畜產環境抗Oxacillin金黃色葡萄球菌菌株親緣性分析

Abstract

本研究的目的在於從畜產動物環境和台灣桃園肉品拍賣市場所採樣分離的葡萄球菌株中，進行抗Oxacillin金黃色葡萄球菌 (Oxacillin-resistant Staphylococcus aureus; ORSA)菌株之腸毒素與分子分型親緣性關係分析。腸毒素檢測是採用葡萄球菌腸毒素逆被動乳膠粒子凝集試驗 (Staphylococcal enterotoxin reversed passive latex agglutination; SET-RPLA)，偵測五種腸毒素型別A、B、C、D及E，同時利用Polymerase chain reactions (PCR) 引子進行上述五種毒素型的確認，同時本研究更進行其他共計9種的毒素基因型分析，以提供未來相關分離株之表現型的研究基礎。ORSA菌株親緣性分析是採用脈衝式膠體電泳技術(Pulse-field gel electrophoresis; PFGE)進行分析，另以多基因位序列分型法(Multi-locus sequence typing; MLST)進行基因序列比較分型。本研究共計鑑定出30株ORSA分離株，其中27株係分離自人類來源，因此來自動物飼養場及操作處理場所的人類來源可能具有高污染潛力風險。本研究分離鑑定出之腸毒素表現型中以B型最高，基因型則有sea, seb, sec, sed, seg, sek, sel, sem, sen, seo 及seq，其中sea, seb, sec, sed, seg已知與食品中毒有關。ORSA分離株依PFGE親緣性分析結果可分為5個族群(clusters)，其中第I族群的相似度高達80%以上，另有7個MLST型別被鑑定出，其中最盛行的型別為ST338/ST338slv 和 ST59，根據MLST進行族群遺傳學研究結果顯示共有6個群聚(clonal complexes; CCs)，其中CC59為最主要的群聚。總結，本研究觀察得知，在畜產工作環境的人類帶有高盛行率的B型腸毒素和ST59及ST338/ST338slv 菌群的ORSA菌株；由於生活之異動，對人類生活週遭環境和畜產生產環境中進一步的追蹤及比較社區型ORSA(Community-acquired Oxacillin-resistant Staphylococcus aureus; CA-ORSA)與醫院感染型ORSA(Hospital-acquired Oxacillin-resistant Staphylococcus aureus; HA-ORSA)的流行病學證據是必要的。

The aim of this study was to characterize Oxacillin-resistant Staphylococcus aureus (ORSA) isolates from livestock environments and meat market workers by molecular epidemiological analysis. Staphylococcal enterotoxin reversed passive latex agglutination (RPLA) and multiplex polymerase chain reactions (PCR) were used to detect enterotoxin-producing Staphylococcus aureus. The molecular genetic similarity of ORSA was also compared by pulse-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). A total of 30 ORSA isolates were identified and 27 of these strains were from human sources - a higher contamination potential from human origin in the animal raising and handling field was suspected. The most common type of enterotoxin detected in this study was type B. Regarding the bacterial phylogenetic analysis of ORSA isolates, five major clusters of PFGE patterns were suggested with >80% similarity in cluster I. Seven MLST patterns were identified with the most prevalent types being ST338/ST338slv and ST59. Population genetic studies based on MLST have shown that major ORSA clones have emerged from six clonal complexes (CCs), with CC59 being the dominant one. In conclusion, a high prevalence of ORSA with enterotoxin type B as well as ST59 and ST338/ST338slv colonization was observed among livestock with human origins in this study. We suggest further tracking and comparing of the epidemiological evidence of community-acquired and hospital-acquired ORSA in human living environments and livestock-producing environments.