Effects of E. coli bivalent vaccine and of host genetic susceptibility to E. coli on the growth performance and faecal microbial profile of weaned pigs.
F4- and F18-positive enterotoxigenic Escherichia coli (ETEC) are well-known pathogens able to cause a severe swine disease with a worldwide economically importance in pig sector   . Vaccination of piglets with an oral live bivalent F4/F18 Escherichia coli vaccine has shown some promise and efficacy results in preventing ETEC post weaning diarrhoea (PWD); however, currently there is a lack of knowledge on its effect on the microbial community. Furthermore, is not known if the effect of vaccination on gut eubiosis can vary according to pigs genetic susceptibility to ETEC F4 and F18.The aim of this study is to evaluate the effect of E. coli bivalent vaccine and the potential influence of host genetic susceptibility to ETEC on health, growth performance and faecal microbial profile of piglets around weaning. To address this issue, a total of 290 piglets at 26 days after birth (d0) were divided into two different groups balanced for body weight: i) vaccine (VAX: 6.33 kg) and control (CO: 6.45 kg). At d0 VAX group was orally inoculated with 2 mL of live non-pathogenic E. coli O8:K87 (F4ac-positive) and O141:K94 (F18ac positive) vaccine (Coliprotec F4/F18; Prevtec Microbia an Elanco Company), while CO was orally inoculated with 2 mL of sterilized water. At d0, and 18 days after the vaccination (d18) piglets were individually weighted, and a faecal sample was collected for microbial profile of V3-V4 regions of the 16S rRNA gene using MiSeq Illumina platform. Bristles were collected for the genotyping analysis of MUC4 and FUT1 polymorphisms. No effect of vaccination and genetic susceptibility was observed on growth performance. The vaccination modulated the fecal microbial composition, reducing the alpha diversity indices (P<0.05) and affecting the beta diversity (R2=0.02; P = 0.05). VAX was discriminated from CO by beneficial bacteria genera including Dialister, Prevotella, Blautia, Ruminiclostridium, Parabacteroides and Faecalibacterium. No interaction between vaccination and animal genetic susceptibility to ETEC was observed. F4 resistant genotype showed a higher alpha diversity index than susceptible ones pre and post-weaing (P< 0.05). These findings contributed to the body of knowledge regarding the beneficial effect of oral live bivalent F4/F18 E. coli vaccine on piglets' gut homeostasis resulting in improved gut eubiosis.