耐甲氧西林金黄色葡萄球菌中盒式染色体重组酶（ccr）的高频和多样性。
High frequency and diversity of cassette chromosome recombinases (ccr) in methicillin-susceptible Staphylococcus sciuri.
机构信息
Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal Laboratory of Bacterial Evolution and Molecular Epidemiology, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal.
Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Rua da Quinta Grande, 6, 2780-156 Oeiras, Portugal Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, 1230 York Avenue, New York, NY 10065, USA.
出版信息
J Antimicrob Chemother. 2014 Jun;69(6):1461-9. doi: 10.1093/jac/dku028. Epub 2014 Feb 16.
OBJECTIVES
Previous studies produced evidence that mecA, the determinant of β-lactam resistance in methicillin-resistant Staphylococcus aureus (MRSA), may have originated in the most primitive and widespread animal commensal species-Staphylococcus sciuri. But how the mecA homologue (mecA1/pbpD) was captured from S. sciuri into the staphylococcal cassette chromosome mec (SCCmec) has remained unclear.
METHODS
To understand the role of S. sciuri in the assembly of SCCmec, we screened 118 methicillin-susceptible S. sciuri isolates for SCCmec central elements-ccr and mec complex (ccrAB, ccrC, mecA, mecI and mecR1)-by dot-blot hybridization. In addition, isolates were typed by PFGE and the chromosomal proximity of SCCmec elements was determined by Southern hybridization. ccr typing was performed by nucleotide sequencing.
RESULTS
ccrAB were identified in 35% of the isolates (n = 41), represented by 24 PFGE types, but ccrC was not found. None of the isolates carried mecA or its regulators, but all isolates carried mecA1/pbpD. In the majority of isolates, ccr and mecA1 were located near orfX, the SCCmec integration site. Moreover, in 31% (n = 13) of the ccrAB-carrying strains, ccrAB, mecA1 and orfX colocalized in the chromosome. The nucleotide sequence of ccrA/ccrB was highly diverse, including ccr genes closely related (80%-97%) to those found in MRSA.
CONCLUSIONS
Our results suggest that S. sciuri was a natural recipient and a rich reservoir of ccr for the assembly of SCCmec. The chromosomal location of mecA1, near orfX, the recognition site of ccr, was probably crucial for its mobilization out of S. sciuri species into SCCmec.
目的
先前的研究表明，耐甲氧西林金黄色葡萄球菌（MRSA）中β-内酰胺类抗生素耐药的决定因子 mecA 可能起源于最原始和广泛存在的动物共生种——松鼠葡萄球菌。但 mecA 同源物（mecA1/pbpD）是如何从松鼠葡萄球菌捕获到葡萄球菌盒式染色体 mec（SCCmec）中的，目前仍不清楚。
方法
为了了解松鼠葡萄球菌在 SCCmec 组装中的作用，我们通过斑点杂交筛选了 118 株甲氧西林敏感型松鼠葡萄球菌分离株的 SCCmec 中心元件-ccr 和 mec 复合物（ccrAB、ccrC、mecA、mecI 和 mecR1）。此外，还通过 PFGE 对分离株进行了分型，并通过 Southern 杂交确定了 SCCmec 元件的染色体接近性。ccr 型通过核苷酸测序确定。
结果
在 35%的分离株（n=41）中鉴定出了 ccrAB，代表了 24 种 PFGE 型，但未发现 ccrC。没有分离株携带 mecA 或其调节剂，但所有分离株都携带 mecA1/pbpD。在大多数分离株中，ccr 和 mecA1 位于 orfX 附近，orfX 是 SCCmec 整合位点。此外，在 31%（n=13）携带 ccrAB 的菌株中，ccrAB、mecA1 和 orfX 共定位在染色体上。ccrA/ccrB 的核苷酸序列高度多样化，包括与 MRSA 中发现的密切相关（80%-97%）的 ccr 基因。
结论
我们的研究结果表明，松鼠葡萄球菌是 SCCmec 组装中 ccr 的天然受体和丰富储库。mecA1 位于 orfX 附近，即 ccr 的识别位点，其染色体位置可能对 mecA1 从松鼠葡萄球菌种转移到 SCCmec 中至关重要。
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