A SUSTAINED OUTBREAK OF CLOSTRIDIUM-DIFFICILE IN A GENERAL-HOSPITAL -PERSISTENCE OF A TOXIGENIC CLONE IN 4 UNITS

OBJECTIVES: To evaluate the endemicity and epidemiology of toxigenic C lostridium difficile in a sustained outbreak of antibiotic-associated diarrhea. SETTING: University-affiliated, 465-bed tertiary care teachi ng hospital with adjacent cancer clinic in Hamilton, Ontario. DESIGN: From August 8, 1991, through August 31, 1993, a total of 187 cases wer e investigated for epidemiologic analysis of toxigenic C difficile fro m stool cultures, to identify the endemic clone(s). To assess the natu re of contamination, cultures of inanimate surfaces in the patient env ironment from the four most affected units (medical teaching, nonteach ing medical, hematologic oncology, and the intensive care unit) were p rocessed for C difficile. The 229 clinical strains and 24 environmenta l strains isolated were typed by numerical analysis of SDS-PAGE protei n patterns. RESULTS: A majority (81%) of cases in the epidemiologic an alysis were associated with a toxigenic electrophoretic (EP) type 1 C difficile that was identical to the strain first isolated from an inde x case that occurred 18 months before the start of this study. Culture and typing of the C difficile strains from the inanimate surfaces in the four most affected units showed that the patient environment was c ontaminated with the toxigenic EP type 1 organism. Six other strains t hat occurred infrequently among cases also were found in the environme nt. CONCLUSIONS. A single predominant toxigenic clone has been implica ted in a sustained outbreak of antibiotic-associated diarrhea that aff ected elderly patients. The ''endemic'' clone transmitted for the 25-m onth study period was linked to an index case shedding a toxigenic EP type 1 strain that occurred 21 months prior to the intial outbreak on the medical teaching unit. The patient environment in the affected uni ts was found to be contaminated with the same clone, possibly due to s hedding of organisms by fecally incontinent symptomatic patients. The extrinsic factors contributing to the endemic transmission of this one clone still are not well understood (Infect Control Hosp Epidemiol 19 94;15:382-389).