- 學位論文
探討Staphylococcus pseudintermedius 之accessory gene regulator (agr) 不同基因分型於毒力因子表現及生物膜形成所扮演的角色
The role of the accessory gene regulator (agr) genotypes in virulence gene expression and biofilm formation of Staphylococcus pseudintermedius
摘要
假中間葡萄球菌 （Staphylococcus pseudintermedius）是引起犬隻膿皮症的伺機性致病菌。近年來，假中間葡萄球菌藉由犬隻造成人類感染的病例越來越多。假中間葡萄球菌引起的軟組織感染（soft-tissue infections, STI）是典型的生物膜相關感染性疾病，使用常規抗生素治療效果有限。此外，最近由耐甲氧西林假中間葡萄球菌（methicillin-resistant S. pseudintermedius, MRSP）所引起的軟組織感染也在犬隻和人類中迅速出現；因此，了解假中間葡萄球菌的致病機制用於開發有效預防及治療假中間葡萄球菌引起感染的策略是非常急迫且必要的。假中間葡萄球菌的生化特性與金黃色葡萄球菌（Staphylococcus aureus）相似，但目前對於假中間葡萄球菌致病機轉的了解仍十分有限。在金黃色葡萄球菌中，葡萄球菌附屬基因調控系統 accessory gene regulator (agr)，是一種群體感應系統也是雙分子調控系統，能調控金黃色葡萄球菌造成疾病的毒力因子表現，但agr在假中間葡萄球菌致病機制中的作用仍不清楚。因此，本研究探討了不同agr分型的假中間葡萄球菌引起軟組織感染的致病特性。為了研究假中間葡萄球菌引起皮膚感染的致病機轉，我們建立小鼠膿皮症模式。本研究依據agr分型，將47株臨床的耐甲氧西林假中間葡萄球菌分離株分為4型，分別為第 I 型（52%）、 第 II 型 （2%）、 第 III 型（35%）、 第 IV 型（10%）。在小鼠活體試驗中，耐甲氧西林假中間葡萄球菌分離株中的agr第III型和第IV型顯示出較強的皮膚感染能力。而耐甲氧西林假中間葡萄球菌抵抗嗜中性白血球毒殺的能力和形成生物膜的能力與耐甲氧西林假中間葡萄球菌所引起皮膚膿腫的致病性無關。在細胞毒性測定、細胞粘附和細胞侵入試驗的結果顯示，agr第III型和第IV型的分離株顯著優於其他agr分型的耐甲氧西林假中間葡萄球菌。綜合來說，假中間葡萄球菌分離株中的agr第III型和第IV型顯示出更強的黏附、侵入和損傷宿主細胞的能力，而這些細菌毒性有助於導致膿皮症的產生。
並列摘要
Staphylococcus pseudintermedius is an opportunistic pathogen for causing pyoderma in dogs. The number of human cases with S. pseudintermedius infection, mainly acquired from dogs, is also increasing during recent years. S. pseudintermedius-induced soft tissue infection (STI) is a typical biofilm-related infectious disease, which is refractory to routine antibiotic treatment. In addition, methicillin resistance S. pseudintermedius-induced STIs in dogs and human are also rapidly emerging recently. Therefore, to understand the pathogenesis of S. pseudintermedius infection for developing the effective strategies for the prevention and treatment of S. pseudintermedius-induced infections is imperative. The biochemical properties of S. pseudintermedius are similar to those of Staphylococcus aureus, but the current understanding of the pathogenesis of S. pseudintermedius is still limited. In S. aureus, accessory gene regulator (agr) system, which is a quorum sensing and a two-component system, mediate S. aureus virulence for causing diseases, but the role of agr in the pathogenesis of S. pseudintermedius is still unknown. Therefore, in this study, the virulence of different agr types of S. pseudintermedius for causing STI was characterized. To investigate the pathogenesis of S. pseudintermedius-induced skin infection, the mouse pyoderma model was established. Fourty-seven clinical MRSP isolates were classified into four types by agr classification, namely type I (52%), type II (2%), type III (35%) and type IV (10%). The agr type III and type IV of MRSP isolates showed stronger ability to cause skin infection in vivo. The abilities of MRSP to resist neutrophil killing and to form the biofilm are not correlated to the virulence of MRSP for causing skin abscesses. The results of cytotoxicity assay, cell adhesion and cell invasion tests showed that agr type III and type IV isolates perform significantly better than other agr types of MRSP for causing skin infection. Taken together, agr type III and type IV of S. pseudintermedius isolates show greater abilities to adhere, invade and damage host cells, which contribute to bacterial virulence for causing pyoderma.