Use of pulsed-field gel electrophoresis for investigation of an outbreak ofClostridium difficile infection among geriatric patients

A six-month outbreak ofClostridium difficile infection among elderly residents of a middle-term-care facility was investigated. Pulsed-field gel electrophoresis was used to genotype 22 outbreak strains and 30 epidemiologically unrelated strains. A prospective case-control study was conducted to identify risk factors for epidemicClostridium difficile-associated diarrhea. All epidemiologically unrelatedClostridium difficile strains of the same serogroup could be differentiated by their DNA patterns with two restriction enzymes (Smal andKspl). Among clustered strains, two epidemic serogroups (C and K) were identified. Two different DNA patterns were identified among serogroup C strains and three among serogroup K strains. Multivariate analysis showed that the risk ofClostridium difficile infection increased with antimicrobial chemotherapy (-lactam agents and pristinamycin) and the presence of a feeding tube. This study confirms the high discriminative power of restriction fragment length polymorphism analysis by pulsed-field gel electrophoresis to describeClostridium difficile epidemiology. The typing results confirm that infection was principally exogenous in this outbreak. Furthermore, they indicate the need to improve all measures limiting transmission of infection.