The relationship between macrolide resistance mechanisms and serotypes of Streptococcus pneumoniae

Yıl 2012, Cilt: 2 Sayı: 3, 124 - 129, 30.01.2014

Nebahat Tiryakioğlu Burak Aksu Ufuk Över Hasdemir

Öz

Objective: Increased resistance rate to macrolides used as empirical treatment of pneumococcal infections is a major problem in our country and all over the world. In our study, we aimed to determine macrolide resistance mechanisms of the erythromycin-resistant Streptococcus pneumonia isolated from clinical samples and to investigate serotype and resistance relationship within our region with the high macrolide resistance rates among pneumococci.

Methods: Fifty isolates were studied for erythromycin, azithromycin, clarithromycin, clindamycin susceptibilities with disk diffusion, and liquid microdilution methods. Genetic determinants of macrolide resistance, mef(A), mef(E), erm(B), erm(TR) genes were investigated by PCR using specific primers for each gene, multiplex PCR was used to determine the serotypes. 

Results: Constitutive and inducible MLSB phenotypes and M phenotype were expressed in 86%, 4% and 10% of the isolates, respectively. Total of 42% of the isolates (n=21) were positive for erm(B), 12% (n=6) for mef(E) gene, in 46% (n=23) of the isolates both genes were detected. Serotype distribution was as follows: 28 (56%) 19F, 6 (12%) 6A/B, 5 (10%) 23F, 1 (2%) 39, 2 (4%) 15A-F, 1 (2%) 14, 1 (% 2) 23B and 6 (%12) isolates were nontypeable. 12 isolates carry erm(B), and 16 isolates carry both erm(B) and mef(E) in serotype 19F. One isolate carries erm(B), and 5 isolates carry both erm(B) and mef(E) in serotype 6A/B. Four isolates carry erm(B) and one isolate carries both erm(B) and mef(E) in serotype 23F.

Conclusion: The most striking results of this study are the presence of macrolide efflux pump coding mef(E) gene in 58% of our isolates, the presence of additional erm(B) gene in %46 of isolates, and high rate of erm(B)+ mef(E) genes combination (56%) in predominant serotype 19F isolates.

Key words: Macrolide resistance, erm(B), mef(E), serotype, Streptococcus pneumoniae

Anahtar Kelimeler

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Streptococcus pneumoniae’da makrolid direnç mekanizmaları ile serotip ilişkisi

Öz

Amaç: Pnömokok enfeksiyonlarının tedavisinde ampirik olarak kullanılan makrolid grubu antibiyotiklerdeki direnç oranlarının artışı, tüm dünyada ve ülkemizde önemli bir sorundur. Çalışmamızda; pnömokoklarda makrolid direncinin yüksek olduğu bölgemizde, başvuran hastaların klinik örneklerinden izole edilen eritromisin dirençli Streptococcus pneumoniae izolatlarında makrolid direnç mekanizmalarının belirlenmesi ve direncin klinik izolatlarımızın serotipleri ile ilişkisinin incelenmesi amaçlanmıştır. 

Yöntemler: Toplam 50 izolatın eritromisin, azitromisin, klaritromisin, klindamisin duyarlılıkları disk difüzyon yöntemi ile; minimum inhibitor konsantrasyonları ise sıvı mikrodilüsyon yöntemi ile belirlenmiştir. Makrolid direncinin genetik determinantları mef(A), mef(E), erm(B), erm(TR) her gene özgü primerler kullanılarak PZR yöntemiyle, serotip tayini ise multipleks PZR ile araştırılmıştır.

Bulgular: İzolatların %86’sı yapısal, %4’ü indüklenebilir MLSB fenotipi; %10’u M fenotipi göstermiştir. İzolatların %42’sinde (n:21) sadece erm(B), %12’sinde (n:6) sadece mef(E) geni, %46’sında da (n:23) her iki gen birlikte saptanmıştır. İzolatların serotip dağılımı; 28’i (%56) 19F, 6’sı (%12) 6A/B, 5’i (%10) 23F, 1’i (%2) 39, 2’si (%4) 15A-F, 1’i (%2) 14, 1’i (%2) 23B şeklindedir; 6 (%12) izolat ise tiplendirilememiştir. 19F serotipindeki izolatların; 12’si sadece erm(B), 16’sı erm(B) ile mef(E) genini birlikte taşımaktadır. 6A/B serotipindeki izolatların 1’i sadece erm(B), 5’i mef(E) ile beraber erm(B) geni bulundurmaktadır. 23F serotipindeki izolatların ise 4’ü sadece mef(E), 1’i mef(E) ile birlikte erm(B) geni taşımaktadır. 

Sonuç: Makrolid atım pompa geni mef(E)’nin kökenlerimizin %58’inde bulunması, %46’sında bu genin erm(B)’ye eşlik ettiğinin gösterilmesi ve koleksiyonumuzda baskın olarak saptanan 19F serotipindeki izolatlarda erm(B)+mef(E) gen birlikteliğinin çok yüksek oranda (%56) bulunması çalışmamızın çarpıcı sonuçlarıdır.

Anahtar Kelimeler : akrolid direnci, erm(B), mef(E), serotip, Streptococcus pneumoniae

Anahtar Kelimeler

Makrolid direnci, erm(B), mef(E), serotip, Streptococcus pneumoniae

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