Effect of mucin 4 allele on susceptibility to experimental infection with enterotoxigenic F4 Escherichia coli in pigs fed experimental diets

Background: This study investigated the validity of the DNA-marker based test to determine susceptibility to ETECF4 diarrhoea by comparing the results of two DNA sequencing techniques in weaner pigs following experimental infection with F4 enterotoxigenic Escherichia coli(ETEC-F4). The effects of diet and genetic susceptibility were assessed by measuring the incidence of piglet post-weaning diarrhoea(PWD), faecal E. coli shedding and the diarrhoea index.Results: A DNA marker-based test targeting the mucin 4 gene(MUC4) that encodes F4 fimbria receptor identified pigs as either fully susceptible(SS), partially or mildly susceptible(SR), and resistant(RR) to developing ETEC-F4 diarrhoea. To further analyse this, DNA sequencing was undertaken, and a significantly higher proportion of C nucleotides was observed for RR and SR at the Xba I cleavage site genotypes when compared to SS. However, no significant difference was found between SR and RR genotypes. Therefore, results obtained from Sanger sequencing retrospectively allocated pigs into a resistant genotype(MUC4–), in the case of a C nucleotide, and a susceptible genotype(MUC4+), in the case of a G nucleotide, at the single nucleotide polymorphism site. A total of 72 weaner pigs(age ~ 21 days), weighing 6.1 ± 1.2 kg(mean ± SEM), were fed 3 different diets:(i) positive control(PC) group supplemented with 3 g/kg zinc oxide(Zn O),(ii) negative control(NC) group(no Zn O or HAMSA),and(iii) a diet containing a 50 g/kg high-amylose maize starch product(HAMSA) esterified with acetate. At days five and six after weaning, all pigs were orally infected with ETEC(serotype O149:F4;toxins LT1, ST1, ST2 and EAST). The percentage of pigs that developed diarrhoea following infection was higher(P = 0.05) in MUC4+ pigs compared to MUC4– pigs(50% vs. 26.8%, respectively). Furthermore, pigs fed Zn O had less ETEC-F4 diarrhoea(P = 0.009) than pigs fed other diets, however faecal shedding of ETEC was similar(P > 0.05) between diets.Conclusion: These results confirm that MUC4+ pigs have a higher prevalence of ETEC-F4 diarrhoea following exposure, and that pigs fed Zn O, irrespective of MUC4 status, have reduced ETEC-F4 diarrhoea. Additionally,sequencing or quantifying the single nucleotide polymorphism distribution at the Xba I cleavage site may be more reliable in identifying genotypic susceptibility when compared to traditional methods.