探討非無菌部位之抗甲氧苯青黴素金黃色葡萄球菌表現型與基因型的相關性

介紹：金黃色葡萄球菌 (Staphylococcus aureus；S. aureus) 為革蘭氏陽性球菌，是皮膚、粘膜呼吸道之常在菌。常造成皮膚軟組織感染、菌血症、肺炎及骨關節炎等，有較高的死亡率與併發症。在台灣已經有60%~80%的S. aureus菌株具有mecA基因，其功能是導致β-lactam類抗生素產生抗藥性，稱抗甲氧苯青黴素金黃色葡萄球菌 (Methicillin-resistant S. aureus；MRSA)。依據其菌種來源和表現的差異分為醫療相關 (Hospital-acquired MRSA；HA-MRSA) 及社區相關 (Community-acquired MRSA；CA-MRSA)。本次研究目的在於探討，自非無菌部位檢體經鑑定分離出MRSA菌株表現型及基因型差異，和HA-MRSA與CA-MRSA型別區分。材料方法：由中山醫學大學附設醫院收集臨床MRSA菌株，這些菌株是臨床實驗室經PhoenixTM 100 system鑑定的，我們再根據Clinical Laboratory Standard Institute (CLSI) 中的瓊膠稀釋法 (agar dilution) 測vancomycin、cefoxitin及oxacillin最低抑制濃度 (minimum inhibitory concentration；MIC) 篩檢出其表現型 (phenotype)，再另一方面藉由聚合酶連鎖反應 (polymerase chain reaction；PCR) 檢測MRSA菌株的SCCmec型別之基因型 (genotype)。結果：總共收集417株MRSA臨床菌株，其MIC有407株為MRSA，10株為MSSA。經PCR方法鑑定出SCCmec分型有415株具有mecA基因，2株不具有mecA基因；為118株HA-MRSA、288株CA-MRSA及9株untypable其基因型和表現型有些許的不同。且主要是以皮膚軟組織感染常見為247株(68%)：其中包括58株HA-MRSA、186株CA-MRSA及3株untypable。結論：隨著環境的改變不斷變遷，抗藥性已成為每年監測重要議題，臨床實驗室的自動化儀器對於MRSA的鑑定足以媲美手動MIC或分子PCR的鑑定，只是面對詭譎多變的MRSA，各種鑑定方法比對臨床資料才是一窺MRSA菌株抗藥性演進的不二法門。

Introduction: Staphylococcus aureus (S. aureus) is Gram positive coccus which is normal flora of skin, mucous and respiratory tract but it usually causes skin and soft tissue infection (SSTI), bacteremia, pneumoniae, osteoarthritis, etc. complicated with high morbidity and mortality. In Taiwan, 60 to 80 percent of S. aureus strains have the mecA gene, whose function is to produce antibiotics resistant to β-lactam antibiotics. They are called methicillin-resistant S. aureus (MRSA). According to the difference of phenotypes and genotypes, it is divided into hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA). The purpose of this study is to investigate correlations between phenotypic and genotypic of MRSA from non-sterile sites specimens and differences between HA-MRSA and CA-MRSA types.Materials and methods: We collected clinical strains of MRSA from Chung Shan Medical University Hospital. Using agar dilution by the Clinical Laboratory Standard Institute (CLSI) of MRSA strains were tested for vancomycin, cefoxitin and oxacillin. Phenotypes was determined by a minimum inhibitory concentration (MIC) screen. While, the genotype of the MRSA strain was detected and typed by polymerase chain reaction (PCR). Results: A total of 417 MRSA clinical isolates were collected. The MICs contained 407 MRSA and 10 MSSA. 415 strains had the mecA gene and 2 strains did not have the mecA gene. The 118 HA-MRSA, 288 CA-MRSA and 9 strains of untypable were slightly different from the genotype and phenotype. The main skin and soft tissue infection (SSTI) were 247 strains: 58 HA-MRSA, 186 CA-MRSA and 3 strains of untypable.Conclusion: As environmental changes continue to changes, S. aureus resistant strains have become an important issue for monitoring every year. The automated laboratory clinical instrumentation for MRSA is comparable to the identification of manual MIC or molecular PCR. However, in the face ever-changing MRSA, various identification methods the clinical data is the only way to get a glimpse of the evolution of resistance to MRSA strains.