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Abstract：
Escherichia coli (E. coli) is closely associated with the occurrence of puerperal metritis in dairy cows. E. coli carries some the virulence and multi-drug resistant genes, which pose a serious threat to the health of postpartum cows. In this study, E. coli was isolated and identified from the uterine contents of postpartum cows with puerperal metritis in the Ningxia region of China, and its phylogenetic subgroups were determined. Meanwhile, virulence and drug resistance genes carried by E. coli and drug sensitivity were detected, and the characteristics of virulence and drug resistance genes distribution in E. coli phylogroups were further analyzed. The results showed that the isolation rate of E. coli in puerperal metritis samples was 95.2%. E. coli was mainly divided into phylogroups B2 and D, followed by groups A and B1, and was more connected to O157:H7, O169:H4, and ECC-1470 type strains. The virulence genes were mainly dominated by ompF (100%), traT (100%), fimH (97%), papC (96%), csgA (95%), Ang43 (93.9%), and ompC (93%), and the resistance genes were dominated by TEM (99%), tetA (71.7%), aac(3)II (66.7%), and cmlA (53.5%). Additionally, it was observed that the virulence and resistance gene phenotypes could be divided into two subgroups, with subgroup B2 and D having the highest distributions. Drug sensitivity tests also revealed that the E. coli was most sensitive to the fluoroquinolones enrofloxacin, followed by macrolides, aminoglycosides, tetracyclines, β-lactams, peptides and sulfonamides, and least sensitive to lincosamides. These results imply that pathogenic E. coli, which induces puerperal metritis of dairy cows in the Ningxia region of China, primarily belongs to the group B2 and D, contains multiple virulence and drug resistance genes, Moreover, E. coli has evolved resistance to several drugs including penicillin, lincomycin, cotrimoxazole, and streptomycin. It will offer specific guidelines reference for the prevention and treatment of puerperal metritis in dairy cows with E. coli infections in the Ningxia region of China.
摘要：
大肠杆菌(E.大肠杆菌)与奶牛产褥期子宫炎的发生密切相关。大肠杆菌携带一些毒力和多重耐药基因，这对产后奶牛的健康构成了严重威胁。在这项研究中,从中国宁夏地区产褥期子宫炎的产后奶牛的子宫内容物中分离并鉴定了大肠杆菌，并确定了其系统发育亚组。同时,检测大肠杆菌携带的毒力、耐药基因和药物敏感性,进一步分析了大肠杆菌系统群的毒力特征和耐药基因分布。结果表明，产褥期子宫炎标本中大肠杆菌的分离率为95.2％。大肠杆菌主要分为系统群B2和D,其次是A组和B1组，并且更多地与O157：H7，O169：H4和ECC-1470型菌株有关。毒力基因主要以ompF(100%)为主,traT(100%)，FIMH（97%），papc(96%),CSGA（95%），Ang43（93.9%），ompC（93%），抗性基因以TEM（99%）为主，tetA（71.7%），aac(3)II(66.7%)，和cmlA(53.5%)。此外,观察到毒力和抗性基因表型可分为两个亚组，子组B2和D的分布最高。药敏试验还显示大肠杆菌对氟喹诺酮类恩诺沙星最敏感,其次是大环内酯类，氨基糖苷类,四环素,β-内酰胺,肽和磺胺类药物，对lincosamides最不敏感.这些结果表明致病性大肠杆菌，在中国宁夏地区奶牛产褥期子宫炎，主要属于B2和D组,含有多种毒力和耐药基因，此外，大肠杆菌已经对包括青霉素在内的几种药物产生了抗药性，林可霉素,复方新诺明,和链霉素.为宁夏地区大肠杆菌感染奶牛产褥期子宫炎的防治提供指导参考。
