Trimethoprim and ciprofloxacin resistance and prescribing in urinary tract infection associated with Escherichia coli: a multilevel model.
OBJECTIVE
Individual and group level factors associated with the probability of antimicrobial resistance of uropathogenic Escherichia coli were analysed in a multilevel model.


METHODS
Adult patients consulting with a suspected urinary tract infection (UTI) in 22 general practices over a 9 month period supplied a urine sample for laboratory analysis. Cases were patients with a UTI associated with a resistant E. coli. Previous antimicrobial exposure and other patient characteristics were recorded from the medical files.


RESULTS
Six hundred and thirty-three patients with an E. coli UTI and a full record for all variables were included. Of the E. coli isolates, 36% were resistant to trimethoprim and 12% to ciprofloxacin. A multilevel logistic regression model was fitted. The odds that E. coli was resistant increased with increasing number of prescriptions over the previous year for trimethoprim from 1.4 (0.8-2.2) for one previous prescription to 4.7 (1.9-12.4) for two and 6.4 (2.0-25.4) for three or more. For ciprofloxacin the ORs were 2.7 (1.2-5.6) for one and 6.5 (2.9-14.8) for two or more. The probability that uropathogenic E. coli was resistant showed important variation between practices and a difference of 17% for trimethoprim and 33% for ciprofloxacin was observed for an imaginary patient moving from a practice with low to a practice with high probability. This difference could not be explained by practice prescribing or practice resistance levels.


CONCLUSIONS
Previous antimicrobial use and the practice visited affect the risk that a patient with a UTI will be diagnosed with an E. coli resistant to this agent, which was particularly important for ciprofloxacin.
Discipline of Bacteriology, NUI Galway, Galway, Ireland. akke.vellinga@nuigalway.ie
Akke
A
Vellinga
Sana
S
Tansey
Belinda
B
Hanahoe
Kathleen
K
Bennett
Andrew W
AW
Murphy
Martin
M
Cormican
D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016022:Case-Control Studies; D002939:Ciprofloxacin / Q000494:pharmacology* / Q000627:therapeutic use; D011307:Drug Prescriptions / Q000706:statistics & numerical data; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000187:drug effects* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011320:Primary Health Care; D011446:Prospective Studies; D012307:Risk Factors; D014295:Trimethoprim / Q000494:pharmacology* / Q000627:therapeutic use; D014552:Urinary Tract Infections / Q000188:drug therapy / Q000382:microbiology*
D000900:Anti-Bacterial Agents; D002939:Ciprofloxacin; D014295:Trimethoprim