Novel Small Molecule Growth Inhibitor Affecting Bacterial Outer Membrane Reduces Extraintestinal Pathogenic Escherichia coli (ExPEC) Infection in Avian Model

Unveiling the traits of antibiotic resistance and virulence in Escherichia coli obtained from poultry waste

Antibiotic resistance and virulence factors in avian pathogenic Escherichia coli (APEC) have become significant concerns, contributing to adverse environmental effects. The extensive use of antibiotics in poultry farming has resulted in the emergence of antibiotic-resistant APEC strains. This study prioritizes the molecular screening of APEC to uncover their antibiotic resistance and virulence attributes, with specific attention to their environmental impact. To address the imperative of understanding APEC pathogenesis, our study analyzed 50 poultry waste samples including 10 poultry litter, 15 fecal matter, 15 wastewater, and 10 anatomical waste samples. For the presence of virulence genes, 35 Escherichia coli isolates were subjected to molecular characterization. Amongst these, 27 were APEC strains demonstrating the presence of at least four virulence genes each. Notably, virulence genes such as fimH, ompA, ybjX, waaL, cvaC, hlyF, iss, ompT, and iroN were observed among all the E. coli isolates. Furthermore, eleven of the APEC strains exhibited resistance to tetracycline, ampicillin, sulphonamides, and fluoroquinolones.These findings highlight the role of APEC as a potential source of environmental pollution serving as a reservoir for virulence and resistance genes. Understanding the dynamics of antibiotic resistance and virulence in APEC is essential due to its potential threat to broiler chickens and the broader population through the food chain, intensifying concerns related to environmental pollution. Recognizing the ecological impact of APEC is essential for developing effective strategies to mitigate environmental pollution and safeguard the health of ecosystems and human populations.

Efficacy of quorum sensing and growth inhibitors alone and in combination against avian pathogenic Escherichia coli infection in chickens

Avian pathogenic E. coli (APEC), a causative agent of colibacillosis, is associated with high mortality and morbidity which results in severe economic losses to the poultry industry worldwide. APEC can be transmitted to humans through the consumption of contaminated poultry products. The limited effect of the current vaccines and the advent of drug-resistant strains have necessitated the development of alternative therapies. Previously, we identified 2 small molecules (SMs; [quorum sensing inhibitor; QSI-5] and [growth inhibitor; GI-7]) with high efficacy in vitro and in chickens subcutaneously challenged with APEC O78. Here, we optimized the oral challenge dose of APEC O78 in chickens to mimic the infection in the natural settings, evaluated the efficacy of the GI-7, QSI-5, and combination of GI-7 and QSI-5 (GI7+ QSI-5) in chickens orally infected with APEC, and compared their efficacy to sulfadimethoxine (SDM), an antibiotic currently used to treat APEC. Using the optimized dose of each SM in drinking water, GI-7, QSI-5, GI7+ QSI-5, and SDM were evaluated in chickens challenged with the optimized dose of APEC O78 (1 × 10⁹ CFU/chicken; orally; d 2 of age) and grown on built-up floor litter. Reduction in mortality was 90, 80, 80, and 70% in QSI-5, GI-7+QSI-5, GI-7, and SDM treated groups compared to the positive control (PC), respectively. GI-7, QSI-5, GI-7+QSI-5, and SDM reduced the APEC load in the cecum by 2.2, 2.3, 1.6, and 0.6 logs and in the internal organs by 1.3, 1.2, 1.4, and 0.4 logs compared to PC (P < 0.05), respectively. The cumulative pathological lesions scores were 0.51, 0.24, 0.0, 0.53, and 1.53 in GI-7, QSI-5, GI-7+QSI-5, SDM, and PC groups, respectively. Overall, GI-7 and QSI-5 individually have promising effects as a potential antibiotic-independent approach to control APEC infections in chickens.

Antimicrobial Resistance and Recent Alternatives to Antibiotics for the Control of Bacterial Pathogens with an Emphasis on Foodborne Pathogens

Antimicrobial resistance (AMR) is one of the most important global public health problems. The imprudent use of antibiotics in humans and animals has resulted in the emergence of antibiotic-resistant bacteria. The dissemination of these strains and their resistant determinants could endanger antibiotic efficacy. Therefore, there is an urgent need to identify and develop novel strategies to combat antibiotic resistance. This review provides insights into the evolution and the mechanisms of AMR. Additionally, it discusses alternative approaches that might be used to control AMR, including probiotics, prebiotics, antimicrobial peptides, small molecules, organic acids, essential oils, bacteriophage, fecal transplants, and nanoparticles.

Xiaochaihu Decoction Treatment of Chicken Colibacillosis by Improving Pulmonary Inflammation and Systemic Inflammation

Chicken colibacillosis-the most common disease of poultry, is caused mainly by avian pathogenic Escherichia coli (APEC). It has a major impact on the poultry industry worldwide. The present study was conducted to investigate the therapeutic effects of Xiaochaihu Decoction (XCHD) supplementation on clinical manifestation, organ index, bacterial load in organ and inflammatory mediators in a chicken model challenged with APEC. The results showed that all doses of XCHD significantly elevated the survival rate of infected chickens. XCHD improved the clinical signs of infected chickens, reduced the organ index, reduced the bacterial load of organs, and inhibited the secretion of serum and pulmonary inflammatory factors IL-1β, IL-6 and TNF- α. Taken together, this study demonstrates that XCHD had protective effects on APEC-infected chickens. Its mechanism includes anti-inflammatory and antibacterial effects. These findings may contribute to the further study of the mechanism of the formula and the prevention or treatment of colibacillosis in poultry. The significance of this study is that it provides a certain theoretical basis for the replacement of antibiotics by XCHD.

Effect of Probiotic E. coli Nissle 1917 Supplementation on the Growth Performance, Immune Responses, Intestinal Morphology, and Gut Microbes of Campylobacter jejuni Infected Chickens

Campylobacter jejuni is the most common cause of bacterial foodborne gastroenteritis and holds significant public health importance. The continuing increase of antibiotic-resistant Campylobacter necessitates the development of antibiotic-alternative approaches to control infections in poultry and in humans. Here, we assessed the ability of E. coli Nissle 1917 (EcN; free and chitosan-alginate microencapsulated) to reduce C. jejuni colonization in chickens and measured the effect of EcN on the immune responses, intestinal morphology, and gut microbes of chickens. Our results showed that the supplementation of 3-week-old chickens daily with free EcN in drinking water resulted in a 2.0 log reduction of C. jejuni colonization in the cecum, whereas supplementing EcN orally three times a week, either free or microencapsulated, resulted in 2.0 and 2.5 log reductions of C. jejuni colonization, respectively. Gavaged free and microencapsulated EcN did not have an impact on the evenness or the richness of the cecal microbiota, but it did increase the villous height (VH), crypt depth (CD), and VH:CD ratio in the jejunum and ileum of chickens. Further, the supplementation of EcN (all types) increased C. jejuni-specific and total IgA and IgY antibodies in chicken’s serum. Microencapsulated EcN induced the expression of several cytokines and chemokines (1.6 to 4.3-fold), which activate the Th1, Th2, and Th17 pathways. Overall, microencapsulated EcN displayed promising effects as a potential nonantibiotic strategy to control C. jejuni colonization in chickens. Future studies on testing microencapsulated EcN in the feed and water of chickens raised on built-up floor litter would facilitate the development of EcN for industrial applications to control Campylobacter infections in poultry.

Evaluation of Novel Quorum Sensing Inhibitors Targeting Auto-Inducer 2 (AI-2) for the Control of Avian Pathogenic Escherichia coli Infections in Chickens

Avian pathogenic Escherichia coli (APEC) associated with colibacillosis results in high morbidity and mortality, and severe economic losses to the poultry industry. APEC is a zoonotic pathogen and can infect humans through contaminated poultry products. Vaccination and antibiotic treatment are currently used to control APEC infections; however, the limited effect of vaccines and the emergence of antibiotic-resistant strains have necessitated the development of novel therapeutics. Here, we evaluated seven quorum sensing inhibitors (QSI) identified in our previous study, in APEC-infected chickens. QSIs were administered orally (~92 to 120 μg/bird) and chickens were challenged subcutaneously with APEC. Among them, QSI-5 conferred the best protection (100% reduction in mortality, 82% to 93% reduction in lesions [airsacculitis, perihepatitis, lung congestion, pericarditis] severity, and 5.2 to 6.1 logs reduction in APEC load). QSI-5 was further tested in chickens raised on built-up floor litter using an optimized dose (1 mg/L) in drinking water. QSI-5 reduced the mortality (88.4%), lesion severity (72.2%), and APEC load (2.8 logs) in chickens, which was better than the reduction observed with currently used antibiotic sulfadimethoxine (SDM; mortality 35.9%; lesion severity up to 36.9%; and APEC load up to 2.4 logs). QSI-5 was detected in chicken's blood after 0.5 h with no residues in muscle, liver, and kidney. QSI-5 increased the body weight gain with no effect on the feed conversion ratio and cecal microbiota of the chickens. Metabolomic studies revealed reduced levels of 5'-methylthioadenosine in QSI-5-treated chicken serum. In conclusion, QSI-5 displayed promising effects in chickens and thus, represents a novel anti-APEC therapeutic. IMPORTANCE Avian pathogenic Escherichia coli (APEC), a subgroup of ExPEC, is a zoonotic pathogen with public health importance. Quorum sensing is a mechanism that regulates virulence, biofilm formation, and pathogenesis in bacteria. Here, we identified a novel quorum sensing autoinducer-2 inhibitor, QSI-5, which showed higher anti-APEC efficacy in chickens compared to the currently used antibiotic, sulfadimethoxine at a much lower dose (up to 4,500 times). QSI-5 is readily absorbed with no residues in the tissues. QSI-5 also increased the chicken's body weight gain and did not impact the cecal microbiota composition. Overall, QSI-5 represents a promising lead compound for developing novel anti-virulence therapies with significant implications for treating APEC infections in chickens as well as other ExPEC associated infections in humans. Further identification of its target(s) and understanding the mechanism of action of QSI-5 in APEC will add to the future novel drug development efforts that can overcome the antimicrobial resistance problem.