Erythromycin Resistance in Group A Strep

During the 1980s, use of erythromycin in Finland tripled. Correspondingly, from 1988 until 1990, resistance of Streptococcus pyogenes to erythromycin increased from 5% to 13%. In 1991, Finnish national guidelines were issued that recommended a reduction of use of erythromycin and other macrolides to treat ambulatory skin and respiratory infections. Infectious disease experts and microbiologists were in accord that prescribing practices needed to change and promulgated education widely to Finnish physicians. Macrolide antibiotic use in 1992-1997 has been 40% less than that prior to the educational emphasis.

Although until 1990 erythromycin was the only available macrolide, by 1995 roxithromycin (Dynabac) held 41% of class prescriptions, azithromycin (Zithromax) 24%, and clarithromycin (Biaxin) 2%.

In 1992, based on testing of almost 40,000 isolates, 16.5% were resistant. By 1993, the percentage had risen to 19.0%. However, beginning in 1994 and continuing through 1996, levels of resistance continued to decline, as manifested by an 8.6% level of resistance in 1996. Though not conclusively established as causal, it appears highly likely that the measured reductions in macrolide resistance were directly related to reduced use. The authors make no comment about whether increased use of alternative classes of antibiotics incurred any noticeable increase in resistance as a result of compensatory growth of their use.

Seppala H, et al. N Engl J Med 1997; 337:441-446.