Molecular epidemiology of extended-spectrum beta-lactamase-producing Klebsiella pneumoniae isolated from neonatal intensive care unit patients involved in hospital infection cases in Rio de Janeiro, Brazil. 
During a two years period, in this study was analyzed the demographic and bacteriologic data of 42 hospitalized newborns attempted by extended-spectrum beta-lactamase-producing Klebsiella pneumoniae sepsis in a neonatal intensive care unit of a public maternity hospital in Rio de Janeiro, Brazil.  The newborns mean age was 10.4 days, with a major prevalence of hospital infection in males (55.0%) than females (45.0%), and a major frequency in vaginal delivery (65.0%) than cesarean delivery (35.0%).  31 patients (77.5%) received a mean of 3 antimicrobials during a 7.9 days before positive blood cultures.  The most important underlying risk conditions were prematurely (87.5%), very low birth weight (55.0%) and asphyxia (40.0%).  Among the isolated strains were detected high resistance proportion to beta-lactams, aminoglycosides, chloramphenicol and trimethoprim-sulfamethoxazole.  6 distinct clones in a cluster of 42 epidemiologically related strains were detected through PFGE profiles.  The isolated strains presented 9 different antimicrobial resistance profiles (ARPs), where the most frequent clones (A, B and D) were distributed in 5, 3 and 5 ARPs, respectively.  Based in the PFGE profiles and isolation periods, apparently the clones A plus A1, B and D caused 3 distinct outbreaks during the study period.