Banerjee Tuhina, Anupurba Shampa
Department of Microbiology, Institute of Medical Sciences, Banaras Hindu University, Varanasi 221005, India.
J Pathog. 2015;2015:692612. doi: 10.1155/2015/692612. Epub 2015 Aug 23.
Along with emergence of multidrug resistance, presence of several virulence factors in enterococci is an emerging concept. This study was undertaken to determine the prevalence of various virulence factors phenotypically and genotypically in enterococci and study their association with multidrug resistance. A total of 310 enterococcal isolates were studied, comprising 155 E. faecium and 155 E. faecalis. Antimicrobial susceptibility testing was done by disc diffusion and agar dilution method. Hemolysin, gelatinase, biofilm production, and haemagglutination were detected phenotypically and presence of virulence genes, namely, asa1, gelE, cylA, esp, and hyl, was detected by multiplex PCR. Of the total, 47.41% isolates were high level gentamicin resistant (HLGRE) and 7.09% were vancomycin resistant (VRE). All the virulence traits studied were found in varying proportions, with majority in E. faecalis (p > 0.05). Strong biofilm producers possessed either asa1 or gelE gene. gelE silent gene was detected in 41.37% (12/29). However, increase in resistance was associated with significant decrease in expression or acquisition of virulence genes. Further, acquisition of vancomycin resistance was the significant factor responsible for the loss of virulence traits. Though it is presumed that increased drug resistance correlates with increased virulence, acquisition of vancomycin resistance might be responsible for reduced expression of virulence traits to meet the "biological cost" relating to VRE.
随着多重耐药性的出现，肠球菌中多种毒力因子的存在是一个新出现的概念。本研究旨在从表型和基因型上确定肠球菌中各种毒力因子的流行情况，并研究它们与多重耐药性的关系。共研究了310株肠球菌分离株，其中包括155株粪肠球菌和155株屎肠球菌。采用纸片扩散法和琼脂稀释法进行药敏试验。通过表型检测溶血素、明胶酶、生物膜形成和血细胞凝集，并通过多重PCR检测毒力基因asa1、gelE、cylA、esp和hyl的存在。在所有分离株中，47.41%对庆大霉素高水平耐药（HLGRE），7.09%对万古霉素耐药（VRE）。所研究的所有毒力特征均以不同比例存在，大多数存在于粪肠球菌中（p>0.05）。强生物膜产生菌拥有asa1或gelE基因。在41.37%（12/29）的菌株中检测到gelE沉默基因。然而，耐药性的增加与毒力基因表达或获得的显著降低相关。此外，获得万古霉素耐药性是导致毒力特征丧失的重要因素。尽管推测耐药性增加与毒力增加相关，但获得万古霉素耐药性可能是导致毒力特征表达降低的原因，以满足与VRE相关的“生物学成本”。
