Department of Medical Microbiology, Faculty of Medicine, Medical University, Sofia, Bulgaria.
Department of Medical Microbiology, Faculty of Medicine, Medical University, Sofia, Bulgaria.
J Glob Antimicrob Resist. 2017 Sep;10:238-242. doi: 10.1016/j.jgar.2017.05.026. Epub 2017 Jul 19.
Streptococcus pyogenes, or group A streptococcus (GAS), is the main etiological agent of bacterial tonsillopharyngitis and a common cause of a wide variety of other mild to severe infections.
Objectives of the present study was to determine and evaluate the distribution of genetic mechanisms associated with certain phenotypes of macrolide resistance in Bulgarian GAS isolated during the years of 2013-2016.
All GAS strains were screened for the macrolide resistance genes erm(A), erm(B) and mef(A), using multiplex polymerase chain reaction (PCR). The minimal inhibitory concentrations (MICs) of erythromycin, azithromycin, clarithromycin, clindamycin were determined by E-tests.
Almost 23% of GAS isolates obtained in 2013-2014 and near 40% of them in 2015-2016 contained various elements of resistance. The predominant gene was mef(A), which encodes an efflux pump (M-phenotype), identified in 57.84% of the macrolide-resistant strains. The next frequently prevalent mechanism was a combination of mef(A) and erm(B) in 22.55%, which determined high-level inducible or constitutive resistance to macrolides, lincosamides and streptogramins (iMLSB or cMLSB). The highest MIC value (>256mg/L) was detected in association with erm(B) (p<0.05). The MIC range was observed to be much higher in the isolates with combinations of resistance genes vs. those with mef genes alone (p<0.05).
The data about the distribution and prevalence of macrolide resistance mechanisms obtained in this study can help in the treatment of persistent and recurrent GAS infections and in the correct choice of empiric therapy.
酿脓链球菌，或 A 组链球菌（GAS），是细菌性扁桃体咽炎的主要病因，也是各种轻度至重度感染的常见原因。
本研究的目的是确定和评估与保加利亚 GAS 某些大环内酯类耐药表型相关的遗传机制的分布，这些 GAS 菌株是在 2013-2016 年期间分离的。
使用多重聚合酶链反应（PCR）筛选所有 GAS 菌株的大环内酯类耐药基因 erm(A)、erm(B)和 mef(A)。使用 E 试验测定红霉素、阿奇霉素、克拉霉素和克林霉素的最小抑菌浓度（MIC）。
在 2013-2014 年获得的近 23%的 GAS 分离株和 2015-2016 年获得的近 40%的 GAS 分离株含有各种耐药元件。主要基因是 mef(A)，它编码一种外排泵（M 表型），在 57.84%的大环内酯类耐药菌株中被发现。下一个常见的机制是 mef(A)和 erm(B)的组合，占 22.55%，这决定了对大环内酯类、林可酰胺类和链阳性菌素类的高水平诱导或组成型耐药（iMLSB 或 cMLSB）。与 erm(B)相关的 MIC 值最高（>256mg/L）（p<0.05）。与单独的 mef 基因相比，携带耐药基因组合的分离株的 MIC 范围明显更高（p<0.05）。
本研究获得的关于大环内酯类耐药机制的分布和流行情况的数据有助于治疗持续性和复发性 GAS 感染，并有助于正确选择经验性治疗。
