Outbreaks associated to bloodstream infections with Staphylococcus aureus and coagulase-negative Staphylococcus spp in premature neonates in a University Hospital from Brazil

Staphylococcus aureus and coagulase-negative staphylococci (CoNS) are among the most important nosocomial pathogens in patients from neonatal intensive care units, mainly in bloodstream infections. The main objective of this study is to determine the occurrence of nosocomial infections by these microorganisms using two surveillance systems (Laboratorial Surveillance and National Nosocomial Infection Surveillance System) and to determine the most important risk factors during a two-year period (2001-2002). Two outbreaks by both methicillin susceptible S. aureus (MSSA) (1.5%) and methicillin resistant CoNS (MRCoNS) (1.0%) were observed, from January to February/02 and August to September/02. Endemic incidence rates of 3.77% and 5.16% of S. aureus and CoNS, respectively were detected. Risk factors included age <= 7 days, hospitalization >= 7 days and utilization of polietilene central vascular catheter (CVC) through vein dissection (phlebotomy), but none of these independent factors were confirmed by the multivariate analysis. However, oxacillin resistant CoNS prevailed (66.0%) in the epidemic episodes. Molecular analysis by pulsed field gel electrophoresis showed the polyclonal nature of S. aureus isolates. In conclusion, two outbreaks were identified of mixed etiology by MSSA and MRCoNS associated to the lack of an adequate material ( central venous catheter) for neonates, related invasive procedure. The outbreaks were controlled with the substitution of polietilene CVC for peripherally inserted central catheter.