EMERGENCE OF STREPTOCOCCUS-PYOGENES STRAINS RESISTANT TO ERYTHROMYCININ GIPUZKOA, SPAIN

The aim of this study was to determine the evolution of resistance to macrolides and other antibiotics in strains of Streptococcus pyogenes isolated in the province of Gipuzkoa, Spain. During the period 1984-19 96, all 2561 strains of Streptococcus pyogenes studied showed full sus ceptibility to penicillin. Until 1990, only 1.2% of Streptococcus pyog enes isolates were resistant to erythromycin. Since then, resistance t o erythromycin increased every year until 1995, when 34.8% (87/250) of Streptococcus pyogenes strains were found to be resistant. In 1996 th e rate of resistance to erythromycin was 17.8% (75/422). During the st udy period, 96.1% (246/256) of the Streptococcus pyogenes isolates res istant to erythromycin were susceptible to clindamycin. Of the remaini ng erythromycin-resistant Streptococcus pyogenes strains, resistance t o clindamycin was constitutive in seven strains and inducible in three . When investigated by the polymerase chain reaction (PCR), all Strept ococcus pyogenes strains resistant to erythromycin and susceptible to clindamycin showed the 1.4 kb fragment of the mefA gene, recently desc ribed as the novel macrolide-efflux-resistance determinant. The most f requent T-agglutination patterns among Streptococcus pyogenes resistan t to erythromycin were T4 and T8,25. The emergence and rapid spread of erythromycin-resistant Streptococcus pyogenes in Gipuzkoa and its rel ationship to the presence of the mefA gene are described.