Objective This study investigated characteristics of biofilm formation in tetracycline-resistant clinical Streptococcus agalactiae (S. agalactiae) isolates, as well as its relationship with resistance genes, virulence factors and MLST.
Methods A sample of 136 S. agalactiae isolates were collected retrospectively in Nanshan People’s Hospital, Shenzhen, 2014-2017. Crystal violet stainingwas performed to detect biofilms. Resistance genes (tetM, tetK, tetO) and virulence factors ( bca, bac, fbsA, fbsB, cpsA, scpB, rib, cps I, bfb, hylB, lmb, cylE) were detected by polymerase chain reaction(PCR) analysis.
Results The prevalence of biofilm formation among the clinical S. agalactiae isolates was 39.7%(54 / 136). The biofilm formation rates of tetracycline sensitive, intermediate and resistant in S. agalactiae were 37.0%(27/73), 0.0%(0/0) and 42.9% (27/63), respectively.There was no significant correlation between biofilm formation and tetracycline resistance in S. agalactiae (P>0.05).Tetracycline resistance genes (tetM, tetK, tetO) had no significant correlation with biofilm formation. Bac gene was not detected in all strains, while fbsB, bfB, hylB, lmb and cylE genes were detected in all strains. Virulence genes bca, fbsA, cpsA, scpB, rib and cps III were significantly correlated with biofilm formation ability.
Conclusion The antimicrobial activity of tetracycline against clinical Streptococcus agalactiae isolates is not associated with biofilm formation. Virulence factors (bca, fbsA, scpB, rib and cps III) were associated with the biofilm formation in S. agalactiae isolates.
摘要： 目的 的本研究旨在探讨无乳链球菌生物膜形成能力及其与四环素耐药情况、四环素耐药基因、毒力基因之 间的关系。 方法 收集深圳市南山区人民医院2014—2017年无乳链球菌临床分离株共136株。用结晶紫染色法检测 无乳链球菌的生物膜形成情况。采用聚合酶链反应(PCR)的方法检测四环素耐药基因（ tetM, tetK, tetO)及毒力基因 ( bca, bac, fbsA, fbsB, cpsA, scpB, rib, cps III, bfb, hylB, lmb, cylE)。 结果 136株无乳链球菌临床分离株生物膜形成率为 39.7%(54/136), 四环素敏感、中介和耐药的无乳链球菌生物膜形成率分别为37.0%(27/73)、0.0%(0/0)和42.9%(27/ 63)；生物膜形成与无乳链球菌四环素耐药性无显著相关性( P>0.05)；四环素耐药基因（ tetM, tetK, tetO)与生物膜形成无 显著相关性；全部菌株均未检测到 bac基因, 全部菌株检测到 fbsB, bfb, hylB, lmb, cylE基因, 毒力基因 bca, fbsA, cpsA, scpB, rib, cps III 与生物膜形成能力显著相关。结论无乳链球菌生物膜形成与四环素耐药无显著相关, 与毒力基因 bca, fbsA, cpsA, scpB, rib, cps III 等可育旨相关。