Factors associated with antibiotic resistance in coliform organisms from community urinary tract infection in Wales

Routine susceptibility data for urinary coliform isolates from community pr actice were analysed in comparison with dispensed antibiotic prescriptions for all conditions and social deprivation data for Bro Taf and North Wales Health Authorities for financial years 1996-1998. Prescribing rates and res istance rates varied widely between practices. Among isolates from practice s with high usage of an antibiotic, rates of resistance to that antibiotic tended to be high, and usage correlated significantly with resistance betwe en practice population units. Cross-correlations were found between usage o f one antibiotic and resistance to another, particularly for trimethoprim a nd ampicillin. Usage, particularly of trimethoprim, was associated with mul ti-resistance to up to four antibiotics. Resistance was more frequent in is olates from males, children and the elderly. Ampicillin resistance correlat ed with social deprivation. Analyses including or excluding potential repea t isolates yielded closely similar results. Indices reflecting sampling beh aviour (laboratory coliform positivity rates, positivity per 1000 registere d patients, specimens submitted per 1000 registered patients) varied widely between surgeries, suggesting lack of consensus on urine sampling policies . These indices showed only weak correlations with usage or resistance. Ass ociations between resistance and usage were compared for isolates from two patient subsets that were likely to differ in their proportions of non-Esch erichia coli isolates: female patients aged 16-55 years; and males, childre n and patients aged >55 years. The latter showed higher base levels of resi stance, but the associations of resistance with usage were statistically in distinguishable for the two populations. The results suggest that usage of antibiotics in a practice population may affect the rate of urinary infecti on caused by resistant coliform organisms in that population.