Animal Enterotoxigenic Escherichia coli

Effects of dietary ε-polylysine supplementation on growth performance, antioxidant capacity, immune function, and intestinal microbiota in growing male minks

Introduction

This study investigated the effects of dietary ε-polylysine (ε-PL) supplementation on the growth performance, antioxidant capacity, immune function and intestinal microbiota in growing male minks.

Methods

Ninety-six 12-week-old male minks were randomly divided into 6 treatments (8 replicates per treatment and 2 minks per replicate). Minks were fed basal diets supplemented with 0 (control), 100, 200, 300, 400, or 500 mg/kg ε-PL for 8 weeks.

Results

Compared with the control, 300-500 mg/kg ε-PL significantly increased the average daily gain (p < 0.05), and significantly decreased the feed-to-gain ratio (p < 0.05) during the whole period and significantly enhanced the body weight at week 8 (p < 0.05), 300-400 mg/kg ε-PL significantly increased the fresh pelt weight (p < 0.05). Compared with the control, 300 mg/kg ε-PL significantly increased serum T-SOD activity and jejunal mucosal T-SOD and GSH-Px activities (p < 0.05). Compared to the control, 200-400 mg/kg ε-PL significantly increased serum IgA level (p < 0.05), 300-400 mg/kg ε-PL significantly increased serum IgM level (p < 0.05), 400-500 mg/kg ε-PL significantly increased serum IgG level (p < 0.05). Compared with the control, 200-400 mg/kg ε-PL significantly increased jejunal mucosal IgA level (p < 0.05), 100 mg/kg ε-PL significantly increased jejunal mucosal IgM level (p < 0.05), 100-400 mg/kg ε-PL significantly increased jejunal mucosal IgG level (p < 0.05). Compared with the control group, all ε-PL supplemented groups significantly decreased serum IL-2 and IL-8 levels compared to the control (p < 0.05). The 16S rRNA sequencing analysis revealed that compared to the control, 300 mg/kg ε-PL significantly increased the relative abundance of Firmicutes and Clostridium_sensu_stricto_1 (p < 0.05), and significantly decreased the relative abundance of Proteobacteria and Escherichia-Shigella in ileal mucosa (p < 0.05). Spearman correlation analysis indicated that the relative abundance of Escherichia-Shigella was negatively correlated with the growth performance. The relative abundance of Clostridium_sensu_stricto_1 was positively correlated with the jejunal mucosal antioxidant indicators and immunoglobulin levels.

Discussion

In conclusion, dietary ε-PL supplementation can improve growth performance, antioxidant capacity, immune function, and gut microbial community in growing male minks, and the optimal dosage of ε-PL is 300 mg/kg.

Porcine β-Defensin 2 Expressed in Pichia pastoris Alleviates Enterotoxigenic Escherichia coli-Induced Intestinal Injury and Inflammatory Response in Mice

Enterotoxigenic Escherichia coli (ETEC), a common intestinal pathogen, can colonize the intestines and induce diarrhea in piglets, which brings great economic losses to the swine industry. Antibiotics are recommended to the treatment for diarrhea caused by ETEC in weaned piglets. However, with the emergence and spread of multidrug-resistant ETEC, there is an urgent need to develop alternatives to antibiotics. Due to the unique antibacterial mechanism of targeting bacterial membranes, antimicrobial peptides (AMPs) are promising candidates. In this study, the activity of crude recombinant porcine β-defensin 2 (rPBD2) expressed in Pichia pastoris (P. pastoris) was measured in vitro. Mice infected with ETEC were orally administered 16, 8, and 4 AU crude rPBD2 for 7 consecutive days to evaluate its anti-infective activity in vivo. The results showed that in addition to broad antibacterial activity against Gram-positive and -negative bacteria, crude rPBD2 displayed high tolerance to temperatures ranging from 20 to 60 °C, a broad range of pH, trypsin, pepsin, and physiological concentrations of salts. In an ETEC-induced mouse model, the oral administration of crude rPBD2 decreased diarrhea scores and the intestinal/carcass ratio and alleviated body weight loss. Additionally, crude rPBD2 decreased bacterial loads in stools and the colon (HP group), and the levels of serum pro-inflammatory cytokines IL-6 (HP group) and TNF-α (HP and MP groups), and increased the villus height and the ratio of villus height to crypt depth (VH/CD) in the ileum (HP and MP groups). Our study provides a cost-effective way for PBD2 production and identifies it as a promising candidate to combat ETEC-induced infection.

Chlorogenic acid mitigates avian pathogenic Escherichia coli-induced intestinal barrier damage in broiler chickens via anti-inflammatory and antioxidant effects

This study was conducted to investigate the protective effects of chlorogenic acid (CGA) on intestinal health in broilers challenged with avian pathogenic Escherichia coli (APEC). One hundred and eighty one-day-old male broiler chicks were divided into three groups with six replicates of ten chicks each for a 21-day trial. The birds in the control and APEC groups were fed a basal diet, while birds in the CGA-treated group received a basal diet supplemented with 1000 mg/kg of CGA. At 14 days, birds in the APEC and CGA groups were administered with an APEC suspension Compared with the APEC group, CGA incorporation decreased mortality and cecal Escherichia coli colonies in bacterially challenged broilers (P < 0.05). Additionally, CGA reduced the relative weight of the heart, liver, kidney, gizzard, proventriculus, and intestine, as well as serum triglyceride level and alanine aminotransferase activity in APEC-challenged broilers (P < 0.05). Supplementing CGA reduced the concentrations of interferon-γ, tumor necrosis factor-α, interleukin-1β, and/or interleukin-6 in serum, duodenum, jejunum, and/or ileum in APEC-challenged broilers presumably through the inactivation of the toll-like receptor 4/myeloid differentiation factor 88 pathway (P < 0.05). CGA administration reduced serum diamine oxidase activity and d-lactate and endotoxin concentrations, but increased the ratio between villus height and crypt depth in duodenum and jejunum of APEC-infected chickens, accompanied by the restored intestinal expression of tight junction proteins (claudin-1, claudin-2, occludin, and zonula occludens-1) and genes involved in apoptosis (B cell lymphoma-2 associated X protein, B cell lymphoma-2, and cysteine-requiring aspartate protease 9) (P < 0.05). Additionally, CGA increased superoxide dismutase, glutathione peroxidase, and catalase activities, and glutathione levels in serum and intestinal mucosa, but inhibited the accumulation of intestinal malondialdehyde in APEC-challenged broilers possibly via activating the nuclear factor-erythroid 2-related factor-2/heme oxygenase-1 pathway (P < 0.05). The results suggested that CGA alleviated APEC-induced intestinal damage in broilers by inhibiting inflammation and oxidative stress. However, its potential application in practical poultry production is contingent upon both its efficacy and cost-effectiveness.

Sialyllactose Attenuates Inflammation and Injury of Intestinal Epithelial Cells upon Enterotoxigenic Escherichia coli Infection

Sialyllactose (SL), a bioactive trisaccharide abundant in porcine colostrum, demonstrates multifunctional properties including antimicrobial activity, immune regulation, and apoptosis inhibition. This research uncovers the mechanisms by which SL mitigates enterotoxigenic Escherichia coli (ETEC)-mediated damage to intestinal barrier integrity, employing IPEC-J2 porcine epithelial models. SL pre-treatment effectively blocked pathogen adhesion by competitively binding to cellular receptors, concurrently mitigating inflammation through significant suppression of TNF-α, IL-1β, and IL-6 expression (p < 0.05). Notably, SL exhibited functional parallels to the NF-κB inhibitor BAY11-7082, jointly enhancing tight junction integrity via ZO-1 protein stabilization and inhibiting pro-inflammatory signaling through coordinated suppression of IκB-α/NF-κB phosphorylation cascades. The dual-action mechanism combines molecular interception of microbial attachment with intracellular modulation of the TLR4/MyD88/NF-κB pathway, effectively resolving both pathogenic colonization and inflammatory amplification. These findings position SL as a potential therapeutic application nutraceutical for livestock, with the capacity to address post-weaning porcine enteritis through functional feed formulations that synergistically enhance intestinal barrier resilience while curbing ETEC-mediated inflammatory pathogenesis.

Benzoic acid as a dietary supplement mitigates inflammation and intestinal injury in acute enterotoxigenic Escherichia coli-infected mice without adverse effects in healthy mice

Benzoic acid is a naturally occurring compound found in fruits and is also commercially synthesized as an additive in the food, feed, and pharmaceutical industries. This study investigated the effects of benzoic acid as a dietary supplement on inflammation and intestinal injury in acute Escherichia coli (ETEC)-infected or healthy mice. Thirty-six BALB/c mice were divided into three groups, with 12 mice in each group for a 16-day feeding trial. In group 1, mice were fed a basal diet, six mice were sacrificed, and six mice were intraperitoneally injected with phosphate-buffered saline on day 15. Groups 2 and 3 were fed a basal diet and a diet containing 0.6% benzoic acid, respectively. Half of the mice in each group were sacrificed, while the others were intraperitoneally injected with ETEC on day 15. The results indicated that benzoic acid had no adverse effects on healthy mice regarding growth, organ indices, inflammation, intestinal injury parameters, and cecal short-chain fatty acid levels. Importantly, benzoic acid reduced inflammation in ETEC-infected mice, as evidenced by decreased serum IL-1β, TNF-α, and INF-γ levels, along with increased jejunal TLR-2 and MyD88 mRNA expression. Besides, benzoic acid mitigated intestinal injury in ETEC-infected mice by increasing the jejunal villus height (VH) and the ratio of VH to crypt depth, elevating jejunal Occludin mRNA levels, decreasing serum D-lactate and diamine oxidase levels, and increasing the cecal acetic acid level. 16s rRNA sequencing revealed that benzoic acid altered the β-diversity of ETEC-infected mice and increased the abundances of Erysipelotrichaceae, Faecalibaculum, and Turicibacter in their gut microbiota. Spearman correlation analysis further indicated that the protective effects of benzoic acid against ETEC infection were closely linked to specific gut microbiota, namely Erysipelotrichaceae, Faecalibaculum, Bifidobacterium, and Limosilactobacillus. Collectively, these findings suggest that benzoic acid could serve as a safe dietary supplement for healthy mice and may alleviate inflammation and intestinal injury in mice with acute ETEC infection.

Impacts of zinc caproate supplementation on growth performance, intestinal health, anti-inflammatory activity, and Zn homeostasis in weaned piglets challenged with Escherichia coli K88

BACKGROUND

Enterotoxigenic Escherichia coli (ETEC) is one of the primary causes of diarrhea in piglets, creating substantial economic losses in the swine farming industry worldwide. This study aimed to investigate the impacts of zinc caproate (ZnCA, C12H22O4Zn) on the intestinal health, growth performance, inflammatory status, and Zn homeostasis of weaned piglets challenged with ETEC K88. In total, 48 weaned piglets (Duroc × Landrace × Yorkshire, 7.78 ± 0.19 kg, 28 d) were selected for a 21-d experiment. Each experimental treatment consisted of 6 replicate pens with 2 piglets each. The treatment conditions were as follows: i) a basal diet (CON), ii) a basal diet + ETEC K88 (NC), iii) a basal diet + 2,500 mg/kg of Zn (provided as zinc oxide, ZnO) + ETEC K88 (PC), and iv) a basal diet + 1,600 mg/kg of Zn (provided as ZnCA) + ETEC K88 (ZnCA).

RESULTS

The addition of 1,600 mg/kg ZnCA to the diet of post-weaning piglets effectively enhanced growth performance and nutrient digestibility and reduced the incidence of diarrhea and inflammatory reactions caused by ETEC K88 infection. These therapeutic effects were comparable to those of pharmacological doses of ZnO. In terms of improving intestinal health and Zn homeostasis in post-weaning piglets challenged with ETEC K88, the effectiveness of 1,600 mg/kg ZnCA surpassed that of pharmacological doses of ZnO.

CONCLUSIONS

Overall, under the experimental conditions of this study, ZnCA exhibited the potential to reduce the pharmacological dosage of ZnO while improving intestinal health and Zn homeostasis in weaned piglets.

Targeting Enterotoxins: Advancing Vaccine Development for Enterotoxigenic Escherichia coli ETEC

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrheal disease worldwide, particularly in children in low- and middle-income countries. Its ability to rapidly colonize the intestinal tract through diverse colonization factors and toxins underpins its significant public health impact. Despite extensive research and several vaccine candidates reaching clinical trials, no licensed vaccine exists for ETEC. This review explores the temporal and spatial coordination of ETEC virulence factors, focusing on the interplay between adherence mechanisms and toxin production as critical targets for therapeutic intervention. Advancements in molecular biology and host-pathogen interaction studies have uncovered species-specific variations and cross-reactivity between human and animal strains. In particular, the heat-labile (LT) and heat-stable (ST) toxins have provided crucial insights into molecular mechanisms and intestinal disruption. Additional exotoxins, such as EAST-1 and hemolysins, further highlight the multifactorial nature of ETEC pathogenicity. Innovative vaccine strategies, including multiepitope fusion antigens (MEFAs), mRNA-based approaches, and glycoconjugates, aim to enhance broad-spectrum immunity. Novel delivery methods, like intradermal immunization, show promise in eliciting robust immune responses. Successful vaccination against ETEC will offer an effective and affordable solution with the potential to greatly reduce mortality and prevent stunting, representing a highly impactful and cost-efficient solution to a critical global health challenge.

Genomic diversity and evolutionary patterns of Edwardsiella ictaluri affecting farmed striped catfish (Pangasianodon hypophthalmus) in Vietnam over 20 years

Edwardsiella ictaluri continues to pose a significant risk to the health and production of striped catfish (Pangasianodon hypophthalmus) in Vietnam. Whilst recent advances in genomic sequencing provide an insight into the global genomic diversity of this important fish pathogen, genome-wide analysis of Vietnamese isolates recovered over time is lacking. In this study, we used a whole-genome sequencing approach to compare the genomes of 31 E. ictaluri isolates recovered over a 20-year period (2001-2021) and performed comparative genomic analysis to explore temporal changes in genome diversity, population structure and mechanisms driving pathogenesis and antimicrobial resistance. Our findings revealed an open pan-genome with 4148 genes and a core genome (3 060 genes) accounting for over two-thirds of the genome. Moreover, we found the genomes sequenced to classify into two distinct lineages and estimated the ancestral origin of these lineages within Vietnam to date back to the 1950s. Plasmids were highly prevalent in Vietnamese E. ictaluri, with isolates harbouring up to four plasmids within their genome. Further, a diverse mobilome was observed with nine different plasmid types detected across the genome collection. Exploration of putative plasmids revealed a diverse set of antimicrobial resistance genes (ARGs) against key antibiotics used in Vietnamese aquaculture and virulence genes associated with protein secretion systems. Correlation analysis revealed the total number of ARGs detected in genomes to increase with isolate recovery time. Whilst the number of virulence genes remained relatively stable, temporal variation was noted in several virulence factors related to motility and immune system modulation. Findings from this study highlight the need for continued genomic surveillance to monitor changes in antimicrobial resistance and pathogenesis, to help inform the development of disease control and management strategies.

Recombinant Saccharomyces cerevisiae EBY100/pYD1-FaeG: a candidate for an oral subunit vaccine against F4+ ETEC infection

Diarrheal diseases attributable to multidrug-resistant F4+ enterotoxigenic Escherichia coli (ETEC) are escalating in severity, posing significant risks to the health and safety of both humans and animals. This study used Saccharomyces cerevisiae EBY100 to display the FaeG subunit of F4 colonizing factor as an oral vaccine against F4+ ETEC infection. Mice were orally immunized twice with 108 CFU of EBY100/pYD1-FaeG, followed by a challenge with F4+ ETEC EC6 on day 7 post-immunization. The results showed that the recombinant strain EBY100/pYD1-FaeG orally enhanced the growth of the small intestine villi, significantly boosted the expression of tight junction proteins (ZO-1, Occludin, MUC2, and Claudin) (P < 0.05), and modulated the gut microbiota composition. Additionally, immunization with EBY100/pYD1-FaeG also upregulated the levels of IL-2, IL-4, and IFN-γ in the intestines of mice (P < 0.01), while serum IgG and fecal sIgA titer significantly increased (P < 0.05). These immune responses enhanced the capacity to fight against ETEC, leading to an increased survival rate of mice and relieved damage to tissues and organs of mice infection. In summary, the study suggested that the recombinant Saccharomyces cerevisiae EBY100/pYD1-FaeG could effectively stimulate the immune response and generate specific antibodies against F4+ ETEC, showing its potential to serve as a subunit oral vaccine candidate for preventing F4+ ETEC infection.IMPORTANCEThe multidrug-resistant F4+ enterotoxigenic Escherichia coli (ETEC) strains are the primary clinical pathogens responsible for post-weaning diarrhea in piglets, resulting in substantial economic losses in the pig farming industry. In the study, we developed an oral vaccine candidate, Saccharomyces cerevisiae EBY100/pYD1-FaeG, to prevent diarrhea caused by multidrug-resistant F4+ ETEC. Oral administration of EBY100/pYD1-FaeG significantly enhanced immune responses, improved intestinal health, and provided protection against F4+ ETEC infection in mice. This approach offers a potential application prospect for preventing F4+ ETEC infections that lead to post-weaning diarrhea in clinical settings and provides a promising solution for addressing the growing threat of antibiotic resistance in bacterial pathogens.

Antibiotic Resistance Profile of Enterovirulent E. coli Isolates Harboring Broad-Spectrum Beta-Lactamase Genes in Cancer Patients at the Laquintinie Hospital in Douala, Littoral Region, Cameroon

Cases of antibiotic-resistant Escherichia coli (E. coli) infections are becoming increasingly frequent and represent a major threat to our ability to treat cancer patients. The emergence of antimicrobial resistance threatens the treatment of E. coli infections. In this study, the antimicrobial profiles, virulent genes, and the frequency of extended-spectrum beta-lactamase (ESBL) gene carriage in fecal E. coli isolates from cancer patients at the Laquintinie Hospital in Douala (Cameroon) were determined. 507 participants were recruited from October 2021 to March 2023, of whom 307 (60.55%) had cancer and 200 (39.45%) did not. Two hundred and two E. coli were isolated from fecal samples of one hundred and fifteen cancer patients and 47 (87) noncancer patients using EMB LEVINE agar. The antimicrobial resistance profile of the isolates was determined using the Kirby-Bauer disk diffusion method. Virulence and resistance genes were detected by simplex polymerase chain reaction (PCR). E. coli showed significant rates of resistance to amoxicillin, cefotaxime, ceftazidime, piperacillin, tetracycline, and ciprofloxacin in cancer patients compared to noncancer patients. The rate of multidrug resistance (MDR) was significantly (p < 0.05) higher in cancer patients than in noncancer patients. Fifty-five enterovirulent E. coli were identified, of which 24 (43.63%) were EPEC, 13 (23.63%) were EAEC, 6 (10.90%) were ETEC, 10 (18.18%) were STEC, and 2 (3.63%) were EIEC. The frequency of beta-lactamase genes in the 55 ESBL-producing enterovirulent E. coli isolates was determined, and 94.54% harbored at least one ESBL gene, distributed as follows: 80.00% for bla TEM, 67.27% for bla CTX-M, 24.63 for bla OXA, and 36.36% for bla SHV genes. Several associations were observed between virulence factors, resistance genes, and the antimicrobial resistance phenotype. This study revealed the real existence of fecal carriage of ESBL-producing enterovirulent E. coli isolates from cancer patients with a high rate of MDR in the latter.

Parameters for one health genomic surveillance of Escherichia coli from Australia

Genomics is a cornerstone of modern pathogen epidemiology yet demonstrating transmission in a One Health context is challenging, as strains circulate and evolve within and between diverse hosts and environments. To identify phylogenetic linkages and better define relevant measures of genomic relatedness in a One Health context, we collated 5471 Escherichia coli genome sequences from Australia originating from humans (n = 2996), wild animals (n = 870), livestock (n = 649), companion animals (n = 375), environmental sources (n = 292) and food (n = 289) spanning over 36 years. Of the 827 multi-locus sequence types (STs) identified, 10 STs were commonly associated with cross-source genomic clusters, including the highly clonal ST131, pandemic zoonotic lineages such as ST95, and emerging human ExPEC ST1193. Here, we show that assessing genomic relationships at ≤ 100 SNP threshold enabled detection of cross-source linkage otherwise obscured when applying typical outbreak-oriented relatedness thresholds ( ≤ 20 SNPs) and should be considered in interrogation of One Health genomic datasets.

Recent Antimicrobial Resistance Situation and Mechanisms of Resistance to Key Antimicrobials in Enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is a major cause of diarrhea in developing countries and is regularly imported into developed countries as a major cause of traveler's diarrhea. ETEC is usually self-limiting and not necessarily treated with antimicrobials, although antimicrobial treatment is recommended in malnourished children, severe cases, and traveler's diarrhea. However, resistant strains to representative therapeutic agents such as ciprofloxacin and azithromycin have been reported in recent years, and multidrug-resistant ETEC has also emerged. This review discusses the recent antimicrobial resistance surveillance in ETEC and the mechanisms of resistance to major antimicrobials.

Saccharomyces yeast postbiotics mitigate mucosal damages from F18+ Escherichia coli challenges by positively balancing the mucosal microbiota in the jejunum of young pigs

BACKGROUND

Enterotoxigenic Escherichia coli (E. coli) is one of the most prevalent causes of diarrhea in young animals. Postbiotics derived from yeast have the potential to positively influence the mucosal microbiota in the jejunum, therefore it was hypothesized that Saccharomyces yeast postbiotics could enhance the microbiota and mucosal immune response in the jejunum, mitigating the effects of infection with enterotoxigenic E. coli. The purpose of this study was to investigate the effects of a Saccharomyces yeast postbiotic on the mucosal microbiota and mucosal immune response in the jejunum of newly weaned pigs challenged with F18+ E. coli.

RESULTS

Thirty-six individually housed nursery pigs were allotted into three treatments utilizing a randomized complete block design; negative control (NC: basal diet, no challenge), positive control (PC: basal diet, challenge), and SYP (basal diet + Saccharomyces yeast postbiotics at 175 g/ton, challenge). On d 7, PC and SYP were orally inoculated with F18+ E. coli, whereas NC received saline. On d 28, pigs were euthanized for sampling of the jejunum to analyze the mucosal microbiota, oxidative stress, immune status, and intestinal morphology. The PC reduced (P < 0.05) growth performance compared to NC. The SYP improved (P < 0.05) fecal score from d 7-18 when compared with PC. SYP reduced (P < 0.05) protein carbonyl, reduced (P < 0.05) gene expression of Toll-like receptor 4, and increased (P < 0.05) gene expression of mammalian target of rapamycin, compared with PC.

CONCLUSIONS

Challenge with F18+ E. coli negatively impacted jejunal mucosa-associated microbiota and jejunal morphology, affecting growth performance. Saccharomyces yeast postbiotics could reduce the negative effects associated with F18+ E. coli infection.

Natural anti-adhesive components against pathogenic bacterial adhesion and infection in gastrointestinal tract: case studies of Helicobacter pylori, Salmonella enterica, Clostridium difficile, and diarrheagenic Escherichia coli

Antimicrobial resistance (AMR) poses a global public health concern. Recognizing the critical role of bacterial adhesion in pathogenesis of infection, anti-adhesive therapy emerges as a promising approach to impede initial bacterial attachment, thus preventing pathogenic colonization and infection. Natural anti-adhesive agents derived from food sources are generally safe and have the potential to inhibit the emergence of resistant bacteria. This comprehensive review explored diverse natural dietary components exhibiting anti-adhesive activities against several model enteric pathogens, including Helicobacter pylori, Salmonella enterica, Clostridium difficile, and three key diarrheagenic Escherichia coli (i.e., enterotoxigenic E. coli, enteropathogenic E. coli, and enterohemorrhagic E. coli). Investigating various anti-adhesive products will advance our understanding of current research of the field and inspire further development of these agents as potential nutraceuticals or adjuvants to improve the efficacy of conventional antibiotics.

Pharmacodynamic Evaluation of Phage Therapy in Ameliorating ETEC-Induced Diarrhea in Mice Models

Enterotoxigenic Escherichia coli (ETEC) is a major pathogen causing diarrhea in humans and animals, with increasing antimicrobial resistance posing a growing challenge in recent years. Lytic bacteriophages (phages) offer a targeted and environmentally sustainable approach to combating bacterial infections, particularly in eliminating drug-resistant strains. In this study, ETEC strains were utilized as indicators, and a stable, high-efficiency phage, designated vB_EcoM_JE01 (JE01), was isolated from pig farm manure. The genome of JE01 was a dsDNA molecule, measuring 168.9 kb, and a transmission electron microscope revealed its characteristic T4-like Myoviridae morphology. JE01 effectively lysed multi-drug-resistant ETEC isolates. Stability assays demonstrated that JE01 retained its activity across a temperature range of 20 °C to 50 °C and a pH range of 3-11, showing resilience to ultraviolet radiation and chloroform exposure. Furthermore, JE01 effectively suppressed ETEC adhesion to porcine intestinal epithelial cells (IPEC-J2), mitigating the inflammatory response triggered by ETEC. To investigate the in vivo antibacterial efficacy of phage JE01 preparations, a diarrhea model was established using germ-free mice infected with a drug-resistant ETEC strain. The findings indicated that 12 h post-ETEC inoculation, intragastric administration of phage JE01 significantly reduced mortality, alleviated gastrointestinal lesions, decreased ETEC colonization in the jejunum, and suppressed the expression of the cytokines IL-6 and IL-8. These results demonstrate a therapeutic benefit of JE01 in treating ETEC-induced diarrhea in mice. Additionally, a fluorescent phage incorporating red fluorescent protein (RFP) was engineered, and the pharmacokinetics of phage therapy were preliminarily assessed through intestinal fluorescence imaging in mice. The results showed that the phage localized to ETEC in the jejunum rapidly, within 45 min. Moreover, the pharmacokinetics of the phage were markedly slowed in the presence of its bacterial target in the gut, suggesting sustained bacteriolytic activity in the ETEC-infected intestine. In conclusion, this study establishes a foundation for the development of phage-based therapies against ETEC.

Effects of dietary Lactobacillus postbiotics and bacitracin on the modulation of mucosa-associated microbiota and pattern recognition receptors affecting immunocompetence of jejunal mucosa in pigs challenged with enterotoxigenic F18+ Escherichia coli

BACKGROUND

Enterotoxigenic Escherichia coli (E. coli) is a threat to humans and animals that causes intestinal disorders. Antimicrobial resistance has urged alternatives, including Lactobacillus postbiotics, to mitigate the effects of enterotoxigenic E. coli.

METHODS

Forty-eight newly weaned pigs were allotted to NC: no challenge/no supplement; PC: F18+ E. coli challenge/no supplement; ATB: F18+ E. coli challenge/bacitracin; and LPB: F18+ E. coli challenge/postbiotics and fed diets for 28 d. On d 7, pigs were orally inoculated with F18+ E. coli. At d 28, the mucosa-associated microbiota, immune and oxidative stress status, intestinal morphology, the gene expression of pattern recognition receptors (PRR), and intestinal barrier function were measured. Data were analyzed using the MIXED procedure in SAS 9.4.

RESULTS

PC increased (P < 0.05) Helicobacter mastomyrinus whereas reduced (P < 0.05) Prevotella copri and P. stercorea compared to NC. The LPB increased (P < 0.05) P. stercorea and Dialister succinatiphilus compared with PC. The ATB increased (P < 0.05) Propionibacterium acnes, Corynebacterium glutamicum, and Sphingomonas pseudosanguinis compared to PC. The PC tended to reduce (P = 0.054) PGLYRP4 and increased (P < 0.05) TLR4, CD14, MDA, and crypt cell proliferation compared with NC. The ATB reduced (P < 0.05) NOD1 compared with PC. The LPB increased (P < 0.05) PGLYRP4, and interferon-γ and reduced (P < 0.05) NOD1 compared with PC. The ATB and LPB reduced (P < 0.05) TNF-α and MDA compared with PC.

CONCLUSIONS

The F18+ E. coli challenge compromised intestinal health. Bacitracin increased beneficial bacteria showing a trend towards increasing the intestinal barrier function, possibly by reducing the expression of PRR genes. Lactobacillus postbiotics enhanced the immunocompetence of nursery pigs by increasing the expression of interferon-γ and PGLYRP4, and by reducing TLR4, NOD1, and CD14.

Predominance of enterotoxigenic Escherichia coli among ESBL/plasmid-mediated AmpC-producing strains isolated from diarrheic foals: a public health concern

BACKGROUND

The upsurge of diarrheagenic E. coli pathotypes carrying extended-spectrum beta-lactamases (ESBLs)/plasmid-mediated AmpC β-lactamase (pAmpC) among animals constitutes an emerging threat for humans and animals. This study investigated the burden of ESBL-/pAmpC-producing diarrheagenic E. coli among diarrheic foals and its potential public health implications. Rectal swabs were collected from 80 diarrheic foals. These swabs were processed to isolate and identify ESBL/pAmpC-producing E. coli using a selective culture medium, biochemical tests, phenotypic identification, and molecular identification of ESBL- and pAmpC-encoding genes. Moreover, all ESBL-/pAmpC-producing E. coli isolates were examined for different virulence genes related to diarrheagenic E. coli pathotypes.

RESULTS

Out of 80 examined foals, 26 (32.5%) were confirmed as ESBL-/pAmpC-producing E. coli, of which 14 (17.5%) animals carried only ESBL-producing E. coli, whereas 12 (15%) animals possessed ESBL-pAmpC-producing E. coli. The only detected diarrheagenic pathotype was enterotoxigenic, encoded by the heat-stable enterotoxin gene (ST) with a prevalence rate of 80.8% (21/26). The ST gene was further characterized where STa, STb, and STa + STb were found in one, four, and 16 strains, respectively. Moreover, all enterotoxigenic E. coli (ETEC) isolates exhibited a multidrug-resistance pattern. The phylogenetic analysis of 3 obtained partial STb sequences revealed high genetic relatedness to ETEC isolates retrieved from humans, conferring such sequences' public health significance.

CONCLUSIONS

These findings highlight that diarrheic foals could serve as a potential reservoir for multidrug-resistant ESBL-/pAmpC-producing enterotoxigenic E. coli.

Lactiplantibacillus argentoratensis AGMB00912 protects weaning mice from ETEC infection and enhances gut health

Maintaining a healthy intestinal environment, optimal epithelial barrier integrity, and balanced gut microbiota composition are essential for the growth performance of weaning pigs. We identified Lactiplantibacillus argentoratensis AGMB00912 (LA) in healthy porcine feces as having antimicrobial activity against pathogens and enhanced short-chain fatty acid (SCFA) production. Herein, we assess the protective role of LA using a weaning mouse model with enterotoxigenic Escherichia coli (ETEC) infection. LA treatment improves feed intake and weight gain and alleviates colon shortening. Furthermore, LA inhibits intestinal damage, increases the small intestine villus height compared with the ETEC group, and enhances SCFA production. Using the Kyoto Encyclopedia of Genes and Genomes and other bioinformatic tools, including InterProScan and COGNIZER, we validated the presence of SCFA-producing pathways of LA and Lactiplantibacillus after whole genome sequencing. LA mitigates ETEC-induced shifts in the gut microbiota, decreasing the proportion of Escherichia and Enterococcus and increasing SCFA-producing bacteria, including Kineothrix, Lachnoclostridium, Roseuburia, Lacrimispora, Jutongia, and Blautia. Metabolic functional prediction analysis revealed enhanced functions linked to carbohydrate, amino acid, and vitamin biosynthesis, along with decreased functions associated with infectious bacterial diseases compared to the ETEC group. LA mitigates the adverse effects of ETEC infection in weaning mice, enhances growth performance and intestinal integrity, rebalances gut microbiota, and promotes beneficial metabolic functions. These findings validate the functionality of LA in a small animal model, supporting its potential application in improving the health and growth performance of weaning pigs.

Detection and molecular characterization of major enteric pathogens in calves in central Ethiopia

BACKGROUND

Calf diarrhea is a major cause of morbidity and mortality in the livestock sector worldwide and it can be caused by multiple infectious agents. In Ethiopia, cattle are the most economically important species within the livestock sector, but at the same time the young animals suffer from high rates of morbidity and mortality due to calf diarrhea. However, studies including both screening and molecular characterization of bovine enteric pathogens are lacking. Therefore, we aimed to both detect and molecularly characterize four of the major enteric pathogens in calf diarrhea, Enterotoxigenic Escherichia coli (E. coli K99 +), Cryptosporidium spp., rotavirus A (RVA), and bovine coronavirus (BCoV) in calves from central Ethiopia. Diarrheic and non-diarrheic calves were included in the study and fecal samples were analyzed with antigen-ELISA and quantitative real-time PCR (qPCR). Positive samples were further characterized by genotyping PCRs.

RESULTS

All four pathogens were detected in both diarrheic and non-diarrheic calves using qPCR and further characterization showed the presence of three Cryptosporidium species, C. andersoni, C. bovis and C. ryanae. Furthermore, genotyping of RVA-positive samples found a common bovine genotype G10P[11], as well as a more unusual G-type, G24. To our knowledge this is the first detection of the G24 RVA genotype in Ethiopia as well as in Africa. Lastly, investigation of the spike gene revealed two distinct BCoV strains, one classical BCoV strain and one bovine-like CoV strain.

CONCLUSIONS

Our results show that Cryptosporidium spp., E. coli K99 + , RVA and BCoV circulate in calves from central Ethiopia. Furthermore, our findings of the rare RVA G-type G24 and a bovine-like CoV demonstrates the importance of genetic characterization.

Host species shapes genotype, antimicrobial resistance, and virulence profiles of enterotoxigenic Escherichia coli (ETEC) from livestock in the United States

Enterotoxigenic Escherichia coli (ETEC) are significant pathogen in both cattle and pigs, causing diarrhea in these animals and leading to economic losses in the livestock industry. Understanding the dissimilarity in genotype, antimicrobial resistance (AMR), and virulence between bovine and swine ETEC is crucial for development of targeted preventive and therapeutic approaches for livestock. However, a comprehensive study on this area remains lacking. Here, we performed whole-genome sequencing-based analyses of bovine (n = 554) and swine (n = 623) ETEC collected in the United States over a 53-year period. We identified distinct ETEC genotypes (fimH type, O antigen, H antigen, sequence type) in cattle and pigs. Furthermore, specific AMR and virulence profiles were associated with bovine and swine ETEC. Compared to swine ETEC, bovine ETEC were less diverse in genotypes and had a significantly (P < 0.001) lower number of AMR genes per isolate but higher co-occurrence of Shiga toxin and enterotoxin genes. Our results provide an overview of the key genomic differences between bovine and swine ETEC in the United States, which might be attributed to host adaptation and antibiotic usage practice. Ongoing surveillance and research are essential to monitor the genetic diversity and AMR patterns of ETEC in different host species.

IMPORTANCE

Enterotoxigenic Escherichia coli (ETEC)-associated diarrhea represent one of the most economically important diseases in the livestock industry. By analyzing over a thousand livestock-derived ETEC samples in the United States, our study unveiled a clear distinction in ETEC's genetic traits (i.e., genotypes, antimicrobial resistance [AMR], and virulence profiles) that might be tied to the different use of antibiotics in cattle and pigs, and the bacteria's adaptation to their specific animal hosts. This understanding is crucial for tailoring preventive and therapeutic strategies. It also highlights the significance of ongoing surveillance and research into the evolution of bacterial pathogens like ETEC in livestock by using advanced techniques such as whole-genome sequencing.

Role of immunomodulatory probiotics in alleviating bacterial diarrhea in piglets: a systematic review

Diarrhea is a common enteric disease in piglets that leads to high mortality and economic losses in swine production worldwide. Antibiotics are commonly used to prevent or treat diarrhea in piglets. However, irrational antibiotic use contributes to the development of resistance in bacteria and antibiotic residues in animal products, threatening public health, while causing gut microbiota dysbiosis and antibiotic-resistant bacterial infection in piglets. Therefore, the quest for alternative products (such as probiotics, prebiotics, organic acids, enzymes, essential oils, medium-chain fatty acids, zinc, and plant extracts) has recently been clearly emphasized through the increase in regulations regarding antibiotic use in livestock production. These antibiotic alternatives could lower the risk of antibiotic-resistant bacteria and meet consumer demand for antibiotic-free food. Several antibiotic alternatives have been proposed, including immunomodulatory probiotics, as candidates to reduce the need for antimicrobial therapy. Many studies have revealed that probiotics can avert and cure bacterial diarrhea by regulating the gut function and immune system of piglets. In this review, we focus on the major pathogenic bacteria causing piglet diarrhea, the research status of using probiotics to prevent and treat diarrhea, their possible mechanisms, and the safety issues related to the use of probiotics. Supplementation with probiotics is a possible alternative to antibiotics for the prevention or treatment of bacterial diarrhea in piglets. Furthermore, probiotics exert beneficial effects on feed efficiency and growth performance of piglets. Therefore, appropriate selection and strategies for the use of probiotics may have a positive effect on growth performance and also reduce diarrhea in piglets. This review provides useful information on probiotics for researchers, pig nutritionists, and the additive industry to support their use against bacterial diarrhea in piglets.

The intrinsic macrolide resistome of Escherichia coli

Intrinsic resistance to macrolides in Gram-negative bacteria is primarily attributed to the low permeability of the outer membrane, though the underlying genetic and molecular mechanisms remain to be fully elucidated. Here, we used transposon directed insertion-site sequencing (TraDIS) to identify chromosomal non-essential genes involved in Escherichia coli intrinsic resistance to a macrolide antibiotic, tilmicosin. We constructed two highly saturated transposon mutant libraries of >290,000 and >390,000 unique Tn5 insertions in a clinical enterotoxigenic strain (ETEC5621) and in a laboratory strain (K-12 MG1655), respectively. TraDIS analysis identified genes required for growth of ETEC5621 and MG1655 under 1/8 MIC (n = 15 and 16, respectively) and 1/4 MIC (n = 38 and 32, respectively) of tilmicosin. For both strains, 23 genes related to lipopolysaccharide biosynthesis, outer membrane assembly, the Tol-Pal system, efflux pump, and peptidoglycan metabolism were enriched in the presence of the antibiotic. Individual deletion of genes (n = 10) in the wild-type strains led to a 64- to 2-fold reduction in MICs of tilmicosin, erythromycin, and azithromycin, validating the results of the TraDIS analysis. Notably, deletion of surA or waaG, which impairs the outer membrane, led to the most significant decreases in MICs of all three macrolides in ETEC5621. Our findings contribute to a genome-wide understanding of intrinsic macrolide resistance in E. coli, shedding new light on the potential role of the peptidoglycan layer. They also provide an in vitro proof of concept that E. coli can be sensitized to macrolides by targeting proteins maintaining the outer membrane such as SurA and WaaG.

Effects of a Nutraceutical Treatment on the Intestinal Microbiota of Sled Dogs

Dog sledding is the main discipline of working dogs on snow, consisting of a team of dogs pulling a sled under the guidance of the owner. To carry out this sport, dogs must have adequate nutrition and vitamin and antioxidant supplementation to ensure that the physical effort is optimal. The present study evaluated the effect that sporting activity and stress have on the canine intestinal microbiota by dividing the dogs into two groups: a control group that did not take any nutraceutical products and the treated group to which a nutraceutical product was administered. The nutraceutical administered in this study is used in all cases of canine intestinal dysbiosis in which it is essential to quickly restore a balanced intestinal microbiota. The results obtained show that in dogs not taking the nutraceutical, there is an increase in bacteria, such as Streptococcus spp. and E. coli, considered enteropathogenic to the detriment of beneficial bacterial species such as Faecalibacterium spp., Turicibacter spp., Blautia spp., Fusobacterium spp., and Clostridium hiranonis. Instead, the group of dogs treated with nutraceutical displays a lower amount of enteropathogenic bacteria and a great increase in the other bacterial species considered beneficial for the animal's health. The results obtained in the present study show that Microbiotal cane® can be used in dogs subject to intense sporting activity by preventing severe alterations at intestinal ecosystem levels by maintaining intestinal bacterial composition as balanced as possible.

Diversity and phage sensitivity to phages of porcine enterotoxigenic Escherichia coli

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.

Bacillus subtilis Feed Supplementation Combined with Oral E. coli Immunization in Sows as a Tool to Reduce Neonatal Diarrhea in Piglets

To investigate the effects of B. subtilis on the specific immune response of lactating sows to E. coli and the diarrhea rate in suckling piglets, thirty large white sows with similar farrowing dates were randomly divided into two groups: a feedback feeding (i.e., feeding a homogenate of intestinal contents and tissues from E. coli-infected piglets to sows; FB) group and a feedback feeding with B. subtilis (FB + BS) group. Serum, colostrum, and intestinal tissues from sows and piglets were collected to assess the immune response and intestinal barrier function at weaning. T and B cells from Peyer's patches (PPs) and mesenteric lymph nodes (MLNs) in lactating mice (with treatments consistent with the sows') were isolated to explore the underlying mechanism. The results showed that, compared with the FB group, the reproductive performance of sows and the growth performance of their offspring were effectively improved in the FB + BS group. Moreover, the levels of IgG/IgA and those of IgG/IgA against E. coli in the serum and colostrum of sows in the FB+BS group were increased (p < 0.05). Meanwhile, the ratio of CD4+/CD8+, CD4+CXCR5+PD1+, and B220+IgA+ cells in MLNs and PPs, and the IgA levels in the mammary glands of mice, were also increased in the FB + BS group (p < 0.05). Notably, in suckling piglets in the FB + BS group, the diarrhea rate was decreased (p < 0.05), and the intestinal barrier function and intestinal flora composition at weaning were significantly improved. Overall, these results indicated that B. subtilis feed supplementation combined with feedback feeding in pregnant and lactating sows can reduce diarrhea in suckling piglets by enhancing the maternal immune response against E. coli and intestinal barrier function in their offspring, improving survival rates and pre-weaning growth.

Effects of Luteolin in an In Vitro Model of Porcine Intestinal Infections

Intestinal infections caused by Escherichia coli and Salmonella enterica pose a huge economic burden on the swine industry that is exacerbated by the development of antimicrobial resistance in these pathogens, thus raising the need for alternative prevention and treatment methods. Our aim was to test the beneficial effects of the flavonoid luteolin in an in vitro model of porcine intestinal infections. We infected the porcine intestinal epithelial cell line IPEC-J2 with E. coli and S. enterica subsp. enterica serovar Typhimurium (106 CFU/mL) with or without previous, concurrent, or subsequent treatment with luteolin (25 or 50 µg/mL), and measured the changes in the reactive oxygen species and interleukin-6 and -8 levels of cells. We also tested the ability of luteolin to inhibit the adhesion of bacteria to the cell layer, and to counteract the barrier integrity damage caused by the pathogens. Luteolin was able to alleviate oxidative stress, inflammation, and barrier integrity damage, but it could not inhibit the adhesion of bacteria to IPEC-J2 cells. Luteolin is a promising candidate to be used in intestinal infections of pigs, however, further studies are needed to confirm its efficacy. The use of luteolin in the future could ultimately lead to a reduced need for antibiotics in pig production.

Baicalin-aluminum complex on the regulation of IPEC-1 infected with enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is the main bacterial cause of diarrhea in weaned piglets. Baicalin-aluminum (BA) complex is the main active ingredient of Scutellaria baicalensis Georgi extracted-aluminum complex, which has been used to treat diarrhea in weaning piglets, however the underlying mechanism remains unclear. To investigate the effects of the BA complex on the regulation of porcine intestinal epithelial (IPEC-1) cells infected with ETEC, IPEC-1 cells were incubated with an ETEC bacterial strain at a multiplicity of infection of 1 for 6 h and then treated with different concentrations of the BA complex for 6 h. ETEC infection increased the levels of cAMP and cGMP, upregulated CFTR (cystic fibrosis transmembrane conductance regulator) mRNA, and downregulated NHE4 mRNA in IPEC-1 cells. Treatment with the BA complex inhibited ETEC adhesion and the production of cAMP and cGMP, reduced CFTR mRNA expression, and increased NHE4 mRNA expression. Overall, the BA complex weakened the adhesion of ETEC to IPEC-1 cells, and inhibited cAMP/cGMP-CFTR signaling in IPEC-1 cells.

Microbiome and metabolome analyses reveal significant alterations of gut microbiota and bile acid metabolism in ETEC-challenged weaned piglets by dietary berberine supplementation

This study mainly investigated the effects of berberine (BBR) on the bile acid metabolism in gut-liver axis and the microbial community in large intestine of weaned piglets challenged with enterotoxigenic Escherichia coli (ETEC) by microbiome and metabolome analyses. Sixty-four piglets were randomly assigned to four groups including Control group, BBR group, ETEC group, and BBR + ETEC group. Dietary BBR supplementation upregulated the colonic mRNA expression of Occludin, Claudin-5, trefoil factor 3 (TFF3), and interleukin (IL)-10, and downregulated colonic IL-1β and IL-8 mRNA expression in piglets challenged with ETEC K88 (p < 0.05). The hepatic non-targeted metabolome results showed that dietary BBR supplementation enriched the metabolic pathways of primary bile acid biosynthesis, tricarboxylic acid cycle, and taurine metabolism. The hepatic targeted metabolome analyses showed that BBR treatment increased the hepatic concentrations of taurocholic acid (TCA) and taurochenodeoxycholic acid (TDCA), but decreased the hepatic cholic acid (CA) concentration (p < 0.05). Further intestinal targeted metabolome analyses indicated that the deoxycholic acid (DCA), hyocholic acid (HCA), 7-ketodeoxycholic acid (7-KDCA), and the unconjugated bile acid concentrations in ileal mucosa was decreased by dietary BBR treatment (p < 0.05). Additionally, BBR treatment significantly upregulated the hepatic holesterol 7 α-hydroxylase (CYP7A1) and sterol 27-hydroxylase (CYP27A1) mRNA expression, and upregulated the ileal mRNA expression of farnesoid X receptor (FXR) and apical sodium-dependent bile acid transporter (ASBT) as well as the colonic mRNA expression of FXR, fibroblast growth factor19 (FGF19), takeda G protein-coupled receptor 5 (TGR5) and organic solute transporters beta (OST-β) in piglets (p < 0.05). Moreover, the microbiome analysis showed that BBR significantly altered the composition and diversity of colonic and cecal microbiota community, with the abundances of Firmicutes (phylum), and Lactobacillus and Megasphaera (genus) significantly increased in the large intestine of piglets (p < 0.05). Spearman correlation analysis showed that the relative abundances of Megasphaera (genus) were positively correlated with Claudin-5, Occludin, TFF3, and hepatic TCDCA concentration, but negatively correlated with hepatic CA and glycocholic acid (GCA) concentration (p < 0.05). Moreover, the relative abundances of Firmicute (phylum) and Lactobacillus (genus) were positively correlated with hepatic TCDCA concentration (p < 0.05). Collectively, dietary BBR supplementation could regulate the gut microbiota and bile acid metabolism through modulation of gut-liver axis, and attenuate the decreased intestinal tight junction expression caused by ETEC, which might help maintain intestinal homeostasis in weaned piglets.

Construction of the ETECFinder database for the characterization of enterotoxigenic Escherichia coli (ETEC) and revision of the VirulenceFinder web tool at the CGE website

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.

Two Novel Bacteriophage Species Against Hybrid Intestinal Pathogenic Escherichia coli/Extraintestinal Pathogenic Escherichia coli Strains

Background

Colibacillosis caused by Escherichia coli is one of the main problems in the swine industry. In addition, the emergence of antimicrobial resistance and the combination of virulence genes among pathotypes have led to the emergence of more virulent pathogenic E. coli strains. Phage therapy has become a promising approach to address these issues.

Materials and Methods

Virulence genes for intestinal pathogenic E. coli (IPEC) and extraintestinal pathogenic E. coli (ExPEC) were investigated in pathogenic E. coli isolated from pigs. In addition, two potential phages, vB_EcoM-RPN187 and vB_EcoM-RPN226, isolated in our previous study, were further characterized in this study.

Results

Both phages were lytic and were highly effective at 20-37°C. Interestingly, they infected the hybrid IPEC/ExPEC strains. vB_EcoM-RPN187 and vB_EcoM-RPN226 possess 167 kbp of linear double-stranded DNA without virulence or antibiotic resistance genes and may be classified as new phage species in the genera Mosigvirus and Tequatrovirus, respectively.

Conclusion

Both phages could be promising candidates for phage therapy against pathogenic E. coli.

The immune response of pregnant sow after vaccination with crude fimbriae (F4) extracts vaccine and immunoprotection of nursery pig against pathogenic E. coli (F4+ETEC)

BACKGROUND

Neonatal and post-weaning diarrhea is a concern disease caused by enterotoxigenic Escherichia coli fimbriae F4 (F4+ETEC) in pig farms. Diarrhea outbreaks are often severe and costly due to the high prevalence and spread of the disease within the same herd. Vaccine is one of strategic solution in protecting pig against F4+ETEC infection in particular pig farm. In present study, we conducted two trials of vaccination with crude F4 fimbriae extract vaccine in pregnant sow and nursery pigs.

METHODS

In experiment 1 (20 sows; non-vaccinated control, n=10), we vaccinated pregnant sows (n=10) twice at 4 wk and 2 wk before farrowing and evaluated impact of vaccination on maternal immunity. The sow serum and colostrum were collected before vaccination, 2 and 4 weeks after vaccination, 6 hours after farrowing, respectively, and the piglet's serum from both groups (2 piglet/sow, 10 piglets from each group) were also collected on 3 days old to measure F4 specific IgG, F4 specific IgA using in house ELISA kit. In experiment 2, to optimize doses and dosage of candidate vaccine in piglets, 18 piglets (3 piglets/group) were allocated into five immunized groups and one control group (unimmunized group), we immunized piglets twice at 4 and 6 weeks old with difference doses (i.e., 0, 50, 100, 150, 200 µg), and for a dose 150 µg, we immunized with two dosages at 1 ml and 2 ml. Piglets were challenged with a 3 ml dose of 3 × 109 CFU/ml bacterial culture of enterotoxigenic Escherichia coli (F4+ETEC) in order to evaluate the efficacy of vaccine. After challenging, the clinical sign of the piglets was daily observed and the rectal swab was performed every day for investigation of the fecal shedding of Escherichia coli (F4+ETEC) by using PCR technique. Serum were collected before, 2 and 4 weeks after vaccination and 1 week after challenge to measure F4 specific IgG, F4 specific IgA using in house ELISA kit and cytokines levels (i.e., IL-1 beta, IL-6, IL-8 and TNF alpha) before and 1 week after challenge using commercial ELISA kit.

RESULTS

The levels of antibody results showed that in experiment 1, the anti-F4 antibody levels both F4 specific IgG and F4 specific IgA in serum and colostrum of vaccinated sow increased significantly after vaccination. The piglets of immunized sows have antibody level both F4 specific IgG and F4 specific IgA in their serum higher than those piglets of unimmunized sows significantly (p < 0.01). In experiment 2, irrespective of different doses and dosage, there is no difference in term of F4 specific IgG and F4 specific IgA levels among immunized groups. However, all of vaccinated piglets showed F4 specific IgG and F4 specific IgA levels higher and the elimination of Escherichia coli (F4+ETEC) in feces post challenge faster (< 3 days) than unvaccinated group (> 5 days). For cytokines levels, a higher level of IL-1 beta, IL-6, IL-8 and TNF alpha at 1 week after challenge in vaccinated groups was found when compared with the levels in non-vaccinated group.

CONCLUSIONS

Our results suggest that crude F4 fimbriae extract autogenous vaccine is a candidate vaccine for protecting piglets against diarrhea disease caused by enterotoxigenic Escherichia coli (F4+ETEC) and vaccination the pregnant sow twice before farrowing is one of strategies to provide maternal derived antibody to the newborn piglets for against enterotoxigenic Escherichia coli (F4+ETEC) during early life.

Seed-specific expression of porcine verotoxigenic Escherichia coli antigens in tobacco plants as a potential model of edible vaccines

Vaccines can reduce the use of antibiotics by preventing specific infective diseases in pigs. Plant-based edible vaccines are particularly attractive because, upon oral ingestion via feed, they can elicit the local immune system against a foreign disease-causing organism. The aim of this study was to engineer two different independent lines of tobacco plants for the seed-specific expression of immunogenic proteins of VTEC as a model of an edible vaccine. For each antigen, fifty Nicotiana tabacum L. cv Xanthi leaf disks were transformed by agroinfection for the seed-specific expression of the structural parts of the fimbrial subunit FedF of F18 and the B-subunit of Vt2e genes. The synthetic genes, optimized by the codon adaptation index for their expression in tobacco, were inserted into expression cassettes under the control of β-conglycinin promoter. Regenerated tobacco plants (T0) were characterized by molecular and immunoenzymatic techniques. Our results showed that both FedF and Vt2eB genes were integrated into tobacco genome efficiently (> 80%) and they are also maintained in the second generation (T1). Western blotting analyses carried out on the positive producing lines, showed the tissue-specific expression in seeds and the temporal protein accumulation in the mid-late maturation phases. The enzyme-linked immunosorbent assay showed seed expression levels of 0.09 to 0.29% (from 138 to 444 µg/g of seeds) and 0.21 to 0.43% (from 321 to 658 µg/g of seeds) of total soluble protein for the FedF and Vt2eB antigens, respectively. This study confirmed the seed-specific expression of the selected antigens in plant seeds. The expression level is suitable for seed-based edible vaccination systems, which could represent a cost-effective way to prevent VTEC infection. Our findings encourage further in vivo studies focused on the activation of the local immune response.

Metallo-Glycodendrimeric Materials against Enterotoxigenic Escherichia coli

Conjugation of carbohydrates to nanomaterials has been extensively studied and recognized as an alternative in the biomedical field. Dendrimers synthesized with mannose at the end group and with entrapped zero-valent copper/silver could be a potential candidate against bacterial proliferation. This study is aimed at investigating the bactericidal activity of metal-glycodendrimers. The Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction was used to synthesize a new mannosylated dendrimer containing 12 mannopyranoside residues in the periphery. The enterotoxigenic Escherichia coli fimbriae 4 (ETEC:F4) viability, measured at 600 nm, showed the half-inhibitory concentration (IC50) of metal-free glycodendrimers (D), copper-loaded glycodendrimers (D:Cu) and silver-loaded glycodendrimers (D:Ag) closed to 4.5 × 101, 3.5 × 101 and to 1.0 × 10-2 µg/mL, respectively, and minimum inhibitory concentration (MIC) of D, D:Cu and D:Ag of 2.0, 1.5 and 1.0 × 10-4 µg/mL, respectively. The release of bacteria contents onto broth and the inhibition of ETEC:F4 biofilm formation increased with the number of metallo-glycodendrimer materials, with a special interest in silver-containing nanomaterial, which had the highest activity, suggesting that glycodendrimer-based materials interfered with bacteria-bacteria or bacteria-polystyrene interactions, with bacteria metabolism and can disrupt bacteria cell walls. Our findings identify metal-mannose-dendrimers as potent bactericidal agents and emphasize the effect of entrapped zero-valent metal against ETEC:F4.

Multidrug-resistant Escherichia coli strains isolated from swine manure biofertilizer in Brazil

Escherichia coli is one of the key bacteria responsible for a variety of diseases in humans and livestock-associated infections around the globe. It is the leading cause of mortality in neonatal and weaned piglets in pig husbandry, causing diarrhea and significant harm to the industry. Furthermore, the frequent and intensive use of antimicrobials for the prevention of diseases, particularly gastrointestinal diseases, may promote the selection of multidrug-resistant (MDR) strains. These resistant genotypes can be transmitted through the excrement of animals, including swine. It is common practice to use porcine manure processed by biodigesters as fertilizer. This study aimed to examine the antimicrobial susceptibility, the presence of virulence genes frequently associated with pathotypes of intestinal pathogenic E. coli (InPEC), and antimicrobial resistance genes (ARGs) of 28 E. coli isolates collected from swine manure fertilizers. In addition, the enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) technique was used to investigate the genetic relationship among the strains. Using disk diffusion, the antimicrobial susceptibility profiles of the strains were determined. Using polymerase chain reaction (PCR), 14 distinct virulence genes associated with the most prevalent diarrhea and intestinal pathogenic E. coli (DEC/InPEC) and five ARGs were analyzed. All isolates tested positive for multidrug resistance. There was no detection of any of the 14 virulence genes associated with InPECs, indicating the presence of an avirulent commensal microbiota. Molecular classification by ERIC-PCR revealed that the majority of isolates (27 isolates) coalesced into a larger cluster with a genetic similarity of 47.7%; only one strain did not cluster in this cluster, indicating a high level of genetic diversity among the analyzed isolates. Thus, it is of the utmost importance to conduct epidemiological surveillance of animal breeding facilities in order to determine their microbiota and formulate plans to reduce the use of antimicrobials and improve animal welfare.

miR-329b-5p Affects Sheep Intestinal Epithelial Cells against Escherichia coli F17 Infection

Diarrhea is the most common issue in sheep farms, typically due to pathogenic Escherichia coli (E. coli) infections, such as E. coli F17. microRNA, a primary type of non-coding RNA, has been shown to be involved in diarrhea caused by pathogenic E. coli. To elucidate the profound mechanisms of miRNA in E. coli F17 infections, methods such as E. coli F17 adhesion assay, colony counting assay, relative quantification of bacterial E. coli fimbriae gene expression, indirect immune fluorescence (IF), Cell Counting Kit-8 (CCK-8), 5-ethynyl-2'-deoxyuridine (EdU), Western blotting (WB), and scratch assay were conducted to investigate the effect of miR-329b-5p overexpression/knock-down on E. coli F17 susceptibility of sheep intestinal epithelial cells (IECs). The findings indicated that miR-329b-5p enhances the E. coli F17 resistance of sheep IECs to E.coli F17 by promoting adhesion between E. coli F17 and IEC, as well as IEC proliferation and migration. In summary, miR-329b-5p plays a crucial role in the defense of sheep IECs against E. coli F17 infection, providing valuable insights into its mechanism of action.

Protecting the piglet gut microbiota against ETEC-mediated post-weaning diarrhoea using specific binding proteins

Post-weaning diarrhoea (PWD) in piglets presents a widespread problem in industrial pig production and is often caused by enterotoxigenic E. coli (ETEC) strains. Current solutions, such as antibiotics and medicinal zinc oxide, are unsustainable and are increasingly being prohibited, resulting in a dire need for novel solutions. Thus, in this study, we propose and evaluate a protein-based feed additive, comprising two bivalent heavy chain variable domain (VHH) constructs (VHH-(GGGGS)3-VHH, BL1.2 and BL2.2) as an alternative solution to manage PWD. We demonstrate in vitro that these constructs bind to ETEC toxins and fimbriae, whilst they do no affect bacterial growth rate. Furthermore, in a pig study, we show that oral administration of these constructs after ETEC challenge reduced ETEC proliferation when compared to challenged control piglets (1-2 log10 units difference in gene copies and bacterial count/g faeces across day 2-7) and resulted in week 1 enrichment of three bacterial families (Prevotellaceae (estimate: 1.12 ± 0.25, q = 0.0054), Lactobacillaceae (estimate: 2.86 ± 0.52, q = 0.0012), and Ruminococcaceae (estimate: 0.66 ± 0.18, q = 0.049)) within the gut microbiota that appeared later in challenged control piglets, thus pointing to an earlier transition towards a more mature gut microbiota. These data suggest that such VHH constructs may find utility in industrial pig production as a feed additive for tackling ETEC and reducing the risk of PWD in piglet populations.

Colonization factors of human and animal-specific enterotoxigenic Escherichia coli (ETEC)

Colonization factors (CFs) are major virulence factors of enterotoxigenic Escherichia coli (ETEC). This pathogen is among the most common causes of bacterial diarrhea in children in low- and middle-income countries, travelers, and livestock. CFs are major candidate antigens in vaccines under development as preventive measures against ETEC infections in humans and livestock. Recent molecular studies have indicated that newly identified CFs on human ETEC are closely related to animal ETEC CFs. Increased knowledge of pathogenic mechanisms, immunogenicity, regulation, and expression of ETEC CFs, as well as the possible spread of animal ETEC to humans, may facilitate the future development of ETEC vaccines for humans and animals. Here, we present an updated review of CFs in ETEC.

Ovomucin Hydrolysates Reduce Bacterial Adhesion and Inflammation in Enterotoxigenic Escherichia coli (ETEC) K88-Challenged Intestinal Epithelial Cells

Enterotoxigenic Escherichia coli (ETEC) K88 is the most common cause of diarrhea in neonatal and postweaning pigs. After adhering to small intestinal epithelial cells via glycoprotein receptor recognition, the pathogen can produce enterotoxins, impair intestinal integrity, trigger watery diarrhea, and induce inflammation via nuclear factor κB (NF-κB) and mitogen-activated protein kinase phosphatase (MAPK) pathways. Inhibiting ETEC K88 adhesion to cell surfaces by interfering with the receptor-fimbriae recognition provides a promising strategy to prevent the initiation and progression of infection. Ovomucin is a highly glycosylated protein in chicken egg white with diverse bioactivities. Ovomucin hydrolysates prepared by the enzymes Protex 26L (OP) and pepsin/pancreatin (OPP) were previously revealed to prevent adhesion of ETEC K88 to IPEC-J2 cells. Herein, we investigated the protective effects of ovomucin hydrolysates on ETEC K88-induced barrier integrity damage and inflammation in IPEC-J2 and Caco-2 cells. Both hydrolysates inhibited ETEC K88 adhesion to cells and protected epithelial cell integrity by restoring transepithelial electronic resistance (TEER) values. Removing sialic acids in the hydrolysates reduced their antiadhesive capacities. Ovomucin hydrolysates suppressed ETEC-induced activation of NF-κB and MAPK signaling pathways in both cell lines. The ability of ETEC K88 in activating calcium/calmodulin-dependent protein kinase 2 (CaMK II), elevating intracellular Ca2+ concentration, and inducing oxidative stress was attenuated by both hydrolysates. In conclusion, this study demonstrated the potential of ovomucin hydrolysates to prevent ETEC K88 adhesion and alleviate inflammation and oxidative stress in intestinal epithelial cells.

Production of a new tetravalent vaccine targeting fimbriae and enterotoxin of enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) is an important type of pathogenic bacteria that causes diarrhea in pigs. The objective of this study was to prepare a novel tetravalent vaccine to effectively prevent piglet diarrhea caused by E. coli. In order to realize the production of K88ac-K99-ST1-LTB tetravalent inactivated vaccine, the biological characteristics, stability, preservation conditions, and safety of the recombinant strain BL21(DE3) (pXKKSL4) were studied, and the vaccine efficacy and minimum immune dose were measured. The results indicated that the biological characteristics, target protein expression, and immunogenicity of the 1st to 10th generations of the strain were stable. Therefore, the basic seed generation was preliminarily set as the 1st to 10th generations. The results of the efficacy tests showed that the immune protection rate could reach 90% with 1 minimum lethal dose (MLD) virulent strain attack in mice. The immunogenicity was stable, and the minimum immune dose was 0.1 mL per mouse. Our research showed that the genetically engineered vaccine developed in this way could prevent piglet diarrhea caused by enterotoxigenic E. coli through adhesin and enterotoxin. In order to realize industrial production of the vaccine as soon as possible, we conducted immunological tests and production process research on the constructed K88ac-K99-ST1-LTB tetravalent inactivated vaccine. The results of this study provide scientific experimental data for the commercial production of vaccines and lay a solid foundation for their industrial production.

Preparation of Bispecific IgY-scFvs Inhibition Adherences of Enterotoxigenic Escherichia coli (K88 and F18) to Porcine IPEC-J2 Cell

Enterotoxigenic Escherichia coli (ETEC) strains are significant contributors to postweaning diarrhea in piglets. Of the ETEC causing diarrhea, K88 and F18 accounted for 92.7%. Despite the prevalence of ETEC K88 and F18, there is currently no effective vaccine available due to the diversity of these strains. This study presents an innovative approach by isolating chicken-derived single-chain variable fragment antibodies (scFvs) specific to K88 and F18 fimbrial antigens from chickens immunized against these ETEC virulence factors. These scFvs effectively inhibited adhesion of K88 and F18 to porcine intestinal epithelial cells (IPEC-J2), with the inhibitory effect demonstrating a dose-dependent increase. Furthermore, a bispecific scFv was designed and expressed in Pichia pastoris. This engineered construct displayed remarkable potency; at a concentration of 25.08 μg, it significantly reduced the adhesion rate of ETEC strains to IPEC-J2 cells by 72.10% and 69.11% when challenged with either K88 or F18 alone. Even in the presence of both antigens, the adhesion rate was notably decreased by 57.92%. By targeting and impeding the initial adhesion step of ETEC pathogenesis, this antibody-based intervention holds promise as a potential alternative to antibiotics, thereby mitigating the risks associated with antibiotic resistance and residual drug contamination in livestock production. Overall, this study lays the groundwork for the development of innovative treatments against ETEC infections in piglets.

Characterization of Antimicrobial Resistance in Escherichia coli Isolated from Diarrheic and Healthy Weaned Pigs in Catalonia

Postweaning diarrhea (PWD) is a multifactorial concern in the swine industry that leads to high antibiotic consumption, usually without testing susceptibility, increasing the risk of the selection of Escherichia coli-resistant strains. In this study, 251 E. coli strains isolated from fecal samples of diarrheic (n = 148) and apparently healthy piglets (n = 103) in farms in Catalonia were tested against their susceptibility to fourteen different antimicrobials. The phenotypic antimicrobial resistance (AMR) testing revealed high levels of AMR, with 41.4% of the isolates presenting a multidrug-resistant (MDR) profile. More specifically, resistance to class D (prudence) antimicrobials such as erythromycin (99.6%), amoxicillin (95.2%), streptomycin (91.6%), tetracycline (88.8%), lincospectin (64.5%), and sulfamethoxazole/trimethoprim (60%) was very high, as well as to class C (caution) antimicrobials such as florfenicol (45%). A special concern was observed for antimicrobial category B (restrict), like quinolones and colistin, that both presented a high rate of resistance. Colistin use was substantially reduced in Spain, but resistance is still present in weaned pigs, presenting a MIC90 of 4 μg/mL. This suggests that reducing antibiotic use is not enough to eliminate this AMR. Finally, it was found that piglets suffering diarrhea were more commonly carriers of MDR strains than the healthy ones (49.3% vs. 35%, p = 0.031). Therefore, given the high rates of resistance to the most commonly used antimicrobials, especially in diseased pigs, a new non-antibiotic-based approach should be implemented for the management of PWD.

A Comprehensive Review of the Common Bacterial Infections in Dairy Calves and Advanced Strategies for Health Management

Dairy farming faces a significant challenge of bacterial infections in dairy calves, which can have detrimental effects on their health and productivity. This review offers a comprehensive overview of the most prevalent bacterial infections in dairy calves, including Escherichia coli, Salmonella typhimurium, Salmonella dublin, Salmonella enterica, Clostridium perfringens, Pasteurella multocida, Listeria monocytogenes, Mycoplasma bovis, and Haemophilus somnus. These pathogens can cause various clinical signs and symptoms, leading to diarrhea, respiratory distress, septicemia, and even mortality. Factors such as management practices, environmental conditions, and herd health influence the incidence and severity of the infections. Efficient management and prevention strategies include good colostrum and nutrient feeding, early detection, appropriate treatment, hygiene practices, and supportive care. Regular health monitoring and diagnostic tests facilitate early detection and intervention. The use of antibiotics should be judicious to prevent antimicrobial resistance and supportive care such as fluid therapy and nutritional support promotes recovery. Diagnostic methods, including immunological tests, culture, polymerase chain reaction (PCR), and serology, aid in the identification of specific pathogens. This review also explores recent advancements in the diagnosis, treatment, and prevention of bacterial infections in dairy calves, providing valuable insights for dairy farmers, veterinarians, and researchers. By synthesizing pertinent scientific literature, this review contributes to the development of effective strategies aimed at mitigating the impact of bacterial infections on the health, welfare, and productivity of young calves. Moreover, more research is required to enhance the understanding of the epidemiology and characterization of bacterial infections in dairy calves.

In Vitro Assessment of Postbiotic and Probiotic Commercial Dietary Supplements Recommended for Counteracting Intestinal Dysbiosis in Dogs

Many environmental aspects influence the preservation of a beneficial microbiome in dogs, and gut dysbiosis occurs when imbalances in the intestinal ecosystem cause functional changes in the microbial populations. The authors evaluated the effects of two specific commercial dietary supplements: a combination of a postbiotic and prebiotics (Microbiotal cane®) and a probiotic product (NBF 1®) recommended for counteracting intestinal dysbiosis in dogs, on the gut canine microbiota composition and its metabolic activities (production of short-chain fatty acids). The investigation was performed using an in vitro fermentation system inoculated with dog fecal samples. Microbiotal cane® promoted a more immediate increase in Lactobacillus spp. after the first 6 h of fermentation, whereas NBF 1® promoted the increase at the end of the process only. The two supplements supported an increase in the Bifidobacterium spp. counts only after 24 h. The in vitro abilities of Microbiotal cane® and NBF 1® to increase selectively beneficial bacterial groups producing acetic, propionic, and butyric acids suggest a possible positive effect on the canine gut microbiota, even if further in vivo studies are needed to confirm the beneficial effects on the intestinal health.

A microencapsulated blend of botanicals supports weaning piglets during a lipopolysaccharide challenge by modulating liver inflammation and intestinal integrity

This study examined the action of a blend of botanicals (BOT) against lipopolysaccharide (LPS)-induced inflammation on cultured hepatocytes and weaning piglets. In vitro studies examined HepG2 cells treated with BOT and challenged with Escherichiacoli LPS for 8 d. BOT treatment reduced IL-6 concentration in cell culture media across time (P < 0.05) and decreased pro-inflammatory cytokine expression on days 1 and 8 of experiment (TNFα, IL-1β; P < 0.05). BOT also increased the expression of antioxidant enzymes (GPX-2, SOD, CAT) on day 8 (P < 0.05), which was supported by lowered reactive oxygen species concentration after LPS challenge (P < 0.1). The in vivo study was conducted with 72 weaning pigs, allotted into 24 pens and divided into 3 groups: a negative control (CTR-, basal diet), a challenged control (CTR+) that received an intraperitoneal injection of E. coli O55:B5 LPS on days 14 and 16, and a challenged treated group which received a diet containing 1.5 g/kg of microencapsulated BOT (BOT+) for the whole duration of the study. Growth performance was determined weekly and, on days 21 (1 animal per pen) and 28 (remaining animals), pigs were sacrificed to collect liver and jejunal tissues. After the challenge, BOT+ pigs had increased BW on days 21 (P < 0.05) and 28 (P < 0.1) compared to CTR+. Similar improvements in average daily gain and FCR on days 14 to 21 (P < 0.05) and 21 to 28 (P < 0.1) were also seen in BOT+ group. In the liver, compared to CTR+ pigs, BOT+ pigs had downregulated expression of TLR-4, IL-6, IFN-γ on day 21 (P < 0.05), and TLR-4, TNF-α, IL-8 on day 28 (P < 0.05). BOT+ also increased GPX-2 expression on days 21 and 28 (P < 0.05), while also upregulating SOD-1 and SOD-2 on day 21 (P < 0.05) and CAT on day 28 (P < 0.05) compared to CTR+. In the jejunum, BOT+ reduced inflammation by affecting cytokine expression (P < 0.05) and increasing the expression of tight-junction proteins, ZO-1 on day 21 and CLD-1 on day 28 (P < 0.05). Furthermore, BOT+ pigs had lower crypt depth on days 21 (P < 0.1) and 28 (P < 0.05), and increased villi-to-crypt ratio on days 21 and 28 (P < 0.05). By day 28, BOT+ intestinal measurements were restored to values similar to the CTR-. Finally, BOT+ also reduced mast cell activation on day 21 (P < 0.05) compared to CTR+. Considering all the findings, BOT controlled inflammatory activation and oxidative stress in liver cells, enhanced intestinal integrity, and as a result improved the growth performance of weaning piglets challenged with LPS.

Enterotoxigenic Escherichia coli heat labile enterotoxin affects neutrophil effector functions via cAMP/PKA/ERK signaling

Enterotoxigenic Escherichia coli (ETEC) are a major cause of diarrheal illness in humans and animals, induced by enterotoxins produced by these pathogens. Despite the crucial role of neutrophils in combatting bacterial infections, our understanding of how enterotoxins impact neutrophil function is limited. To address this knowledge gap, we used heat-labile enterotoxin (LT) and heat-stable enterotoxin a (STa) to investigate their impact on the effector functions of neutrophils. Our study reveals that pSTa does not exert any discernible effect on the function of neutrophils. In contrast, LT altered the migration and phagocytosis of neutrophils and induced the production of inflammatory factors via activation of cAMP/PKA and ERK1/2 signaling. LT also attenuated the release of neutrophil extracellular traps by neutrophils via the PKA signaling pathway. Our findings provide novel insights into the impact of LT on neutrophil function, shedding light on the underlying mechanisms that govern its immunoregulatory effects. This might help ETEC in subverting the immune system and establishing infection.

ArcA positively regulates the expression of virulence genes and contributes to virulence of porcine Shiga toxin-producing enterotoxigenic Escherichia coli

IMPORTANCE

Enterotoxigenic Escherichia coli (ETEC) cause severe diarrhea in humans and animals, leading to death and huge economic loss worldwide. Thus, elucidation of ETEC's pathogenic mechanisms will provide powerful data for the discovery of drugs serving as prevention or therapeutics against ETEC-caused diarrheal diseases. Here, we report that ArcA plays an essential role in the pathogenicity and virulence regulation in ETEC by positively regulating the expression of several key virulence factors including F18 fimbriae, heat-labile and heat-stable toxins, Shiga toxin 2e, and hemolysin, under microaerobic conditions and in vivo. Moreover, we found that positive regulation of several virulence genes by ArcA requires a global repressor H-NS (histone-like nucleoid structuring), implying that ArcA may exert positive effects by antagonizing H-NS. Collectively, our data established a key role for ArcA in the pathogenicity of porcine ETEC and ETEC strains isolated from human infections. Moreover, our work reveals another layer of regulation in relation to oxygen control of virulence factors in ETEC.

The diverse landscape of AB5-type toxins

AB5-type toxins are a group of secreted protein toxins that are central virulence factors for bacterial pathogens such as Shigella dysenteriae, Vibrio cholerae, Bordetella pertussis, and certain lineages of pathogenic Escherichia coli and Salmonella enterica. AB5 toxins are composed of an active (A) subunit that manipulates host cell biology in complex with a pentameric binding/delivery (B) subunit that mediates the toxin's entry into host cells and its subsequent intracellular trafficking. Broadly speaking, all known AB5-type toxins adopt similar structural architectures and employ similar mechanisms of binding, entering and trafficking within host cells. Despite this, there is a remarkable amount of diversity amongst AB5-type toxins; this includes different toxin families with unrelated activities, as well as variation within families that can have profound functional consequences. In this review, we discuss the diversity that exists amongst characterized AB5-type toxins, with an emphasis on the genetic and functional variability within AB5 toxin families, how this may have evolved, and its impact on human disease.

A Virus-like Particle-Based F4 Enterotoxigenic Escherichia coli Vaccine Is Inhibited by Maternally Derived Antibodies in Piglets but Generates Robust Responses in Sows

F4-positive enterotoxigenic Escherichia coli is associated with diarrhea and poor growth outcomes in neonatal and newly weaned piglets and is thus a major economic and welfare burden in the swine industry. Vaccination of sows with F4 fimbriae protects against the neonatal disease via passive transfer of maternal immunity. However, this strategy does not protect against infection post-weaning. Consequently, prevention and treatment methods in weaner pigs heavily rely on the use of antimicrobials. Therefore, in order to reduce antimicrobial consumption, more effective prophylactic alternatives are needed. In this study, we describe the development of a capsid virus-like particle (cVLP)-based vaccine targeting the major F4 fimbriae subunit and adhesion molecule, FaeG, and evaluate its immunogenicity in mice, piglets, and sows. cVLP-display significantly increased systemic and mucosal antibody responses towards the recombinant FaeG antigen in mice models. However, in piglets, the presence of anti-F4 maternally derived antibodies severely inhibited the induction of active humoral responses towards the FaeG antigen. This inhibition could not be overcome, even with the enhanced immunogenicity achieved via cVLP display. However, in sows, intramuscular vaccination with the FaeG.cVLP vaccine was able to generate robust IgG and IgA responses that were comparable with a commercial fimbriae-based vaccine, and which were effectively transferred to piglets via colostrum intake. These results demonstrate that cVLP display has the potential to improve the systemic humoral responses elicited against low-immunogenic antigens in pigs; however, this effect is dependent on the use of antigens, which are not the targets of pre-existing maternal immunity.

Expression analysis of TLR signaling pathway genes under lipopolysaccharide-induced and E. coli F17-infected sheep intestinal epithelial cells

Escherichia coli (E. coli) F17 is one of the main pathogens causing diarrhea in young livestock. The specific F17 fimbriae and lipopolysaccharide (LPS) in the surface components of E. coli F17 induces immune activation via interacting with the intestinal epithelial cells (IECs)-expressed innate immune toll-like receptors (TLRs) signaling pathway. In this study, the expression patterns of eight canonical genes from the TLR signaling pathway (IL-6, IL-8, IL-1β, TLR4, MyD88, CD14, TNF-α and TRAF6) were analyzed in LPS-induced IECs, E. coli F17-infected IECs and ileum tissue of E. coli F17-infected lambs. The results showed that increased expression levels of all the studied genes were observed following post-LPS-induced and E. coli F17-infected treatment, with TLR4 having the highest up-regulated expression multiple (compared to NC, fold change = 17.94 and 20.11, respectively), and CD14 having the lowest up-regulated expression multiple (fold change = 2.68 and 1.59, respectively), and higher expression levels of all the studied TLR signaling pathway genes were observed in ileum tissue of E. coli F17 antagonistic (AN) lambs than in E. coli F17 sensitive (SE) lambs. Furthermore, when compared to LPS-induced IECs, E. coli F17-infected IECs showed a more pronounced increase in the expression of IL6, TLR4 and TNF-α, indicating the different roles of these genes in the IECs resistance to E. coli F17 infection. Our results demonstrate that the TLR signaling pathway likely promotes immune activation and provide the first evidence that TLRs have a significant potential to protect against E. coli F17 infections.