Yu Dongliang, Pi Borui, Chen Yan, Wang Yanfei, Ruan Zhi, Otto Michael, Yu Yunsong
Institute of Developmental and Regenerative Biology, Hangzhou Normal University, Hangzhou, China ; Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, China.
PLoS One. 2014 Jan 23;9(1):e87346. doi: 10.1371/journal.pone.0087346. eCollection 2014.
Staphylococcal cassette chromosome (SCC) elements contribute considerably to virulence and resistance to antibiotic agents in staphylococci. SCC elements in coagulase-negative staphylococci (CoNS) are highly diverse and there is evidence suggesting that they serve as a reservoir for antibiotic resistance genes in methicillin-resistant Staphylococcus aureus (MRSA). However, only a small number of SCC elements have been characterized in CoNS and their exact roles in the emergence and evolution of MRSA remain to be demonstrated. Here, we determined the structure of an SCC composite island (CISH32) found in the clinical Staphylococcus haemolyticus isolate SH32 by whole-genome DNA sequencing. CISH32 was 48 kb in length and mainly composed of two imperfect SCC elements, namely (i) a ΨSCCmec(SH32) part containing a class C1 mec gene complex but lacking ccr genes and (ii) a SCCSH32 part with a ccrA5B3 gene complex but lacking mec genes. In addition, CISH32 contained a type III restriction-modification system and several resistance loci, for example genes conferring resistance to cadmium and arsenic. ΨSCCmec(SH32) is almost entirely identical to a pseudo SCCmec element found in S. haemolyticus WCH1 and shares pronounced sequence similarity to a ΨSCCmec element of S. haemolyticus JCSC1435. However, staphylococci other than S. haemolyticus, including S. aureus and S. epidermidis, contain homologs of SCCSH32 that are more similar to SCCSH32 than those elements found in S. haemolyticus, suggesting that CISH32 of S. haemolyticus SH32 was assembled in recent evolutionary events. Moreover, the composite structure of CISH32 indicates that the detection of class C1 mec and ccrA5B3 gene complexes in S. haemolyticus does not always indicate the existence of a UT9-type SCCmec element, which has remained questionable.
葡萄球菌盒式染色体（SCC）元件对葡萄球菌的毒力和抗生素耐药性有很大影响。凝固酶阴性葡萄球菌（CoNS）中的SCC元件高度多样，有证据表明它们是耐甲氧西林金黄色葡萄球菌（MRSA）抗生素耐药基因的储存库。然而，CoNS中只有少数SCC元件得到了表征，它们在MRSA出现和进化中的确切作用仍有待证明。在此，我们通过全基因组DNA测序确定了临床溶血葡萄球菌分离株SH32中发现的一个SCC复合岛（CISH32）的结构。CISH32长度为48 kb，主要由两个不完整的SCC元件组成，即（i）一个ΨSCCmec(SH32)部分，包含一个C1类mec基因复合体但缺乏ccr基因，以及（ii）一个带有ccrA5B3基因复合体但缺乏mec基因的SCCSH32部分。此外，CISH32包含一个III型限制修饰系统和几个耐药位点，例如赋予对镉和砷耐药性的基因。ΨSCCmec(SH32)几乎与溶血葡萄球菌WCH1中发现的一个假SCCmec元件完全相同，并且与溶血葡萄球菌JCSC1435的一个ΨSCCmec元件有明显的序列相似性。然而，除溶血葡萄球菌外的其他葡萄球菌，包括金黄色葡萄球菌和表皮葡萄球菌，含有SCCSH32的同源物，这些同源物比溶血葡萄球菌中发现的那些元件与SCCSH32更相似，这表明溶血葡萄球菌SH32的CISH32是在最近的进化事件中组装而成的。此外，CISH32的复合结构表明，在溶血葡萄球菌中检测到C1类mec和ccrA5B3基因复合体并不总是表明存在一直存在疑问的UT9型SCCmec元件。
