Detection of toxigenic Clostridioides [Clostridium] difficile: Usefulness of two commercially available enzyme immunoassays and a PCR assay on stool samples and stool isolates

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.

Laboratory Diagnostic Methods for Clostridioides difficile Infection: the First Systematic Review and Meta-analysis in Korea

Background

Various methods are used for the diagnosis of Clostridioides difficile infection (CDI). We systematically analyzed and investigated the performance of current laboratory diagnostic methods for CDI.

Methods

We performed systematic review and meta-analysis of studies in PubMed, Web of Science, Cochrane Library, and KoreaMed. The following methods were evaluated glutamate dehydrogenase (GDH) enzyme immunoassays (GDH EIAs), toxin A and B detection by enzyme immunoassays (toxin AB EIAs), and nucleic acid amplification tests (NAATs) for C. difficile toxin genes. The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of each method were calculated.

Results

Based on 39 studies, the pooled sensitivities/specificities were 92.7%/94.6%, 57.9%/97.0%, and 90.0%/95.8% for GDH EIAs, toxin AB EIAs, and NAATs, respectively, compared with those of toxigenic culture. The pooled sensitivities of automated EIAs were significantly higher than those of non-automated EIAs for both GDH and toxins A and B. The pooled sensitivity of Xpert C. difficile was significantly higher than those of other NAATs. PPVs increased as CDI prevalence increased, and NPVs were excellent when CDI prevalence was low; at CDI prevalence of 5%, PPV = 37%-65% and NPV = 97%-100%; at CDI prevalence of 50%, PPV = 92%-97% and NPV = 65%-98%.

Conclusions

Toxin AB EIAs still show unsatisfactory sensitivity, whereas GDH EIAs and NAATs show relatively high sensitivity. However, toxin AB EIAs are the most specific tests. This study may provide useful information for CDI diagnosis.

Evaluation of glutamate dehydrogenase (GDH) and toxin A/B rapid tests for Clostridioides (prev. Clostridium) difficile diagnosis in a university hospital in Minas Gerais, Brazil

Clostridioides (Clostridium) difficile is responsible for most cases of nosocomial diarrhea and, despite the high prevalence of the disease worldwide, the best laboratory diagnostic approach to diagnose C. difficile infection (CDI) is a subject of ongoing debate. Although the use of multiple tests is recommended, the cost of these algorithms commonly exceeds the affordability in some countries. Thus, to improve CDI diagnosis in a university hospital in Brazil, this study analyzed two immunochromatographic tests and one enzyme immunoassay (ELISA) to evaluate the detection of glutamate dehydrogenase (GDH) and A/B toxins of C. difficile. Stool samples of 89 adult patients presenting nosocomial diarrhea during hospitalization were included. The toxigenic culture was used as the reference method. GDH detection by both commercial tests showed high sensitivity (100%) and specificity (92.1%). On the other hand, toxin-based methods showed a sensitivity between 19.2 and 57.7%. In conclusion, the results suggest that rapid tests for GDH detection are not only suitable for CDI diagnosis as screening tests but also as a single method.

A Two-Step Approach for Diagnosing Glutamate Dehydrogenase Genes by Conventional Polymerase Chain Reaction from Clostridium difficile Isolates

BACKGROUND

Clostridium difficile is the major causative agent of nosocomial antibiotic-associated colitis. The gold standard for C. difficile detection is stool culture followed by cytotoxic assay, although it is laborious and time-consuming. We developed a screening test based on a two-step conventional polymerase chain reaction (PCR) approach to detect gluD, the glutamate dehydrogenase (GDH) enzyme gene, which is a marker for screening of C. difficile. Targeting gluD comparing to the conserved stable genetic element of pathogenicity locus (PaLoc), with an accessory gene of Cdd3, was an effective method for the detection of this pathogen from patients with enterocolitis.

METHODS

Fresh fecal samples of the patients who were clinically suspicious for antibiotic-associated colitis were collected. Stool specimens were cultured on the cycloserine-cefoxitin fructose agar (CCFA) in an anaerobic condition, following alcohol shock treatment and enrichment in Clostridium difficile Brucella broth (CDBB). On confirmed colonies, PCR was carried out for detection of PaLoc subsidiary gene, Cdd3, and toxicogenic genes, tcdA and tcdB. The gluD that is GDH gene detection was performed by conventional PCR on the extracted DNA from 578 fresh stool samples.

RESULTS

57 (9.8%) strains of C. difficile were approved by conventional PCR for gluD and Cdd3 genes, in which 37 (6.4%) colonies had tcdA+/tcdB+ genotype, 2 (0.3%) tcdA+/tcdB-, 4 (0.7%) tcdA-/ tcdB+ and the remaining 14 (2.4%) colonies were tcdA and tcdB negative.

CONCLUSION

These results demonstrate that targeting gluD by PCR is quite promising for rapid detection of C. difficile from fresh fecal samples. Furthermore, the multiple-gene analysis for tcdA and tcdB assay proved a reliable approach for diagnosing of toxigenic strains among clinical samples.