Methicillin-susceptible Staphylococcus aureus in skin and soft tissue infections, Northern Italy

During February 2004-September 2006, familial clusters and sporadic cases of Staphylococcus aureus skin and soft tissue infections were observed in a suburban area near Milan in northern Italy. Molecular typing of the isolates showed an epidemic methicillin-susceptible S. aureus (MSSA) strain, spa type 005 and sequence type 22 that harbored Panton-Valentine leukocidin (PVL) genes. The first case-patients were neonates or mothers who had recently delivered in the local hospital. Examination of the medical records showed a cluster of postpartum mastitis and neonatal skin infections antedating the emergence of infections in the community. Nasal swabs of neonates, mothers, and hospital staff were positive for the epidemic MSSA. Hospital circulation of the strain was interrupted by implementation of infection control measures, although infections continued to occur in the community. The PVL-positive MSSA strain resembles typical community-acquired methicillin-resistant S. aureus in its ability to cause prolonged community and hospital outbreaks of skin infections.