Usefulness of molecular epidemiology for outbreak investigations.

We conducted a retrospective review of nosocomial outbreak investigations conducted by the Hospital Infections Program, Centers for Disease Control and Prevention, from January 1991 through March 1994. Selected outbreaks have demonstrated the utility of molecular methods such as plasmid analysis, plasmid restriction endonuclease analysis, ribotyping, restriction fragment polymorphism, pulsed-field gel electrophoresis, and polymerase chain reaction in confirming the clonality of the outbreak and in confirming the source of the outbreak implicated in the epidemiologic investigation. These data show that molecular typing of isolates is particularly useful when combined with epidemiologic investigations of nosocomial outbreaks.