Contamination of expressed human breast milk with an epidemic multiresistant Staphylococcus aureus clone

Nosocomial infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major cause of outbreaks in intensive care units. Infants mak e up a sector of the population that presents a high risk for MRSA infectio ns. Mother-to-infant transmission has been indicated as a possible cause of MRSA infections in neonates, The occurrence and characteristics of MRSA in samples of banked human milk were investigated by selective culture, antib iogram and pulsed-field gel electrophoresis. MRSA contamination was found i n 11% of 500 samples of expressed, fresh-frozen milk from 500 different don ors at five Brazilian milk banks, The great majority of the contaminated sa mples passed breast milk quality control criteria for dispensing as raw mil k under Brazilian and American guidelines. Most of the MRSA isolates belong ed to the Brazilian epidemic clone, which is reported to be widespread in s everal Brazilian states, in Argentina and in Portugal. It is concluded that expressed breast milk can be a reservoir of multiresistant S, aureus epide mic clones. Studies are necessary to assess the source of contamination and potential role of MRSA-contaminated milk in the transmission of MRSA to ne onates.