Nosocomial outbreak of Clostridium difficile-associated diarrhoea due to aclindamycin-resistant enterotoxin A-negative strain

A clindamycin-resistant toxin A-negative, toxin B-positive Clostridium diff icile strain caused an outbreak among 24 hospitalized patients at the Depar tment of Surgery, the Intensive Care unit, and the Department of Internal M edicine of an 800-bed academic hospital. Nineteen patients had undergone a surgical intervention and all 24 patients received at least one dose of ant ibiotics prior to the development of Clostridium difficile-associated diarr hoea. Twenty-seven episodes of Clostridium difficile-associated diarrhoea i n 24 patients were categorized as mild (n=19), severe (n=7), or fatal (n=1) . Relapses occurred in three patients. Nineteen of the 27 episodes required anti-Clostridium difficile treatment. Molecular typing performed by arbitr ary primer polymerase chain reaction (PCR) and PCR amplification of rRNA in tergenic spacer regions revealed that the outbreak strains recovered from c ulture were identical. The outbreak strain belonged to serogroup F and was resistant to erythromycin, clindamycin., and tetracycline, whereas suscepti bility to chloramphenicol varied. No phenotypic activity of enterotoxin A w as detected. A deletion of approximately 1.7 kb was found in the toxin A ge ne. Cytotoxin B had an unusual effect on cell culture assays that, at first , was not recognized as Clostridium difficile specific but could be neutral ized with anti-Clostridium difficile B cytotoxin.