Prospective evaluation of the Meridian Illumigene™ loop-mediated amplification assay and the Gen Probe ProGastro™ Cd polymerase chain reaction assay for the direct detection of toxigenic Clostridium difficile from fecal samples

Accuracy of diagnostic assays for the detection of Clostridioides difficile: A systematic review and meta-analysis

INTRODUCTION

Clostridioides difficile Infection (CDI) has been identified as one of the main causes of nosocomial infection all across the world. Rapid diagnosis of CDI is difficult and poses a significant challenge to physicians worldwide. We undertook a systematic review and meta-analysis to evaluate rapid tests' diagnostic accuracy against toxigenic culture as the reference standard for CDI.

METHOD

We searched the PubMed/MEDLINE and EMBASE databases for the relevant records. The QUADAS-2 tool was used to assess the quality of the studies. Diagnostic accuracy measures [i.e., sensitivity, specificity, diagnostic odds ratio (DOR), positive likelihood ratios (PLR), negative likelihood ratios (NLR), and the area under the curve (AUC)] were pooled with a random-effects model. All statistical analyses were performed with Meta-DiSc (Version 1.4, Cochrane Colloquium, Barcelona, Spain) and RevMan (version 5.3; The Nordic Cochrane Centre, the Cochrane Collaboration, Copenhagen, Denmark).

RESULTS

We reviewed retrieved records and identified 63 studies that met the inclusion criteria. 26 were about enzyme immunoassay (EIA) (our main index test). The sensitivity of GDH and Tox A/B EIAs were 82% (95% CI: 79-84) and 75% (95% CI: 70-79), respectively. On the other hand, the specificity of GDH EIA was 91% (95% CI: 90-92) and the specificity of Tox A/B EIA was 95% (95% CI: 94-96). Among other index tests, BD Max with 92% has the most sensitivity and cell cytotoxicity neutralization assay (CCNA) has the most specificity (100%).

CONCLUSION

This meta-analysis demonstrated that EIAs could be reliable methods for detecting CDI based on their sensitivity, specificity, time and cost-effectiveness, and simplicity in the procedure. Further work to improve rapid tests would benefit from improvements to the methodology.

Loop mediated isothermal amplification of Clostridioides difficile isolates in gastrointestinal patients

This study investigated the prevalence of Clostridioides difficile by culture, multiplex polymerase chain reaction (M-PCR), and loop mediated isothermal amplification (LAMP) in patients with suspected C. difficile infections (CDIs). Also, the results of three methods were compared. All stool specimens collected from CDI suspected patients were cultured on selective C. difficile cycloserine-cefoxitin fructose agar and incubated in an anaerobic jar up to 7 days. The bacterial isolates were identified using standard tests. Multiplex-PCR (M-PCR) was performed for detection of tcdA, tcdB, and tpi genes. The LAMP assay was performed to detect the tcdB gene of C. difficile. C. difficile was isolated from 20.0% (n = 10/50) of samples by culture. M-PCR showed that 34.0% (n = 17/50) of the specimens were positive for C. difficile based on the presence of tpi gene. Out of the 17 C. difficile, 13 strains (76.0%) were positive for tcdB gene using M-PCR. However, the LAMP assay showed that 30.0% (15/50) of specimens were positive for the presence of tcdB gene. M-PCR and LAMP methods showed 100.0% sensitivity compared to the culture method. However, the specificity of the LAMP (87.5%) was relatively higher than the M-PCR (82.5%) compared to the culture. Based on the results of this study, the prevalence of toxigenic C. difficile strains was high in suspected CDI patients. So, the differentiation between toxigenic and non-toxigenic strains is necessary. Our data showed that the LAMP assay is a good method for direct detection of toxigenic C. difficile strains from stool specimens.

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.

A Laboratory Medicine Best Practices Systematic Review and Meta-analysis of Nucleic Acid Amplification Tests (NAATs) and Algorithms Including NAATs for the Diagnosis of Clostridioides (Clostridium) difficile in Adults

The evidence base for the optimal laboratory diagnosis of Clostridioides (Clostridium) difficile in adults is currently unresolved due to the uncertain performance characteristics and various combinations of tests. This systematic review evaluates the diagnostic accuracy of laboratory testing algorithms that include nucleic acid amplification tests (NAATs) to detect the presence of C. difficile The systematic review and meta-analysis included eligible studies (those that had PICO [population, intervention, comparison, outcome] elements) that assessed the diagnostic accuracy of NAAT alone or following glutamate dehydrogenase (GDH) enzyme immunoassays (EIAs) or GDH EIAs plus C. difficile toxin EIAs (toxin). The diagnostic yield of NAAT for repeat testing after an initial negative result was also assessed. Two hundred thirty-eight studies met inclusion criteria. Seventy-two of these studies had sufficient data for meta-analysis. The strength of evidence ranged from high to insufficient. The uses of NAAT only, GDH-positive EIA followed by NAAT, and GDH-positive/toxin-negative EIA followed by NAAT are all recommended as American Society for Microbiology (ASM) best practices for the detection of the C. difficile toxin gene or organism. Meta-analysis of published evidence supports the use of testing algorithms that use NAAT alone or in combination with GDH or GDH plus toxin EIA to detect the presence of C. difficile in adults. There is insufficient evidence to recommend against repeat testing of the sample using NAAT after an initial negative result due to a lack of evidence of harm (i.e., financial, length of stay, or delay of treatment) as specified by the Laboratory Medicine Best Practices (LMBP) systematic review method in making such an assessment. Findings from this systematic review provide clarity to diagnostic testing strategies and highlight gaps, such as low numbers of GDH/toxin/PCR studies, in existing evidence on diagnostic performance, which can be used to guide future clinical research studies.

Selected Topics in Anaerobic Bacteriology

Alteration in the host microbiome at skin and mucosal surfaces plays a role in the function of the immune system, and may predispose immunocompromised patients to infection. Because obligate anaerobes are the predominant type of bacteria present in humans at skin and mucosal surfaces, immunocompromised patients are at increased risk for serious invasive infection due to anaerobes. Laboratory approaches to the diagnosis of anaerobe infections that occur due to pyogenic, polymicrobial, or toxin-producing organisms are described. The clinical interpretation and limitations of anaerobe recovery from specimens, anaerobe-identification procedures, and antibiotic-susceptibility testing are outlined. Bacteriotherapy following analysis of disruption of the host microbiome has been effective for treatment of refractory or recurrent Clostridium difficile infection, and may become feasible for other conditions in the future.

Optimizing the diagnostic testing of Clostridium difficile infection

INTRODUCTION

Clostridium difficile infection (CDI) is the leading cause of hospital-acquired diarrhea and is associated with a considerable health and cost burden. However, there is still not a clear consensus on the best laboratory diagnosis approach and a wide variation of testing methods and strategies can be encountered.

AREAS COVERED

We aim to review the most practical aspects of CDI diagnosis providing our own view on how to optimize CDI diagnosis. Expert commentary: Laboratory diagnosis in search of C. difficile toxins should be applied to all fecal diarrheic samples reaching the microbiology laboratory in patients > 2 years old, with or without classic risk factors for CDI. Detection of toxins either directly in the fecal sample or in the bacteria isolated in culture confirm CDI in the proper clinical setting. Nuclear Acid Assay techniques (NAAT) allow to speed up the process with epidemiological and therapeutic consequences.

Comparison of a novel chemiluminescent based algorithm to three algorithmic approaches for the laboratory diagnosis of Clostridium difficile infection

Background

Rapid commercial assays, including nucleic acid amplification tests and immunoassays for Clostridium. difficile toxins, have replaced the use of older assays. They are included in a two-step algorithm diagnosis, including first the detection of the glutamate dehydrogenase (GDH) as a screening method and second the detection of toxins as a confirmatory method. Although assays that detect the presence of free toxins in feces are known to lack sensitivity, they are preferable to confirm infection. We evaluated the accuracy of the chemiluminescence-based method detecting C.difficile GDH and free toxins A/B (DiaSorin algorithm) to an enzyme-immunoassay (EIA) for GDH with a molecular toxins test (Meridian algorithm), EIA-GDH and an EIA-toxins A/B algorithm (Alere algorithm) with and without toxigenic culture for confirmation.

Findings

A total of 468 diarrhoeal and loose stool samples were included in the study. A positive result was defined by a positive GDH and a positive toxin test. Discordant samples were resolved using an enriched toxigenic culture considered as the reference method. After resolution, the DiaSorin algorithm showed a high sensitivity (86.7 %) compared to that of the Alere algorithm with (60.0 %) and without (50.0 %) confirmation by culture and was as sensitive as the Meridian algorithm (90.0 %), while the specificities were similar: 99.1, 99.5, 99.5 and 98.9 %, respectively.

Conclusions

The DiaSorin algorithm was as sensitive as an algorithm including nucleic acid amplification test for toxins. Chemiluminescence toxin-enhanced signal assay compensates the lack of sensitivity usually observed for EIA tests for toxins.

Diagnostic accuracy of loop-mediated isothermal amplification in detection of Clostridium difficile in stool samples: a meta-analysis

INTRODUCTION

Clostridium difficile infection (CDI) remains a diagnostic challenge for clinicians. More recently, loop-mediated isothermal amplification (LAMP) has become readily available for the diagnosis of CDI, and many studies have investigated the usefulness of LAMP for rapid and accurate diagnosis of CDI. However, the overall diagnostic accuracy of LAMP for CDI remains unclear. In this meta-analysis, our aim was to establish the overall diagnostic accuracy of LAMP in detection of Clostridium difficile (CD) in stool samples.

MATERIAL AND METHODS

A search was done in PubMed, MEDLINE, EMBASE and Cochrane Library databases up to February 2014 to identify published studies that evaluated the diagnostic role of LAMP for CD. Methodological quality was assessed according to the quality assessment for studies of diagnostic accuracy (QUADAS) instrument. The sensitivities (SEN), specificities (SPE), positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odds ratio (DOR) were pooled statistically using random effects models. Statistical analysis was performed by employing Meta-Disc 1.4 software. Summary receiver operating characteristic (SROC) curves were used to summarize overall test performance. Funnel plots were used to test the potential publication bias.

RESULT

A total of 9 studies met inclusion criteria for the present meta-analysis. The pooled SEN and SPE for diagnosing CD were 0.93 (95% CI: 0.91-0.95) and 0.98 (95% CI: 0.98-0.99), respectively. The PLR was 47.72 (95% CI: 15.10-150.82), NLR was 0.07 (95% CI: 0.04-0.14) and DOR was 745.19 (95% CI: 229.30-2421.72). The area under the ROC was 0.98. Meta-regression indicated that the total number of samples was a source of heterogeneity for LAMP in detection of CD. The funnel plots suggested no publication bias.

CONCLUSIONS

The LAMP meets the minimum desirable characteristics of a diagnostic test of SEN, SPE and other measures of accuracy in the diagnosis of CD, and it is suitable as a rapid, effective and reliable stand-alone diagnostic test for diagnosis of CDI, potentially decreasing morbidity and nosocomial spread of CD.

Evaluation of the illumigene C. difficile assay for toxigenic Clostridium difficile detection: a prospective study of 302 consecutive clinical fecal samples

Toxigenic Clostridium difficile is a major pathogen causing nosocomial diarrhea. Consequently, rapid detection of toxigenic C. difficile is very important in clinical laboratories. The illumigene C. difficile DNA amplification assay (illumigene; Meridian Bioscience, Inc.) is a rapid method that detects the toxin A gene (tcdA) by loop-mediated isothermal amplification. In the present study, we evaluated the diagnostic performance of the illumigene assay using 302 consecutive stool specimens in comparison with the VIDAS C. difficile A&B enzyme-linked fluorescent immunoassay (VIDAS-CDAB; bioMérieux). Toxigenic culture was used as the reference method. The sensitivity, specificity, positive predictive value, and negative predictive value of the illumigene assay were 88.1%, 96.7%, 86.7%, and 97.1%, respectively, while those of the VIDAS-CDAB assay were 40.4%, 98.8%, 87.5%, and 88.5%, respectively. It is of note that use of a combination of the illumigene and VIDAS-CDAB assays did not improve any of the 4 evaluated parameters (88.1%, 95.5%, 82.5%, and 97.1%, respectively). The illumigene assay showed limits of detection of 250 and 11,467 CFU/mL for ATCC 9688 (tcdA+, tcdB+, cdtB-) and ATCC 43598 (tcdA-, tcdB+, cdtB-) reference strains, respectively, and there was no cross-reactivity with 8 frequently isolated bacterial species. In conclusion, the illumigene assay might be a useful method for rapid detection of toxigenic C. difficile in clinical laboratories. Additionally, the VIDAS-CDAB assay seems unnecessary if the illumigene assay is used.

Evaluation of a chromogenic culture medium for the detection of Clostridium difficile

PURPOSE

Clostridium difficile (C. difficile) is an important cause of nosocomial diarrhea. Diagnostic methods for detection of C. difficile infection (CDI) are shifting to molecular techniques, which are faster and more sensitive than conventional methods. Although recent advances in these methods have been made in terms of their cost-benefit, ease of use, and turnaround time, anaerobic culture remains an important method for detection of CDI.

MATERIALS AND METHODS

In efforts to evaluate a novel chromogenic medium for the detection of C. difficile (chromID CD agar), 289 fecal specimens were analyzed using two other culture media of blood agar and cycloserine-cefoxitin-fructose-egg yolk agar while enzyme immunosorbent assay and polymerase chain reaction-based assay were used for toxin detection.

RESULTS

ChromID showed the highest detection rate among the three culture media. Both positive rate and sensitivity were higher from chromID than other culture media. ChromID was better at detecting toxin producing C. difficile at 24 h and showed the highest detection rate at both 24 h and 48 h.

CONCLUSION

Simultaneous use of toxin assay and anaerobic culture has been considered as the most accurate and sensitive diagnostic approach of CDI. Utilization of a more rapid and sensitive chromogenic medium will aid in the dianogsis of CDI.

tcdA As a diagnostic target in a loop-mediated amplification assay for detecting toxigenic Clostridium difficile

BACKGROUND

The illumigene® (Meridian Bioscience, Inc., Cincinnati, OH) and GeneOhm® (BD Diagnostics, La Jolla, CA) Clostridium difficile assays target the tcdA gene and tcdB gene, respectively. We assessed the use of tcdA as the molecular target in the illumigene® C. difficile loop-mediated amplification assay in detecting a wide variety of C. difficile strains including those with tcdA deletions.

METHODS

We tested 38 C. difficile strains and 108 patient stool specimens using the illumigene® assay. The GeneOhm® real-time polymerase chain reaction (PCR) assay served as the reference method. Discordant results were resolved by repeat testing, anaerobic culture, and a laboratory-developed real-time PCR targeting tcdA and tcdB.

RESULTS

Both illumigene® and GeneOhm® assays detected all 37 C. difficile toxin B(+) strains representing seven toxinotypes and including four toxin A(-) B(+) isolates. No cross-reactivity with 20 other Clostridium species or toxin-negative C. difficile was observed in either assay. Among patient stool specimens, agreement was 94.4% (102/108). After discordant result resolution, agreement was 96.3% (104/108). Specimens with initially discordant results had target concentrations approaching the limit of detection for the two commercial assays. Discordance appeared unrelated to whether tcdA or tcdB was the amplification target.

CONCLUSION

The tcdA 5' region used by the illumigene® assay is a practical target for toxigenic C. difficile detection.

Detection of Streptococcus pyogenes by use of Illumigene group A Streptococcus assay

The performance of the Illumigene group A Streptococcus assay was evaluated by comparing it to culture using 437 consecutive throat swabs. The Illumigene assay was also directly compared to PCR with 161 samples. This Illumigene assay is rapid and easy to perform. The assay also has high sensitivity (100%) compared to culture or PCR and high specificity (99.2%) compared to PCR. A total of 8.8% of the isolates were erythromycin resistant, and 6.9% were clindamycin resistant.

Evaluation of Clostridium difficile fecal load and limit of detection during a prospective comparison of two molecular tests, the illumigene C. difficile and Xpert C. difficile/Epi tests

In a large prospective comparison, the illumigene test detected Clostridium difficile in 98% of toxin-positive and 58% of toxin-negative samples confirmed positive by other methods. The Xpert was uniformly sensitive. Most samples with discrepant results had C. difficile concentrations below the illumigene limit of detection. The significance of low-level C. difficile detection needs investigation.

Performance of Clostridium difficile toxin enzyme immunoassay and nucleic acid amplification tests stratified by patient disease severity

Many clinical laboratories in the United States are transitioning from toxin enzyme immunoassays (EIA) to nucleic acid amplification tests (NAATs) as the primary diagnostic test for Clostridium difficile infection (CDI). While it is known that the analytical sensitivity of the toxin EIA is poor, there are limited clinical data on the performance of these assays for patients with mild or severe CDI. Two hundred ninety-six hospital inpatients with diarrhea and clinical suspicion for CDI were tested prospectively by toxin EIA, by C. difficile NAAT, and with a reference standard toxigenic culture. Following completion of laboratory testing, retrospective chart reviews were performed to stratify patients into mild and severe disease groups based on clinical criteria using a standard point-based system. One hundred forty-three patients with CDI confirmed by toxigenic culture were evaluated in this study. Among the patients with mild CDI, 49% tested positive by toxin EIA and 98% tested positive by NAAT. Among patients with severe CDI, 58% tested positive by toxin EIA and 98% tested positive by NAAT. Increased CDI disease severity was not associated with an increased sensitivity of EIA (P = 0.31). These data demonstrate that toxin EIA performs poorly both for patients with severe CDI and for those with mild CDI and support the routine use of NAAT for the diagnosis of CDI. The presence of stool toxin measured by EIA does not correlate with disease severity.

Molecular techniques for diagnosis of Clostridium difficile infection: systematic review and meta-analysis

OBJECTIVE

To assess the usefulness of 2 rapid molecular diagnostic techniques, polymerase chain reaction (PCR) and loop-mediated isothermal amplification (LAMP), in Clostridium difficile infection (CDI).

METHODS

We conducted a systematic review and meta-analysis to evaluate the accuracy of PCR and LAMP in diagnosis of CDI, including studies that used toxigenic culture or cytotoxicity assay as reference standard.

RESULTS

A search of PubMed and CinAHL medical databases yielded 25 PCR studies, including 11,801 samples that met inclusion criteria and 6 heterogeneous studies that evaluated LAMP. With toxigenic culture as a standard, pooled sensitivity was 0.92 (95% confidence interval [CI], 0.91-0.94); specificity, 0.94 (95% CI, 0.94-0.95); and diagnostic odds ratio, 378 (95% CI, 260-547). With cytotoxicity as a standard, pooled sensitivity was 0.87 (95% CI, 0.84-0.90); specificity, 0.97 (95% CI, 0.97-0.98); and diagnostic odds ratio, 370 (95% CI, 226-606).

CONCLUSION

Polymerase chain reaction is a highly accurate test for identifying CDI. Heterogeneity in LAMP studies did not allow meta-analysis; however, further research into this promising method is warranted.

Evaluation of three enzyme immunoassays and a loop-mediated isothermal amplification test for the laboratory diagnosis of Clostridium difficile infection

The laboratory diagnosis of Clostridium difficile infection (CDI) consists of the detection of toxigenic Clostridium difficile, and/or its toxins A or B in stool preferably in a two-step algorithm. In a prospective study, we compared the performance of three toxin enzyme immunoassays (EIAs)-ImmunoCard Toxins A & B, Premier Toxins A & B and C. diff Quik Chek Complete, which combines a toxins test and a glutamate dehydrogenase (GDH) antigen EIA in one device -and the loop-mediated isothermal amplification assay Illumigene C. difficile. In total 986 stool samples were analyzed. Compared with toxigenic culture as the gold standard, sensitivities, specificities, PPV and NPV values of the toxin EIAs were 41.1-54.8 %, 98.9-100 %, 75.0-100 % and 95.5-96.5 % respectively, of the Illumigene assay 93.3 %, 99.7 %, 95.8 % and 99.5 %. Illumigene assays performed significantly better for non-014/020 PCR-ribotypes than for C. difficile isolates belonging to 014/020. Discrepant analysis of three culture-negative, but Illumigene-positive samples, revealed the presence of toxin genes using real-time PCRs. In addition to the GDH EIA (NPV of 99.8 %), the performance of Illumigene allows this test to be introduced as a first screening test for CDI- or as a confirmation test for GDH -positive samples, although the initial invalid Illumigene result of 4.4 % is a point of concern.

Clostridium difficile: epidemiology, pathogenesis, management, and prevention of a recalcitrant healthcare-associated pathogen

Clostridium difficile is the leading cause of healthcare-associated infectious diarrhea. Although C difficile is part of normal flora in some healthy individuals, patients with selective risk factors are often vulnerable to the toxigenic potential of this virulent healthcare pathogen. The spectrum of C difficile infection (CDI) is highly variable, ranging from mild to severe illness, presenting with single to multiple disease recurrences. Current approaches to treatment are based on severity of illness, number of recurrences, and clinical presentation. Oral vancomycin and metronidazole have formed the foundation for treatment of CDI, but therapeutic failures are commonly reported, especially involving hypervirulent clones. Alternative therapies, including newer antimicrobials, probiotics, immunotherapy, and fecal transplantation, have all met with varying degrees of efficacy. Although toxigenic culture (TC) testing from anaerobic culture remains the gold standard, newer technologies, including enzyme immunoassay, common antigen (glutamate dehydrogenase) testing, and real-time polymerase chain reaction (PCR) are less time-consuming and rapid. However, TC and PCR have reported high specificity and sensitivity when compared with other laboratory tests. Because of the significant morbidity and mortality associated with CDI, a high index of suspicion is warranted. Prevention and eradication of CDI require a multidisciplinary approach, including early disease recognition through appropriate surveillance, implementation of effective contact isolation strategies, adherence to environmental controls, judicious hand hygiene, evidence-based treatment, and management that includes antibiotic stewardship, continuous education of healthcare workers, and administrative support.