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 noninvasive (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.

The aims of this study were to determine endemic and epidemic infection due to Gram-negative bacilli, risk factors associated with colonization and infection by these organisms and the resistance phenotypes (ESBL, AmpC) in neonates admitted in a High Risk Nursery. The study was conducted during a 21 month period and included: a prospective study to evaluate the neonates with hospital infection and the use of third-generation cephalosporins; a case-control study to determine the risk factors associated with colonization/infection. Rectal and oropharynx cultures were also performed in four opportunities (September and November 2001, February and August 2002). The isolates for which the resistance of ceftazidime was 2 µg/mL were suspected of producing ESBL or AmpC β-lactamases. The incidence of infection by Gram-negative bacilli was 2.4% (89/ 3.708 neonates), and sepsis (35.9%) and conjunctivitis (31.4%) were the most common infections. The endemic infections were more prevalent (73.9%) and usually associated with Enterobacteriaceae (95.5%), being these organisms also related to colonization, corresponding mainly to isolates of Enterobacter spp. and Klebsiella spp. Two outbreaks of Pseudomonas aeruginosa (n=10) and Acinetobacter baumannii (n=11) were identified during the survey. Univariate analysis showed that risk factors for Gram-negative bacilli infection considered significant included: the length of stay before infection/colonization, exposure to antimicrobial agents, mechanical ventilation, central venous catheters, parenteral nutrition and surgery. The majority of resistance to ceftazidime among Enterobacteriaceae isolates (80.9%) was from ESBL phenotype. Administration of thirdgeneration cephalosporins (ceftriaxone) led to the emergence of these multiresistant Gram-negative bacilli in the neonatal unit.