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 mg/mL were suspected of producing ESBL or AmpC b-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 third-generation cephalosporins (ceftriaxone) led to the emergence of these multiresistant Gram-negative bacilli in the neonatal unit.
infection; colonization; neonates; Gram-negative bacilli; resistance phenotype
