[Correlation between antibiotic prescription and decreased antimicrobial resistance in the health area of Zamora]

Abstract

Objective: To describe the trends in prescribing antibiotics and analyze a possible relationship with the evolution of antimicrobial sensitivity in respiratory pathogens isolated in the health area of Zamora (Spain).

Materials and methods: Descriptive study investigating the prescription of antimicrobials and the evolution of resistance in Streptococcus pyogenes, Streptococcus pneumoniae and Haemophilus influenzae, from 1996 to 2005. Antibiotic use is expressed in doses per 1,000 inhabitants per day (DHD). The chi(2) test, exact tests, Spearman correlation coefficients, and a time series analysis were used to analyze the trends.

Results: A total of 1301 S. pyogenes strains were isolated. All were sensitive to penicillin, with decreasing percentages of resistance to erythromycin and increasing percentages of resistance to clindamycin. Among 579 pneumococcal strains isolated, a significant decreasing resistance to penicillin, amoxicillin-clavulanic, cefotaxime and cefuroxime was observed; resistance to erythromycin and azithromycin increased during the first few years, but decreased later. Among a total of 769 strains of H. influenzae, all were sensitive to cefotaxime and highly sensitive to amoxicillin-clavulanic acid and cefuroxime; resistance to ampicillin was maintained and there was a significant decreasing resistance to azithromycin. Simultaneously, there was a progressive decrease in overall antibiotic use (20.45 DHD in 1996; 18.90 DHD in 2005). Prescription of penicillins remained stable, with increased use of amoxicillin-clavulanic, decreased use of cephalosporins and macrolides (except azithromycin), and increased use of fluorquinolones. We observed a significant correlation between prescription and resistance.

Conclusions: A recovery of sensitivity to antibiotics was seen in respiratory pathogens parallel to a progressive decrease in prescription of antibiotics.