北台灣無色素金黃色葡萄球菌之 特性探討

Abstract

金黃色葡萄球菌一般具有能夠合成金黃色葡萄球菌色素”staphyloxanthin”的基因，但少數為缺乏色素，澳洲Giffard研究團隊分析缺乏色素菌株─MSHR1132，並在西元2015年正式將其發表名為Staphylococcus argenteus之新菌種。S. argenteus在台灣還未有相關的研究報導；本實驗室發現早在西元2000年(0.7%)、2005年(3%)時此菌群就已存在，在近年2010年(13%)、2011年(17%)和2012年(16.5%)有增加的趨勢且維持相當比例；本研究分析發現96株dnaJ不典型且缺乏色素菌株，進一步確認為S. argenteus。共可分成五種MLST型別，分別是ST2250、ST2793、ST1223、ST2198和Unknown type，其中以ST2250占最多比例有74%(71 of 96)；ST2250特別的是擁有和MSHR1132極為相似的CRISPR/Cas免疫系統，以及能夠依spacer種類和數量分為不同CRISPR型別，我們也觀察到一些spacer會與特定direct repeat一起增減之現象，推測應存在著某種特殊機制並或許有助於基因編輯工具的發展。我們使用16S rRNA序列比對與nuc PCR皆無法區分S. argenteus和S. aureus；MALDI-TOF MS的分析顯示兩者確實有不同的表現。目前臨床鑑定還未能將兩者區分，本實驗室發現以dnaJ PCR-RFLP的鑑定方法能快速且正確分辨S. argenteus和S. aureus菌株。

Most Staphylococcus aureus have the genes for production of staphyloxanthin, but some don’t. A new species lacking pigment designated as Staphylococcus argenteus sp. nov. was published in 2015. It has not been reported in Taiwan yet. We found that S. argenteus isolate has existed in 2000 (0.7%) in Northern Taiwan, followed by 5 (3%) isolates in 2005, and 29 isolates (13%) in 2010. The isolation of it continued in 2011 (17%) and 2012 (16.5%). In this study, we analyzed 96 S. argenteus that could be divided into five MLST types: ST2250, ST2793, ST1223, ST2198 and one unknown ST type. ST2250 is the major clone of these isolates, presents in 74% (71 of 96). In addition, we found ST2250 is unique because all of it possesses the CRISPR/Cas system. And it can be designated as different CRISPR types according to the arrangement of direct repeat (DR) and spacer variants. We also observed the certain spacer is cross-linked to specific DR, results in a set of “spacer-DR” disappeared or integrated into some types. It was proposed that there must be an unknown and special mechanism on CRISPR/Cas system in ST2250 and may be helpful to develop more convinent tool for genome editing in the future. On other hand, S. argenteus can’t be distinguished from S. aureus by 16S rRNA or nuc PCR. We also performed MALDI-TOF MS analysis to determine their different profiles. Most impotantly, we found that dnaJ PCR-RFLP is a fast and correct method can be used to differentiate between S. argenteus and S. aureus in this study.