مرکز منطقه ای اطلاع رساني علوم و فناوري - Investigation of Macrolide Resistance Mechanisms in Streptococcus pneumoniae: Results of Marmara University Hospital Between 2005-2008

Abstract :

Objective: In this study, we aimed to determine the phenotypic characteristics and genetic determinants of macrolide resistance in the clinical isolates of Streptococcus pneumoniae. Materials and Methods: In 50 erythromycin resistant S. pneumoniae isolates, 14-, 15- membered macrolides and lincosamide susceptibilities were determined by both disk diffusion and broth microdilution methods. The erythromycin-clindamycin double disk method was applied for the detection of macrolide resistance phenotypes. Genetic determinants of macrolide resistance, erm(B), erm(TR) and mef(A)/(E) were investigated by Polymerase Chain Reaction (PCR). Results: The percentages of the isolates presenting Macrolide-Lincosamide-Streptogramin B (MLSB) and M phenotypes were 86% (cMLSB phenotype: 76%; iMLSB phenotype: 10%) and 14%, respectively. According to the PCR results, 18 isolates (36%) had erm(B) gene, 11 isolates (22%) had mef(E)/(A) gene and the remaining 21 (%42) isolates had both erm(B) and mef(A)/(E) genes. All erm(B) positive isolates (78%) presented high level macrolide and lincosamide resistance. Seven out of 11 isolates carrying the mef(A)/(E) gene alone presented M phenotype with low level macrolide MICs. Conclusion: The demonstration of the mef(A)/(E) gene either alone or together with erm(B) in a high proportion of the isolates (64%) in addition to the high rate of M phenotype (14%) signifies that active macrolide efflux together with the ribosomal target mutation has a significant role in the macrolide resistance of our pneumococcal isolates.