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Gambino M, Kushwaha SK, Wu Y, van Haastrecht P, Klein-Sousa V, Lutz VT, Bejaoui S, Jensen CMC, Bojer MS, Song W, Xiao M, Taylor NMI, Nobrega FL, Brøndsted L. Diversity and phage sensitivity to phages of porcine enterotoxigenic Escherichia coli. Appl Environ Microbiol 2024; 90:e0080724. [PMID: 38940562 PMCID: PMC11267873 DOI: 10.1128/aem.00807-24] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2024] [Accepted: 06/05/2024] [Indexed: 06/29/2024] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a diverse and poorly characterized E. coli pathotype that causes diarrhea in humans and animals. Phages have been proposed for the veterinary biocontrol of ETEC, but effective solutions require understanding of porcine ETEC diversity that affects phage infection. Here, we sequenced and analyzed the genomes of the PHAGEBio ETEC collection, gathering 79 diverse ETEC strains isolated from European pigs with post-weaning diarrhea (PWD). We identified the virulence factors characterizing the pathotype and several antibiotic resistance genes on plasmids, while phage resistance genes and other virulence factors were mostly chromosome encoded. We experienced that ETEC strains were highly resistant to Enterobacteriaceae phage infection. It was only by enrichment of numerous diverse samples with different media and conditions, using the 41 ETEC strains of our collection as hosts, that we could isolate two lytic phages that could infect a large part of our diverse ETEC collection: vB_EcoP_ETEP21B and vB_EcoS_ETEP102. Based on genome and host range analyses, we discussed the infection strategies of the two phages and identified components of lipopolysaccharides ( LPS) as receptors for the two phages. Our detailed computational structural analysis highlights several loops and pockets in the tail fibers that may allow recognition and binding of ETEC strains, also in the presence of O-antigens. Despite the importance of receptor recognition, the diversity of the ETEC strains remains a significant challenge for isolating ETEC phages and developing sustainable phage-based products to address ETEC-induced PWD.IMPORTANCEEnterotoxigenic Escherichia coli (ETEC)-induced post-weaning diarrhea is a severe disease in piglets that leads to weight loss and potentially death, with high economic and animal welfare costs worldwide. Phage-based approaches have been proposed, but available data are insufficient to ensure efficacy. Genome analysis of an extensive collection of ETEC strains revealed that phage defense mechanisms were mostly chromosome encoded, suggesting a lower chance of spread and selection by phage exposure. The difficulty in isolating lytic phages and the molecular and structural analyses of two ETEC phages point toward a multifactorial resistance of ETEC to phage infection and the importance of extensive phage screenings specifically against clinically relevant strains. The PHAGEBio ETEC collection and these two phages are valuable tools for the scientific community to expand our knowledge on the most studied, but still enigmatic, bacterial species-E. coli.
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Scheutz F, Nielsen CH, von Mentzer A. Construction of the ETECFinder database for the characterization of enterotoxigenic Escherichia coli (ETEC) and revision of the VirulenceFinder web tool at the CGE website. J Clin Microbiol 2024; 62:e0057023. [PMID: 38656142 PMCID: PMC11237473 DOI: 10.1128/jcm.00570-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2023] [Accepted: 03/05/2024] [Indexed: 04/26/2024] Open
Abstract
The identification of pathogens is essential for effective surveillance and outbreak detection, which lately has been facilitated by the decreasing cost of whole-genome sequencing (WGS). However, extracting relevant virulence genes from WGS data remains a challenge. In this study, we developed a web-based tool to predict virulence-associated genes in enterotoxigenic Escherichia coli (ETEC), which is a major concern for human and animal health. The database includes genes encoding the heat-labile toxin (LT) (eltA and eltB), heat-stable toxin (ST) (est), colonization factors CS1 through 30, F4, F5, F6, F17, F18, and F41, as well as toxigenic invasion and adherence loci (tia, tibAC, etpBAC, eatA, yghJ, and tleA). To construct the database, we revised the existing ETEC nomenclature and used the VirulenceFinder webtool at the CGE website [VirulenceFinder 2.0 (dtu.dk)]. The database was tested on 1,083 preassembled ETEC genomes, two BioProjects (PRJNA421191 with 305 and PRJNA416134 with 134 sequences), and the ETEC reference genome H10407. In total, 455 new virulence gene alleles were added, 50 alleles were replaced or renamed, and two were removed. Overall, our tool has the potential to greatly facilitate ETEC identification and improve the accuracy of WGS analysis. It can also help identify potential new virulence genes in ETEC. The revised nomenclature and expanded gene repertoire provide a better understanding of the genetic diversity of ETEC. Additionally, the user-friendly interface makes it accessible to users with limited bioinformatics experience. IMPORTANCE Detecting colonization factors in enterotoxigenic Escherichia coli (ETEC) is challenging due to their large number, heterogeneity, and lack of standardized tests. Therefore, it is important to include these ETEC-related genes in a more comprehensive VirulenceFinder database in order to obtain a more complete coverage of the virulence gene repertoire of pathogenic types of E. coli. ETEC vaccines are of great importance due to the severity of the infections, primarily in children. A tool such as this could assist in the surveillance of ETEC in order to determine the prevalence of relevant types in different parts of the world, allowing vaccine developers to target the most prevalent types and, thus, a more effective vaccine.
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Talaat KR, Porter CK, Chakraborty S, Feijoo BL, Brubaker J, Adjoodani BM, DeNearing B, Prouty MG, Poole ST, Bourgeois AL, Billingsley M, Sack DA, Eder-Lingelbach S, Taucher C. Validation of a Human Challenge Model Using an LT-Expressing Enterotoxigenic E. coli Strain (LSN03-016011) and Characterization of Potential Amelioration of Disease by an Investigational Oral Vaccine Candidate (VLA1701). Microorganisms 2024; 12:727. [PMID: 38674674 PMCID: PMC11051778 DOI: 10.3390/microorganisms12040727] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2024] [Revised: 03/22/2024] [Accepted: 03/23/2024] [Indexed: 04/28/2024] Open
Abstract
Controlled human infection models are important tools for the evaluation of vaccines against diseases where an appropriate correlate of protection has not been identified. Enterotoxigenic Escherichia coli (ETEC) strain LSN03-016011/A (LSN03) is an LT enterotoxin and CS17-expressing ETEC strain useful for evaluating vaccine candidates targeting LT-expressing strains. We sought to confirm the ability of the LSN03 strain to induce moderate-to-severe diarrhea in a healthy American adult population, as well as the impact of immunization with an investigational cholera/ETEC vaccine (VLA-1701) on disease outcomes. A randomized, double-blinded pilot study was conducted in which participants received two doses of VLA1701 or placebo orally, one week apart; eight days after the second vaccination, 30 participants (15 vaccinees and 15 placebo recipients) were challenged with approximately 5 × 109 colony-forming units of LSN03. The vaccine was well tolerated, with no significant adverse events. The vaccine also induced serum IgA and IgG responses to LT. After challenge, 11 of the placebo recipients (73.3%; 95%CI: 48.0-89.1) and 7 of the VLA1701 recipients (46.7%; 95%CI: 24.8-68.8) had moderate-to-severe diarrhea (p = 0.26), while 14 placebo recipients (93%) and 8 vaccine recipients (53.3%) experienced diarrhea of any severity, resulting in a protective efficacy of 42.9% (p = 0.035). In addition, the vaccine also appeared to provide protection against more severe diarrhea (p = 0.054). Vaccinees also tended to shed lower levels of the LSN03 challenge strain compared to placebo recipients (p = 0.056). In addition, the disease severity score was lower for the vaccinees than for the placebo recipients (p = 0.046). In summary, the LSN03 ETEC challenge strain induced moderate-to-severe diarrhea in 73.3% of placebo recipients. VLA1701 vaccination ameliorated disease severity, as observed by several parameters, including the percentage of participants experiencing diarrhea, as well as stool frequency and ETEC severity scores. These data highlight the potential value of LSN03 as a suitable ETEC challenge strain to evaluate LT-based vaccine targets (NCT03576183).
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Xu H, Gong J, Lu P, Azevedo P, Li L, Yu H, Yang C. Functional evaluation of Bacillus licheniformis PF9 for its potential in controlling enterotoxigenic Escherichia coli in weaned piglets. Transl Anim Sci 2024; 8:txae050. [PMID: 38665217 PMCID: PMC11044710 DOI: 10.1093/tas/txae050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Accepted: 04/02/2024] [Indexed: 04/28/2024] Open
Abstract
During the bacterial selection, isolate PF9 demonstrated tolerance to low pH and high bile salt and an ability to extend the lifespan of Caenorhabditis elegans infected with enterotoxigenic Escherichia coli (ETEC; P < 0.05). Thirty-two weaned piglets susceptible to ETEC F4 were randomly allocated to four treatments as follows: 1) non-challenged negative control group (NNC; basal diet and piglets gavaged with phosphate-buffered saline), 2) negative control group (NC; basal diet and piglets challenged with ETEC F4, 3 × 107 CFU per pig), 3) positive control (PC; basal diet + 80 mg·kg-1 of avilamycin and piglets challenged with ETEC F4), and 4) probiotic candidate (PF9; control basal diet + 2.5 × 109 CFU·kg-1 diet of B. licheniformis PF9 and piglets challenged with ETEC F4). The infection of ETEC F4 decreased average daily gain and gain:feed in the NC group when compared to the NNC group (P < 0.05). The inoculation of ETEC F4 induced severe diarrhea at 3 h postinoculum (hpi), 36, 40 hpi in the NC group when compared to the NNC group (P < 0.05). The supplementation of B. licheniformis PF9 significantly relieved diarrhea severity at 3 hpi when compared to the NC group (P < 0.05). The inoculation of ETEC F4 reduced duodenal, jejunal, and ileal villus height (VH) in the NC group when compared to the NNC group. A significant (P < 0.05) decrease was detected in the duodenal VH in the PC and NNC groups. Moreover, the NNC group had a reduced relative mRNA level of Na+-glucose cotransporter 1 (SGLT1) when compared to the NC group (P < 0.05). Compared to the NC and NNC groups, the supplementation of B. licheniformis PF9 increased the relative mRNA levels of aminopeptidase N, occludin, zonula occludens-1, and SGLT1 (P < 0.05). The supplementation of B. licheniformis PF9 also significantly increased the relative mRNA level of excitatory amino acid transporter 1 when compared to the NC group (P < 0.05). Piglets supplemented with B. licheniformis PF9 showed lower relative abundance of Bacteroidetes in the colon than piglets from the NNC group (P < 0.05). The NNC group had a higher relative abundance of Firmicutes in the ileum than all the challenged piglets (P < 0.05); however, a lower relative abundance of Proteobacteria in the ileum and colon was observed in the NC group (P < 0.05). This study provides evidence that B. licheniformis PF9 has the potential to improve the gut health of piglets under challenging conditions.
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Pajuelo MJ, Noazin S, Cabrera L, Toledo A, Velagic M, Arias L, Ochoa M, Moulton LH, Saito M, Gilman RH, Chakraborty S. Epidemiology of enterotoxigenic Escherichia coli and impact on the growth of children in the first two years of life in Lima, Peru. Front Public Health 2024; 12:1332319. [PMID: 38584932 PMCID: PMC10995271 DOI: 10.3389/fpubh.2024.1332319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/11/2024] [Indexed: 04/09/2024] Open
Abstract
Background Enterotoxigenic E. coli (ETEC) is a leading cause of diarrheal morbidity and mortality in children, although the data on disease burden, epidemiology, and impact on health at the community level are limited. Methods In a longitudinal birth cohort study of 345 children followed until 24 months of age in Lima, Peru, we measured ETEC burden in diarrheal and non-diarrheal samples using quantitative PCR (LT, STh, and STp toxin genes), studied epidemiology and measured anthropometry in children. Results About 70% of children suffered from one or more ETEC diarrhea episodes. Overall, the ETEC incidence rate (IR) was 73 per 100 child-years. ETEC infections began early after birth causing 10% (8.9-11.1) ETEC-attributable diarrheal burden at the population level (PAF) in neonates and most of the infections (58%) were attributed to ST-ETEC [PAF 7.9% (1.9-13.5)] and LT + ST-ETEC (29%) of which all the episodes were associated with diarrhea. ETEC infections increased with age, peaking at 17% PAF (4.6-27.7%; p = 0.026) at 21 to 24 months. ST-ETEC was the most prevalent type (IR 32.1) with frequent serial infections in a child. The common colonization factors in ETEC diarrhea cases were CFA/I, CS12, CS21, CS3, and CS6, while in asymptomatic ETEC cases were CS12, CS6 and CS21. Only few (5.7%) children had repeated infections with the same combination of ETEC toxin(s) and CFs, suggested genotype-specific immunity from each infection. For an average ETEC diarrhea episode of 5 days, reductions of 0.060 weight-for-length z-score (0.007 to 0.114; p = 0.027) and 0.061 weight-for-age z-score (0.015 to 0.108; p = 0.009) were noted in the following 30 days. Conclusion This study showed that ETEC is a significant pathogen in Peruvian children who experience serial infections with multiple age-specific pathotypes, resulting in transitory growth impairment.
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Gutiérrez RL, Porter CK, Harro C, Talaat K, Riddle MS, DeNearing B, Brubaker J, Maciel M, Laird RM, Poole S, Chakraborty S, Maier N, Sack DA, Savarino SJ. Efficacy Evaluation of an Intradermally Delivered Enterotoxigenic Escherichia coli CF Antigen I Fimbrial Tip Adhesin Vaccine Coadministered with Heat-Labile Enterotoxin with LT(R192G) against Experimental Challenge with Enterotoxigenic E. coli H10407 in Healthy Adult Volunteers. Microorganisms 2024; 12:288. [PMID: 38399692 PMCID: PMC10892241 DOI: 10.3390/microorganisms12020288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/16/2024] [Accepted: 01/26/2024] [Indexed: 02/25/2024] Open
Abstract
BACKGROUND Enterotoxigenic E. coli (ETEC) is a principal cause of diarrhea in travelers, deployed military personnel, and children living in low to middle-income countries. ETEC expresses a variety of virulence factors including colonization factors (CF) that facilitate adherence to the intestinal mucosa. We assessed the protective efficacy of a tip-localized subunit of CF antigen I (CFA/I), CfaE, delivered intradermally with the mutant E. coli heat-labile enterotoxin, LTR192G, in a controlled human infection model (CHIM). METHODS Three cohorts of healthy adult subjects were enrolled and given three doses of 25 μg CfaE + 100 ng LTR192G vaccine intradermally at 3-week intervals. Approximately 28 days after the last vaccination, vaccinated and unvaccinated subjects were admitted as inpatients and challenged with approximately 2 × 107 cfu of CFA/I+ ETEC strain H10407 following an overnight fast. Subjects were assessed for moderate-to-severe diarrhea for 5 days post-challenge. RESULTS A total of 52 volunteers received all three vaccinations; 41 vaccinated and 43 unvaccinated subjects were challenged and assessed for moderate-to-severe diarrhea. Naïve attack rates varied from 45.5% to 64.7% across the cohorts yielding an overall efficacy estimate of 27.8% (95% confidence intervals: -7.5-51.6%). In addition to reducing moderate-severe diarrhea rates, the vaccine significantly reduced loose stool output and overall ETEC disease severity. CONCLUSIONS This is the first study to demonstrate protection against ETEC challenge after intradermal vaccination with an ETEC adhesin. Further examination of the challenge methodology is necessary to address the variability in naïve attack rate observed among the three cohorts in the present study.
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Gutiérrez RL, Riddle MS, Porter CK, Maciel M, Poole ST, Laird RM, Lane M, Turiansky GW, Jarell A, Savarino SJ. A First in Human Clinical Trial Assessing the Safety and Immunogenicity of Two Intradermally Delivered Enterotoxigenic Escherichia coli CFA/I Fimbrial Tip Adhesin Antigens with and without Heat-Labile Enterotoxin with Mutation LT(R192G). Microorganisms 2023; 11:2689. [PMID: 38004700 PMCID: PMC10672875 DOI: 10.3390/microorganisms11112689] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2023] [Revised: 10/25/2023] [Accepted: 10/31/2023] [Indexed: 11/26/2023] Open
Abstract
INTRODUCTION Enterotoxigenic E. coli (ETEC) is a leading cause of diarrhea in travelers as well as for children living in low- to middle-income countries. ETEC adhere to intestinal epithelium via colonization factors (CFs). CFA/I, a common CF, is composed of a polymeric stalk and a tip-localized minor adhesive subunit, CfaE. Vaccine delivery by the transcutaneous immunization of dscCfaE was safe but was poorly immunogenic in a phase 1 trial when administered to volunteers with LTR(192G) and mLT. To potentially enhance the immunogenicity of CfaE while still delivering via a cutaneous route, we evaluated the safety and immunogenicity of two CfaE constructs administered intradermally (ID) with or without mLT. METHODS CfaE was evaluated as a donor strand-complemented construct (dscCfaE) and as a chimeric construct (Chimera) in which dscCfaE replaces the A1 domain of the cholera toxin A subunit and assembles non-covalently with the pentamer of heat-labile toxin B (LTB). Subjects received three ID vaccinations three weeks apart with either dscCfaE (1, 5, and 25 µg) or Chimera (2.6 and 12.9 µg) with and without 0.1 µg of mLT. Subjects were monitored for local and systemic adverse events. Immunogenicity was evaluated by serum and antibody-secreting cell (ASC) responses. RESULTS The vaccine was well-tolerated with predominantly mild and moderate local vaccine site reactions characterized by erythema, induration and post-inflammatory hyperpigmentation. High rates of serologic and ASC responses were seen across study groups with the most robust responses observed in subjects receiving 25 µg of dscCfaE with 0.1 mcg of LT(R192G). CONCLUSION Both ETEC adhesin vaccine prototypes were safe and immunogenic when co-administered with mLT by the ID route. The observed immune responses induced with the high dose of dscCfaE and mLT warrant further assessment in a controlled human infection model.
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Lee W, Sung S, Ha J, Kim E, An ES, Kim SH, Kim SH, Kim HY. Molecular and Genomic Analysis of the Virulence Factors and Potential Transmission of Hybrid Enteropathogenic and Enterotoxigenic Escherichia coli (EPEC/ETEC) Strains Isolated in South Korea. Int J Mol Sci 2023; 24:12729. [PMID: 37628911 PMCID: PMC10454139 DOI: 10.3390/ijms241612729] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2023] [Revised: 08/06/2023] [Accepted: 08/10/2023] [Indexed: 08/27/2023] Open
Abstract
Hybrid strains Escherichia coli acquires genetic characteristics from multiple pathotypes and is speculated to be more virulent; however, understanding their pathogenicity is elusive. Here, we performed genome-based characterization of the hybrid of enteropathogenic (EPEC) and enterotoxigenic E. coli (ETEC), the strains that cause diarrhea and mortality in children. The virulence genes in the strains isolated from different sources in the South Korea were identified, and their phylogenetic positions were analyzed. The EPEC/ETEC hybrid strains harbored eae and est encoding E. coli attaching and effacing lesions and heat-stable enterotoxins of EPEC and ETEC, respectively. Genome-wide phylogeny revealed that all hybrids (n = 6) were closely related to EPEC strains, implying the potential acquisition of ETEC virulence genes during ETEC/EPEC hybrid emergence. The hybrids represented diverse serotypes (O153:H19 (n = 3), O49:H10 (n = 2), and O71:H19 (n = 1)) and sequence types (ST546, n = 4; ST785, n = 2). Furthermore, heat-stable toxin-encoding plasmids possessing estA and various other virulence genes and transporters, including nleH2, hlyA, hlyB, hlyC, hlyD, espC, espP, phage endopeptidase Rz, and phage holin, were identified. These findings provide insights into understanding the pathogenicity of EPEC/ETEC hybrid strains and may aid in comparative studies, virulence characterization, and understanding evolutionary biology.
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Girardi P, Harutyunyan S, Neuhauser I, Glaninger K, Korda O, Nagy G, Nagy E, Szijártó V, Pall D, Szarka K, Kardos G, Henics T, Malinoski FJ. Evaluation of the Safety, Tolerability and Immunogenicity of ShigETEC, an Oral Live Attenuated Shigella-ETEC Vaccine in Placebo-Controlled Randomized Phase 1 Trial. Vaccines (Basel) 2022; 10:vaccines10020340. [PMID: 35214798 PMCID: PMC8879453 DOI: 10.3390/vaccines10020340] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2022] [Revised: 01/20/2022] [Accepted: 01/26/2022] [Indexed: 12/11/2022] Open
Abstract
Background: Shigella spp. and enterotoxigenic Escherichia coli (ETEC) cause high morbidity and mortality worldwide, yet no licensed vaccines are available to prevent corresponding infections. A live attenuated non-invasive Shigella vaccine strain lacking LPS O-antigen and expressing the ETEC toxoids, named ShigETEC was characterized previously in non-clinical studies. Methods: ShigETEC was evaluated in a two-staged, randomized, double-blind and placebo-controlled Phase I clinical trial. A single dose of increasing amounts of the vaccine was given to determine the maximum tolerated dose and increasing number of immunizations were administered with an interval based on the duration of shedding observed. Results: Oral immunization with ShigETEC was well tolerated and safe up to 4-time dosing with 5 × 1010 colony forming units. ShigETEC induced robust systemic immune responses against the Shigella vaccine strain, with IgA serum antibody dominance, as well as mucosal antibody responses evidenced by specific IgA in stool samples and in ALS (Antibodies in Lymphocyte Supernatant). Anti- ETEC toxin responses were detected primarily in the 4-times immunized cohort and for the heat-labile toxin correlated with neutralizing capacity. Conclusion: ShigETEC is a promising vaccine candidate that is scheduled for further testing in controlled human challenge studies for efficacy as well as in children in endemic setting for safety and immunogenicity.
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Carroll CJ, Hocking DM, Azzopardi KI, Praszkier J, Bennett-Wood V, Almeida K, Ingle DJ, Baines SL, Tauschek M, Robins-Browne RM. Re-evaluation of a Neonatal Mouse Model of Infection With Enterotoxigenic Escherichia coli. Front Microbiol 2021; 12:651488. [PMID: 33815340 PMCID: PMC8013722 DOI: 10.3389/fmicb.2021.651488] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2021] [Accepted: 02/17/2021] [Indexed: 12/03/2022] Open
Abstract
Enterotoxigenic E. coli (ETEC) is a common cause of diarrhea in children in low- and middle-income countries, and in travelers to these countries. ETEC is also an important cause of morbidity and premature mortality in piglets, calves, goat kids and lambs. The major virulence determinants of ETEC are enterotoxins and colonization factors, which enable the pathogen to colonize the small intestine and deliver enterotoxins, such as the heat-stable enterotoxins, STp and STh, to epithelial cells. Because most ETEC strains are host-specific, there are few convenient animal models to investigate the pathogenesis of ETEC infections or to evaluate specific anti-ETEC interventions, such as drugs and vaccines. An exception is ETEC strains bearing F41 pili, which mediate intestinal colonization of various young animals, including neonatal mice, to cause disease and in some cases death. In this study, we used the archetypal F41-producing bovine ETEC strain, B41 (O101:NM; K99, F41, STp) to validate and further explore the contribution of F41 and STp to bacterial virulence. By using targeted gene deletion and trans-complementation studies, augmented by whole genome sequencing, and in vitro and animal studies of virulence, we established that F41 mediates colonization of the mouse intestine and is essential for bacterial virulence. In addition, we showed for the first time that STp is as important as F41 for virulence. Together, these findings validate the use of neonatal mice to study the pathogenesis of F41-bearing ETEC and to investigate possible specific anti-ETEC interventions including vaccines that target heat-stable enterotoxins.
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A Spontaneous rapZ Mutant Impairs Infectivity of Lytic Bacteriophage vB_EcoM_JS09 against Enterotoxigenic Escherichia coli. mSphere 2021; 6:6/2/e01286-20. [PMID: 33658278 PMCID: PMC8546717 DOI: 10.1128/msphere.01286-20] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Our understanding of the mechanisms underlying phage-bacterium interactions remains limited. In Escherichia coli, RapZ regulates glucosamine-6-phosphate (GlcN6P) metabolism, the formation of which initiates synthesis of the bacterial cell envelope, including lipopolysaccharides (LPS). However, the role of RapZ, if any, on phage infectivity remains to be investigated. Here, we isolated strains of enterotoxigenic E. coli (ETEC) resistant to its specific lytic bacteriophage vB_EcoM_JS09 (JS09) in a phage aerosol spray experiment. Whole-genome analysis of phage-resistant bacteria revealed the rapZ gene acquired a premature stop mutation at amino acid 227. Here, we report that the mutation in the rapZ gene confers resistance by inhibiting 93.5% phage adsorption. Furthermore, this mutation changes the morphology of phage plaques, reduces efficiency of plating and phage propagation efficiency, and impairs the infectivity of phage JS09 against ETEC. Using scanning electron microscopy assays, we attribute the inability of the phage to adsorb to the loss of receptors in strains with defective RapZ. Analysis of the LPS profile shows that strains with defective RapZ inhibit phage infection by changing the LPS profile in E. coli. Preincubation of phage JS09 with LPS extracted from a wild-type (WT) strain blocked infection, suggesting LPS is the host receptor for phage JS09 adsorption. Our data uncover the mechanism by which ETEC resists infection of phage JS09 by mutating the rapZ gene and then increasing the expression of glmS and changing the phage receptor-LPS profile. These findings provide insight into the function of the rapZ gene for efficient infection of phage JS09. IMPORTANCE The development of phage-resistant bacteria is a challenging problem for phage therapy. However, our knowledge of phage resistance mechanisms is still limited. RapZ is an RNase adaptor protein encoded by the rapZ gene and plays an important function in Gram-positive and Gram-negative bacteria. Here, we report the whole-genome analysis of a phage-resistant enterotoxigenic Escherichia coli (ETEC) strain, which revealed that the rapZ gene acquired a premature stop mutation (E227Stop). We show that the premature stop mutation of rapZ impairs the infectivity of phage JS09 in ETEC. Furthermore, our findings indicate that ETEC becomes resistant against the adsorption and infection of phage JS09 by mutating the rapZ gene, increasing the expression of glmS, and changing the phage receptor-LPS profile. It is also first reported here that RapZ is essential for efficient infection of phage JS09.
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Application of a Novel Epitope- and Structure-Based Vaccinology-Assisted Fimbria-Toxin Multiepitope Fusion Antigen of Enterotoxigenic Escherichia coli for Development of Multivalent Vaccines against Porcine Postweaning Diarrhea. Appl Environ Microbiol 2020; 86:AEM.00274-20. [PMID: 32144103 DOI: 10.1128/aem.00274-20] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Accepted: 03/02/2020] [Indexed: 11/20/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) strains producing K88 (F4) or F18 fimbriae and enterotoxins are the predominant cause of pig postweaning diarrhea (PWD). We recently identified neutralizing epitopes of fimbriae K88 and F18, heat-labile toxin (LT), heat-stable toxins type I (STa) and type II (STb), and Shiga toxin 2e (Stx2e). In this study, we explored a novel epitope- and structure-based vaccinology platform, multiepitope fusion antigen (MEFA), for PWD vaccine development. By using an epitope substitution LT toxoid, which lacks enterotoxicity but retains immunogenicity, as the backbone to present neutralizing epitopes of two ETEC fimbriae and four toxins, we generated PWD fimbria-toxin MEFA to mimic epitope native antigenicity. We then examined MEFA protein immunogenicity and evaluated MEFA application in PWD vaccine development. Mice subcutaneously immunized with PWD MEFA protein developed strong IgG responses to K88, F18, LT, and STb and moderate responses to the toxins Stx2e and STa. Importantly, MEFA-induced antibodies inhibited adherence of K88 or F18 fimbrial bacteria to pig intestinal cells and also neutralized LT, STa, STb, and Stx2e toxicity. These results indicated that PWD fimbria-toxin MEFA induced neutralizing antibodies against an unprecedent two fimbriae and four toxins and strongly suggested a potential application of this MEFA protein in developing a broadly protective PWD vaccine.IMPORTANCE ETEC-associated postweaning diarrhea (PWD) causes significant economic losses to swine producers worldwide. Currently, there is no effective prevention against PWD. A vaccine that blocks ETEC fimbriae (K88 and F18) from attaching to host receptors and prevents enterotoxins from stimulating water hypersecretion in pig small intestinal epithelial cells can effectively protect against PWD and significantly improves pig health and well-being. The fimbria-toxin MEFA generated from this study induced neutralizing antibodies against both ETEC fimbriae and all four ETEC toxins, suggesting a great potential of this fimbria-toxin MEFA in PWD vaccine development and further supporting the general application of this novel MEFA vaccinology platform for multivalent vaccine development.
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F4- and F18-Positive Enterotoxigenic Escherichia coli Isolates from Diarrhea of Postweaning Pigs: Genomic Characterization. Appl Environ Microbiol 2020; 86:AEM.01913-20. [PMID: 32948526 DOI: 10.1128/aem.01913-20] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Accepted: 09/07/2020] [Indexed: 12/11/2022] Open
Abstract
This study aimed to characterize in silico enterotoxigenic Escherichia coli F4- and F18-positive isolates (n = 90) causing swine postweaning diarrhea, including pathogenic potential, phylogenetic relationship, antimicrobial and biocide resistance, prophage content, and metal tolerance rates. F4 strains belonged mostly to the O149 and O6 serogroups and ST100 and ST48 sequence types (STs). F18 strains were mainly assigned to the O8 and O147 serogroups and ST10, ST23, and ST42. The highest rates of antimicrobial resistance were found against streptomycin, sulfamethoxazole, tetracycline, trimethoprim, and ampicillin. No resistance was found toward ciprofloxacin, cefotaxime, ceftiofur, and colistin. Genes conferring tolerance to copper (showing the highest diversity), cadmium, silver, and zinc were predicted in all genomes. Enterotoxin genes (ltcA, 100% F4, 62% F18; astA, 100% F4, 38.1% F18; sta, 18.8% F4, 38.1% F18; stb, 100% F4, 76.2% F18) and fimbria-encoding genes typed as F4ac and F18ac were detected in all strains, in addition to up to 16 other virulence genes in individual strains. Phage analysis predicted between 7 and 20 different prophage regions in each strain. A highly diverse variety of plasmids was found; IncFII, IncFIB, and IncFIC were prevalent among F4 isolates, while IncI1 and IncX1 were dominant among F18 strains. Interestingly, F4 isolates from the early 1990s belonged to the same clonal group detected for most of the F4 strains from 2018 to 2019 (ONT:H10-A-ST100-CH27-0). The small number of single-nucleotide polymorphism differences between the oldest and recent F4 ST100 isolates suggests a relatively stable genome. Overall, the isolates analyzed in this study showed remarkably different genetic traits depending on the fimbria type.IMPORTANCE Diarrhea in the postweaning period due to enterotoxigenic E. coli (ETEC) is an economically relevant disease in pig production worldwide. In Denmark, prevention is mainly achieved by zinc oxide administration (to be discontinued by 2022). In addition, a breeding program has been implemented that aims to reduce the prevalence of this illness. Treatment with antimicrobials contributes to the problem of antimicrobial resistance (AMR) development. As a novelty, this study aims to deeply understand the genetic population structure and variation among diarrhea-associated isolates by whole-genome sequencing characterization. ST100-F4ac is the dominant clonal group circulating in Danish herds and showed high similarity to ETEC ST100 isolates from China, the United States, and Spain. High rates of AMR and high diversity of virulence genes were detected. The characterization of diarrhea-related ETEC is important for understanding the disease epidemiology and pathogenesis and for implementation of new strategies aiming to reduce the impact of the disease in pig production.
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Improvement of the Enterotoxigenic Escherichia coli Infection Model for Post-Weaning Diarrhea by Controlling for Bacterial Adhesion, Pig Breed and MUC4 Genotype. Vet Sci 2020; 7:vetsci7030106. [PMID: 32784676 PMCID: PMC7557722 DOI: 10.3390/vetsci7030106] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 07/29/2020] [Accepted: 08/06/2020] [Indexed: 11/17/2022] Open
Abstract
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 104.0 to 106.4 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).
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Ji X, Liang B, Sun Y, Zhu L, Zhou B, Guo X, Liu J. An Extended-Spectrum Beta-Lactamase-Producing Hybrid Shiga-Toxigenic and Enterotoxigenic Escherichia coli Strain Isolated from a Piglet with Diarrheal Disease in Northeast China. Foodborne Pathog Dis 2020; 17:382-387. [PMID: 32043914 DOI: 10.1089/fpd.2019.2720] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Shiga-toxigenic Escherichia coli (STEC) and enterotoxigenic E. coli (ETEC) can cause diarrhea in piglets. This is the first report and complete genome sequence of an extended-spectrum β-lactamase-producing hybrid STEC/ETEC strain isolated from a piglet with diarrhea on a swine farm in China. We investigated the virulence genes and phylogenetic diversity with publicly available E. coli genomes. Both E. coli strains S17-13 and S17-20 harbored multiple virulence genes, mainly including stx2e and eastA genes. Other important virulence genes (estIa, estIb, fedABCDEF, and hlyABCD) were located in the plasmid p1713-1 of S17-13, which could be transferred from E. coli S17-13 to S17-20 by conjugation. The presence of virulence genes associated with different pathogroups (STEC or ETEC) confirmed the hybrid status of E. coli strain S17-13. Phylogenetic analysis showed that STEC/ETEC S17-13, STEC S17-20, avian pathogenic E. coli (APEC) O78, and APEC ACN001 are located in the same evolutionary branch, indicating that they may originate from a common ancestor. It is crucial to understand the phylogeny of pathogenic bacteria to evaluate how they have evolved and to monitor the emergence of potential new pathogens. The emergence of novel hybrid E. coli strains presents a new public health risk. More attention must be paid to these hybrid pathogens during typing and epidemiological surveillance of E. coli infections, which challenges the traditional diagnostics of E. coli infections.
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Reggi S, Giromini C, Dell’Anno M, Baldi A, Rebucci R, Rossi L. In Vitro Digestion of Chestnut and Quebracho Tannin Extracts: Antimicrobial Effect, Antioxidant Capacity and Cytomodulatory Activity in Swine Intestinal IPEC-J2 Cells. Animals (Basel) 2020; 10:ani10020195. [PMID: 31979207 PMCID: PMC7070574 DOI: 10.3390/ani10020195] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2019] [Revised: 01/15/2020] [Accepted: 01/17/2020] [Indexed: 12/27/2022] Open
Abstract
Quebracho (Qu) and chestnut (Ch) are natural sources of tannins and they are currently used in animal nutrition as feed ingredients. However, to date the bio-accessibility, antimicrobial, antioxidant, and intestinal epithelial cell stimulatory doses of Qu and Ch have not been determined. Our study investigates the antioxidant and E. coli F4+ and F18+ growth inhibitory activity of Qu, Ch, and their combinations after solubilization in water (to evaluate the already bio-accessible molecules) and after simulated gastro-intestinal digestion in vitro. The effect of an in vitro digested Ch and Qu combination was also tested on intestinal epithelial IPEC-J2 cells experimentally stressed with hydrogen peroxide (H2O2) and Dextran Sodium Sulfate (DSS). The results showed that undigested Qu and Ch alone, and in combination, exerted a valuable antioxidant capacity and E. coli F4+ and F18+ growth inhibitory activity. The concentration of 1200 µg/mL exhibited the highest E. coli growth inhibitory activity for all the samples tested. In addition, after in vitro digestion, Qu and Qu50%-Ch50% maintained E. coli growth inhibitory activity and a modest antioxidant capacity. Three hours pre-treatment with in vitro digested Qu50%-Ch50% counteracted the H2O2 and DSS experimentally-induced stress in the intestinal IPEC-J2 cells. Ch and Qu tannin extracts, particularly when combined, may exert E. coli F4+ and F18+ growth inhibitory activity and valuable antioxidant and cell viability modulation activities.
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Ares MA, Abundes-Gallegos J, Rodríguez-Valverde D, Panunzi LG, Jiménez-Galicia C, Jarillo-Quijada MD, Cedillo ML, Alcántar-Curiel MD, Torres J, Girón JA, De la Cruz MA. The Coli Surface Antigen CS3 of Enterotoxigenic Escherichia coli Is Differentially Regulated by H-NS, CRP, and CpxRA Global Regulators. Front Microbiol 2019; 10:1685. [PMID: 31417507 PMCID: PMC6681793 DOI: 10.3389/fmicb.2019.01685] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2019] [Accepted: 07/09/2019] [Indexed: 12/16/2022] Open
Abstract
Enterotoxigenic Escherichia coli produces a myriad of adhesive structures collectively named colonization factors (CFs). CS3 is a CF, which is assembled into fine wiry fibrillae encoded by the cstA-H gene cluster. In this work we evaluated the influence of environmental cues such as temperature, osmolarity, pH, and carbon source on the expression of CS3 genes. The transcription of cstH major pilin gene was stimulated by growth of the bacteria in colonization factor broth at 37°C; the presence of glycerol enhanced cstH transcription, while glucose at high concentration, high osmolarity, and the depletion of divalent cations such as calcium and magnesium repressed cstH expression. In addition, we studied the role of H-NS, CpxRA, and CRP global regulators in CS3 gene expression. H-NS and CpxRA acted as repressors and CRP as an activator of cstH expression. Under high osmolarity, H-NS, and CpxRA were required for cstH repression. CS3 was required for both, bacterial adherence to epithelial cells and biofilm formation. Our data strengthens the existence of a multi-factorial regulatory network that controls transcription of CS3 genes in which global regulators, under the influence of environmental signals, control the production of this important intestinal colonization factor.
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Li Q, Burrough ER, Gabler NK, Loving CL, Sahin O, Gould SA, Patience JF. A soluble and highly fermentable dietary fiber with carbohydrases improved gut barrier integrity markers and growth performance in F18 ETEC challenged pigs1. J Anim Sci 2019; 97:2139-2153. [PMID: 30888017 PMCID: PMC6488326 DOI: 10.1093/jas/skz093] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2018] [Accepted: 03/18/2019] [Indexed: 11/13/2022] Open
Abstract
This study aimed to evaluate the effects of a source of dietary soluble (SF) and insoluble fiber (IF) without or with exogenous carbohydrases (xylanase, β-glucanase, and pectinase) on diarrhea incidence, selected immune responses, and growth performance in enterotoxigenic Escherichia coli (ETEC)-challenged pigs. Sixty weaned pigs (6.9 ± 0.1 kg BW, ~23 d of age) were blocked by initial BW and placed in individual pens. Pens were randomly assigned to one of six treatments (n = 10 per treatment), including a nonchallenged control (NC), a positive challenge control (PC), the PC + a soluble fiber diet (10% sugar beet pulp) without (SF-) or with carbohydrases (SF+), and PC + an IF diet (15% corn distillers dried grains with solubles) without (IF-) or with carbohydrases (IF+). The control diet was primarily based on corn and soybean meal with 13.5% whey powder. The two sources of fiber were added at the expense of cornstarch in the control diet. Pigs were orally inoculated with 6 mL hemolytic F18 ETEC (~3.5 × 109 cfu/mL) or sham infected with 6 mL phosphate-buffered saline on day 7 (0 d postinoculation, dpi) postweaning. All ETEC challenged pigs were confirmed to be genetically susceptible to F18 ETEC. Pigs had free access to feed and water throughout the 14-d trial. Pig BW and feed intake were recorded on dpi -7, 0, and 7 or 8. Fecal swabs were collected on dpi -7, 0, 1, 2, 3, 5, and 7 or 8 to evaluate hemolytic E. coli shedding. Fecal score was visually ranked daily postchallenge to evaluate diarrhea incidence. Blood samples were collected on dpi -1, 3, and 7 or 8 at necropsy and intestinal tissues were collected at necropsy. Pigs on PC had lower dpi 1 to 7 ADG and ADFI than those on NC (P < 0.05). Compared with PC pigs, SF+ pigs had greater ADG during both pre- and postchallenge period (P < 0.05). The IF- increased postchallenge diarrhea incidence compared with PC (P < 0.05). Pigs on SF- had lower ileal E. coli attachment than PC (P < 0.05). The SF+ reduced haptoglobin and IF+ reduced C-reactive protein on dpi 3 compared with PC (P < 0.05). Compared with PC pigs, SF+ pigs tended to have lower ileal tumor necrosis factor alpha and greater ileal occludin (OCLN) mRNA (P < 0.10) and had greater (P < 0.05) colonic OCLN mRNA levels. Collectively, IF- increased incidence of diarrhea and fecal E. coli shedding compared with PC. The SF+ pigs had improved growth compared with PC pigs, likely due in part to a reduction in inflammatory intermediates.
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Hu D, Rampoldi A, Bratus-Neuenschwander A, Hofer A, Bertschinger HU, Vögeli P, Neuenschwander S. Effective genetic markers for identifying the Escherichia coli F4ac receptor status of pigs. Anim Genet 2019; 50:136-142. [PMID: 30724375 DOI: 10.1111/age.12770] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/13/2018] [Indexed: 11/28/2022]
Abstract
The F4ac receptor locus (F4acR), which encodes susceptibility or resistance to Escherichia coli diarrhoea, is inherited as an autosomal recessive monogenetic trait. F4acR is localized on pig chromosome 13 (SSC13q41-q44) near the MUC13 gene. Two flanking markers (CHCF1 and ALGA0106330) with a high linkage disequilibrium (LD) with F4acR were found to be effective for the genetic identification of F4ac-resistant pigs in the Swiss Large White breed (one recombinant out of 2034 genotyped pigs). Three recombinant boars, one each from the Duroc, Swiss Landrace and Piétrain breeds, were genotyped with seven different markers and phenotyped by means of a microscopic adhesion test. Only ALGA0072075, CHCF1 and CHCF3 indicated the correct phenotype. To test the effect of the resistance allele on production traits, 530 Large White pigs from the national test station were investigated. A significant difference existed among the F4acR locus genotypes in the intramuscular fat content of the longissimus dorsi muscle, whereas no other production traits were influenced by the resistance allele. The frequency of the CHCF1-C and ALGA0106330-A alleles associated with resistance in the Swiss Large White population was 60%, which is advantageous for implementing this trait in a breeding programme to select for E. coli F4ac-resistant animals. The selection of resistant pigs should start on the male side due to the inability of resistant sows to produce sufficient amounts of protecting antibodies in the colostrum. Selection of genetically F4ac-resistant pigs is a sustainable and suitable alternative to decreasing animal loss and antibiotic use due to diarrhoea.
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Crofts AA, Giovanetti SM, Rubin EJ, Poly FM, Gutiérrez RL, Talaat KR, Porter CK, Riddle MS, DeNearing B, Brubaker J, Maciel M, Alcala AN, Chakraborty S, Prouty MG, Savarino SJ, Davies BW, Trent MS. Enterotoxigenic E. coli virulence gene regulation in human infections. Proc Natl Acad Sci U S A 2018; 115:E8968-E8976. [PMID: 30126994 PMCID: PMC6156659 DOI: 10.1073/pnas.1808982115] [Citation(s) in RCA: 46] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is a global diarrheal pathogen that utilizes adhesins and secreted enterotoxins to cause disease in mammalian hosts. Decades of research on virulence factor regulation in ETEC has revealed a variety of environmental factors that influence gene expression, including bile, pH, bicarbonate, osmolarity, and glucose. However, other hallmarks of the intestinal tract, such as low oxygen availability, have not been examined. Further, determining how ETEC integrates these signals in the complex host environment is challenging. To address this, we characterized ETEC's response to the human host using samples from a controlled human infection model. We found ETEC senses environmental oxygen to globally influence virulence factor expression via the oxygen-sensitive transcriptional regulator fumarate and nitrate reduction (FNR) regulator. In vitro anaerobic growth replicates the in vivo virulence factor expression profile, and deletion of fnr in ETEC strain H10407 results in a significant increase in expression of all classical virulence factors, including the colonization factor antigen I (CFA/I) adhesin operon and both heat-stable and heat-labile enterotoxins. These data depict a model of ETEC infection where FNR activity can globally influence virulence gene expression, and therefore proximity to the oxygenated zone bordering intestinal epithelial cells likely influences ETEC virulence gene expression in vivo. Outside of the host, ETEC biofilms are associated with seasonal ETEC epidemics, and we find FNR is a regulator of biofilm production. Together these data suggest FNR-dependent oxygen sensing in ETEC has implications for human infection inside and outside of the host.
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Bijvelds MJC, Tresadern G, Hellemans A, Smans K, Nieuwenhuijze NDA, Meijsen KF, Bongartz JP, Ver Donck L, de Jonge HR, Schuurkes JAJ, De Maeyer JH. Selective inhibition of intestinal guanosine 3',5'-cyclic monophosphate signaling by small-molecule protein kinase inhibitors. J Biol Chem 2018; 293:8173-8181. [PMID: 29653944 PMCID: PMC5971447 DOI: 10.1074/jbc.ra118.002835] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2018] [Revised: 04/11/2018] [Indexed: 11/06/2022] Open
Abstract
The guanosine 3',5'-cyclic monophosphate (cGMP)-dependent protein kinase II (cGKII) serine/threonine kinase relays signaling through guanylyl cyclase C (GCC) to control intestinal fluid homeostasis. Here, we report the discovery of small-molecule inhibitors of cGKII. These inhibitors were imidazole-aminopyrimidines, which blocked recombinant human cGKII at submicromolar concentrations but exhibited comparatively little activity toward the phylogenetically related protein kinases cGKI and cAMP-dependent protein kinase (PKA). Whereas aminopyrimidyl motifs are common in protein kinase inhibitors, molecular modeling of these imidazole-aminopyrimidines in the ATP-binding pocket of cGKII indicated an unconventional binding mode that directs their amine substituent into a narrow pocket delineated by hydrophobic residues of the hinge and the αC-helix. Crucially, this set of residues included the Leu-530 gatekeeper, which is not conserved in cGKI and PKA. In intestinal organoids, these compounds blocked cGKII-dependent phosphorylation of the vasodilator-stimulated phosphoprotein (VASP). In mouse small intestinal tissue, cGKII inhibition significantly attenuated the anion secretory response provoked by the GCC-activating bacterial heat-stable toxin (STa), a frequent cause of infectious secretory diarrhea. In contrast, both PKA-dependent VASP phosphorylation and intestinal anion secretion were unaffected by treatment with these compounds, whereas experiments with T84 cells indicated that they weakly inhibit the activity of cAMP-hydrolyzing phosphodiesterases. As these protein kinase inhibitors are the first to display selective inhibition of cGKII, they may expedite research on cGMP signaling and may aid future development of therapeutics for managing diarrheal disease and other pathogenic syndromes that involve cGKII.
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Field D, Baghou I, Rea MC, Gardiner GE, Ross RP, Hill C. Nisin in Combination with Cinnamaldehyde and EDTA to Control Growth of Escherichia coli Strains of Swine Origin. Antibiotics (Basel) 2017; 6:antibiotics6040035. [PMID: 29231854 PMCID: PMC5745478 DOI: 10.3390/antibiotics6040035] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2017] [Revised: 12/06/2017] [Accepted: 12/07/2017] [Indexed: 12/21/2022] Open
Abstract
Post-weaning diarrhoea (PWD) due to enterotoxigenic Escherichia coli (ETEC) is an economically important disease in pig production worldwide. Although antibiotics have contributed significantly to mitigate the economic losses caused by PWD, there is major concern over the increased incidence of antimicrobial resistance among bacteria isolated from pigs. Consequently, suitable alternatives that are safe and effective are urgently required. Many naturally occurring compounds, including the antimicrobial peptide nisin and a number of plant essential oils, have been widely studied and are reported to be effective as antimicrobial agents against pathogenic microorganisms. Here, we evaluate the potential of nisin in combination with the essential oil cinnamaldehyde and ethylenediaminetetraacetic acid (EDTA) to control the growth of E. coli strains of swine origin including two characterized as ETEC. The results reveal that the use of nisin (10 μM) with low concentrations of trans-cinnamaldehyde (125 μg/mL) and EDTA (0.25–2%) resulted in extended lag phases of growth compared to when either antimicrobial is used alone. Further analysis through kill curves revealed that an approximate 1-log reduction in E. coli cell counts was observed against the majority of targets tested following 3 h incubation. These results highlight the potential benefits of combining the natural antimicrobial nisin with trans-cinnamaldehyde and EDTA as a new approach for the inhibition of E. coli strains of swine origin.
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Zeinalzadeh N, Salmanian AH, Goujani G, Amani J, Ahangari G, Akhavian A, Jafari M. A Chimeric protein of CFA/I, CS6 subunits and LTB/STa toxoid protects immunized mice against enterotoxigenic Escherichia coli. Microbiol Immunol 2017; 61:272-279. [PMID: 28543534 DOI: 10.1111/1348-0421.12491] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2016] [Revised: 05/02/2017] [Accepted: 05/18/2017] [Indexed: 01/21/2023]
Abstract
Enterotoxigenic Escherichia Coli (ETEC) strains are the commonest bacteria causing diarrhea in children in developing countries and travelers to these areas. Colonization factors (CFs) and enterotoxins are the main virulence determinants in ETEC pathogenesis. Heterogeneity of CFs is commonly considered the bottleneck to developing an effective vaccine. It is believed that broad spectrum protection against ETEC would be achieved by induced anti-CF and anti-enterotoxin immunity simultaneously. Here, a fusion antigen strategy was used to construct a quadrivalent recombinant protein called 3CL and composed of CfaB, a structural subunit of CFA/I, and CS6 structural subunits, LTB and STa toxoid of ETEC. Its anti-CF and antitoxin immunogenicity was then assessed. To achieve high-level expression, the 3CL gene was synthesized using E. coli codon bias. Female BALB/C mice were immunized with purified recombinant 3CL. Immunized mice developed antibodies that were capable of detecting each recombinant subunit in addition to native CS6 protein and also protected the mice against ETEC challenge. Moreover, sera from immunized mice also neutralized STa toxin in a suckling mouse assay. These results indicate that 3CL can induce anti-CF and neutralizing antitoxin antibodies along with introducing CFA/I as a platform for epitope insertion.
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Li P, Lin JE, Snook AE, Waldman SA. ST-Producing E. coli Oppose Carcinogen-Induced Colorectal Tumorigenesis in Mice. Toxins (Basel) 2017; 9:toxins9090279. [PMID: 28895923 PMCID: PMC5618212 DOI: 10.3390/toxins9090279] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2017] [Revised: 08/31/2017] [Accepted: 09/06/2017] [Indexed: 01/04/2023] Open
Abstract
There is a geographic inequality in the incidence of colorectal cancer, lowest in developing countries, and greatest in developed countries. This disparity suggests an environmental contribution to cancer resistance in endemic populations. Enterotoxigenic bacteria associated with diarrheal disease are prevalent in developing countries, including enterotoxigenic E. coli (ETEC) producing heat-stable enterotoxins (STs). STs are peptides that are structurally homologous to paracrine hormones that regulate the intestinal guanylyl cyclase C (GUCY2C) receptor. Beyond secretion, GUCY2C is a tumor suppressor universally silenced by loss of expression of its paracrine hormone during carcinogenesis. Thus, the geographic imbalance in colorectal cancer, in part, may reflect chronic exposure to ST-producing organisms that restore GUCY2C signaling silenced by hormone loss during transformation. Here, mice colonized for 18 weeks with control E. coli or those engineered to secrete ST exhibited normal growth, with comparable weight gain and normal stool water content, without evidence of secretory diarrhea. Enterotoxin-producing, but not control, E. coli, generated ST that activated colonic GUCY2C signaling, cyclic guanosine monophosphate (cGMP) production, and cGMP-dependent protein phosphorylation in colonized mice. Moreover, mice colonized with ST-producing E. coli exhibited a 50% reduction in carcinogen-induced colorectal tumor burden. Thus, chronic colonization with ETEC producing ST could contribute to endemic cancer resistance in developing countries, reinforcing a novel paradigm of colorectal cancer chemoprevention with oral GUCY2C-targeted agents.
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Hodson C, Yang J, Hocking DM, Azzopardi K, Chen Q, Holien JK, Parker MW, Tauschek M, Robins-Browne RM. Control of Virulence Gene Expression by the Master Regulator, CfaD, in the Prototypical Enterotoxigenic Escherichia coli Strain, H10407. Front Microbiol 2017; 8:1525. [PMID: 28848532 PMCID: PMC5554520 DOI: 10.3389/fmicb.2017.01525] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Accepted: 07/28/2017] [Indexed: 12/24/2022] Open
Abstract
Enterotoxigenic Escherichia coli (ETEC) is the most common bacterial cause of diarrhea in children in developing countries, as well as in travelers to these countries. To cause disease, ETEC needs to produce a series of virulence proteins including enterotoxins, colonization factors and secretion pathways, which enable this pathogen to colonize the human small intestine and deliver enterotoxins to epithelial cells. Previously, a number of studies have demonstrated that CfaD, an AraC-like transcriptional regulator, plays a key role in virulence gene expression by ETEC. In this study, we carried out a transcriptomic analysis of ETEC strain, H10407, grown under different conditions, and determined the complete set of genes that are regulated by CfaD. In this way, we identified a number of new target genes, including rnr-1, rnr-2, etpBAC, agn43, flu, traM and ETEC_3214, whose expression is strongly activated by CfaD. Using promoter-lacZ reporters, primer extension and electrophoretic mobility shift assays, we characterized the CfaD-mediated activation of several selected target promoters. We also showed that the gut-associated environmental signal, sodium bicarbonate, stimulates CfaD-mediated upregulation of its virulence target operons. Finally, we screened a commercial small molecule library and identified a compound (CH-1) that specifically inhibited the regulatory function of CfaD, and by 2-D analoging, we identified a second inhibitor (CH-2) with greater potency.
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