Comparative jejunal expression of MUC 13 in Indian native pigs differentially adhesive to diarrhoeagenic E. coli

Antibiotic resistant Escherichia coli from diarrheic piglets from pig farms in Thailand that harbor colistin-resistant mcr genes

Antibiotic-resistant Escherichia coli is one of the most serious problems in pig production. This study aimed to determine the antibiotic susceptibility and genotypes profiles of diarrhoeagenic E. coli that causes diarrhea in piglets. Thirty-seven pathogenic E. coli strains were used in this study. These were isolated from rectal swabs of diarrheic piglets from farms in Thailand from 2018 to 2019. Escherichia coli isolates were highly resistant to amoxicillin (100%), followed by oxytetracycline (91.9%), enrofloxacin (89.2%), trimethoprim/sulfamethoxazole (86.5%), amoxicillin: clavulanic acid (81.1%), colistin and gentamicin (75.7%), ceftriaxone and ceftiofur (64.9%), ceftazidime (35.1%) and 97.3% showed multidrug-resistance (MDR). There were 8 (21.6%) mcr-1 carriers, 10 (27.0%) mcr-3 carriers and 10 (27.0%) co-occurrent mcr-1 and mcr-3 isolates. The phenotype-genotype correlation of colistin resistance was statistically significant (performed using Cohen's kappa coefficient (κ = 0.853; p < 0.001)). In addition, PCR results determined that 28 of 37 (75.7%) isolates carried the int1 gene, and 85.7% int1-positive isolates also carried the mcr gene. Genetic profiling of E. coli isolates performed by ERIC-PCR showed diverse genetics, differentiated into thirteen groups with 65% similarity. Knowledge of the molecular origins of multidrug-resistant E. coli should be helpful for when attempting to utilize antibiotics in the pig industry. In terms of public health awareness, the possibility of transmitting antibiotic-resistant E. coli from diarrheic piglets to other bacteria in pigs and humans should be of concern.

Improvement of the Enterotoxigenic Escherichia coli Infection Model for Post-Weaning Diarrhea by Controlling for Bacterial Adhesion, Pig Breed and MUC4 Genotype

Enterotoxigenic Escherichia coli (ETEC) is a major cause of post-weaning diarrhea (PWD) in pigs and causes significant damage to the swine industry worldwide. In recent years, there has been increased regulation against the use of antibacterial agents in swine due to their health risks. Utilizing experimental models that consistently recapitulate PWD is important for the development of non-antibacterial agents against PWD in pigs. In this study, we established a highly reproducible PWD infection model by examining differences in adhesion of ETEC to the intestinal tissue as well as the association between MUC4 polymorphisms and sensitivity to PWD. Post-weaning diarrhea differences between pig breeds were also examined. The adhesion to enterocytes varied from 10^4.0 to 10^6.4 CFU/mL even among the F4 ETEC strains. Experimental infection revealed that PWD can be induced in all MUC4 genotypes after infection with 10¹⁰ CFU/pig of highly adherent ETEC, although there were variable sensitivities between the genotypes. Lowly adherent ETEC did not cause PWD as efficiently as did highly adherent ETEC. The incidence of PWD was confirmed for all pigs with the ETEC-susceptible MUC4 genotypes in all of the breeds. These results indicate that high-precision and reproducible experimental infection is possible regardless of pig breeds by controlling factors on the pig-end (MUC4 genotype) and the bacterial-end (adhesion ability).

Association of ACK1, TFRC polymorphism with diarrhoeagenic E. coli adhesion patterns and their jejunal expression profile in Indian Ghurrah pigs

A total of 9 SNPs located in TFRC and ACK1 genes of SSC13q41 genomic region were examined for their association with the adhesion pattern of native Indian pigs using local isolate of diarrhoeagenic E. coli. Phenotypic evaluation of adhesion pattern of 150 pigs revealed 116 animals positive for adhesion, whereas 34 animals had non-adhesive phenotype. Among the adhesive animals, 6, 87 and 23 pigs were strongly adhesive, weakly adhesive and adhesive, respectively. PCR-RFLP study revealed 8 polymorphic SNPs with low to moderate PIC ranging from 7.39 to 37.25% and low to high heterozygosities (8-70%). The loci g.291 C > T, rs81218930 C > T, rs318751568 C > T of TFRC and g.93222 C > A g.94600 C > T of ACK1 showed significant departure from HWE. The genotypic frequencies of the SNPs as well as the haplotypes did not differ significantly (P > 0.05) across the adhesion patterns except one SNP (ACK1-g.107371 A > C). Among the g.107371 A > C genotypes observed, CA was associated with non-adhesive phenotype. Furthermore, TFRC mRNA expression levels were found to be significantly (P < 0.05) different among various adhesive phenotypes, whereas that of ACK1 was significantly (P < 0.05) different between non-adhesive and adhesive groups. The significant association of SNP (ACK1-g.107371 A > C), which was also previously reported to influence ETECF4 mediated diarrhoea susceptibility, implicates its wider application in genetic control of piglet diarrhoea. Furthermore, the up-regulation of TFRC gene expression in adhesive group supports its proposed role in activation of immune cells against E. coli and intracellular iron transport.

Resistance to ETEC F4/F18-mediated piglet diarrhoea: opening the gene black box

Diarrhoea, a significant problem in pig rearing industry affecting pre- and post-weaning piglets is caused by enterotoxigenic Escherichia coli (ETEC). The ETEC are classified as per the fimbriae types which are responsible for bacterial attachment with enterocytes and release of toxins causing diarrhoea. However, genetic difference exists for susceptibility to ETEC infection in piglets. The different phenotypes found in pigs determine their (pigs') susceptibility or resistance towards fimbrial subtypes/variants (F4ab, F4ac, F4ad and F18). Specific receptors are present on intestinal epithelium for attachment of these fimbriae, which do not express to same level in all animals. This differential expression is genetically determined and thus their genetic causes (may be putative candidate gene or mutations) render some animals resistant or susceptible to one or more fimbrial subtypes. Genetic linkage studies have revealed the mapping location of the receptor loci for the two most frequent variants F4ab and F4ac to SSC13q41 (i.e. q arm of 13th chromosome of Sus scrofa). Some SNPs have been identified in mucin gene family, transferring receptor gene, fucosyltransferase 1 gene and swine leucocyte antigen locus that are proposed to be linked mutations for resistance/susceptibility towards ETEC diarrhoea. However, owing to the variety of fimbrial types and subtypes, it would be difficult to identify a single causative mutation and the candidate loci may involve more number of genes/regions. In this review, we focus on the genetic mutations in genes involved in imparting resistance/susceptibility to F4 or F18 ETEC diarrhoea and possibilities to use them as marker for selection against susceptible animals.

Effect of Mucin13 gene polymorphism on diarrhoeagenic <i>E. coli</i> adhesion pattern and its expression analysis in native Indian pigs

Abstract. We identified genetic polymorphism in Mucin13 gene affecting E. coli adhesion patterns using (local isolate) diarrhoeagenic E. coli in Indian desi pigs. Five SNPs and one indel previously reported to be associated with enterotoxigenic E. coli (ETEC) F4ab/ac adhesion pattern were examined by designing PCR-RFLP protocol. The genotypic frequencies of only one SNP (g.22304A > G) differed significantly (at P≤0.05) in adhesive, non-adhesive and weakly adhesive population. The AA (306 sbp, 231 bp), AG (306, 231, 108, 198 bp) and GG (231, 198 bp, 108 b) genotypes of g.22304A > G locus were observed with frequencies 50.0 %, 21.25 % and 28.75 %, respectively and AG genotype was significantly (P≤0.05) associated with a non-adhesive pattern. The polymorphism information content of SNPs ranged from 17.67 (g.22124T > C) to 37.36 % (g.21471C > T) loci. Three loci (g.21471C > T, g.22124T > C and g.22304A > G) were significantly departed from Hardy–Weinberg equilibrium. The linkage disequilibrium analysis revealed locus g.22124T > C and g.22304A > G were significantly (P≤0.05) associated with each other. Expression profiling of target gene in jejuna of animals having AA, AG and GG genotypes revealed differences in various genotypes with the highest in the AA, moderate in the GG and low levels in the AG genotype, although they were statistically non-significant (at P≤0.05). The absence of significant effect of genotypes on MUC13 mRNA expression indicates no direct functional role, although the structural role can not be ignored as the putative receptor gene is located within targeted genomic region. Further, reports of same SNP association with an ETEC F4ab/ac adhesion pattern indicate the target gene's role in diarrhoea even caused by other strains of E. coli which is not ETEC.