Epidemiology of Clostridium difficile infection in a large teaching hospital in Singapore

Hsien Koh, Tse; Ling Tan, Ai; Lee Tan, Mee; Wang, Grace; Peng Song, Keang

Summary Aims We undertook this study to define the incidence of toxigenic Clostridium difficile in our hospital and to characterise the isolates. Methods All unformed stool was tested for the presence of Toxin A (TcdA) and Toxin B (TcdB), and cultured for C. difficile. Culture filtrates were also tested for TcdA and TcdB. Detection of tcdA and tcdB genes was carried out for A2B+ strains by polymerase chain reaction (PCR).The minimum inhibitory concentrations (MICs) of metronidazole, vancomycin and clindamycin for all isolates were tested using the Etest. PCR ribotyping was carried out on all isolates. Results The incidence of Clostridium difficile associated disease (CDAD) was 3.2 cases per 1000 admissions or discharges and 53.8 cases per 100000 patient days. Most cases occurred in renal and haematology patients. CDAD was more common in patients aged over 50 years and of male gender. The Indian population was under-represented. Fourteen (11.8%) isolates were A-B+. All strains were susceptible to metronidazole but one strain showed intermediate resistance to vancomycin. Only 12.8% of the isolates were susceptible to clindamycin. Thirty-five isolates had PCR ribotype A, of which 29 (83%) had a clindamycin MIC >256mg/L. Thirty-three had PCR ribotype B, of which only one (3%) had a clindamycin MIC >256mg/L. The 14 A-B+ strains were all PCR ribotype C, and had a range of MICs for clindamycin from 2 to >256mg/L. Conclusions: The incidence of CDAD in our hospital is relatively low. Isolates remain susceptible to metronidazole and vancomycin.