一株猪源新型ST9-MRSA-SCCmecXII菌株进化及可移动耐药基因元件分析

Evolution and Mobile Antibiotic Resistance Genetic Element Analysis of Novel Porcine ST9-MRSA-SCCmecXII Strain

摘要:

耐甲氧西林金黄色葡萄球菌（Methicillin-resistant Staphylococcus aureus, MRSA）被WHO列为高度优先级细菌病原体，广泛存在于畜产品中，并通过食品加工链传播。笔者从病猪脾脏分离出一株新型多重耐药ST9-MRSA-SCCmecXII菌株HP。为了解该新型MRSA的耐药性和遗传进化特征，采用K-B纸片扩散法、PCR扩增、全基因组测序（二代+三代）及比较基因组学分析HP的耐药表型、耐药基因（Antibiotic Resistance Gene, ARG）、可移动遗传元件（Mobile Genetic Element, MGE）及进化关系。结果显示，HP对β-内酰胺类、氟喹诺酮类等11种抗生素耐药，而对万古霉素、替考拉宁和利奈唑胺等敏感。PCR检测到9种ARGs，全基因组测序和数据库比对出42种ARGs，主要包括β-内酰胺类、氨基糖苷类及MLS类等，其中9个ARGs位于基因岛HPGI1上，1个ARG位于质粒plasmid 2上。进化分析显示，HP与1株牛奶源和2株猪源ST9-MRSA-SCCmecXII亲缘关系较近，且携带相似的MGEs（SCCmecXII、转座子及基因岛）。该结果表明新型菌株HP耐药谱复杂，携带多种ARGs和MGEs，具有沿不同宿主及食品加工链传播的风险。该文为ST9-SCCmecXII新型MRSA在食品加工链传播的早期预警及有效控制提供科学信息和遗传学依据。

Abstract:

Classified as a high-priority pathogen by the World Health Organization, methicillin-resistant Staphylococcus aureus (MRSA) has been widely found in livestock products and is transmitted along the food processing chain. A novel multidrug-resistant ST9-MRSA-SCCmecXII strain, HP, was isolated from the spleen of a diseased pig with the aim to gain insight into the antibiotic resistance and genetic evolutionary characteristics of this MRSA. Its resistance phenotypes, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and evolutionary relationships with other strains were comprehensively analyzed using the Kirby-Bauer disc diffusion method, PCR amplification, whole-genome sequencing (second- and third-generation), and comparative genomics. The results showed that HP exhibited resistance to 11 antibiotics, such as β-lactams and fluoroquinolones. In contrast, it demonstrated susceptibility to vancomycin, teicoplanin, and linezolid. Nine ARGs were identified using PCR, whereas whole-genome sequencing and database comparison led to the detection of 42 ARGs, predominantly comprising β-lactams, aminoglycosides, and macrolide-lincosamide-streptogramins. Of these, nine ARGs were on the genomic island HPGI1 and one ARG was on plasmid 2. Evolutionary analysis revealed that HP exhibited a strong correlation with one milk-derived and two porcine ST9-MRSA-SCCmecXII strains and carried similar MGEs, including SCCmecXII, transposons, and genomic islands. The novel strain HP exhibits a complex resistance profile with multiple ARGs and MGEs, indicating potential risks of transmission between different hosts and throughout the food processing chain. These findings provides a genetic basis for early warning and effective control of ST9-MRSA-SCCmecXII transmission in the food processing chain.