Publication: Streptococcus pneumoniae'da makrolid direnç mekanizmalarının Araştırılması: 2005-2008, Marmara Üniversitesi hastanesi sonuçları
Abstract
Amaç: Bu çalışmada enfeksiyon etkeni olarak izole edilen Streptococcus pneumoniae izolatlarında, makrolid direncinin fenotipik karakteristiklerinin ve genetik determinantlarının belirlenmesi amaçlanmıştır. Gereç ve Yöntemler: Eritromisin direnci gösteren 50 S. pneumoniae izolatının 14-, 15- üyeli makrolid ve linkozamid duyarlılıkları disk difüzyon ve sıvı mikrodilüsyon yöntemleriyle saptanmıştır. Makrolid direnç fenotiplerini belirlemek üzere eritromisin-klindamisin çift disk testi kullanılmıştır. Makrolid direncinin genetik determinantları, mef(E)/(A), erm(B) ve erm(TR)nin saptanmasında Polimeraz Zincir Reaksiyonu (PZR) yöntemi kullanılmıştır. Bulgular: İzolatlarımızın % 86sı Makrolid-Linkozamid Streptogramin B (MLSB) (%76 cMLSB ve %10 iMLSB), % 14ü M fenotipi göstermiştir. PZR sonuçlarına göre 18 izolatta (% 36) tek başına erm(B); 11 izolatta (% 22) tek başına mef(E)/(A) geni; geri kalan 21 (% 42) izolatta ise her iki gen birlikte saptanmıştır. erm(B) geni taşıyan tüm izolatlar (%78), yüksek düzey makrolid ve linkozamid direnci gösterirken, mef(E)/(A) genini tek başına taşıyan 11 izolatın 7si M, 4ü MLSB fenotipi göstermiştir. M fenotipindeki izolatların makrolid MİKleri ise düşük düzeyde bulunmuştur. Sonuç: Çalışmamızda mef(A)/(E) geninin tek başına ya da erm(B) ile birlikte izolatların %64ü tarafından taşındığının gösterilmesi ayrıca M fenotipine sahip izolatların oranının da oldukça yüksek (%14) bulunması, aktif makrolid pompasının, ribozomal hedef mutasyonuyla birlikte hastanemiz pnömokok izolatlarının makrolid direncinde çok önemli rolü olduğunu ortaya koymaktadır.
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.
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.