Correlation of Drug Utilization Data for Trimethoprim in a Defined Population with Patterns of Resistance among Bacteria Causing Urinary Tract Infections

Data from the continuous monitoring of outpatient prescriptions performed since 1970 among the inhabitants in the county of Jämtland were used to correlate the individual utilization of the antibacterial drug trimethoprim to the occurrence of resistance to this drug among pathogenic bacteria isolated in samples from the same population. There was a good correlation between the use of trimethoprim among female and male patients of different age groups and the occurrence of drug resistant bacteria in samples from the corresponding groups of patients. From total distribution data it was estimated that approximately 3% of the population received trimethoprim in 1984. In the oldest age groups one third of the county population was exposed to trimethoprim during a 6-year period. That this intensive use of the drug exerted a pronounced selection pressure for resistant strains in the population at large is indicated by the finding that one third of the patients harbouring resistant bacterial strains had never been treated with trimethoprim. This is interpreted as a reflection of trimethoprim resistance selected to such a ubiquity that it is spread independently of individual drug therapy.