Effect of macrolide consumption on erythromycin resistance in Streptococcus pyogenes in Finland in 1997-2001

The aim of this study was to investigate the association between regional macrolide resistance in Streptococcus pyogenes and macrolide use in Finland. During 1997 - 2001, a total of 50,875 S. pyogenes isolates were tested for erythromycin susceptibility in clinical microbiology laboratories throughout Finland. The local erythromycin resistance levels were compared with the regional consumption data of all macrolides pooled and, separately, with the use of azithromycin. The regional resistance rates of 1 year were compared with the regional consumption of the previous year and with the average rates of use for the 2 previous years. A linear mixed model for repeated measures was used in modeling the association. A statistically significant association existed between regional erythromycin resistance in S. pyogenes and consumption of macrolides; association with azithromycin use alone was not found.