Risk factors for specific methicillin-resistant Staphylococcus aureus clones in a Korean hospital

Objectives: To analyse the risk factors for nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infections caused by different clonal types. Methods: A total of 134 non-duplicate nosocomial MRSA isolates were analysed for clonal types by molecular typing techniques. The medical records of 90 patients who had documented MRSA infection were evaluated retrospectively. Results: Two predominant MRSA clones of sequence types (STs) ST239 (n = 75) and ST5 (n = 39) accounted for 85% of the isolates. Management of patients in the departments of orthopaedic surgery, neurosurgery and plastic surgery was identified as a risk factor for infection with MRSA of ST239, while the presence of intravascular catheters was a risk factor for infection with ST5. Pulmonary infection was significantly higher in the patients infected with ST239 strains than in the patients infected with ST5 strains (P < 0.05). The overall mean duration of antimicrobial therapy for the patients with ST239 infection was significantly more than that for the patients with ST5 infection (P < 0.05). Conclusions: ST239 and ST5 were the predominant MRSA clones in the study hospital. Risk factors were significantly different between ST239 and ST5 strains. The results of this study will be of use in designing larger prospective epidemiological studies for MRSA infection based on clonal types.