Epidemiology and susceptibility of serratia marcescens in a large general hospital over an 8-year period.

Over the 8 year period 1988-1995, 1367 isolates of Serratia marcescens were isolated from 582 patients on 12 different wards of a large Dublin hospital and were particularly associated with the surgical intensive care unit. The annual incidence was over 200 isolates from 1990 to 1992 but fell to below 100 following the opening in April 1992 of a replacement surgical hospital incorporating a new intensive care unit on the same site. The most common source of S. marcescens was sputum from patients. Strain identities were determined by serotyping and phage typing at least one isolate from each of 311 of the 582 patients. The results showed that a single epidemic strain of serotype O14:K14 was present in 69% of these patients, and persisted throughout the hospital for the whole of the eight-year period. This strain was recovered from a variety of clinical specimens, including blood cultures. A minor outbreak involving a serotype O16:K28 strain also occurred and this strain also persisted from at least 1989 to 1994. Extensive surveillance failed to reveal an environmental source or faecal carriage. The likely mode of transmission appears to have been via staff hands from both symptomatic and asymptomatic patients acting as reservoirs of the organism, as has commonly been reported for this species.