汉中地区猪肉来源ST59和ST398型耐甲氧西林金黄色葡萄球菌生物学特性研究

Study on biological characteristics of ST59 and ST398 methicillin-resistant Staphylococcus aureus isolated from pork in Hanzhong

中文关键词:  猪肉  ST59 MRSA  ST398 MRSA  耐药特性  毒力特性

英文关键词:pork  methicillin-resistant Staphylococcus aureu  drug resistance characteristics  virulence characteristics

中文摘要:

      目的 阐明汉中地区零售猪肉中ST59和ST398型耐甲氧西林金黄色葡萄球菌(methicillin-resistant Staphylococcus aureus, MRSA)分子流行特征、耐药及毒力特性的差异, 评估其潜在的公共卫生风险。方法 采用全基因组测序技术对分离株进行多位点序列(multilocus sequence typing, MLST)分型、葡萄球菌蛋白A基因(staphylococcal protein A gene, spa)分型及葡萄球菌染色体盒(staphylococcal chromosomal cassette mec, SCCmec)分型, 并预测其耐药基因与毒力基因谱。通过微量肉汤稀释法进行抗菌药物敏感性实验; 采用绵羊红细胞溶血实验评估溶血活性, 微孔板结晶紫染色法评估生物被膜形成能力。结果 在43株MRSA分离株中, ST59 (51.16%, 22/43)和ST398 (46.51%, 20/43)为优势型别。ST59菌株分子分型呈现高度同质性, 主要集中于spa t437型(81.82%)和SCCmec IVa(2B)型(90.91%); 而ST398菌株则表现出高度遗传多样性, 呈现多种spa型和SCCmec型。ST398菌株对庆大霉素、四环素、左氧氟沙星、克林霉素及复方新诺明的耐药率均显著高于ST59菌株(P<0.01)。ST398菌株携带更丰富的获得性耐药基因, 包括高携带率的tet(M) (95.00%)、lnu(B) (75.00%)、lsa(E) (90.00%)和dfrG (90.00%), 3株菌携带poxtA基因; 而ST59菌株的耐药基因谱相对简单。在毒力特性方面, ST398菌株表现出强的溶血活性; ST59菌株则具有更强的生物被膜形成能力, 并携带更复杂的毒力基因谱, 其免疫逃逸基因sak、scn及肠毒素基因seb、sek、seq的携带率显著高于ST398菌株。结论 汉中地区零售猪肉制品中MRSA的主要流行克隆为ST59和ST398。两者不同的生物学特性对公共卫生构成差异化的挑战, 需实施针对性监测与防控措施。

英文摘要:

      Objective To elucidate the differences in molecular epidemiological characteristics, antibiotic resistance and virulence properties of methicillin-resistant Staphylococcus aureus (MRSA) ST59 and ST398 in retail pork in the Hanzhong, and assess their potential public health risks. Methods Whole-genome sequencing was used to perform multilocus sequence typing (MLST), staphylococcal protein A gene (spa) typing, and staphylococcal cassette chromosome mec (SCCmec) typing for the isolates, and their resistance and virulence gene profiles were predicted. Antimicrobial susceptibility testing was conducted using the broth microdilution method; sheep red blood cell hemolysis test was used to evaluate hemolytic activity, and microplate crystal violet staining was employed to assess biofilm-forming ability. Results Among the 43 MRSA isolates, ST59 (51.16%, 22/43) and ST398 (46.51%, 20/43) were the dominant types. ST59 strains showed high homogeneity in molecular typing, mainly clustering in spa t437 (81.82%) and SCCmec IVa(2B) (90.91%); in contrast, ST398 strains exhibited high genetic diversity with various spa types and SCCmec types. The resistance rates of ST398 strains to gentamicin, tetracycline, levofloxacin, clindamycin and trimethoprim-sulfamethoxazole were significantly higher than those of ST59 strains (P<0.01). ST398 strains carried more abundant acquired resistance genes, including high carriage rates of tet(M) (95.00%), lnu(B) (75.00%), lsa(E) (90.00%) and dfrG (90.00%). Additionally, 3 strains carried the poxtA gene; while the resistance gene profile of ST59 strains was relatively simple. In terms of virulence characteristics, ST398 strains showed strong hemolytic activity; ST59 strains had stronger biofilm-forming ability and carried a more complex virulence gene profile, with significantly higher carriage rates of immune escape genes sak, scn, and enterotoxin genes seb, sek, seq compared to ST398 strains. Conclusion The main prevalent clones of MRSA in retail pork products in Hanzhong are ST59 and ST398. The different biological characteristics pose differential challenges to public health, requiring targeted monitoring and prevention measures.