金黃色葡萄球菌的最低抑制濃度與分子生物分型的相關性研究

金黃色葡萄球菌是一種能夠引起人類各種疾病細菌之一。抗甲氧西林金黃色葡萄球菌（Methicillin-resistant Staphylococcus aureus），簡稱MRSA是在金黃色葡萄球菌感染治療後引對於methicillin或oxacillin抗藥性的菌株。MRSA感染的兩種主要類型：醫院獲得MRSA（Hospital-acquired MRSA ，HA-MRSA）和社區獲得MRSA（Community acquired MRSA，CA-MRSA）。HA-MRSA和CA-MRSA臨床上有不相同的表現，然而，無論HA-MRSA和CA-MRSA都具有可移動mecA基因而對β-內酰胺類抗生素產生耐藥性。然而，HA-MRSA和CA-MRSA臨床上卻有不同的表現及不同分子特徵。因此，本研究的目的是去分析本院MRSA的分子流行病學特徵的表現型和基因型相關性。從2011年10月到2012年9月，在中山醫學大學附設醫院進行，我們總共從血液的臨床檢體收集115株不重複的S.aureus 菌株。所有菌株的oxacillin 和 cefoxitin最低液菌濃度（Minimal inhibition concentration ，MIC)藥敏試驗是採用瓊脂稀釋法(agar dilution method)偵測。MRSA mecA的基因鑑定是利用DNA用作模板，多重PCR（M-PCR）測定基因編碼盒式染色體重組（CCR）配合物和(mec)基因複合物型（SCCmec）類型。結果顯示從研究結果發現MRSA 中oxacillin有60 /115( 5 0. 2 %)，cefoxitin有58/115(5 0 . 4 %)。使用M-PCR對SCCmec type I是0.9 %、type II 19.1 %, type IV 15.6 %, type V 6.1% 和 type Vt 3.5%。總共醫院型34 /115( 29.6 %) and 社區型MRSA 29/115 ( 25.2 %)。從我們研究中證實CLSI的建議cfoxitin MIC較oxacillin更可以偵測MRSA，如果將菌株培養在沒有添加NaCl及 2％的NaCl，在使用MIC或許可以用來區分社區型MRSA或是醫院型MRSA。

Staphylococcus aureus has been recognized as one of the most important bacteria that cause disease in humans. Methicillin-resistant Staphylococcus aureus (MRSA) infection is caused by a strain of staph bacteria that''s become resistant to the antibiotics commonly used to treat ordinary staph infections. There are two main types of MRSA infections: Hospital-acquired MRSA (HA-MRSA) and Community acquired MRSA (CA-MRSA).Both HA-MRSA and CA-MRSA harbor a mobile mecA gene encoded their drug resistance against beta-lactams antibiotics. Nevertheless, HA-MRSA and CA-MRSA have distinct clinical different manifestations and molecular characteristics. Herein, we made a survey to understand the phenotypes and genotypes of the molecular epidemiologic characteristics of MRSA.A total 115 strains S. aureus were collected from Chung Shan University Hospital between October 2011 and September 2012. All of them grew from blood samples and non-duplicate strains. Minimum inhibitory concentrations (MICs) of antibiotics were determined by agar dilution method according to the Clinical and Laboratory Standards Institute (CLSI). Genomic was MRSA used DNA as templates and the types of gene encoding cassette chromosome recombinase (ccr) complex and mecA gene complex (SCCmec) were determined by multiplex PCR (M-PCR). The results of MICs demonstrate 60 /115( 5 0. 2 %) were MRSA by oxacillin MICs, 58/115(5 0 . 4 %) by cefoxitin, On the other hand, mecA gene was detected form 77/115( 70 %) by M-PCR. Of them, SCCmec type I is 0.9 %, type II 1 9 .1 %, type III 9.6 %, type IV 1 5 . 6 %, type V 6.1% and type Vt 3.5%. Hence, the HA-MRSA is 34 /115( 29.6 %) and CA-MRSA 29/115 ( 25.2 %) . Accidentally we found most oxacillin MICs of CA-MRSA are increase by 2 % NaCl culture media whereas HA-MRSA have the same MICs with or without 2 % NaCl. Therefore, this study proved that cefoxitin MIC is the reliable indicator for clinical laboratory to detect MRSA. We also found 2%NaCl culture media might be a potentially effective method to identified CA-MRSA from HA-MRSA in clinical settings.