EPIDEMIOLOGY OF COMMUNITY-ACQUIRED CLOSTRIDIUM-DIFFICILE-ASSOCIATED DIARRHEA

The epidemiology of clinically recognized community-acquired Clostridi um difficile-associated diarrhea was assessed in a retrospective cohor t study of members of a health maintenance organization (HMO). Potenti al cases were identified through positive toxin assay results and conf irmed by review of automated full-text medical records. Of 51 cases id entified (7.7 per 100,000 person-years), 42 (82%) were diagnosed and t reated exclusively in the ambulatory care setting; 33 cases occurred w ithin 42 days after 494,491 exposures to antibiotics dispensed by an H MO pharmacy. Antibiotic-specific attack rates varied from 0 to 2040 ca ses per 100,000 exposures. Increased age was associated with C. diffic ile-associated diarrhea (P < .001). Age-adjusted antibiotic-specific a ttack rates were at least 10-fold higher (P < .05) for nitrofurantoin, cefuroxime, cephalexin plus dicloxacillin, ampicillin/clavulanate plu s cefaclor, and ampicillin/clavulanate plus cefuroxime than for ampici llin or amoxicillin; several other antibiotics were associated with si milar but not significantly increased risks.