Translational Approach to Induce and Evaluate Verocytotoxic E. coli O138 Based Disease in Piglets.

Luciana Rossi,Pietro Riccaboni,Paolo Trevisi,Antonella Baldi,Eugenio Scanziani,Eugenio Demartini,Lauretta Turin,Paola Dall’Ara,Giovanni Loris Alborali,Matteo Dell’Anno,Joel Fernando Soares Filipe,Federica Riva

doi:10.3390/ani11082415

Abstract

Simple SummaryThe aim of the study was to set up experimental conditions to simulate the simultaneous outbreak of post-weaning diarrhea and enterotoxaemia in weaned piglets, through verocytotoxic O138 Escherichia coli challenge. Zootechnical, clinical, microbiological, histological and immunological parameters were evaluated along the follow-up of control and infected groups. Results showed that experimental infection significantly affected the clinical status. Infected animals showed significant higher total median scores of epiphora, vitality, hair irregularity, oedema and depression; in addition, they displayed evident inflammatory infiltrate of lymphocytes, and follicular hyperplasia, increase of IgG in the intestinal crypts and CD3-positive T cells in intestinal epithelium. The infection model, carried out on receptor-mediated susceptible piglets, allowed to identify a discriminative panel of clinical symptoms related to Escherichia coli O138 infection and could be used to assess the protective effect of antibiotic alternatives.Pig livestock was influenced by several global concerns that imposed a re-thinking of the farming system, which included the reduction in chemical dependency and the development of antimicrobial alternatives. Post-weaning diarrhea and enterotoxaemia caused by Escherichia coli, are serious threats that are responsible for the economic losses related to mortality, morbidity and stunted growth in weaning piglets. The aim of the study was to set up experimental conditions to simulate the simultaneous outbreak of post-weaning diarrhea and enterotoxaemia in weaned piglets, through verocytotoxic O138 Escherichia coli challenge, with a multidisciplinary approach. Eighteen piglets susceptible to F18 VTEC infection were selected by polymerase chain reaction for polymorphism on the fucosyltransferase 1 gene and randomly divided in two experimental groups, non-infected controls (C; n = 6) and infected ones (I; n = 12) and housed into individual pens at the same environmental conditions for 29 days. At day 20, I pigs were orally inoculated with Escherichia coli O138 and fed a high protein ration for 3 days. Zootechnical, clinical, microbiological, histological and immunological parameters were evaluated along the follow up (3 and 9 days). Experimental infection, confirmed by bacteria faecal shedding of the I group, significantly affected the clinical status. The I group showed significantly higher total scores, corresponding to medians of the sum of daily scores from days 1 to 3 (Σ3) and 1 to 9 (Σ9) post infection, epiphora, vitality, hair irregularity, oedema and depression. Histological examination showed evident inflammatory infiltrate of lymphocytes, and follicular hyperplasia in I pigs; in the same group, the immunohistochemical and immunological assays revealed an increase in IgG in the intestinal crypts and CD3-positive T cells in intestinal epithelium. The experimental Escherichia coli infection in controlled conditions is crucial for both the evaluation of innovative compounds and the elucidation of the mechanisms associated with the persistence of antibacterial resistant strains. In conclusion, the adopted infection model, carried out on receptor-mediated susceptible piglets, allowed us to identify a discriminative panel of clinical symptoms related to Escherichia coli O138 infection, and could be used to assess the protective effect of antibiotic alternatives.

Highlights

Improving the sustainability of pig livestock is a priority of global policies, in line with the agroecology principles, that imposed a re-thinking of the farming system, including the reduction in chemical dependency and the development of antimicrobial alternatives [1,2,3,4].The most critical phase of pig production is weaning, characterized by gastrointestinal disorders, such as post-weaning diarrhea (PWD), mainly due to Escherichia coli O138, O139, and O141 serogroups, which causes important economic losses [5,6]
The polymorphism analyses on the FUT1 gene proved that all piglets used in this study were susceptible to F18 VTEC infection
In order to reduce the number of animals, piglets were chosen after polymorphism analysis of the FUT1 gene, correlated with F18 receptor expression [36], susceptible to infection with E. coli O138

Summary

Introduction

Improving the sustainability of pig livestock is a priority of global policies, in line with the agroecology principles, that imposed a re-thinking of the farming system, including the reduction in chemical dependency and the development of antimicrobial alternatives [1,2,3,4]. The most critical phase of pig production is weaning, characterized by gastrointestinal disorders, such as post-weaning diarrhea (PWD), mainly due to Escherichia coli O138, O139, and O141 serogroups, which causes important economic losses (mortality, morbidity and stunted growth) [5,6]. Two important bacterial virulence factors are F18 adhesive fimbriae and verocytoxin (VT2e), often found in association in the β-haemolytic O138 E. coli strain [7,8]. A number of innovative replacements have been thoroughly discussed, such as edible vaccines, immunotherapeutics, bacteriophages, antimicrobial peptides, gut microbiota modulators, plant extracts, and integrated approaches [18,19,20,21]

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