Importance for Resistance at the Community Level

Antimicrobial resistance is influenced by selective forces related to the community volume of antimicrobial use (15,16). Many correlational studies have demonstrated that countries with higher antimicrobial consumption have higher rates of antimicrobial resistance (17-19). Consumption of beta-lactams is correlated with community levels of erythromycin and penicillin resistance, and macrolides can be strong drivers for local differences in erythromycin and penicillin resistance (17). Although these ecologic studies are not definitive proof of causality, the biologic plausibility and consistency of their findings are striking, and more ideal human experimental conditions are unlikely to be met (17).

A pair of natural experiments has shown that it is possible to reverse the trend toward increasing antimicrobial resistance. For example, in Finland during the 1980s, erythromycin consumption nearly tripled, and streptococcal erythromy-cin resistance increased from 5% to 13% between 1988 and 1990. Widely publicized recommendations were directed at physicians and the public to decrease outpatient macrolide use. The subsequent 43% decrease in macrolide consumption in Finland was followed by a fall in the prevalence of macrolide-resistant streptococci from a peak of 19.0% in 1993 to 15.6% by 1994, and 8.6% by 1996 (20).

In Iceland, the first penicillin-resistant S. pneumoniae (PRSP) was isolated in 1988. By 1993, PRSP accounted for nearly 20% of pneumococcal infections. PRSP surveillance among healthy day care children was instituted, and children found to be carrying PRSP were asked not to attend day care while they had symptoms of upper respiratory infection. Educational messages regarding appropriate antibiotic use were targeted to the public through the media, and the medical community through professional meetings and journals. The focus was on more selective diagnosis and antimicrobial treatment of otitis media, the most frequent reason for pediatric antimicrobial treatment. Propitiously, government outpatient antibiotic subsidies ended in 1991, making families responsible for the full cost of outpatient antimicrobial prescriptions. Antibiotic sales in Iceland declined (although not shown to be statistically significant), and PRSP infection declined from a peak of nearly 20% in 1993 to 16.9% in 1994. In 1992, 47% of healthy day care children were pneumococcal carriers and 20% of these organisms were PRSP. By 1995, 52% of children carried pneumococcus, of which 15% were PRSP (21).

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