Oral antimicrobial susceptibilities of Streptococcus pyogenes recently isolated in five countries

Between July 1998 and July 1999 1050 clinical isolates of Streptococcus pyo genes were collected from 11 study centres in five countries. Isolates were shipped to a co-ordinating laboratory for NCCLS specified broth microdilut ion susceptibility testing for penicillin, cefaclor, azithromycin, clarithr omycin, erythromycin and roxithromycin. All 1050 isolates of S. pyogenes te sted were susceptible to penicillin (MIC less than or equal to0.12 mug/ml) and cefaclor (MIC less than or equal to0.25 mug/ml). Azithromycin, clarithr omycin and erythromycin resistance rates were 15.9%, 15.4% and 15.8%, respe ctively. MIC(90)s for penicillin, cefaclor, azithromycin, clarithromycin, e rythromycin, and roxithromycin were 0.015, 0.12, >4, 8, >1 and 16 mug/ml, r espectively. Macrolide (erythromycin) resistance rates were highest in stud y centres in Italy (31.0%) and Spain (26.6%). Lower macrolide resistance ra tes were identified in study centres in Turkey (4.8%), France (3.8%), and S weden (3.7%). In conclusion, the isolates of S. pyogenes tested were univer sally susceptible to B-lactam antibiotics such as penicillin and cefaclor, while resistance to macrolides was significant and ranged from 3.2% to 31%.