通辽地区犊牛腹泻大肠杆菌耐药性检测及一株多重耐药菌全基因组测序分析

【背景】大肠杆菌(Escherichia coli)是引起犊牛腹泻的最主要病原菌，其耐药性菌株的不断出现引起广泛关注。【目的】了解内蒙古自治区通辽市犊牛腹泻大肠杆菌耐药性及耐药基因流行情况。【方法】从通辽市多个旗县采集犊牛腹泻样品40份，经细菌分离纯化及16S rRNA基因测序，最终鉴定出20株大肠杆菌。采用药敏试验和PCR方法对分离菌进行耐药性及耐药基因检测分析，并对其中1株多重耐药菌株进行全基因组测序。【结果】20株分离菌均具有多重耐药性，对链霉素、环丙沙星、恩诺沙星和复方新诺明的耐药率达80%以上。所检耐药基因中，aphA1、strB、TEM-1和qnrS检出率达100%。通过对代表性菌株TL-13全基因组测序发现，其基因组大小为4897185bp，GC含量为50.68%，同时携带2个质粒，大小分别为108288bp(pTL13-1)和64018bp(pTL13-2)。质粒中共携带18个可移动耐药基因。【结论】通辽地区犊牛腹泻大肠杆菌多重耐药性普遍存在，4种常见耐药基因普遍流行。

Drug resistance of Escherichia coli strains causing calf diarrhea in Tongliao and whole-genome sequencing of a multi-drug resistant strain

Background] Escherichia coli is the main pathogen causing diarrhea and the emerging of the drug-resistant strains has aroused wide concern. Objective] To understand the prevalence of drug resistance and drug resistance genes of E.coli causing calf diarrhea in Tongliao city, Inner Mongolia Autonomous Region. Methods] Forty samples of calves suffering from diarrhea were collected from multiple banners and counties of Tongliao, from which 20 strains of E.coli were isolated and identified via 16S rRNA gene sequencing. Drug sensitivity test and PCR were conducted to study the drug resistance and drug resistance genes of the isolated strains. The whole genome of a multi-drug resistant strain was sequenced. Results] All the 20 isolates had multi-drug resistance and showed the drug resistance rate above 80% to streptomycin, ciprofloxacin, enrofloxacin, and compound sulfamethoxazole. The detection rates of aphA1, strB, TEM-1, and qnrS were 100%. The strain TL-13 had the genome size of 4 897 185 bp and the GC content of 50.68%, and it carried two plasmids with the sizes of 108 288 bp (pTL13-1) and 64 018 bp (pTL13-2), respectively. The plasmids carried 18 mobile drug resistance genes. Conclusion] The E.coli strains causing calf diarrhea in Tongliao generally have multi-drug resistance, and the four common resistance genes were prevalent.