APMIS : acta pathologica, microbiologica, et immunologica Scandinavica
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Neonatal intensive care units (NICUs) are vulnerable to nosocomial outbreaks caused by multiresistant Enterobacteriaceae, but no reports of NICU outbreaks of extended-spectrum β-lactamase (ESBL) producing Klebsiella pneumoniae have previously been published from countries with a low level of antimicrobial resistance such as the Scandinavian countries. We describe a clonal outbreak of CTX-M-15 -producing Klebsiella pneumoniae affecting 58 infants in the neonatal intensive care unit at Stavanger University Hospital, Norway, during a period of 4 months, 2008-2009. The clone spread widely and rapidly in the NICU, and extensive interventions were required to terminate the outbreak. ⋯ Breast milk samples from 3/18 (17%) mothers of colonized infants were positive for ESBL-producing K. pneumoniae. Vertical transmission of ESBL-producing bacteria has been shown previously,but the possibility of transmission of ESBL-producing K. pneumoniae through expressed breast milk is reported here for the first time. The increasing occurrence of ESBL-producingEnterobacteriaceae should therefore encourage changes in diagnostic routines for bacterial screening of breast milk.