Sequential hospitalwide outbreaks of resistant Serratia and Klebsiella infections.

Late in 1973 at the Nashville Veterans Administration Hospital, an intrusion of Serratia marcescens infections that were resistant to gentamicin sulfate and other antimicrobial agents occurred. This abated somewhat, only to be superseded by another wave of multiply-resistant infections due to Klebsiella pneumoniae beginning in the spring of 1974. Approximately 400 patients had substantial infections with these organisms during the 2 1/4 year period, imposing considerable morbidity and mortality. Due to the serious and lasting impact that these events imposed on patient care in our hospital, we sought explanations for the sequential infectious outbreaks. Both may have arisen because of the same persisting pressures favoring prevalence of multidrug-resistant bacteria. Indirect evidence including the sequential order of the outbreaks, similarity of antibiotograms, transferable multiple drug resistance from Serratia to Klebsiella, and possession of approximately equal molecular weight plasmids supported the notion that the two outbreaks were causally related.