First outbreak of extended-spectrum β-lactamase-producing Klebsiella pneumoniae in a Norwegian neonatal intensive care unit; associated with contaminated breast milk and resolved by strict cohorting

APMIS. 2012 Aug;120(8):612-21. doi: 10.1111/j.1600-0463.2012.02879.x. Epub 2012 Mar 24.


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. In contrast to previous outbreaks, only one infant acquired a systemic infection caused by the outbreak strain, probably due to a favourable epidemic strain lacking the most common virulence factors. A probable index case was identified, due to multiple positive breast milk samples collected from the infant's mother before and after the infant's transfer from another hospital. 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-producing’Enterobacteriaceae should therefore encourage changes in diagnostic routines for bacterial screening of breast milk.

MeSH terms

  • Anti-Bacterial Agents / therapeutic use
  • Cohort Studies
  • Cross Infection / diagnosis
  • Cross Infection / epidemiology*
  • Cross Infection / microbiology*
  • Cross Infection / transmission
  • Disease Outbreaks
  • Drug Resistance, Multiple, Bacterial
  • Female
  • Hospitals, University
  • Humans
  • Infant, Newborn
  • Infectious Disease Transmission, Vertical
  • Intensive Care Units, Neonatal
  • Klebsiella Infections / diagnosis
  • Klebsiella Infections / epidemiology
  • Klebsiella Infections / microbiology*
  • Klebsiella Infections / transmission*
  • Klebsiella pneumoniae / drug effects
  • Klebsiella pneumoniae / enzymology*
  • Klebsiella pneumoniae / isolation & purification*
  • Milk, Human / microbiology*
  • Norway / epidemiology
  • beta-Lactamases / biosynthesis*
  • beta-Lactamases / metabolism


  • Anti-Bacterial Agents
  • beta-Lactamases