The psm-mec element and other regulatory factors such as sarA, agrA , and RNAIII are responsible for maintaining the genetic framework for enhanced virulence of MRSA. psm-mec is found predominantly in the staphylococcal cassette chromosome (SCC mec ). sar A, agr A, and RNAIII control gene expression to facilitate adaptation in certain environment. Genome-wide approaches have shown that expression of virulence factors is frequently regulated at transcriptional, translational level, and mRNA degradation level. In this study, transcriptional responses of psm-mec gene in accordance with other regulatory factors sarA, agrA, and RNAIII were observed under normal conditions as well as when exposed to 2 μg/ml and 6 μg/ml of oxacillin stress. One-way t-test was carried out for analysing RQ values obtained through real-time PCR. This study showed downregulation of psm-mec gene and upregulation of other regulatory genes at lower concentration of oxacillin. However, this was reverse when exposed against higher concentration of oxacillin. It was observed from the study that the expression of virulence factors were dependent on each other under different concentration of oxacillin. Thus, this study highlights that psm-mec, sarA, agrA , and RNAIII gene are under direct control of antibiotic pressure in a concentration-dependent manner.

中文翻译：

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苯唑西林胁迫下耐甲氧西林金黄色葡萄球菌中psm-mec系统的表达模式

psm-mec 元件和其他调节因子如 sarA、agrA 和 RNAIII 负责维持增强 MRSA 毒力的遗传框架。psm-mec 主要存在于葡萄球菌盒式染色体 (SCC mec) 中。sar A、agr A 和 RNAIII 控制基因表达以促进在特定环境中的适应。全基因组方法表明，毒力因子的表达经常在转录、翻译水平和 mRNA 降解水平上受到调节。在这项研究中，在正常条件下以及暴露于 2 μg/ml 和 6 μg/ml 苯唑西林应激时，psm-mec 基因的转录反应与其他调节因子 sarA、agrA 和 RNAIII 一致。进行单向 t 检验以分析通过实时 PCR 获得的 RQ 值。该研究表明，在较低浓度的苯唑西林下，psm-mec 基因下调，其他调控基因上调。然而，当暴露于更高浓度的苯唑西林时，情况正好相反。从研究中观察到，不同浓度苯唑西林下毒力因子的表达相互依赖。因此，这项研究强调了 psm-mec、sarA、agrA 和 RNAIII 基因以浓度依赖性方式直接受抗生素压力控制。