四川地区大口黑鲈源鰤诺卡菌耐药性与耐药基因分析

Analysis of drug resistance and drug resistance genes of Nocardiae seriola from Micropterus salmoides in Sichuan

鰤诺卡菌(Nocardia seriolae)是严重危害大口黑鲈的病原菌,为了解四川大口黑鲈主养区N.seriolae的耐药性与耐药基因流行情况,从四川大口黑鲈主养区分离鉴定N.seriolae 20株。采用微量肉汤稀释法测定分离菌株的耐药表型,发现20株N.seriola对多西环素、替米考星、庆大霉素等敏感率为100%,对青霉素、头孢噻呋、头孢西丁等药物的耐药率为100%,对恩诺沙星、磺胺异恶唑、氟苯尼考耐药率分别为45%、40%和20%,其中10株菌表现出多重耐药性,且不同区域的分离株耐药表型存在差异。超高通量荧光定量PCR法检测分离菌中6类78种耐药基因分布情况,结果显示,6类耐药基因均可在20株分离菌中检出,其中tetA、tetG、tetS、aacC、blaTEM、floR、acrA、acrB的检出率达100%,其他耐药基因检出率介于5%~95%,且存在地区与菌株差异,表明四川大口黑鲈N.seriolae具有进一步进化为多重耐药的潜在风险。

Nocardia seriolae is a pathogen that seriously harms Micropterus salmoides.To understand the drug resistance and the prevalence of drug resistance genes in N.seriolae in the main breeding area for Micropterus salmoides of Sichuan,20 strains of N.seriolae were isolated and identified from Sichuan from 2018 to 2019.Micro broth dilution method was used to determine the drug-resistant phenotype of the isolated strains.It was found that the sensitivity rates of N.seriolae to doxycycline,tilmicosin,gentamicin,etc.were 100%,the drug resistance rates to penicillin,ceftiofur,cefoxitin,etc.were 100%,and the resistance rates to enrofloxacin and florfenicol were 45%and 20%,respectively.Ten strains showed multi-drug resistance,and the drug-resistant phenotypes of the isolates are different.The distribution of 78 drug resistance genes in 6 classes was detected by the ultra-high-throughput fluorescence quantitative PCR method.The results showed that all 6 classes of resistant genes could be detected in 20 isolates,the detection rate of tetA,tetG,tetS,aacC,acrA,acrB,floR and blaTEM reached 100%,and the detection rate of other resistance genes ranged from 5%to 95%,with regional and bacterial differences,indicating that the Sichuan N.seriolae has the potential to evolve into multiple drug resistance.