Microbiology Department, Faculty of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran.
School of Medicine, Shahroud University of Medical Sciences, Shahroud, Iran.
BMC Microbiol. 2021 Jun 25;21(1):192. doi: 10.1186/s12866-021-02257-4.
Methicillin-resistant Staphylococcus aureus (MRSA)-bloodstream infections (BSI) are predominantly seen in the hospital or healthcare-associated host. Nevertheless, the interactions of virulence factor (VFs) regulators and β-lactam resistance in MRSA-BSI are unclear. This study aims to characterize the molecular relationship of two-component systems of VFs and the expression of the β-lactamase gene in MRSA-BSI isolates. In this study, 639 samples were collected from BSI and identified by phenotypic methods. We performed extensive molecular characterization, including SCCmec type, agr type, VFs gene profiles determinations, and MLST on isolates. Also, a quantitative real-time PCR (q-RT PCR) assay was developed for identifying the gene expressions.
Ninety-one (91) S. aureus and 61 MRSA (67.0%) strains were detected in BSI samples. The presence of VFs and SCCmec genes in MRSA isolates were as follows: tst (31.4%), etA (18.0%), etB (8.19%), lukS-PVL (31.4%), lukF-PV (18.0%), lukE-lukD (16.3%), edin (3.2%), hla (16.3%), hlb (18.0%), hld (14.7%), hlg (22.9%), SCCmecI (16.3%), SCCmecII (22.9%), SCCmecIII (36.0%), SCCmecIV (21.3%), and SCCmecV (16.3%). Quantitative real-time PCR showed overexpression of mecRI and mecI in the toxigenic isolates. Moreover, RNAIII and sarA genes were the highest expressions of MRSA strains. The multi-locus sequence typing data confirmed a high prevalence of CC5, CC8, and CC30. However, ST30, ST22, and ST5 were the most prevalent in the resistant and toxigenic strains.
We demonstrated that although regulation of β-lactamase gene expressions is a significant contributor to resistance development, two-component systems also influence antibiotic resistance development in MRSA-BSI isolates. This indicates that resistant strains might have pathogenic potential. We also confirmed that some MLST types are more successful colonizers with a potential for MRSA-BSI.
耐甲氧西林金黄色葡萄球菌（MRSA）-血流感染（BSI）主要见于医院或与医疗保健相关的宿主中。然而，MRSA-BSI 中毒力因子（VF）调节剂和β-内酰胺耐药之间的相互作用尚不清楚。本研究旨在描述 VF 双组分系统的分子关系，并研究 MRSA-BSI 分离株中β-内酰胺酶基因的表达。本研究从 BSI 中采集了 639 个样本，并通过表型方法进行了鉴定。我们对分离株进行了广泛的分子特征描述，包括 SCCmec 型、agr 型、VF 基因谱测定和 MLST。此外，还开发了一种定量实时 PCR（q-RT-PCR）检测方法来鉴定基因表达。
BSI 样本中检测到 91 株金黄色葡萄球菌和 61 株 MRSA（67.0%）。MRSA 分离株中 VF 和 SCCmec 基因的存在情况如下：tst（31.4%）、etA（18.0%）、etB（8.19%）、lukS-PVL（31.4%）、lukF-PV（18.0%）、lukE-lukD（16.3%）、edin（3.2%）、hla（16.3%）、hlb（18.0%）、hld（14.7%）、hlg（22.9%）、SCCmecI（16.3%）、SCCmecII（22.9%）、SCCmecIII（36.0%）、SCCmecIV（21.3%）和 SCCmecV（16.3%）。定量实时 PCR 显示毒力株中 mecRI 和 mecI 的表达过度。此外，RNAIII 和 sarA 基因是 MRSA 菌株表达最高的基因。多位点序列分型数据证实 CC5、CC8 和 CC30 高度流行。然而，ST30、ST22 和 ST5 是耐药和毒力株中最常见的类型。
本研究表明，尽管β-内酰胺酶基因表达的调控是耐药发展的重要因素，但双组分系统也会影响 MRSA-BSI 分离株的抗生素耐药性发展。这表明耐药菌株可能具有致病性。我们还证实，一些 MLST 类型是更成功的定植者，具有 MRSA-BSI 的潜力。
