BackgroundTo investigate clusters ofSerratia marcescens(SM) bloodstream infections (BSIs) at health care facilities in several states and determine whether contaminated prefilled heparin and isotonic sodium chloride solution (hereinafter, saline) syringes from a single manufacturer (company X) were the likely cause, we performed an outbreak investigation of inpatient and outpatient health care facilities from October 2007 through February 2008.MethodsActive case finding for clusters of SM BSIs. Information on SM BSIs was obtained, and SM blood isolates were sent to the Centers for Disease Control and Prevention (CDC). Culture specimens were taken from various lots of prefilled heparin and saline syringes by health care facilities and the CDC to test for the presence of SM. The SM isolates from syringes and blood were compared by pulsed-field gel electrophoresis.ResultsA total of 162 SM BSIs in 9 states were reported among patients at facilities using prefilled heparin and/or saline syringes made by company X. Cultures of unopened prefilled heparin and saline syringes manufactured by company X grew SM. Of 83 SM blood isolates submitted to the CDC from 7 states, 70 (84%) were genetically related to the SM strain isolated from prefilled syringes. A US Food and Drug Administration inspection revealed that company X was not in compliance with quality system regulations.ConclusionsA multistate outbreak of SM BSIs was associated with intrinsic contamination of prefilled syringes. Our investigation highlights important issues in medication safety, including (1) the importance of pursuing possible product-associated outbreaks suggested by strong epidemiologic data even when initial cultures of the suspected product show no contamination and (2) the challenges of medical product recalls when production has been outsourced from one company to another.