C. difficile Toxin B (ribotype 027)

The aim of the study was to show that the multi-step algorithm contributes to fast and more accurate diagnostics and enables to start an early treatment of C.difficile infection (CDI). Materials for the study was 2,894 stool samples suspected of having CDI, were analyzed retrospectively. The biological samples from a nearby region were tested by different testing methods in Klinicka Biochemia laboratory in Zilina. The laboratory diagnosis was performed according to two- or three-step algorithm. The cultivation methods and identification of C.dificille strains by MALDI-TOF MS was performed. Most of the samples suspected of CDI could be assessed as negative within the applied two-step algorithm. In discordant results - samples with GDH positive and toxins A/B negative results were tested by further methods with higher sensitivity - ELISA test and the real-time PCR method in three-strp algorithm. The most positive results were from the departments of internal medicine and long-term-care patients over 60 years of age. Seasonality has shown a slight increase in positivity in the spring and autumn months, especially in 2015. The algorithm contributed to increasing the accuracy of the CDI suspect samples to reduce morbidity and mortality as well as the economic burden on CDI.

For the microbiological diagnosis of a Clostridium (C.) difficile infection (CDI), a two-test algorithm consisting of a C. difficile glutamate dehydrogenase (GDH)-immunoassay followed by a toxin-immunoassay in positive cases is widely used. In this study, two chemiluminescent immunoassays (CLIAs), one for GDH and the other for the toxins A and B, have been evaluated systematically using appropriate reference methods. Three-hundred diarrhoeal stool specimens submitted for CDI diagnosis were analysed by the LIAISON CLIAs (DiaSorin). Toxigenic culture (TC) and cell cytotoxicity assay (CCTA) were used as "gold standard" reference methods. In addition, GDH and toxin A and B enzyme immunoassays (EIAs), C. diff Chek-60 and toxin A/B II (TechLab), and the Cepheid Xpert C. difficile polymerase chain reaction (PCR) were performed. C. difficile was grown in 42 (14%), TC was positive in 35 (11.7%) and CCTA in 25 (8.3%) cases. CLIAs were more sensitive but less specific than the respective EIAs. Using culture as reference, the sensitivity of the GDH CLIA was 100%. In comparison to CCTA sensitivity, specificity, positive predictive value and negative predictive value of the two-test algorithm were 88, 99.3, 91.7 and 98.9% by CLIAs and 72, 99.6, 94.7 and 97.5% by EIAs. Discrepant results by CLIAs were more frequent than that by EIAs (9% vs. 6.3%); in those cases, PCR allowed for the accurate detection of toxigenic strains. Due to performance characteristics and testing comfort, CLIAs in combination with PCR represent a favourable option for the rapid laboratory C. difficile diagnostics.