Predominance of a single restriction endonuclease analysis group with intrahospital subgroup diversity among Clostridium difficile isolates at two Chicago hospitals.

OBJECTIVE

To determine the epidemiology and relatedness of Clostridium difficile isolates in two geographically separated hospitals in a large metropolitan area, each with unique patients and personneL DESIGN: Observational descriptive molecular epidemiology of clinical C. difficile isolates.

SETTING

Two tertiary-care hospitals in Chicago.

METHODS

Consecutive C. difficile isolates from the clinical laboratory of a Veterans Affairs hospital during a 13-month period were typed by restriction endonuclease analysis (REA). During an overlapping 3-month period, stool specimens that tested positive for C. difficile toxin from patients at a nearby county hospital were cultured and the recovered isolates typed by the same method.

RESULTS

Nineteen (68%) of 28 nosocomial isolates at the smaller, Veterans Affairs hospital belonged to REA group K. Within this group of closely related strains, 9 distinct REA types were recognized. Twenty-one (72%) of 29 nosocomial isolates at the larger, county hospital also belonged to group K. However, the predominant REA types within group K differed markedly at each institution.

CONCLUSIONS

These findings demonstrate a high degree of similarity among nosocomial C. difficile strains from different hospitals in the same city and suggest the possibility of an extended outbreak of a prototype group K strain with subsequent genetic drift at the two different institutions.