Risk factors for mortality of nosocomial methicillin-resistant Staphylococcus aureus (MRSA) bloodstream infection: With investigation of the potential role of community-associated MRSA strains

Objectives: The difference in the outcomes of nosocomial bloodstream infection (BSI) caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strains and healthcare-associated MRSA (HA-MRSA) strains remains unclear. Methods: From January 1, 2006 to December 31, 2008, all adult patients hospitalized at National Taiwan University Hospital with nosocomial MRSA BSI were analyzed. Available MRSA isolates were submitted for subsequent microbiologic studies to determine whether they belonged to CA-MRSA strains. Results: In total, 308 patients were enrolled and 253 MRSA isolates were available. Forty-seven isolates belonged to CA-MRSA strains. The all-cause mortality rates on Day 14 and Day 30 were 19.8% and 30.5%, respectively, and were not different between those caused by CA-MRSA and HA-MRSA strains. The independent risk factors for Day 14 mortality were septic shock, thrombocytopenia, and an inadequate serum trough level of vancomycin (p = <0.0001, 0.0003, and 0.0381, respectively). Those for Day 30 mortality were septic shock, anemia, thrombocytopenia, presence of underlying malignancies, and MRSA isolates with a vancomycin minimum inhibitory concentration of 2 mg/L (p = <0.0001, 0.0425, 0.0007, 0.0098, and 0.0012, respectively). Conclusions: The mortality rates of nosocomial MRSA BSI were not different between that caused by CA-MRSA and HA-MRSA strains.