Plasmid-mediated antibiotic resistance in a changing hospital environment: Efficacy of control measures

A cross-transmission outbreak of gentamicin-resistant Serratia marcescens infection, followed by smaller outbreaks of gentamicin-resistant Klebsiella pneumoniae and Providentia rettgeri infection, occurred in a Veterans Administration hospital that was in the process of becoming a major teaching hospital within a new medical school. The resistant Serratia isolates carried a single plasmid, which was found only occasionally in other gentamicin-resistant bacterial species. Amikacin-resistant Serratia marcescens emerged despite infrequent use of amikacin. Environmental contamination with gentamicin-resistant Serratia was documented, in one instance, on the day following transfer of all patients in the hospital to a new facility. Control measures were thought to be responsible, at least in part, for the eventual decline in frequency of gentamicin-resistant bacteria.