Characteristics of hospital patients colonized with livestock-associated meticillin-resistant Staphylococcus aureus (MRSA) CC398 versus other MRSA clones.

Meticillin-resistant Staphylococcus aureus (MRSA) associated with the clonal complex (CC) 398 has emerged among livestock and humans exposed to these animals. MRSA CC398 has so far contributed relatively little to spread of MRSA and the burden of disease in the healthcare setting. This study aimed to assess whether demographic and clinical differences in patients colonized with MRSA CC398 and those carrying other MRSA clones contribute to the observed differences in transmission and infection rates. Age, sex, length of stay (LOS), diagnoses and medical procedures were assessed in all patients with MRSA admitted to a university hospital in 2008 and 2009. S. aureus protein A gene (spa) typing was performed on the first MRSA isolate from each patient. Patients colonized or infected with MRSA that had spa types indicative of CC398 (MRSA CC398) were compared with patients who had other MRSA clones (MRSA non-CC398). Age (53 vs 59 years), mean LOS (8 vs 13 days) and percentage of patients admitted to an intensive care unit (12% vs 17%) differed significantly between MRSA CC398 and MRSA non-CC398 patients, respectively. The mean numbers and types of diagnoses and medical procedures performed for patients in these two groups also differed significantly. The differences in patient characteristics could explain, at least in part, the relatively low rates of transmission and infection associated with MRSA CC398 in the healthcare setting.