Identification of Novel Components Influencing Colonization Factor Antigen I Expression in Enterotoxigenic Escherichia coli

Abstract

Colonization factors (CFs) mediate early adhesion of Enterotoxigenic Escherichia coli (ETEC) in the small intestine. Environmental signals including bile, glucose, and contact with epithelial cells have previously been shown to modulate CF expression in a strain dependent manner. To identify novel components modulating CF surface expression, 20 components relevant to the intestinal environment were selected for evaluation. These included mucin, bicarbonate, norepinephrine, lincomycin, carbon sources, and cations. Effects of individual components on surface expression of the archetype CF, CFA/I, were screened using a fractional factorial Hadamard matrix incorporating 24 growth conditions. As most CFs agglutinate erythrocytes, surface expression was evaluated by mannose resistant hemagglutination. Seven components, including porcine gastric mucin, lincomycin, glutamine, and glucose were found to induce CFA/I surface expression in vitro in a minimal media while five others were inhibitory, including leucine and 1,10-phenanthroline. To further explore the effect of components positively influencing CFA/I surface expression, a response surface methodology (RSM) was designed incorporating 36 growth conditions. The optimum concentration for each component was identified, thereby generating a novel culture media, SP1, for CFA/I expression. CFs closely related to CFA/I, including CS4 and CS14 were similarly induced in SP1 media. Other epidemiologically relevant CFs were also induced when compared to the level obtained in minimal media. These results indicate that although CF surface expression is complex and highly variable among strains, the CF response can be predicted for closely related strains. A novel culture media inducing CFs in the CF5a group was successfully identified. In addition, mucin was found to positively influence CF expression in strains expressing either CFA/I or CS1 and CS3, and may function as a common environmental cue.

HldE Is Important for Virulence Phenotypes in Enterotoxigenic Escherichia coli

“…The cfaABCE operon is positively regulated by the trans-encoded CfaD protein belonging to the family of AraC transcriptional regulators and negatively regulated by histone-like protein H-NS and cAMP receptor protein (CRP) (Caron and Scott, 1990 ; Jordi et al, 1992a ; Munson and Scott, 1999 ; Pilonieta et al, 2007 ; Bodero and Munson, 2009 ). In addition, several environmental factors of the intestinal lumen influence CFA/I expression including iron levels, pH, and gastric mucin (Haines et al, 2015 ). The etpBAC and cfaABCE operons are located on the same plasmid carried by ETEC and share inducing cues such as iron starvation.…”

Enterotoxigenic and Enterohemorrhagic <i>Escherichia coli</i>: Survival and Modulation of Virulence in the Human Gastrointestinal Tract

“…On the contrary, Sturbelle et al [88] did not observe any effect of norepinephrine or epinephrine on the in vitro growth of a piglet ETEC strain, and Haines et al [62] found a significant inhibition of porcine ETEC growth by norepinephrine. However, a significant increase in motility and expression of F4 fimbriae and LT toxin-encoding genes was shown in the ETEC culture supplemented with conditioned medium (containing autoinducers) and epinephrine [88].…”

“…However, a significant increase in motility and expression of F4 fimbriae and LT toxin-encoding genes was shown in the ETEC culture supplemented with conditioned medium (containing autoinducers) and epinephrine [88]. Lastly, Haines et al [62] found that norepinephrine inhibited CFA/I expression in an ETEC strain isolated from humans.…”

“…In this study, the transcriptional response to bile salts was strain-dependent, suggesting that the results should not be extrapolated to the entire pathovar without further investigation. Finally, at the protein level, 1.5 g/L bile salts were required for surface expression of at least CS5, CS7, CS8, CS12, CS14, CS17, and CS19 [62][63][64]. Haines et al [62] have shown that bile salts seem not to be required for the expression of CS1, CS2, and CS3, while the opposite was demonstrated by Sjoling et al [63].…”

“…Finally, at the protein level, 1.5 g/L bile salts were required for surface expression of at least CS5, CS7, CS8, CS12, CS14, CS17, and CS19 [62][63][64]. Haines et al [62] have shown that bile salts seem not to be required for the expression of CS1, CS2, and CS3, while the opposite was demonstrated by Sjoling et al [63]. These results suggest that both interaction of LT toxin with its receptor and expression of ETEC colonization factors may be differentially induced along the human intestine where bile acid concentrations range from 2 to 20 g/L.…”