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Relationship between heat-labile enterotoxin secretion capacity and virulence in wild type porcine-origin enterotoxigenic Escherichia coli strains.

Wijemanne P, Xing J, Berberov EM, Marx DB, Francis DH, Moxley RA - PLoS ONE (2015)

Bottom Line: Maximum Likelihood 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 ATP-binding capacity of GspE and LT secretion, and between the latter and virulence.

View Article: PubMed Central - PubMed

Affiliation: School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America.

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 to measure 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-enterotoxigenic WT 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. Maximum Likelihood 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 ATP-binding capacity of GspE and LT secretion, and between the latter and virulence.

No MeSH data available.


Related in: MedlinePlus

Photograph at necropsy of piglet 15 h after inoculation with enterotoxigenic E. coli strain 3030–2.Spiral colon (SC) is diffusely hemorrhagic, and jejunum (J) is hyperemic; both spiral colon and jejunum are distended with watery ingesta.
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pone.0117663.g004: Photograph at necropsy of piglet 15 h after inoculation with enterotoxigenic E. coli strain 3030–2.Spiral colon (SC) is diffusely hemorrhagic, and jejunum (J) is hyperemic; both spiral colon and jejunum are distended with watery ingesta.

Mentions: All piglets inoculated with 3030–2 or 2534–86 developed gross and microscopic lesions in the intestines compatible with shock (Figs. 4–8). Both small and large intestines were affected with hyperemia, hemorrhage and necrosis; these lesions were most severe in the mucosa, and were compatible with what we have previously described as hemorrhagic enteritis [4]. Histologically, necrotic epithelial cells in affected intestines had either sloughed or were in the process of it with formation of subepithelial clefts and exposure of the basal lamina. Intact small intestinal epithelium in all pigs inoculated with 2534–86 and 3030–2, but none inoculated with G58–1, had E. coli cells adherent to their apical surfaces, and in the case of pigs with lesions of shock had bacteria adherent to the exposed basal lamina. Platelet-fibrin thrombi and intravascular bacteria were seen in mucosal capillaries and venules of all piglets inoculated with 2534–86 and 3030–2, but in none of the piglets inoculated with G58–1. In all piglets inoculated with 2534–86 or 3030–2 but none inoculated with G58–1, either the respective inoculum strain, endotoxin activity or both were detected in blood samples obtained at necropsy. Mean endotoxin activity measured 0.49 ± 0.23 endotoxin units per ml in blood samples testing positive.


Relationship between heat-labile enterotoxin secretion capacity and virulence in wild type porcine-origin enterotoxigenic Escherichia coli strains.

Wijemanne P, Xing J, Berberov EM, Marx DB, Francis DH, Moxley RA - PLoS ONE (2015)

Photograph at necropsy of piglet 15 h after inoculation with enterotoxigenic E. coli strain 3030–2.Spiral colon (SC) is diffusely hemorrhagic, and jejunum (J) is hyperemic; both spiral colon and jejunum are distended with watery ingesta.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4358887&req=5

pone.0117663.g004: Photograph at necropsy of piglet 15 h after inoculation with enterotoxigenic E. coli strain 3030–2.Spiral colon (SC) is diffusely hemorrhagic, and jejunum (J) is hyperemic; both spiral colon and jejunum are distended with watery ingesta.
Mentions: All piglets inoculated with 3030–2 or 2534–86 developed gross and microscopic lesions in the intestines compatible with shock (Figs. 4–8). Both small and large intestines were affected with hyperemia, hemorrhage and necrosis; these lesions were most severe in the mucosa, and were compatible with what we have previously described as hemorrhagic enteritis [4]. Histologically, necrotic epithelial cells in affected intestines had either sloughed or were in the process of it with formation of subepithelial clefts and exposure of the basal lamina. Intact small intestinal epithelium in all pigs inoculated with 2534–86 and 3030–2, but none inoculated with G58–1, had E. coli cells adherent to their apical surfaces, and in the case of pigs with lesions of shock had bacteria adherent to the exposed basal lamina. Platelet-fibrin thrombi and intravascular bacteria were seen in mucosal capillaries and venules of all piglets inoculated with 2534–86 and 3030–2, but in none of the piglets inoculated with G58–1. In all piglets inoculated with 2534–86 or 3030–2 but none inoculated with G58–1, either the respective inoculum strain, endotoxin activity or both were detected in blood samples obtained at necropsy. Mean endotoxin activity measured 0.49 ± 0.23 endotoxin units per ml in blood samples testing positive.

Bottom Line: Maximum Likelihood 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 ATP-binding capacity of GspE and LT secretion, and between the latter and virulence.

View Article: PubMed Central - PubMed

Affiliation: School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, Nebraska, United States of America.

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 to measure 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-enterotoxigenic WT 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. Maximum Likelihood 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 ATP-binding capacity of GspE and LT secretion, and between the latter and virulence.

No MeSH data available.


Related in: MedlinePlus