A multistate outbreak of Serratia marcescens bloodstream infection associated with contaminated intravenous magnesium sulfate from a compounding pharmacy

Background. In contrast to pharmaceutical manufacturers, compounding pharmacies adhere to different quality-control standards, which may increase the likelihood of undetected outbreaks. In 2005, the Centers for Disease Control and Prevention received reports of cases of Serratia marcescens bloodstream infection occurring in patients who underwent cardiac surgical procedures in Los Angeles, California, and in New Jersey. An investigation was initiated to determine whether there was a common underlying cause. Methods. A matched case-control study was conducted in Los Angeles. Case record review and environmental testing were conducted in New Jersey. The Centers for Disease Control and Prevention performed a multistate case-finding investigation; isolates were compared using pulsed-field gel electrophoresis analysis. Results. Nationally distributed magnesium sulfate solution (MgSO4) from compounding pharmacy X was the only significant risk factor for S. marcescens bloodstream infection ( odds ratio, 6.4; 95% confidence interval, 1.1-38.3) among 6 Los Angeles case patients and 18 control subjects. Five New Jersey case patients received MgSO4 from a single lot produced by compounding pharmacy X; culture of samples from open and unopened 50-mL bags in this lot yielded S. marcescens. Seven additional case patients from 3 different states were identified. Isolates from all 18 case patients and from samples of MgSO4 demonstrated indistinguishable pulsed-field gel electrophoresis patterns. Compounding pharmacy X voluntarily recalled the product. Neither the pharmacy nor the US Food and Drug Administration could identify a source of contamination in their investigations of compounding pharmacy X. Conclusions. A multistate outbreak of S. marcescens bloodstream infection was linked to contaminated MgSO4 distributed nationally by a compounding pharmacy. Health care personnel should take into account the different quality standards and regulation of compounded parenteral medications distributed in large quantities during investigations of outbreaks of bloodstream infection.