Beijing Key Laboratory of Detection Technology for Animal-Derived Food Safety, College of Veterinary Medicine, China Agricultural University, Beijing 100193, P. R. China.
J Antimicrob Chemother. 2014 Apr;69(4):919-23. doi: 10.1093/jac/dkt482. Epub 2013 Dec 8.
To investigate the genetic basis of pleuromutilin resistance in coagulase-negative staphylococci of porcine origin that do not carry known pleuromutilin resistance genes and to determine the localization and genetic environment of the identified resistance gene.
Plasmid DNA of two pleuromutilin-resistant Staphylococcus cohnii and Staphylococcus simulans isolates was transformed into Staphylococcus aureus RN4220. The identified resistance plasmids were sequenced completely. The candidate gene for pleuromutilin resistance was cloned into shuttle vector pAM401. S. aureus RN4220 transformants carrying this recombinant shuttle vector were tested for their MICs.
S. cohnii isolate SA-7 and S. simulans isolate SSI1 carried the same plasmid of 5584 bp, designated pSA-7. A variant of the vga(E) gene was detected, which encodes a 524 amino acid ATP-binding cassette protein. The variant gene shared 85.7% nucleotide sequence identity and the variant protein 85.3% amino acid sequence identity with the original vga(E) gene and Vga(E) protein, respectively. The Vga(E) variant conferred cross-resistance to pleuromutilins, lincosamides and streptogramin A antibiotics. Plasmid pSA-7 showed an organization similar to that of the apmA-carrying plasmid pKKS49 from methicillin-resistant S. aureus and the dfrK-carrying plasmid pKKS966 from Staphylococcus hyicus. Sequence comparisons suggested that recombination events may have played a role in the acquisition of this vga(E) variant.
A novel vga(E) gene variant was identified, which was located on a small plasmid and was not associated with the transposon Tn6133 [in contrast to the original vga(E) gene]. The plasmid location may enable its further dissemination to other staphylococci and possibly also to other bacteria.
研究不携带已知截短侧耳素耐药基因的猪源凝固酶阴性葡萄球菌中截短侧耳素耐药的遗传基础，并确定所鉴定耐药基因的定位和遗传环境。
将两种截短侧耳素耐药的凝固酶阴性葡萄球菌（S. cohnii 和 S. simulans）分离株的质粒 DNA 转化为金黄色葡萄球菌 RN4220。对鉴定出的耐药质粒进行了全序列测序。克隆截短侧耳素耐药候选基因到穿梭载体 pAM401 中。携带该重组穿梭载体的金黄色葡萄球菌 RN4220 转化体被测试其 MIC 值。
S. cohnii 分离株 SA-7 和 S. simulans 分离株 SSI1 携带相同的 5584 bp 质粒，命名为 pSA-7。检测到 vga(E) 基因的变体，该基因编码一个 524 个氨基酸的三磷酸腺苷结合盒蛋白。变体基因与原始 vga(E)基因和 Vga(E)蛋白分别共享 85.7%的核苷酸序列同一性和 85.3%的氨基酸序列同一性。Vga(E) 变体赋予对截短侧耳素、林可酰胺类和糖肽类抗生素的交叉耐药性。质粒 pSA-7 显示出与耐甲氧西林金黄色葡萄球菌携带的 apmA 质粒 pKKS49 和猪葡萄球菌携带的 dfrK 质粒 pKKS966 相似的组织。序列比较表明，重组事件可能在获得这种 vga(E) 变体中发挥了作用。
鉴定出一种新型 vga(E) 基因变体，位于小质粒上，与转座子 Tn6133 无关（与原始 vga(E)基因相反）。质粒位置可能使其能够进一步传播到其他葡萄球菌，也可能传播到其他细菌。
