An outbreak of Serratia marcescens associated with the anesthetic agent propofol

Background: In October 1999, 7 patients with postoperative infections caused by Serratia marcescens were identified at a community hospital in Ontario, Canada. We describe the investigation of this outbreak. Methods: We undertook a case-control study to determine risk factors associated with infection. Case subjects consisted of patients who had undergone surgery and acquired bacteremia or wound infections that, when cultured, grew S marcescens. Control subjects were selected from the cohort of patients who underwent surgery at the same hospital during the outbreak period. Chart reviews were conducted for case and control subjects. Environmental samples were taken from medications and liquids in the operating rooms and from one health care professional who was involved in all the cases. S marcescens isolates were forwarded to a reference laboratory for pulsed field gel electrophoresis. Results: We identified 7 case subjects and 29 control subjects. Five patients had bacteremia and 2 patients had wound infections. Two patients with bacteremia died. All patients with bacteremia or wound infections were exposed to a single anesthetist (anesthetist A) and were administered the anesthetic medication propofol. These patients were more than 40 times more likely to have had anesthetist A administer their anesthetic (OR 41.6, 95% CI 3.6–1120) and 22 times more likely to have received propofol (OR 22, 95% CI 2.1–550) than were control subjects. None of the environmental samples or cultures from anesthetist A were positive for S marcescens. Six of the 7 human isolates had an identical pulsed field gel electrophoresis pattern, and the seventh was untypeable. Conclusions: This outbreak of postoperative infections was very strongly linked to the use of propofol by one anesthetist. Health care professionals must follow strict aseptic techniques when using propofol and should review these techniques regularly.