Outbreak of Serratia marcescens Infections in a Cardiothoracic Surgical Intensive Care Unit

Abstract

An outbreak of infections with pigmented Serratia marcescens involving 3 patients in a cardiothoracic surgical intensive care unit is reported. A respirator is thought to have been the source of pneumonia in 2 patients, and fomite spread from 1 of these is considered responsible for the induction of fatal endocarditis in the third patient. This outbreak demonstrates the rapid dissemination of a bacterial strain within the unit, several methods of dissemination, the wide variation in apparent virulence of the organism, the alterations of antibacterial host defense which made bacterial disease possible and which determined the site of infection, and the difficulties of adequate therapy. The third patient is the seventh reported with serratia infection of a prosthetic heart valve.