54株猪源肠外致病性大肠杆菌血清型、系统进化群和基因型

Serotypes, phylogenetic groups and genotypes of 54 extraintestinal pathogenic Escherichia coli from pig

摘要:

【背景】近年来，我国规模猪场着重加强了对猪繁殖与呼吸综合征、猪圆环病毒病、猪瘟、猪伪狂犬病、猪链球菌病、副猪嗜血杆菌病等疫病的防控，却忽视了由肠外致病性大肠杆菌(Extraintestinal Pathogenic Escherichia coli，ExPEC)对猪群健康产生的潜在危害性，了解和掌握猪源ExPEC流行特征意义显著。【目的】探究临床分离的54株猪源ExPEC血清型、系统进化群和基因型的分布及流行特征。【方法】应用玻板凝集试验和试管凝集试验鉴定O抗原血清型，采用PCR技术检测系统进化群鉴定相关基因、28个ExPEC相关毒力基因以及多位点序列分型相关基因。【结果】受试菌中有52株确定了O抗原血清型，其中40株为O38 (74.1%)，为优势血清型；8株为O127 (14.8%)，O93和O11均2株(各占3.7%)。受试菌中44株为B2群(81.5%)，是主要系统进化群，D群和B1群均5株(各占9.3%)；28个ExPEC相关毒力基因中ompA、ibeA、fimH、traT、focD、papA、iroN、iutA、iucD、cvaC、tsh、kpsMTⅡ、iss和ompT出现的频率超过50%，其中ompA和ibeA检出率分别达100%和96.3%，为高度流行的毒力基因，未检到cnf1，而bmaE、malX和iha更倾向分布于D群菌株中。受试菌共呈现31种ST型，其中ST10和ST648均5株(各占9.3%)，ST410和ST101均4株(各占7.4%)。【结论】猪源ExPEC优势血清型及系统进化群在不同地区、不同时段上的流行分布均存在一定差异，呈现动态过程，O38作为优势血清型目前尚未见报道，具有高致病性的B2群和D群菌株有逐渐增多的趋势。ST型复杂多样，呈现遗传多样性，在一定程度上与人源和禽源ExPEC具有相同的遗传背景。

Abstract:

[Background] In recent years, pig farms have focused on the prevention and control of porcine reproductive and respiratory syndrome, porcine circovirus, classical swine fever, porcine pseudorabies, swine streptococcus and haemophilus parasuis disease, but ignored the potential harm of extraintestinal pathogenic Escherichia coli (ExPEC) to pig health. It is of great significance to understand the epidemic characteristics of ExPEC. [Objective] To study the distribution and epidemic characteristics of serotypes, phylogeny groups and genotypes of 54 strains of ExPEC isolated from pigs. [Methods] The glass plate agglutination test and the test tube agglutination test were used to identify the O antigen serotype. The PCR technology detection system phylogeny groups identified related genes, 28 ExPEC-related virulence genes, and multi-site sequence typing-related genes. [Results] Of the tested bacteria, 52 strains were identified the O antigen serotype, of which 40 strains were O38 (74.1%), the dominant serotype, 8 strains were O127 (14.8%), and O93 and O11 were both 2 strains (3.7% each). Among the tested bacteria, 44 strains belong to group B2 (81.5%), which is the main phylogenetic group. Group D and group B1 each have 5 strains (9.3% each); The frequency of ompA, ibeA, fimH, traT, focD, papA, iroN, iutA, iucD, cvaC, tsh, kpsMTⅡ, iss, and ompT was more than 50% of 28 ExPEC-related virulence genes, the detection rates of ompA and ibeA were 100% and 96.3% respectively, which were highly prevalent virulence genes. cnf1 was not detected, but bmaE, malX and iha were more likely to be distributed in group D strains. The tested bacteria showed a total of 31 types of ST, including 5 strains of ST10 and ST648 (9.3% each), and 4 strains of ST410 and ST101 (7.4% each). [Conclusion] The prevalence of pig-derived ExPEC serotypes and phylogenetic groups in different regions and at different times have certain differences, showing a dynamic process. There is no report of O38 as the dominant serotype, and the highly pathogenic B2 and D strains have a trend of increasing gradually. The ST type is complex and diverse, presenting genetic diversity, and to some extent has the same genetic background as human and avian ExPEC.