耐甲氧西林凝固酶阴性葡萄球菌临床分离株中 SCCmec 元件的多样性。
Diversity of SCCmec elements in methicillin-resistant coagulase-negative staphylococci clinical isolates.
机构信息
Center of Infectious Diseases, West China Hospital, Sichuan University, Chengdu, China.
出版信息
PLoS One. 2011;6(5):e20191. doi: 10.1371/journal.pone.0020191. Epub 2011 May 26.
BACKGROUND
Methicillin-resistant coagulase-negative staphylococci (MR-CoNS) are opportunistic pathogens and serve as a large reservoir of staphylococcal cassette chromosome mec (SCCmec). Characterization of SCCmec in MR-CoNS can generate useful information on the mobilization and evolution of this element.
METHODOLOGY/PRINCIPAL FINDINGS: Non-repetitive MR-CoNS clinical isolates (n = 84; 39 S. epidermidis, 19 S. haemolyticus, 9 S. hominis, 6 S. capitis, 4 S. warneri, 2 S. cohnii, 2 S. saprophyticus, 1 S. kloosii, 1 S. simulans and 1 S. massiliensis) were collected. All isolates could grow on plates with 4 mg/L cefoxitin and all had mecA as detected by PCR. Strain typing using RAPD and ERIC-PCR revealed that almost all isolates were of different strains. SCCmec typing was performed using multiplex PCR published previously. For isolates in which SCCmec could not be typed, the mec complex classes were determined by additional PCR and the ccr genes were amplified with published or newly-designed primers and then sequenced. SCCmec types were assigned for 63 isolates by multiplex PCR and were assigned for 14 other isolates by PCR targeting mec and ccr. Among 77 isolates with determined SCCmec types, 54 had a single type, including type III (n = 19), IV (n = 14), V (n = 10), II (n = 2), I (n = 1), VIII (n = 1) and five unnamed types (n = 7), while 23 isolates had two types, III+V (n = 12), II+V (n = 8), II+IV (n = 2) or IV+V (n = 1). The five unnamed types were assigned UT1 (class A mec, ccrA1/ccrB4), UT2 (class C1 mec, ccrA4/ccrB4), UT3 (class A mec, ccrA5/ccrB3), UT4 (class C2 mec, ccrA2/ccrB2 plus ccrC1) and UT5 (class A mec, ccrA1/ccrB1 plus ccrC1).
CONCLUSIONS/SIGNIFICANCE: SCCmec types III, IV and V were prevalent in MR-CoNS and many isolates could harbor more than one type. Several new types of SCCmec were identified, highlighting the great genetic diversity and the need of developing classification schemes for SCCmec in MR-CoNS.
背景
耐甲氧西林凝固酶阴性葡萄球菌（MR-CoNS）是机会致病菌，也是葡萄球菌盒式染色体 mec（SCCmec）的重要储库。对 MR-CoNS 中 SCCmec 的特征分析可以为该元件的移动和进化提供有用的信息。
方法/主要发现：收集了 84 株非重复的 MR-CoNS 临床分离株（39 株表皮葡萄球菌、19 株溶血葡萄球菌、9 株人葡萄球菌、6 株头状葡萄球菌、4 株沃氏葡萄球菌、2 株科氏葡萄球菌、2 株腐生葡萄球菌、1 株金黄葡萄球菌、1 株模仿葡萄球菌和 1 株马萨利葡萄球菌）。所有分离株均能在含有 4mg/L 头孢西丁的平板上生长，且均通过 PCR 检测到 mecA。使用先前发表的 RAPD 和 ERIC-PCR 进行菌株分型显示，几乎所有分离株均属于不同的菌株。使用先前发表的多重 PCR 进行 SCCmec 分型。对于不能通过多重 PCR 分型的分离株，通过附加 PCR 确定 mec 复合物的类别，并使用已发表或新设计的引物扩增 ccr 基因，然后对其进行测序。77 株分离株通过多重 PCR 确定 SCCmec 型，14 株分离株通过针对 mec 和 ccr 的 PCR 确定 SCCmec 型。在确定 SCCmec 型的 77 株分离株中，54 株具有单一型，包括 III 型（19 株）、IV 型（14 株）、V 型（10 株）、II 型（2 株）、I 型（1 株）、VIII 型（1 株）和五个未命名型（7 株），而 23 株具有两种型，III+V 型（12 株）、II+V 型（8 株）、II+IV 型（2 株）或 IV+V 型（1 株）。这五个未命名的类型被分配为 UT1（A 类 mec，ccrA1/ccrB4）、UT2（C1 类 mec，ccrA4/ccrB4）、UT3（A 类 mec，ccrA5/ccrB3）、UT4（C2 类 mec，ccrA2/ccrB2 加 ccrC1）和 UT5（A 类 mec，ccrA1/ccrB1 加 ccrC1）。
结论/意义：MR-CoNS 中流行的 SCCmec 型为 III、IV 和 V 型，许多分离株可携带一种以上的类型。鉴定了几种新的 SCCmec 型，突出了其巨大的遗传多样性，需要为 MR-CoNS 中的 SCCmec 制定分类方案。
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