High prevalence of erythromycin resistance of Streptococcus pyogenes in Greek children

Background. Macrolide resistance among Streptococcus pyogenes strains is in creasing in many European countries. Greece was not considered a country wi th high prevalence of macrolide-resistant S. pyogenes strains, and until no w the genetic mechanism of resistance was unknown. Methods. During the 25-month period from December, 1998, to December, 2000, pharyngeal cultures for S. pyogenes were performed on 743 Greek children w ith the clinical diagnosis of pharyngitis. The children were 1 to 16 years old (median age, 7 years) and were living in Central and Southern Greece. S . pyogenes isolates were tested for their susceptibility to erythromycin, c larithromycin, azithromycin, clindamycin, penicillin G, amoxicillin/clavula nate and cefprozil. The erythromycin-resistant isolates were further studie d for their genetic mechanism of resistance by means of PCR. Results. Of a total of 275 S. pyogenes isolates recovered, 105 (38%) were e rythromycin-resistant (MIC less than or equal to 1 mug/ml), with 54, 45 and 1% of them carrying mef(A), erm(A) [subclass erm(TR)] and erm(B) gene, res pectively. The prevalence of erythromycin-resistant strains was 29 and 42% during the time periods December, 1998, to December, 1999, and January, 200 0, to December, 2000, respectively. All erythromycin-resistant isolates wer e also resistant to clarithromycin and azithromycin. The isolates carrying the erm(A) gene were inducibly resistant to clindamycin. The 275 S. pyogene s isolates had ceprozil MICs less than or equal to 0.032 mug/ml.