SUMMARY

In total, 413 clinical isolates of Streptococcus pneumoniae were collected from four University laboratories in Sofia, Pleven, Plovdiv and Varna for the period of 2006-2008. 150 strains (36, 3%) of all 413 tested S. pneumoniae were erythromycin-resistant (ERSP). The most prevalence of ERSP were observed in children under 5 years (80.0%). The results of conventional PCR showed presence of erm(Â) gene among 64.7 % of the strains, mef(Å) gene among 29.3%, and 9 strains (6%) carried both erm(Â)+mef (Å). Serotypes 6Â, 19F and 19A were the most prevalent among ERSP with erm(Â) gene, and serotype 14 was predominant among strains harboring mef (E) gene. Phenotypic characterization of ERSP with the triple-disc test (4) completely confirmed the genotype: 106 strains were with MLSb phenotype (70.7%, including the 9-th strains harboring both erm (Â)+mef (Å) genes) and 44 were with Ì phenotype (29.3%). Ìacrolides are widespread used antibiotics in therapy of pneumococcus infections in our country and ERSP increased with accelerated rates: from 20 % in 2000, to 25 % in 2005 (5), till 36 % in the present research. The efflux mechanism of macrolide resistance, which were predominant before in Bulgaria (5), now give place to widely spread MLSB phenotype and genotype reffering with target modification. The dissemination of macrolide resistance encoded by erm (Â) gene were 30 % in 2000, increased to 43% in 2005 and 70 % in 2008