 94.9% for the BDmax™ Cdiff, followed by GenomEra™ C. difficile with 93.2%, and Simplexa™ C. difficile Direct with 89.8%. The specificities of all assays were 100%. GenomEra™ C. difficile had the highest retesting rate (12%). Simplexa™ C. difficile Direct benefits from both short hands-on time and total-turnaround time and 0% retesting. The differences in performance and accuracy between these three molecular assays are insignificant and all may be used as part of the routine algorithm for detection of C. difficile.

Management of Clostridioides (formerly Clostridium) difficile infection (CDI) in solid organ transplant recipients: Guidelines from the American Society of Transplantation Community of Practice

These updated guidelines from the American Society of Transplantation Infectious Diseases Community of Practice address the prevention and management of Clostridium difficile infection in solid organ transplant (SOT) recipients. Clostridioides (formerly Clostridium) difficile infection (CDI) is among the most common hospital acquired infections. In SOT recipients, the incidence of CDI varies by type and number or organs transplanted. While a meta-analysis of published literature found the prevalence of postoperative CDI in the general surgical population to be approximately 0.51%, the prevalence of CDI that is seen in the solid organ transplant population ranges from a low of 3.2% in the pancreatic transplant population to 12.7% in those receiving multiple organ transplants. There are no randomized, controlled trials evaluating the management of CDI in the SOT population. Herein is a review and summary of the currently available literature that has been synthesized into updated treatment guidelines for the management of CDI in the SOT population.