携带bla CTX-M禽大肠杆菌的多重耐药特征和体外致病性研究

Multi-drug resistance characteristics and in vitro pathogenicityin bla CTX-M -carrying avian Escherichia coli

【目的】探究携带bla CTX-M禽大肠杆菌的分子流行特点。【方法】检测76株携带bla CTX-M禽大肠杆菌的多重耐药谱、系统进化分群及毒力基因,并分析毒力基因与耐药特点、系统进化分群之间的关联性。【结果】药敏结果显示,携带bla CTX-M禽大肠杆菌对氟苯尼考的耐药率最高,达85.53%(65/76);其次是恩诺沙星,为48.68%(37/76);最常见的多重耐药谱为氟苯尼考+恩诺沙星+乙酰甲喹,达10.53%(8/76)。系统进化分群结果显示,主要的亚群为C群和B1群;其中,C群检出率最高,达53.95%(41/76);其次是B1群,为30.26%(23/76);E群、A群、D群和F群的检出率分别为9.21%(7/76)、2.63%(2/76)、2.63%(2/76)和1.32%(1/76);未检测出B2群和分支I群。毒力基因检测结果显示,76株携带bla CTX-M禽大肠杆菌均检出了至少4种毒力因子,且有11株菌同时携带至少11种毒力基因;其中,有13株菌同时检出禽致病性大肠杆菌(avian pathogenic Escherichia coli,APEC)的5个标志性毒力基因(iroN、iutA、hly、OmpT和iss),检出率为17.11%;有11株菌检出ColV质粒的标志基因(cva/cvi、iroN、iucD/iutA、etsAC、OmpT/hlyF和sitA),检出率为14.47%;有28株菌检出耶尔森菌强毒力岛(high pathogenitility island,HPI)的标志基因irp-2和fyuA,检出率为36.82%。【结论】携带bla CTX-M禽大肠杆菌多为多重耐药菌,且多重耐药菌株携带ColV毒力质粒可能性更高;携带bla CTX-M禽大肠杆菌的多重耐药与致病性有关联,即携带bla CTX-M禽大肠杆菌具有多重耐药的同时,具有致病的可能性更高。

【Objective】To further understand the molecular epidemic characteristics of bla CTX-M-carrying avian Escherichia coli.【Method】The multiple drug resistance profile,phylogenetic grouping,and virulence genes of 76 strains of bla CTX-M-carrying avian Escherichia coli were detected,and the correlation between virulence genes and drug resistance characteristics,as well as phylogenetic groups,was analyzed.【Result】Antimicrobial susceptibility test results showed that bla CTX-M-carrying avian Escherichia coli had the highest antibiotic resistance rate to florfenicol,reaching 85.53%(65/76),followed by enrofloxacin 48.68%(37/76),and the most common multidrug resistance spectrum was florfenicol+enrofloxacin+acetaquine,reaching 10.53%(8/76).Through multiple PCR for phylogenetic groups,it was found that the main subgroups were group C and group B1,and the group C has the highest detection rate of 53.95%(41/76),followed by group B1,with 30.26%(23/76).The detection rates of group E,group A,group D,and group F were 9.21%(7/76),2.63%(2/76),2.63%(2/76),and 1.32%(1/76),respectively.None of strains belonged to group B2 and branch I.The results of virulence genes testing showed that at least 4 virulence factors were carried in 76 strains of bla CTX-M-carrying avian Escherichia coli,and 11 strains carried at least 11 virulence genes at the same time.Among them,13 strains simultaneously carried five marker virulence genes(iroN,iutA,hly,OmpT and iss)of avian pathogenic Escherichia coli(APEC),with a detection rate of 17.11%,while 11 strains had marker genes of ColV plasmid(cva/cvi,iroN,iucD/iutA,etsAC,OmpT/hlyF,and sitA),with a detection rate of 14.47%,and 28 strains harbored high pathogenitility island(HPI)marker genes irp-2 and fyuA,with a detection rate of 36.82%.【Conclusion】The bla CTX-M-carrying avian Escherichia coli is mostly multidrug resistant,and the multidrug resistance of the bacteria is more likely to carry ColV virulence plasmid.The multidrug resistance of bla CTX-M-carrying avian Escherichia coli is positive correlation with its pathogenicity.