Infection and colonization by Staphylococcus aureus in a high risk nursery of a Brazilian teaching hospital.

Neonates are susceptible to nosocomial infections due to immunological immaturity, prolonged hospital stay and the use of invasive procedures. We evaluated the incidence of infections and the prevalence of colonization by MRSA (Methicillin-resistant Staphylococcus aureus) and MSSA (Methilin-susceptible Staphylococcus aureus), as well as colonization risk factors. Staphylococcal infections were observed by analyzing medical records in the HICS (Hospital Infection Control Service) and the HRN (High Risk Nursery). Additionally, four inquiries concerning colonization prevalence were made for S. aureus, from January/2000 to December/2002. Clinical specimens from the nostrils, mouth and anus were cultivated in mannitol-salt agar plates and identification was made through standard methods. The frequency of neonates colonized by S. aureus was 49%. MSSA was more prevalent (57%) than MRSA (43%). Risk factors related to the acquisition of MRSA were: low weight and antibiotic use., Hospital stay was the only variable significantly associated with colonization by S. aureus. The incidence of infections by S. aureus during the last three years was 2.18% (159 cases). Nine of them (5.5%) were associated with MRSA and 150 (94.5%) with MSSA. Staphylococcal infections were considered as invasive (sepsis) and non-invasive (conjunctivitis, cutaneous), corresponding to 31% and 69%, respectively. The MRSA phenotype in infection was rare compared with methicillin-susceptible samples, although S. aureus, MRSA and MSSA colonization rates were high.