Phenotypic Characterization of Non-toxigenic Clostridioides difficile Strains Isolated From Patients in Mexico

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.

Detection and Genomic Characterisation of Clostridioides difficile from Spinach Fields

“…Our remaining soil isolate was ribotype 511 and has not been associated with animal, food or human sources. However, due to the ribotype's lack of toxin genes, it may be carried asymptomatically [118] or be associated with hospital-acquired diarrhoea [119]. WGS analysis suggested that RT511 was most closely related to strain C. difficile W0003a, previously observed in clinical isolates in Korea [103].…”

Characterization of Non-Toxigenic Clostridioides difficile Strains Isolated from Preterm Neonates and In Vivo Study of Their Protective Effect

“…The persistence of NTCD may stem from specific factors, or selective advantages allowing the occupation of the ecological niche. Concerning the antimicrobial susceptibility patterns, a recent work reported a higher resistance to MTZ in NTCD compared to toxigenic strains [ 32 ]. We did not confirm this finding since no MTZ MIC was above 0.75 mg/L ( Table S1 ).…”

Elucidating human gut microbiota interactions that robustly inhibit diverse Clostridioides difficile strains across different nutrient landscapes

“…MS001 has a much higher number of genes (4110) compared to the other strains (ranging from 3629 to 3892) ( Table S3 ), and uniquely lacks the toxins TcdA and TcdB. Indeed, non-toxigenic C. difficile strains have distinct phenotypes compared to toxigenic strains, as a consequence of the variability in their genome 49 . In general, there is no pattern between the C. difficile isolates from healthy and sick individuals in terms of their genotype.…”