Veterinary and Biomedical Sciences, Department of
Document Type
Article
Date of this Version
2015
Citation
Wijemanne P, Xing J, Berberov EM, Marx DB, Francis DH, Moxley RA (2015) Relationship between Heat-Labile Enterotoxin Secretion Capacity and Virulence in Wild Type Porcine-Origin Enterotoxigenic Escherichia coli Strains. PLoS ONE 10(3): e0117663. doi:10.1371/journal.pone.0117663
Abstract
Heat-labile enterotoxin (LT) is an important virulence factor secreted by some strains of enterotoxigenic Escherichia coli (ETEC). The prototypic human-origin strain H10407 secretes LT via a type II secretion system(T2SS). We sought to determine the relationship between the capacity to secrete LT and virulence in porcine-origin wild type (WT) ETEC strains. Sixteen WT ETEC strains isolated from cases of severe diarrheal disease were analyzed by GM1ganglioside enzyme- linked immunosorbent assay tomeasure LT concentrations in culture supernatants. All strains had detectable LT in supernatants by 2 h of culture and 1 strain, which was particularly virulent in gnotobiotic piglets (3030-2), had the highest LT secretion level all porcine-origin WT strains tested (P<0.05). The level of LT secretion (concentration in supernatants at 6-h culture) explained 92%of the variation in time-to-a-moribund-condition (R2 = 0.92, P<0.0001) in gnotobiotic piglets inoculated with either strain 3030-2, or an ETEC strain of lesser virulence (2534-86), or a non-enterotoxigenicWT strain (G58-1). All 16 porcine ETEC strains were positive by PCR analysis for the T2SS genes, gspD and gspK, and bioinformatic analysis of 4 porcine-origin strains for which complete genomic sequences were available revealed a T2SS with a high degree of homology to that of H10407.MaximumLikelihood phylogenetic trees constructed using T2SS genes gspC, gspD, gspE and homologs showed that strains 2534-86 and 3030-2 clustered together in the same clade with other porcine-origin ETEC strains in the database, UMNK88 and UMN18. Protein modeling of the ATPase gene (gspE) further revealed a direct relationship between the predicted ATP-binding capacities and LT secretion levels as follows: H10407, -8.8 kcal/mol and 199 ng/ml; 3030-2, -8.6 kcal/mol and 133 ng/ml; and 2534-86, -8.5 kcal/mol and 80 ng/ml. This study demonstrated a direct relationship between predicted ATPbinding capacity of GspE and LT secretion, and between the latter and virulence.
Included in
Biochemistry, Biophysics, and Structural Biology Commons, Cell and Developmental Biology Commons, Immunology and Infectious Disease Commons, Medical Sciences Commons, Veterinary Microbiology and Immunobiology Commons, Veterinary Pathology and Pathobiology Commons
Comments
© 2015 Wijemanne et al. This is an open access article distributed under the terms of the Creative Commons Attribution License.