Extended-spectrum beta-lactamase producing Klebsiella pneumoniae in neonatal intensive care unit.

摘要

OBJECTIVES: Extended-spectrum beta-lactamase producing (ESBL) Klebsiella pneumoniae is an important cause of nosocomial infections in neonatal intensive care units (NICUs). Our objectives were to determine (1) the incidence of ESBL K. pneumoniae in our NICU, (2) the frequency of SHV-1 and SHV-2 gene acquisition among ESBL K. pneumoniae isolates, (3) the risk factors associated with ESBL K. pneumoniae infection and (4) the clinical outcomes of infected infants. STUDY DESIGN: We conducted a prospective surveillance study in our NICU over a period of 1 year on all neonates admitted without evidence of early sepsis. We collected specimens from blood, urine, cerebrospinal fluid, swabs from wounds and throat and endotracheal tube aspirates of infants whenever sepsis was suspected. Bacterial isolates were identified via clinical morphology, Gram stain and standard biochemical tests. Antimicrobial susceptibility was determined by disc diffusion method, and phenotypic confirmation of ESBL production was done by the double-disc synergy test and Etest. Genetic detection of SHV-1 and SHV-2 genes in ESBL K. pneumoniae isolates was done by polymerase chain reaction (PCR) and restriction fragment length polymorphisms. Risk factors associated with ESBL K. pneumoniae infection were analysed by both univariate and multiple logistic regression methods. RESULTS: A total of 980 cultures were obtained from 380 neonates, and 372 screening cultures were collected from the environment. K. pneumoniae was cultured from 27 (7%) infants (3.8/1000 patient-days); of them, 18 (67%) were ESBL producers. PCR amplicons revealed the presence of SHV-2 in all 18 isolates (100%), and SHV-1 gene in 8 isolates (44%). Independent risk factors for ESBL K. pneumoniae infection were mechanical ventilation (OR: 4.2, confidence interval (CI): 1.6-11.0); birth weight <1500 g (OR: 3.2, CI: 1.2-8.3) ); duration of hospitalization >15 days (OR: 4.1, CI: 1.2-14.4); total parenteral nutrition (OR: 4.9, CI: 1.1-21.7); and previous use of oxyimino-antibiotics (OR: 4.9, CI: 1.1-21.5). ESBL was associated with higher mortality (RR=3.1, CI: 1.04-9.1) and prolonged hospitalization in those who survived (OR=3.8 CI: 1.02-11.2). Environmental cultures (n=372) had ESBL K. pneumoniae in nine isolates: four from suction tubes, two from the incubators and three from the hands of care givers. CONCLUSION: ESBL K. pneumoniae is a significant source for mortality and morbidity in infants admitted to NICU. Use of oxyimino-antibiotics is a significant risk factor for infection. The clinical significance for the SHV-1 and SHV-2 genes should be further explored.