Antimicrobial drug use and macrolide-resistant **Streptococcus pyogenes**, Belgium

Abstract: In Belgium, decreasing macrolide, lincosamide, streptogramins B, and tetracycline use during 19972007 correlated significantly with decreasing macrolide-resistant Streptococcus pyogenes during 19992009. Maintaining drug use below a critical threshold corresponded with low-level macrolide-resistant S. pyogenes and an increased number of erm(A)-harboring emm77 S. pyogenes with low fitness costs.