Stojanov Miloš, Moreillon P, Sakwinska O
Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
Institute of Microbiology, University Hospital of Lausanne, Lausanne, Switzerland.
BMC Res Notes. 2015 Dec 29;8:828. doi: 10.1186/s13104-015-1815-3.
Methicillin-resistance in staphylococci is conferred by the mecA gene, located on the genomic island Staphylococcal Cassette Chromosome mec (SCCmec). SCCmec mobility relies on the Ccr recombinases, which catalyze insertion and excision form the host's chromosome. Although being a crucial step in its horizontal transfer, little is known about the dynamics of SCCmec excision.
A quantitative PCR-based method was used to measure the rate of SCCmec excision by amplifying the chromosome-chromosome junction and the circularized SCCmec resulting from excision. SCCmec excision rate was measured in methicillin-resistant Staphylococcus aureus (MRSA) strain N315 at various growth times in broth cultures. In the present experimental settings, excision of SCCmec occurred at a rate of approximately 2 × 10(-6) in MRSA N315.
This work brings new insights in the poorly understood SCCmec excision process. The results presented herein suggest a model in which excision occurs during a limited period of time at the early stages of growth.
葡萄球菌中的耐甲氧西林特性由位于基因组岛葡萄球菌盒式染色体mec（SCCmec）上的mecA基因赋予。SCCmec的移动性依赖于Ccr重组酶，其催化在宿主染色体上的插入和切除。尽管这是其水平转移中的关键步骤，但关于SCCmec切除的动力学知之甚少。
使用基于定量PCR的方法，通过扩增染色体-染色体连接点以及切除产生的环化SCCmec来测量SCCmec的切除率。在肉汤培养物中的不同生长时间，对耐甲氧西林金黄色葡萄球菌（MRSA）菌株N315的SCCmec切除率进行了测量。在本实验条件下，MRSA N315中SCCmec的切除率约为2×10⁻⁶。
这项工作为人们了解甚少的SCCmec切除过程带来了新的见解。本文给出的结果提示了一个模型，即切除发生在生长早期的有限时间段内。
