Molecular epidemiology of Clostridium difficile in a tertiary hospital of China

Clostridium difficile infection (CDI) is caused by toxin-producing strains. It accounts for 20-30 % of antibiotic-associated diarrhoea and particularly accounts for 90 % of pseudomembranous colitis. The epidemiological study of C. difficile is thus important. In this study, we report the molecular epidemiology and ward distribution of C. difficile in a tertiary hospital of China. A total of 161 toxigenic strains were isolated from 1845 patients originating from different wards and the strains were characterized based on toxin profile and multilocus sequence typing. Variable isolation rates were observed in different wards and the occurrence was higher in intensive care unit and geriatric wards. Toxin gene profiling revealed that, out of the 161 isolates, 134 (83.2)% were positive for both toxin A (tcdA) and toxin B (tcdB) (A+B+) followed by toxin A-negative and B-positive (A-B+) (16.8 %) isolates. However, only three of the toxigenic strains (1.9 %) were positive for both the cdtA and cdtB genes. Based on the molecular epidemiology study, a total of 30 different sequence types (STs), including one new ST (ST-220), were distinguishable. ST-54 was the most prevalent (23.0 %), followed by ST-35 (19.3 %) and ST-37 (10.0 %). None of the isolates belonged to ST-1 (ribotype 027) or ST-11 (ribotype 078). Taken together, the toxin profile and the molecular epidemiological data showed that all the ST-37 clades were of toxin type A-B+, which accounted for 59.3 % of all type A-B+ isolates. Meanwhile the clade 1 genotype, ST-54, was widely distributed among the geriatric, infection and haematology wards. There was no outbreak of C. difficile infection during our study; however the possibility of prolonged outbreaks cannot be completely ignored.