Contribution of efflux to cefuroxime resistance in clinical isolates of Escherichia coli

Scand J Infect Dis. 2003;35(8):464-70. doi: 10.1080/00365540310014639.


Retrospective data showed that resistance to cefuroxime among clinical blood culture isolates of Escherichia coli (2.67%) was more common than resistance to cefotaxime (0.59%) and ceftazidime (1.48%). 30 clinical isolates of E. coli with various degrees of resistance to cefuroxime were selected for the present studies. Antibiotic susceptibility to beta-lactam antibiotics was determined with the disc-diffusion method and for cefuroxime also with the E-test. The ability to grow in the presence of organic solvents was determined as a phenotypical measure of efflux. The organic solvent tolerance (OST) was graded on a scale from 1 to 5. Antibiotic susceptibility to cefuroxime, cefotaxime, ceftazidime and loracarbef was also determined in the presence of a known efflux pump inhibitor, MC-207,110. The strains that were organic solvent tolerant had significantly higher minimal inhibitory concentration (MIC) values for cefuroxime than the other E. coli strains (median 24 mg/l, range 4 to > 256 mgn/l vs median 4 mg/l, range 2-64 mg/l) and significantly lower cefuroxime zone diameters (p < 0.02). In the strains with most pronounced organic solvent tolerance, i.e. the cyclohexane-tolerant strains, the cefuroxime MIC values were decreased 2-fold (p < 0.03) and the zone diameters increased (p < 0.02) by the addition of an efflux pump inhibitor, MC-207,110. The findings supported the hypothesis that efflux contributes to cefuroxime resistance in E. coli.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bacterial Outer Membrane Proteins / pharmacology*
  • Cefotaxime / pharmacology*
  • Culture Media
  • Drug Interactions
  • Drug Resistance, Microbial
  • Escherichia coli / drug effects*
  • Escherichia coli / isolation & purification*
  • Female
  • Humans
  • Male
  • Microbial Sensitivity Tests
  • Sensitivity and Specificity
  • Statistics, Nonparametric
  • Sweden
  • beta-Lactamases / pharmacology


  • Anti-Bacterial Agents
  • Bacterial Outer Membrane Proteins
  • Culture Media
  • beta-Lactamases
  • Cefotaxime