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Journal of Clinical Microbiology, February 2008, p. 560-567, Vol. 46, No. 2
0095-1137/08/$08.00+0     doi:10.1128/JCM.00832-07
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Colonization and Persistence of Antibiotic-Resistant Enterobacteriaceae Strains in Infants Nursed in Two Neonatal Intensive Care Units in East London, United Kingdom

Barts and The London NHS Trust, Whitechapel, London E1 1BB, United Kingdom,¹ Homerton University Hospital NHS Foundation Trust, Homerton Row, London E9 6SR, United Kingdom,² Barts and The London NHS Trust, Queen Mary's School of Medicine and Dentistry, Wolfson Institute, Charterhouse Square, London EC1M 6BQ, United Kingdom,³ University College Hospital, Euston Road, London, United Kingdom⁴

Received 19 April 2007/ Returned for modification 1 October 2007/ Accepted 13 November 2007

Stool samples were collected from infants nursed in two neonatal intensive care units (NICUs) in East London, United Kingdom. The aim of the study was to determine the incidence of and risk factors for the carriage of multiresistant Enterobacteriaceae strains (MRE; resistant to three or more classes of antibiotic) and the extent of the persistence of resistant strains following discharge. Sixty-two (50%) of 124 infants had acquired MRE by 2 weeks of postnatal age, and 69 (56%) infants had acquired MRE by discharge. The proportions of infants at 2 weeks carrying strains that were resistant to antibiotics were the following: tetracycline, 79%; amoxicillin, 78%; cephalosporins, 31%; trimethoprim, 20%; piperacillin-tazobactam, 11%; chloramphenicol, 9%; and aminoglycoside, 4%. A gestational age of less than 26 weeks was a risk factor for colonization with MRE at discharge, but not at 2 weeks. Analysis within a NICU showed that exposure of an infant to a specific antibiotic in the NICU was not a risk factor for the carriage of a strain resistant to that antibiotic. Estimates of persistence from discharge to 6 months were the following: for tetracycline, 57% (95% confidence intervals [CI], 0.35 to 0.87); chloramphenicol, 49% (95% CI, 0.20 to 0.83); trimethoprim, 45% (95% CI, 0.22 to 0.74); piperacillin-tazobactam, 42% (95% CI, 0.20 to 0.71); and augmentin, 34% (95% CI, 0.11 to 0.66). Strains resistant to cephalosporins or aminoglycosides showed lower levels of persistence. Nine of 34 infants (26.5%) with Escherichia coli and 4 (7.1%) of 56 infants with Klebsiella spp. at discharge carried strains indistinguishable by randomly amplified polymorphic DNA and antibiotic susceptibility patterns at 6 months. MRE were found at high frequency in the infants during their stay in the NICU and persisted in a proportion of infants.

Published ahead of print on 26 November 2007.