猪源耐大观霉素金黄色葡萄球菌中spd阳性新型质粒的鉴定

Identification of the novel spd-positive plasmid in spectinomycin-resistant Staphylococcus aureus isolated from swine sources

从重庆养猪场采集猪鼻腔拭子,采用含256 mg/L大观霉素的金黄色葡萄球菌显色培养基和BP培养基,结合生化试验、PCR和16S rRNA测序分离鉴定耐大观霉素金黄色葡萄球菌;提取分离株质粒,测定序列后分析其遗传背景;将提取的质粒电转化到金黄色葡萄球菌RN4220中,检测分离株及金黄色葡萄球菌RN4220的耐药性。结果显示,从106份鼻腔拭子中分离得到7株耐大观霉素金黄色葡萄球菌,仅1株金黄色葡萄球菌CQRC1携带大观霉素耐药基因spd,且该基因位于大小为5653 bp的新型质粒pCQRC1上。电转化pCQRC1质粒可提高金黄色葡萄球菌RN4220对大观霉素MIC值64倍以上。质粒pCQRC1测序分析发现其仅编码Rec、Rep、Spd和Pre/Mob 4个蛋白。质粒pCQRC1的出现可能会促进大观霉素耐药性的快速传播,这为大观霉素耐药性的风险评估提供了数据支持。

In order to clarify the molecular epidemiological characteristics of spectinomycin-resistant Staphylococcus aureus(S.aureus)in pig farms,nose swabs were collected from pig farms of Chongqing,and spectinomycin-resistant S.aureus were isolated and identified by screening via chromogenic medium containing 256 mg/L of spectinomycin and BP medium in combination with biochemical tests,PCR and 16S rRNA sequencing.The plasmids of the isolates were extracted,and their genetic background was analyzed after sequence determination.The extracted plasmids were electrotransformed into S.aureus RN4220,and the drug resistance of the isolates and S.aureus RN4220 was detected.Of 106 samples collected by nose swabs,seven spectinomycin-resistant S.aureus strains were obtained,and only one strain,designated CQRCl,carried the spectinomycin resistant gene spd,it located in the novel plasmid pCQRC1 of size 5653 bp.The MIC values of S.aureus RN4220 obtaining pCQRC1 by electroporation increased over 64 folds.pCQRC1 only encoded four proteins,including Rec,Rep,Spd and Pre/Mob.Emergence of pCQRC1 may facilitate rapid dissemination of spectinomycin resistance,which provides data support for risk evaluation of spectinomycin resistance.