Motallebirad Tahereh, Fazeli Hossein, Azadi Davood, Shokri Dariush, Moghim Sharareh, Esfahani Bahram Nasr
Department of Bacteriology and Virology, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran.
Department of Basic and Laboratory Sciences, Khomein University of Medical Sciences, Khomein, Iran.
Adv Biomed Res. 2021 Sep 29;10:27. doi: 10.4103/abr.abr_269_20. eCollection 2021.
Documented streptococcal resistance to erythromycin has recently been raised. The aim of this study is to identify the molecular mechanism of erythromycin resistance among group B (GBS) strains and to correlate with the clinical origin of strains.
A total number of 134 colonizing ( = 36), invasive ( = 36), noninvasive ( = 46), and asymptomatic ( = 16) GBS isolates were characterized by the detection of gene, capsular serotyping, antibiotic susceptibility profiles using disc diffusion method, and screening of the , , and resistance genes.
The distribution of capsular serotypes was as follow: serotype III (24.6%), Ia (21.6%), V (17.9%), Ib (14.9%), II (8.9%), IV (8.9%), VI (1.5%), and VII (1.5%). From 134 GBS isolates, 51 (38%) isolates were resistant to erythromycin. The constitutive macrolide lincosamide streptogrmin B (MLSB) was the most common resistance phenotype (62.7%), followed by inducible MLSB (27.4%) and M phenotype (9.8%). Erythromycin resistance rate was higher among asymptomatic GBS strains (13/16, 81.2%). Serotype III was the most prevalent type among resistant isolates (41.1%). The ermB gene highly distributed among resistant strains (64.7%), followed by (21.5%) and (9.8%). The gene was related to constitutive MLSB phenotype (84.3%, < 0.05) and serotypes III (61.9%), Ib (87.5%), and V (83.3%). All M phenotype strains harbored gene and were in association with serotype Ia (90%).
The current study suggests that ribosomal modification with erm genes is the main mechanism of erythromycin resistance. Because of relatively high prevalence of erythromycin resistance, double disc test highly recommended for GBS disease treatment and intrapartum prophylaxis among penicillin intolerant patients in our region.
近期有文献报道B族链球菌（GBS）对红霉素产生耐药性。本研究旨在确定GBS菌株中红霉素耐药的分子机制，并将其与菌株的临床来源相关联。
共对134株定植（n = 36）、侵袭性（n = 36）、非侵袭性（n = 46）和无症状（n = 16）GBS分离株进行了以下特征分析：检测基因、荚膜血清分型、采用纸片扩散法进行抗生素敏感性分析以及筛查ermA、ermB和mefA耐药基因。
荚膜血清型分布如下：血清型III（24.6%）、Ia（21.6%）、V（17.9%）、Ib（14.9%）、II（8.9%）、IV（8.9%）、VI（1.5%）和VII（1.5%）。在134株GBS分离株中，51株（38%）对红霉素耐药。组成型大环内酯 - 林可酰胺 - 链阳菌素B（MLSB）是最常见的耐药表型（62.7%），其次是诱导型MLSB（27.4%）和M表型（9.8%）。无症状GBS菌株中的红霉素耐药率更高（13/16，81.2%）。血清型III是耐药分离株中最常见的类型（41.1%）。ermB基因在耐药菌株中高度分布（64.7%），其次是ermA（21.5%）和mefA（9.8%）。ermB基因与组成型MLSB表型（84.3%，P < 0.05）以及血清型III（61.9%）、Ib（87.5%）和V（83.3%）相关。所有M表型菌株均携带mefA基因，且与血清型Ia相关（90%）。
本研究表明，erm基因介导的核糖体修饰是红霉素耐药的主要机制。鉴于红霉素耐药性相对较高，强烈建议在本地区对不耐受青霉素的患者进行GBS疾病治疗和产时预防时采用双纸片试验。
