| 摘要: | ?黃色葡萄球菌（Staphylococcus aureus；S. aureus）為革?氏陽性菌中主要致病菌，它對於臨床上常用的抗生素或殺菌劑往往也存在著廣泛的抗藥性。我們的研究目的是利用各種不同的分子分型方式來探討中台灣地區的MRSA（methicillin-resistant S. aureus）是否有主要的型別在散布及QacA/B藥物輸出幫浦對於臨床上MRSA的相關感染是否有影響。
96株MRSA和60株MSSA（methicillin-susceptible S. aureus）來自不同病患的血液培養陽性菌株其收集時間分別為2008年7月至12月和2008年7月至2009年12月。針對96株MRSA，各種分子分型：包括spa分型、SCCmec分型、mec基因相關的直接重複片段數目（mec-associated direct repeat unit；dru）和毒素基因（sea、seb、sec、tst、lukS/F）是否存在被偵測和確認。菌株對殺菌劑的抗藥性基因（qacA/B和smr）和對chlorhexidine的最低抑菌濃度（minimal inhibitory concentration；MIC）也分別被測定。之後以案例對照研究的方式來分析何者是含chlorhexidine中心靜脈導管相關的血流感染之危險因子。
在96株MRSA中，第二型SCCmec有38株、第三型有28株、第四型有18株而第五型有12株。在38株SCCmec第二型的菌株中，有31株（81.6%）其分子spa分型為t002並同時有4個dru的重覆片段，其中有21株（67.7%）和25株（80.6%）分別帶有sec和tst毒素基因。28株SCCmec第三型的菌株中，其中的15株（53.6%）帶有sea毒素基且其spa typing為t037，且帶有14個dru的重覆片段。18株SCCmec第四型的菌株中有有13株（72.2%）帶有seb毒素基因且其spa typing為t437，並且帶有9個dru的重覆片段。在12株SCCmec第五型的菌株中，其中有9株是屬於type VT，而且這9株全部都帶有Panton-Valentine leukocidin（PVL）毒性基因，且其中的5株（55.6%）其spa typing為t437且帶有11個dru的重覆片段。經由多變相邏輯?邅k並將性別和年齡校正之後來探討臨床診斷為含chlorhexidine導管確定相關的血流感染其相關危險因子的分析中，抗藥基因qacA/B的存在以及chlorhexidine的MIC≧2 ug/ml具有顯著的意義，其勝算比（Odds ratios）在以156株?黃色葡萄球菌（60株MSSA + 96株MRSA）為分析對象下分別為9.264和8.134；而以96株MRSA為探討對象之下其勝算比則分別為6.097和4.373。
總結來說，我們的研究証實了在台灣有幾個主要分子型別的MRSA在散佈著，此外對於逐漸在MRSA中增加的aqcA/B抗藥性基因也可能是含chlorhexidine中心靜脈導管相關的血流感染的風險因子。因此橫向多地區且縱向較長時間的前瞻性監測，對於了解MRSA在台灣的演化以及qacA/B在?黃色葡萄球菌中的散佈是否會增加臨床相關感染症的發生率，是重要且必須的。
Staphylococcus aureus is an important causative agent of a wide variety of diseases in both hospital or community associated infections. The clinical importance of S. aureus is attributed to its high virulence and rapid development of drug resistance. It can also colonize in skin and nasal cavity of healthy people. The goal of this study was to delineate the molecular characteristics of methicillin-resistant Staphylococcus aureus (MRSA) in Taiwan and survey the impact of the chlorhexidine-resistant genes qacA/B on the effectiveness of chlorhexidine-impregnated catheters in the prevention of MRSA infections.
Sixty methicillin-sensitive Staphylococcus aureus (MSSA) and 96 MRSA isolates from the blood cultures of different patients were collected during July of 2008 to Dec of 2009 and July to Dec of 2008 respectively. The spa typing, SCCmec typing, mec-associated direct repeat unit (dru) copy numbers and toxin genes (sea, seb, sec, tst, lukS/F) of each MRSA isolate were determined. Detection of the biocide- and disinfectant-resistant genes (qacA/B and smr) was performed by PCR and the minimal inhibitory concentration (MIC) of chlorhexidine for each isolates were determined by agar dilution methods. A case control study was conducted to determine whether more clinical S. aureus isolates from chlorhexidine-impregnated catheter-related bloodstream infections (CRBSI) have the biocide-resistant genes (qacA/B or smr) than those from other infections.
Thirty-eight, 28, 18, and 12 MRSA isolates were SCCmec type II, SCCmec type III, SCCmec type IV, and SCCmec type V, respectively. Most (31/38, 81.6%) of the SCCmec type II isolates were of spa t002 with 4 dru repeats. Some of them also carried the sec or tst toxin gene (67.7% and 80.6% respectively). Of the 28 SCCmec type III MRSA isolates, 15 (53.6%) were of t037 with 14 dru repeats, and all also carried the sea gene. Of the 18 SCCmec type IV MRSA isolates, 13 (72.2%) were of t437 with 9 dru repeats, and 10 of them also had the seb gene. Among the SCCmec type V MRSA isolates, nine were type VT. Five (55.6%) of them were of t437 with 11 dru repeats, and all contained the lukS/F gene. The chlorhexidine MIC50 of MSSA and MRSA isolates were 1 |
