Outpatient use of erythromycin: link to increased erythromycin resistance in group A streptococci.

Resistance to erythromycin in group A streptococci has become an important problem among outpatients in Finland. The prevention of such problems requires information about the relationship between antimicrobial consumption and antimicrobial resistance. Having found considerable variation among health authority areas in the proportions of group A streptococci resistant to erythromycin, we investigated the potential impact of local differences in the consumption of this agent on the development of resistance. In 1992, 10,162 group A streptococcal isolates (nearly 100% were from outpatients) collected from 206 health authority areas were tested for erythromycin resistance; 1,647 isolates (16%) were resistant. Logistic regression analysis showed that the proportion of isolates resistant to erythromycin clearly increased with increasing local erythromycin consumption by outpatients in 1991 (P = .006). This positive association indicates that a prudent policy for the treatment of outpatients is essential to maintenance of the effectiveness of antimicrobial agents.