BackgroundWe aimed to determine the genetic relatedness between Staphylococcus epidermidis colonizing breast milk (BM) and BM-fed neonates during the first month of life.MethodsS. epidermidis was isolated from the stool and skin swabs of 20 healthy term and 49 preterm neonates hospitalized in the neonatal intensive care unit and from the BM of mothers once a week and typed by multilocus variable-number tandem-repeat analysis. Virulence-related genes were determined by PCR.ResultsThe gut (95%) and skin (100%) of term neonates were colonized with strains genetically similar to those in BM and carrying mecA and IS256 at low rate (both <6.7%). In preterm neonates, colonization with strains genetically similar to those in BM was low on the skin (34.7%) and in the gut in the first week of life (14.3%), but the prevalence of mecA (>90.6%) and IS256 (>61.7%) was high. By the fourth week, in the gut of preterm neonates the prevalence of mecA (73.8%) and IS256 (18.4%) decreased, but colonization with strains genetically similar to those in BM increased (83.7%).ConclusionDuring early life, the skin and gut of preterm neonates is colonized with S. epidermidis that is distinct from strains found in BM, but gradually the gut is enriched with strains genetically similar to those in BM, as in term neonates.