Outbreak of ampicillin-resistant Enterococcus faecium--risk factors for faecal colonisation

APMIS. 2000 Apr;108(4):296-302. doi: 10.1034/j.1600-0463.2000.d01-60.x.


Since January 1995 there has been a nosocomial outbreak at Haukeland University Hospital involving more than 330 patients with clinical infections caused by ampicillin-resistant Enterococcus faecium (ARE) (minimum inhibitory concentration > or =32 mg/l). Rectal carriage of ARE was initially observed on two medical wards only. Here the ARE colonisation rate has remained high. To assess risk factors for ARE colonisation we performed a case-control study including 37 rectal carriers of ARE and 83 non-carriers on these wards. Significant differences were found between cases and controls with respect to the mean number of days on antimicrobial treatment (13.3 for carriers, 5.5 for non-carriers, p<0.001), mean number of different antibiotics prescribed (2.8 for carriers, 2.1 for non-carriers, p= 0.008) and mean number of days in hospital (18.4 vs 10.2, p=0.001). Unadjusted statistical analysis showed that several antibiotics were risk factors for ARE carriage. Logistic regression analysis showed that fluoroquinolone prescription (OR=3.5, p=0.01) and more than 10 days of antibiotic use (OR= 3.3, p=0.01) were significant risk factors. An additional follow-up screening of previous carriers revealed no colonisation 8 to 36 (median 9) months after discharge from hospital (n=17). Prolonged antimicrobial therapy and broad-spectrum antibiotics seem to facilitate nosocomial ARE colonisation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Ampicillin Resistance*
  • Analysis of Variance
  • Anti-Bacterial Agents / therapeutic use*
  • Carrier State / epidemiology*
  • Case-Control Studies
  • Cross Infection / drug therapy
  • Cross Infection / epidemiology*
  • Cross Infection / transmission
  • Disease Outbreaks*
  • Enterococcus faecium* / isolation & purification
  • Feces / microbiology*
  • Gram-Positive Bacterial Infections / drug therapy
  • Gram-Positive Bacterial Infections / epidemiology*
  • Gram-Positive Bacterial Infections / transmission
  • Hospital Bed Capacity, 500 and over
  • Hospitals, University
  • Humans
  • Length of Stay
  • Norway / epidemiology
  • Prevalence
  • Regression Analysis
  • Risk Factors


  • Anti-Bacterial Agents