Streptococcus pyogenes resistance to erythromycin in relation to macrolide consumption in Spain (1986-1997)

The relationship between Streptococcus pyogenes resistance to erythromycin and macrolide consumption in Spain was studied. Erythromycin resistance was highly correlated with the consumption of total macrolides (r = 0.88, P < 0.01). When macrolides were grouped into posological subgroups according to their pharmacokinetic and pharmacodynamic properties and analysed separately, erythromycin resistance appeared to be related mainly to those macrolides taken twice daily (bd) (r = 0.86, P < 0.01) and those taken once daily (od) (r = 0.87, P< 0.01), but not to those taken four (qds) or three times a day (tds) (r = -0.04, P = 0.90). A progressive increase in the erythromycin resistance curve was seen after the consecutive introduction of both bd and od macrolides, which contributed to the increase in the total macrolide consumption, replacing tds macrolide prescription. Although this ecological analysis cannot establish an unequivocal causal relationship between antibiotic consumption and S. pyogenes resistance, the data are consistent with the hypothesis that widespread use of macrolides, mainly of bd and od macrolides, resulted in an increased prevalence of S, pyogenes resistant to erythromycin in Spain.