Prior antibiotics and risk of antibiotic-resistant community-acquired urinary tract infection: a case-control study.
BACKGROUND
To assess the effect of previous antibiotic use on the risk of a resistant Escherichia coli urinary tract infection (UTI), we undertook a case-control study with prospective measurement of outcomes in 10 general practices in the UK.


METHODS
Urinary samples from all patients with symptoms suggestive of UTIs were sought, and those with a laboratory-proven E. coli infection were interviewed and their medical records examined. Case patients were those with ampicillin- or trimethoprim-resistant infections and control patients had infections that were susceptible to antibiotics, including ampicillin and trimethoprim.


RESULTS
Risk of ampicillin-resistant E. coli infection in 903 patients was associated with amoxicillin prescriptions of >or=7 days duration in the previous 1 month [odds ratio (OR)=3.91, 95% CI 1.64-9.34] and previous 2-3 months (2.29, 1.12-4.70) before illness onset. For prescriptions <7 days duration, there was no statistically significant association. Higher doses of amoxicillin were associated with lower risk of ampicillin resistance. For trimethoprim-resistant E. coli infections, the OR was 8.44 (3.12-22.86) for prescriptions of trimethoprim of >or=7 days in the previous month and 13.91 (3.32-58.31) for the previous 2-3 months. For trimethoprim prescriptions of <7 days, the OR was 4.03 (1.69-9.59) for the previous month but prescribing in earlier periods was not significantly associated with resistance.


CONCLUSIONS
Within the community setting, exposure to antibiotics is a strong risk factor for a resistant E. coli UTI. High-dose, shorter-duration antibiotic regimens may reduce the pressure on the emergence of antibiotic resistance.
Hillier
Sharon
S
Department of Epidemiology, Centre for Health Sciences Research, Cardiff University, Neuadd Meirionydd, Heath Park, Cardiff CF14 4YS, UK.
Roberts
Zoe
Z
Dunstan
Frank
F
Butler
Chris
C
Howard
Anthony
A
Palmer
Stephen
S
D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D000892:Anti-Infective Agents, Urinary / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D016022:Case-Control Studies; D017714:Community-Acquired Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D024881:Drug Resistance, Bacterial; D004363:Drug Utilization; D004926:Escherichia coli / Q000187:drug effects; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D010406:Penicillins / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D012307:Risk Factors; D014295:Trimethoprim / Q000008:administration & dosage / Q000494:pharmacology / Q000627:therapeutic use; D014296:Trimethoprim Resistance; D006113:United Kingdom / Q000453:epidemiology; D014552:Urinary Tract Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology
D000900:Anti-Bacterial Agents; D000892:Anti-Infective Agents, Urinary; D010406:Penicillins; D014295:Trimethoprim