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

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.