Department of Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-ku, Tokyo 113-8421, Japan.
Antimicrob Agents Chemother. 2010 Apr;54(4):1469-75. doi: 10.1128/AAC.00575-09. Epub 2010 Jan 19.
Macrococcus is a bacterial genus that is closely related to Staphylococcus, which typically is isolated from animal skin and products. The genome analysis of multidrug-resistant Macrococcus caseolyticus strain JCSC5402, isolated from chicken, previously led to the identification of plasmid pMCCL2, which carries a transposon containing an unusual form of the Macrococcus mec gene complex (mecA(m)-mecR1(m)-mecI(m)-blaZ(m)). In M. caseolyticus strain JCSC7096, this mec transposon containing the mec gene complex (designated Tn6045 in this study) was found integrated downstream of orfX on the chromosome. Tn6045 of JCSC7096 was bracketed by the direct repeat sequences (DR) specifically recognized by cassette chromosome recombinase (CCR). A non-mecA-containing staphylococcal cassette chromosome (SCC) element, designated SCC(7096), was integrated next to the mec transposon and separated from the latter by a DR. Nested PCR experiments showed that the mec transposon not only was excised singly but also coexcised with SCC(7096) from the chromosome at the DRs. The coexcised elements formed the extrachromosomal closed circular DNA of the SCCmec-like element. SCCmec is known to be the mobile element conveying methicillin (meticillin) resistance in staphylococci. However, its origin has been unknown. Our observation revealed a potential mechanism of the generation of a new SCCmec-like element in M. caseolyticus, a commensal bacterium of food animals.
马红球菌是一种与葡萄球菌密切相关的细菌属，通常从动物皮肤和产品中分离出来。先前对分离自鸡的多药耐药马红球菌 JCSC5402 菌株的基因组分析导致了质粒 pMCCL2 的鉴定，该质粒携带一个转座子，其中包含一种不寻常形式的马红球菌 mec 基因复合物（mecA(m)-mecR1(m)-mecI(m)-blaZ(m)）。在马红球菌 JCSC7096 菌株中，这个包含 mec 基因复合物的 mec 转座子（在本研究中被指定为 Tn6045）被发现整合在染色体上 orfX 的下游。JCSC7096 的 Tn6045 被盒式染色体重组酶（CCR）特异性识别的直接重复序列（DR）包围。一个不含有 mecA 的葡萄球菌盒式染色体（SCC）元件，被指定为 SCC(7096)，被整合在 mec 转座子旁边，并且通过 DR 与后者分离。嵌套 PCR 实验表明，mec 转座子不仅可以单独切除，而且可以与 SCC(7096)一起从染色体上的 DR 处切除。共同切除的元件形成了 SCCmec 样元件的染色体外闭合环状 DNA。SCCmec 是已知在葡萄球菌中传递甲氧西林（meticillin）耐药性的可移动元件。然而，其起源尚不清楚。我们的观察揭示了马红球菌中一种新的 SCCmec 样元件的产生的潜在机制，马红球菌是食品动物的共生菌。
