Abstract
Clostridioides difficile is a Gram positive, sporulated, rod-shape, anaerobic pathogen responsible for nosocomial diarrhea and colitis, mainly in antibiotic treated patients. C. difficile produce two toxins responsible for disease, toxin A (TcdA) and toxin B (TcdB), although not all strains produce them. Non-toxigenic C. difficile (NTCD) strains are able to colonize the intestinal mucosa and are often isolated from asymptomatic individuals. NTCD are poorly studied, their evolutionary history has not been elucidated, and their relationship with illness remains controversial. The aim of this work was to analyze the phenotype of NTCD strains isolated from clinical cases in hospitals of México, and whether NTCD strains present characteristics that differentiate them from the toxigenic strains. Seventy-four C. difficile strains isolated from patients were tested for cytotoxicity and 14 were identified as NTCD strains. We analyzed phenotypical characteristics that are important for the biology of C. difficile like colony morphology, antibiotic resistance, motility, sporulation, and adherence. Strains were also genotyped to determine the presence of genes coding for TcdA, TcdB and binary toxin and ribotyped for 027 type. When compared with toxigenic strains, NTCD strains presented an enlarged branched colony morphology, higher resistance to metronidazole, and increased sporulation efficiency. This phenotype has been reported associated with mutations that regulates phenotypic characteristics like swimming, sporulation or adhesion. Our results show that phenotype of NTCD strains is heterogeneous but still present characteristics that differentiate them from toxigenic strains.
Highlights
Clostridioides difficile has emerged as a healthcare problem worldwide, C. difficile colitis has been one of the most costly and common causes of diarrhea during the last 20 years, causing millions of deaths every year (Garey et al, 2010)
A total of 74 C. difficile strains isolated from patients were tested for cytotoxicity and 14 of these strains were identified as Non-toxigenic C. difficile (NTCD) strains, since they had no cytotoxic effect on either, Vero (Supplementary Figure S1) or HT29 cells
When we analyzed the colony morphology of NTCD strains, we identified that NTCD strains have more ruffled edges
Summary
Clostridioides difficile has emerged as a healthcare problem worldwide, C. difficile colitis has been one of the most costly and common causes of diarrhea during the last 20 years, causing millions of deaths every year (Garey et al, 2010). The infection may present different clinical characteristics, including diarrhea, pseudomembranous colitis, fulminant colitis, toxic megacolon, and even death. An important factor to consider in the transmission of C. difficile infection (CDI) is the asymptomatic carriage of strains, which has been reported in up to 18% of asymptomatic people (Donskey et al, 2015). C. difficile was considered as part of the normal intestinal microbiota, until 1970 when it was identified as an opportunistic pathogen. The administration of antibiotics disrupts the composition of gut microbiota causing a dysbiosis which results in reduced resistance to pathogens and C. difficile spores takes advantage of this to germinate and colonize the host
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