42 Invasive Bacterial Infections Caused by Extended-Spectrum β-Lactamase (ESBL) Producing Microorganisms in Neonatal Intensive Care Unit (NICU) Setting.

Abstract

Purpose: Recently, we have noticed an increased incidence of infections caused by antibiotic-resistant pathogens including ESBL-producing microorganisms in our NICU patients. The purpose of this study was to investigate the incidence, predisposing conditions and treatment outcome of ESBL-producing Klebsiella species and E. coli invasive infections in our neonatal intensive care unit population.Methods: Review of medical and microbiological records of neonates with invasive infections caused by Klebsiella and E. coli who were treated at Children's Hospital of Michigan NICU during a 2-year period.Results: During the 2-year study period (January 2003-December 2004), 88 patients with positive cultures for Klebsiella or E. coli were identified. Of the 88 positive cultures, 52 were determined to be true infections and 36 were considered to represent colonization. The 52 infected patients had a median age of 30 days (3-300 days) and 27 (52%) were male. Infecting organisms were recovered from blood in 16 (30.8%), CSF 1 (1.9%), peritoneal fluid 2 (3.8%), lung tissue 2 (3.8%), bronchoalveolar lavage 1 (1.9%), urine 20 (38.5%), sputum 7 (13.5%) and open wound swabs 3 (5.8%). E. coli was isolated from 24 patients (46.2%), K. pnemoniae 19 (36.5%), K. oxytoca 5 (9.6%) and E. coli plus K. pnemoniae from 4 (7.7%). Six of the bacteremic patients had at least one other positive culture. Among the bacterial isolates, 1/24 (4.2%) E. coli, 10/19 (52.6%) K. pneumoniae and 2/5 (40%) K. oxytoca were ESBL enzyme producers. Logistic regression analysis indicated that only treatment with 3rd or 4th generation cephalosporin during the 3 months prior to onset of infection was associated with an increased risk of acquiring ESBL-producing Klebsiella or E. coli infections (P=.002; OR 14.0; CI95, 2.6 to 73.6). All except one ESBL-producing isolate were susceptible to the two carbapenems, imipenem and meropenem (MIC<4μg/ml). Among 13 patients with infections caused by ESBL-producing microorganisms, 5 were treated with a carbapenem and 4 improved; 8 were not treated with a carbapenem and 4, who were bacteremic, died.Conclusions: Half of the Klebsiella isolates that caused infections in our NICU patients were ESBL-producing strains. Treatment with 3rd or 4th generation cephalosporins within the previous 3 months was associated with an increased risk of acquiring ESBL-producing Klebsiella or E. coli infections. Treatment of ESBL-producing Klebsiella or E. coli infections with a carbapenem was associated with a favorable outcome in our patients.