Outbreak of Serratia marcescens bloodstream infections in cardiac surgery patients—Kentucky, 2004

Abstract

BACKGROUND: Outbreaks of bacteremia following cardiac surgery (CS) have been associated with contamination of equipment and medications. Following detection of Serratia marcescens (SM) cases among CS patients, we conducted an investigation to identify potential sources of contamination and to define prevention measures. METHODS: A case was defined as SM bacteremia occurring in a patient who had CS between August 24 and September 30, 2004. Data on CS patients colonized or infected with SM in other sites were also analyzed. To identify risk factors, we conducted a case-control study comparing each case of SM bacteremia to two randomly selected controls who underwent CS during the outbreak period. To determine potential sources of SM in the environment, we performed observations of CS procedures and collected samples (e.g., water, open vials, cleaning products, and surfaces of equipment) from operating rooms. All patient isolates were evaluated by pulsed-field gel electrophoresis (PFGE) and antimicrobial susceptibility testing. RESULTS: Seven patients with SM bacteremia were identified. Four additional patients had SM identified in pericardium, urine, and sputum cultures. Three patients with SM bacteremia developed signs and symptoms of infection within two hours after CS. All patient isolates, except one sputum isolate, were indistinguishable by PFGE. Patients with SM bacteremia were more likely to have received the proteinase inhibitor, aprotinin, a medication administered during CS from single-use vials (odds ratio [OR] 25.3, p = 0.01) and to have their CS performed in one of two adjacent operating rooms (OR 18.2, p = 0.02). Although no contamination of vials or other environmental sources of infection were detected, our observations of CS procedures revealed suboptimal hand hygiene and equipment cleaning, and retaining of open, single-use vials of medication after each patient. CONCLUSIONS: In our investigation, we observed significant breaches in infection control practices, which may have led to contamination of the operating rooms' environment and single-use medication vials, such as aprotinin. Our findings underscore the importance of careful attention to infection control measures and to proper medication handling.