Clostridium difficile in a geriatric unit: a prospective epidemiological study employing a novel S-layer typing method.

Clostridium difficile is the major identifiable cause of antibiotic-associated diarrhoea in the UK. The aim of this study was to employ traditional culture, toxin detection and a novel typing method to determine the level of C. difficile colonization and disease in a population of elderly patients and to investigate the association between strains in the patients and their environment. Three hundred and ninety patients between 62 and 101 years of age admitted to a geriatric unit in the Royal Victoria Hospital (RVH), Edinburgh, were investigated for the presence of C. difficile. C. difficile was cultured from 100 (26 %) patients using pre-reduced cycloserine-cefoxitin egg yolk agar, and toxin(s) was detected in the faeces of 34 of these patients using the Techlab ELISA test kit for the detection of C. difficile toxins A and/or B. Toxin(s) was detected in a further 18 patients from whom no C. difficile was detected in culture. Of the patients in whom C. difficile was detected, 49 % had diarrhoea, with the highest proportion of patients with diarrhoea being both culture- and toxin-positive for C. difficile. Environmental sampling of the patient environment yielded C. difficile from 14 % of samples. The organism was most frequently isolated from floors, sluice-rooms and toilet areas. The variation in the molecular mass of the C. difficile S-layer proteins was exploited as the basis of a novel typing method for C. difficile. Isolates from patients in the RVH were given a four-digit 'S-type' number based on their S-layer protein profile. A total of seven S-types were identified, with one type, toxigenic S-type 5236, accounting for 73 % of all clinical isolates and 91 % of environmental isolates.