Outbreak of Methicillin-Resistant Staphylococcus aureus (MRSA) in a Neonatal Intensive Care Unit: Aggressive Control Measures To Stop the Epidemic

BACKGROUND: MRSA is a major nosocomial pathogen in NICUs. Several reports documented control of MRSA outbreaks in NICUs through isolation of colonized/infected infants and mupirocin use for decolonization of neonates and/or healthcare workers (HCWs). OBJECTIVE: 1)To identify the best containment measures avoiding the Unit closure 2)To determine the molecular epidemiological characteristics of MRSA isolates. DESIGN/METHODS: Our Unit is a 50-bed Unit composed of two areas: a 25-bed intensive-care and a 25-bed intermediate-care area. After some cases of MRSA infection occurred, a prospective epidemiological study was performed in both areas from July 2010 through November 2010. Surveillance cultures were obtained from all neonates (nares and pharynx with a single swab, rectum, umbilicus/axilla) at admission, at room-changing and once weekly, from HCWs (nares) and from the environment. All strains were typed by repetitive sequence-based polymerase chain reaction (rep-PCR). Other measures were also taken: universal precautions were intensified (handwashing, gloves, masks), education of the staff was stressed, colonized babies were strictly cohorted and treated with nasal mupirocin. Because the outbreak continued, all neonates in the Unit were bathed with diluted chlorhexidine gluconate and treated with nasal mupirocin. RESULTS: The MRSA colonization rate at the beginning of the study was high (53%). 300 neonates underwent surveillance cultures (5484 samples); 102/300 (34%) infants had positive swabs. The median time from admission to the first positive culture was 17 days. 11/102 (10.7%) colonized infants became infected; no deaths nor sequelae were observed. 19/157 (12.1%) HCWs had positive swabs. All MRSA isolates from infants and HCWs were homologous at the 95% level, indicating a difference of 1 band or less. All cultures obtained from the environment were negative. Eradication of MRSA outbreak was achieved after treatment of all neonates in the Unit. CONCLUSIONS: Because MRSA has become an important cause of outbreaks, early action is essential to prevent acquisition and transmission of MRSA in NICUs. A high colonization rate justifies the application of very aggressive infection control measures, such as antibiotic treatment of all neonates in NICUs, to stop the epidemic without closing the Unit.