Evaluation of resistance mechanisms and serotype and genotype distributions of macrolide-resistant strains in clinical isolates of Streptococcus pneumonia in Aydın, Turkey

Macrolide resistance mechanisms in 89 Streptococcus pneumoniae strains isolated from several clinical samples between February 2007 and May 2009 were investigated. Erythromycin resistance was noted in 35 (40%) S. pneumoniae strains. In these strains, the most frequent resistance phenotype was cMLS(B) (74%), and the most frequent resistance genotype was ermB (82%). Both ermB and mefA genes were positive in 20% of macrolide-resistant strains. While no resistance to vancomycin, linezolid and telithromycin was noted in 89 S. pneumoniae strains, 12 (13%) strains were penicillin resistant, 26 (30%) strains were clindamycin resistant, 35 (40%) were azithromycin resistant, 32 (36%) strains were tetracycline resistant, and 1 (1%) strain was levofloxacin resistant. The serotype distribution of 35 macrolide-resistant S. pneumoniae strains revealed that the most frequent serotype was serogroup 19 (45%). Multidrug resistance was present in 19 (86%) of 22 strains carrying only the ermB resistance gene. No clonal dissemination was noted in the macrolide-resistant pneumococcal strains. These findings suggest that macrolide resistance rates, resistance phenotype and genotype, as well as resistant serotypes of S. pneumoniae strains should be continuously monitored in our country.