Antimicrobial Drug Use and Macrolide-Resistant Streptococcus pyogenes, Belgium

In Belgium, decreasing macrolide, lincosamide, streptogramins B, and tetracycline use during 1997-2007 correlated significantly with decreasing macrolide-resistant Streptococcus pyogenes during 1999-2009. 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. ; This study was partly funded by the Belgian Antibiotic Policy Coordination Committee.