Outbreak among healthy newborns due to a new variant of USA300-related meticillin-resistant Staphylococcus aureus

Background: The prevalence of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) is increasing throughout the world and is an important cause of skin and soft tissue infection (SSTI) in children and neonates. Aim: To describe the successful control of an outbreak caused by a new strain of CA-MRSA in a newborn nursery. Methods: The investigation of the outbreak in July 2012 is reported with the control measures taken. Molecular typing of the MRSA isolates was performed. Findings: An outbreak of SSTI caused by CA-MRSA occurred in a newborn nursery. Sixneonates were infected in a one-month period [infection rate: 8.5% (6/71)]. A new variant of CA-MRSA was responsible, which was characterized as USA300-related, Panton-Valentine Leucocidin (PVL) positive, arginine catabolic mobile element (ACME) negative, sequence type 8 (ST8), staphylococcal cassette chromosome mec (SCC. mec) type IVa, agr type I and spa type t008. The outbreak among term neonates followed a rapid transmission pattern and was successfully controlled by implementing various outbreak control measures, including universal chlorhexidine bathing. Conclusion: This is the first report of a hospital outbreak caused by a USA300-related CA-MRSA clone in Korea. Early recognition and reinforcement of infection control measures are important in decreasing transmission of CA-MRSA in a hospital setting.