Enterobacteriaceae infections of very low birth weight infants in Polish neonatal intensive care units: resistance and cross-transmission.

Background: The aims of our study were analysis of the occurrence of infections by members of the Enterobacteriaceae family in 6 Polish neonatal intensive care units in 2009, their drug resistance, the epidemiology of extended-spectrum beta-lactamase (ESBL)-producing strains and the possibility of using modern tools of microbiology diagnosis in infection control, especially for the reduction of antimicrobial resistance. Methods: A prospective surveillance covered 910 newborns. Case patients were defined as neonates with very low birth weight who had clinical signs of septicemia, pneumonia or necrotizing enterocolitis. Early-onset infection was defined as infection diagnosed within 3 days after delivery. Results: The incidence of Enterobacteriaceae infections was 2.6/1000 patient-days. The risk of Enterobacteriaceae pneumonia increased with the length of hospitalization (P = 0.0356). The most common pathogen was Escherichia coli (12.4% of all strains, in early-onset infection 18.5%) and Klebsiella spp. (9.1% of all). The ESBL phenotype was found in 37% of isolates, of which 89.3% were producing CTX-M-type, 70.2% TEM-type and 8.5% SHV-type. Epidemic clones were detected in the 2 studied neonatal intensive care units: 6 of the 9 ESBL-positive Enterobacter cloacae and 16 of the 18 ESBL-positive Klebsiella pneumoniae strains were classified into 1 epidemic clone, which showed resistance to penicillin without inhibitors, amoxycillin/clavulanic acid, cephalosporins, aztreoname, aminoglycosides and trimethoprim/sulfamethoxazole. Conclusions: Enterobacteriaceae bacilli are a significant problem in neonatal intensive care units, especially in early-onset infection and for long hospitalized very low birth weight infants. The observed high drug resistance was in large part related to the dominance of epidemic strains as a result of horizontal transmission. The best way to reduce drug resistance would be adequate procedures of isolation and hand hygiene.