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Avirulent K88 (F4)+ Escherichia coli strains constructed to express modified enterotoxins protect young piglets from challenge with a virulent enterotoxigenic Escherichia coli strain that expresses the same adhesion and enterotoxins

Author:
Santiago-Mateo, Kristina, Zhao, Mojun, Lin, Jun, Zhang, Weiping, Francis, David H.
Source:
Veterinary microbiology 2012 v.159 no.3-4 pp. 337-342
ISSN:
0378-1135
Subject:
adhesins, adhesion, blood proteins, cell culture, diarrhea, enterotoxigenic Escherichia coli, enterotoxins, epithelial cells, fimbriae, genes, heat stability, ileum, jejunum, models, nonpathogenic strains, piglets, placebos, plasmid vectors, vector control, virulence, weight loss
Abstract:
Virulence of enterotoxigenic Escherichia coli (ETEC) is associated with fimbrial adhesins and enterotoxins such as heat-labile (LT) and/or heat-stable (ST) enterotoxins. Previous studies using a cell culture model suggest that exclusion of ETEC from attachment to epithelial cells requires expression of both an adhesin such as K88 (F4) fimbriae, and LT. To test the ability of non-pathogenic E. coli constructs to exclude virulent ETEC sufficiently to prevent clinical disease, we utilized a piglet ETEC challenge model. Thirty-nine 5-day-old piglets were inoculated with a placebo (control), or with either of the three K88⁺E. coli strains isogenic with regard to modified LT expression: 8017 (pBR322 plasmid vector control), non-toxigenic mutant 8221 (LTR₁₉₂G) in pBR322, or 8488, with the LT gene fused to the STb gene in pBR322 (LTR₁₉₂G-STb). Piglets were challenged with virulent ETEC Strain 3030-2 (K88⁺/LT/STb) 24h post-inoculation. K88ac receptor-positive piglets in the control group developed diarrhea and became dehydrated 12–24h post-challenge. Piglets inoculated with 8221 or 8488 did not exhibit clinical signs of ETEC disease; most piglets inoculated with 8017 showed diarrhea. Control pigs exhibited significant weight loss, increased blood total protein, and higher numbers of colony-forming units of 3030-2 E. coli in washed ileum and jejunum than treated pigs. This study shows for the first time that pre-inoculation with an avirulent strain expressing adhesive fimbriae and a non-toxic form of LT provides significant short term protection from challenge with a virulent ETEC strain that expresses the same fimbrial adhesion and enterotoxin.
Agid:
400227