Molecular surveillance of methicillin-susceptible Staphylococcus aureus at a neonatal intensive care unit in Brazil

Background: We evaluated the relationship among hospital infection and colonization by methicillin-susceptible Staphylococcus aureus (MSSA), clonal spread. and associated risk factors in a neonatal intensive care unit (NICU) of the Uberlandia Federal University-affiliated hospital in Brazil. Methods: Between February 2004 and June 2005, a longitudinal surveillance study was carried out in an NICU with neonates presenting infections, through both the NNIS system and S aureus punctual colonization prevalence inquests. Results: The overall rate of infection incidence was 23/1000 patient-days. Of all the neonates assessed, 15 were infected and 15 colonized. Sepsis was the most frequent infection, whereas anterior nare was the most isolated site. Antibiotics use, central vascular catheter (CVC). and CVC use more than 7 days and its insertion by phlebotomy were the risk factors for colonization/infection. Molecular analysis showed polyclonal origin (12 genotypes), with predominance of a genotype ("B"). and clonal identity between colonization and infection samples. Conclusion: The analysis by means of classical epidemiology and molecular techniques pointed out that methicillin-susceptible Staphylococcus aureus infections were associated with previous colonization by the pathogen. with evidence of horizontal transmission within the unit.