Analysis of two Clostridium difficile outbreaks in an acute health care facility

Abstract

BACKGROUND: Many Clostridium difficile infection (CDI) cases are classified as health care–associated (HA)-CDI using standard definitions. However, this classification may not be accurate and may lead to the declaration of outbreaks when the acquisition of C. difficile is not HA, and the source of infection or strain type are unknown. OBJECTIVE: To characterize C. difficile ribotypes to establish the relationship between CDI cases involved in two outbreaks at a Canadian hospital, and to determine whether there was a common source of infection between the outbreaks. METHODS: C. difficile isolates from infected patients involved in two CDI outbreaks affecting two wards (A and B) were analyzed using ribotyping and mutlilocus sequence typing (MLST) techniques. Antibiotic use and length of hospital stay for the CDI cases during the outbreaks were also analyzed by reviewing patient charts. RESULTS: C. difficile was isolated from 19 of 22 CDI patients. Twelve patients in ward A carried 10 different ribotypes, of which eight were isolated once. Similarly, seven patients in ward B carried five different ribotypes, of which four were isolated once. Only three ribotypes – 027, 056, and 106 – were isolated in both wards, of which at least two isolates of ribotype 027 and ribotype 056 belonged to different MLST groups, indicating genetic diversity, even among the shared ribotypes between the two wards. All CDI patients were isolated throughout their hospital stay. The CDI cases did not show an association with the length of hospital stay. Antibiotic use was also documented before and after the onset of HA-CDI. A common pattern of exposure to multiple antibiotics and proton pump inhibitors was noticed before the onset of CDI that continued afterward. CONCLUSION: Two concurrent CDI outbreaks in two separate wards involving 22 patients admitted to a Canadian acute health care facility in 2012 are reported. On examining these two outbreaks, there was no evidence to support ongoing nosocomial transmission of C. difficile among these patients. The genetic diversity of recovered C. difficile isolates suggested that the outbreaks could not be attributed to a common source or sustained transmission of an outbreak strain.