Double-blind study to compare the selection of antibiotic resistance by amoxycillin or cephradine in the commensal flora

Lancet. 1983 Sep 3;2(8349):529-32. doi: 10.1016/s0140-6736(83)90566-4.


Elderly patients with acute urinary infections were treated in a double-blind study with either amoxycillin or cephradine. In 52 patients who had received amoxycillin for one week about a third of all intestinal Escherichia coli were highly resistant to amoxycillin, and many were resistant to tetracycline, trimethoprim, or chloramphenicol. Cephradine selected less resistance. At a week after completion of chemotherapy, cephradine-resistant E coli were replaced by sensitive cultures at a greater frequency than were amoxycillin-resistant E coli. Neither antibiotic altered the skin flora. Amoxycillin, but not cephradine, selected for Enterobacteriaceae in the saliva. The propensity of amoxycillin to select resistance in E coli will limit its usefulness in treating urinary infections.

Publication types

  • Clinical Trial
  • Comparative Study
  • Randomized Controlled Trial

MeSH terms

  • Acute Disease
  • Aged
  • Amoxicillin / pharmacology*
  • Amoxicillin / therapeutic use
  • Cephalosporins / pharmacology*
  • Cephradine / pharmacology*
  • Cephradine / therapeutic use
  • Clinical Trials as Topic
  • Double-Blind Method
  • Escherichia coli / drug effects
  • Escherichia coli Infections / drug therapy
  • Female
  • Humans
  • Intestines / microbiology
  • Male
  • Middle Aged
  • Penicillin Resistance
  • Random Allocation
  • Saliva / microbiology
  • Skin / microbiology
  • Urinary Tract Infections / drug therapy


  • Cephalosporins
  • Amoxicillin
  • Cephradine