Nutritional Strategies to Control Salmonella & E. Coli in Poultry

Introduction

Salmonella and Escherichia coli (E. coli) are bacteria that commonly contaminate poultry production and pose significant risks (Ngai et al., 2021). Salmonella is a rod-shaped bacterium responsible for salmonellosis, a major food safety concern globally, with poultry being a primary transmission route to humans (Ruvalcaba-Gómez et al., 2022; Orimaye et al., 2024). E. coli can also cause illness and mortality in poultry and humans (Islam & Yang, 2017; Mak et al., 2022). Contaminated poultry products, including meat and eggs, are linked to a notable percentage of Salmonella infections in humans, causing symptoms like diarrhea, fever, and abdominal pain and contributing to foodborne outbreaks and economic losses (Khan, 2018; El-Saadony et al., 2022; Raut et al., 2023; Orimaye et al., 2024). In poultry production, these pathogens can lead to diseases such as colibacillosis and salmonellosis, resulting in economic losses due to mortality, reduced growth, and market constraints (Islam & Yang, 2017; Mak et al., 2022; Orimaye et al., 2024).

The widespread use and misuse of conventional antimicrobials (antibiotics) in poultry production, both for disease treatment and growth promotion, have unfortunately driven the development and spread of antimicrobial drug resistance (AMR) in bacteria like Salmonella and E. Coli (Hossain et al., 2020; Ngai et al., 2021; Abreu et al., 2023). This resistance makes infections harder to treat in both animals and humans, posing a serious public health threat (Hossain et al., 2020; Abreu et al., 2023). In response to this challenge, there is a growing focus on nutritional strategies and non-antibiotic approaches to control these pathogens in poultry (Ricke et al., 2020; Ruvalcaba-Gómez et al., 2022; Abreu et al., 2023; Raut et al., 2023).

These innovative approaches include feed additives such as prebiotics, probiotics, organic acids, enzymes, and herbal extracts (Ricke, 2018; Yadav & Jha, 2019; Abd El-Hack et al., 2022; El-Saadony et al., 2022). This article aims to explore the role of these nutritional interventions and other non-antibiotic methods in modulating the gut microbiota, improving poultry health, and ultimately reducing Salmonella and E. coli contamination in poultry production.

Sources of Salmonella And E. Coli Infections in Poultry

Sources of Escherichia coli and Salmonella infections are significant concerns in poultry production, impacting the health and development of broilers and layers alike (Mak et al., 2022; Abreu et al., 2023; Orimaye et al., 2024). Poultry farms themselves can act as reservoirs for antibiotic-resistant E. coli, Salmonella spp., and Staphylococcus spp., posing a risk to the food chain and public health (Hossain et al., 2020). Contaminated poultry feed is a well-recognized source of Salmonella and E. Coli (Ricke et al., 2020; Ngai et al., 2021; Gosling et al., 2021; El-Saadony et al., 2022), with surveys in Kenya, for example, revealing the presence of both pathogens in various feed types (Ngai et al., 2021). Furthermore, feed ingredients can also harbor Salmonella, and even dust within poultry houses has been shown to contain viable antimicrobial-resistant E. coli for extended periods (Ricke et al., 2020; Becker et al., 2021). The environment within poultry houses, including litter, droppings, and water, can become contaminated with these bacteria (Hossain et al., 2020). For instance, higher bacterial counts are often found in poultry litter and droppings due to the release of gut microbes (Hossain et al., 2020; Ricke et al., 2020). Poor hygiene practices during processing on slaughter slabs can also lead to cross-contamination of poultry carcasses with Salmonella (Orimaye et al., 2024).

Effects of Salmonella And E. Coli Infections in Poultry

The negative effects of E. coli and Salmonella infections on chicken health are considerable. E. coli is a major cause of mortality in the poultry industry, especially early chick mortality (Islam & Yang, 2017). Infections can lead to diseases like colibacillosis, causing economic losses and impacting bird performance (Islam & Yang, 2017; Mak et al., 2022). Salmonella infection in poultry can result in gastroenteritis, impaired digestive tract functionality, and the potential for bacterial translocation (Orimaye et al., 2024). Even birds that do not show clinical illness can carry Salmonella and contaminate processing facilities (El-Saadony et al., 2022).

This can lead to human health hazards through contaminated poultry products. Moreover, Salmonella can persist and spread on farms through biofilm formation, potentially involving antibiotic-resistant strains. The impact of these infections is not specific to a single type of chicken; broilers raised for meat and laying hens producing eggs are both susceptible (Abreu et al., 2023; Orimaye et al., 2024). Control measures, including maintaining Salmonella-free chickens and implementing strict biosecurity practices across all stages of production, from feed formulation to processing, are crucial to mitigate these negative effects (Ruvalcaba-Gómez et al., 2022; Raut et al., 2023). Novel bacterial control strategies, such as bacteriophages, probiotics, and antimicrobial peptides, are being investigated to combat these infections in poultry production as alternatives to conventional antimicrobials (Abreu et al., 2023).

Resistance of Salmonella and E. Coli Infections in Poultry Production and Food Processing

Salmonella and E. coli infection resistance poses a significant challenge throughout poultry production and food processing, affecting both layer and broiler chickens. A major concern is the development of antimicrobial resistance (AMR) (Abreu et al., 2023). The widespread use of conventional antimicrobials in poultry production has unfortunately led to the rise of multidrug-resistant bacteria, including Salmonella and E. coli, which is a serious public health issue (Abreu et al., 2023).

Studies have detected antibiotic-resistant E. coli, Salmonella spp., and Staphylococcus spp. in various components of the poultry farm environment, increasing the risk of these resistant bacteria entering the food chain. Notably, resistance to antibiotics like colistin has been observed in E. coli and Salmonella isolated from poultry farms (Hossain et al., 2020). Furthermore, poultry feed can serve as a continuous source of Salmonella and E. coli contamination, with both pathogens being identified in various feed types (Ngai et al., 2021).

The survival of Salmonella in poultry feed can even be strain-dependent (Ricke et al., 2020). In processing facilities, Salmonella's ability to form biofilms on surfaces provides a mechanism for persistence and resistance to cleaning and disinfection efforts (Ruvalcaba-Gómez et al., 2022). These biofilms can harbor antibiotic-resistant strains, making their eradication more difficult (Ruvalcaba-Gómez et al., 2022; Abreu et al., 2023). If hygienic practices are insufficient, cross-contamination during poultry processing can readily spread Salmonella to carcasses, creating a hazard for human health (El-Saadony et al., 2022).

Even within the birds, different serovars of Salmonella may exhibit varying levels of acid tolerance, which can influence their survival in the gastrointestinal tract and potentially their resistance to certain control measures (Ricke, 2018). The poultry farm environment itself, including litter, droppings, and water sources, can become reservoirs for these bacteria, contributing to persistent infections and the potential for horizontal transmission within flocks (Hossain et al., 2020; Orimaye et al., 2024). Therefore, a multifaceted approach encompassing prudent antimicrobial use, stringent biosecurity measures throughout the production chain, and effective sanitation in processing plants is crucial to combat the resistance of Salmonella and E. Coli (Ricke et al., 2020; El-Saadony et al., 2022). Novel control strategies are under investigation to reduce reliance on traditional antibiotics and limit the dissemination of AMR (Abreu et al., 2023).

Nutritional Additives as a Solution to Salmonella and E. Coli Infections in Poultry Production and Food Processing

Utilising nutritional additives in poultry feed presents a promising strategy to control Salmonella and E. coli infections directly at the source – the poultry farm – thereby reducing the risk of contamination during subsequent food processing (Ruvalcaba-Gómez et al., 2022; Raut et al., 2023). As conventional antibiotics face increasing scrutiny due to antimicrobial resistance, these alternatives offer a proactive approach to maintaining bird health and producing safer poultry products (Mak et al., 2022; Abreu et al., 2023). Several types of feed additives have demonstrated potential in this regard.

Probiotics, defined as live microorganisms that benefit the host when administered in suitable concentrations, exert their protective effects through various mechanisms (El-Saadony et al., 2022). They can competitively exclude pathogenic bacteria like Salmonella and E. coli by occupying attachment sites in the gut and competing for nutrients (Islam & Yang, 2017). Certain probiotics also release bacteriostatic and bactericidal agents that directly inhibit the growth of these pathogens. Furthermore, probiotics can modulate the host's immune system, enhancing its ability to fight off infections (Islam & Yang, 2017; El-Saadony et al., 2022). For instance, Lactobacillus-based probiotics have been shown to enhance mucosal immunity (Abd El-Hack et al., 2022). Probiotics can also contribute to a lower intestinal pH, creating an environment less favorable for the survival of Salmonella and E. Coli (El-Saadony et al., 2022). Examples include the use of Bacillus probiotics to reduce Salmonella Enteritidis in layer ceca and Lactobacillus salivarius supplementation showing effects on Salmonella pullorum infection resistance (Abd El-Hack et al., 2022; Ruvalcaba-Gómez et al., 2022; Abreu et al., 2023).
Prebiotics are non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, thus improving host health. By promoting the growth of beneficial gut bacteria, prebiotics can indirectly create a barrier against pathogen colonization. The fermentation of prebiotics by these beneficial bacteria often results in the production of short-chain fatty acids (SCFAs), which can have inhibitory effects on Salmonella and E. coli and contribute to gut health. Novel sources of non-digestible oligosaccharides, such as cereal grain brans, are being explored for their potential to limit Salmonella establishment in poultry (Ricke, 2018).
Synbiotics combine the benefits of both probiotics and prebiotics, aiming to deliver live beneficial bacteria along with a substrate that specifically supports their growth and activity in the gut. This synergistic approach can enhance the colonization and efficacy of the probiotic strains in combating Salmonella and E. Coli (El-Saadony et al., 2022).
Postbiotics involve utilizing non-viable bacteria or their metabolic by-products, including inactivated organic acids, short-chain fatty acids, enzymes, cells, exopolysaccharides, peptides, and plasmalogens. These can exert direct antimicrobial effects against pathogens like Salmonella and help to reinforce the gut microbiota and stimulate beneficial bacteria. Oral administration of postbiotics has shown promise in significantly reducing Salmonella infections in poultry (Ruvalcaba-Gómez et al., 2022; Orimaye et al., 2024).
Organic acids and their salts are well-known for their antimicrobial properties. They can penetrate the bacterial cell wall, disrupt cellular metabolism, and lower intracellular pH, thereby inhibiting the growth of Salmonella and E. coli in the feed and the poultry gut. The use of organic acids in feed and water has demonstrated potential in controlling Salmonella Enteritidis persistence in experimentally infected birds (Gosling et al., 2021; Fathima et al., 2022; Raut et al., 2023).
Phytobiotics, or herbal extracts, contain bioactive compounds that can exhibit antibacterial properties. These compounds may alter the permeability and fluidity of bacterial cell membranes, leading to growth inhibition. For example, incorporating thymol into poultry diets has shown to improve performance and regulate feed intake in broilers challenged with Salmonella Typhimurium (Orimaye et al., 2024).
Other nutritional strategies under investigation include the use of antimicrobial peptides, nanoparticles with antimicrobial properties (Abreu et al., 2023), and feed enzymes that improve nutrient digestibility, reducing the availability of undigested nutrients for pathogenic bacteria in the lower gut (Yadav & Jha, 2019). Furthermore, adequate levels of essential amino acids, such as threonine, are crucial for maintaining intestinal integrity and immune function, which can enhance resistance to Salmonella and E. coli infections (Adedokun & Olojede, 2019). Supplementation with dietary manganese (Mn) has also shown evidence of decreasing Salmonella numbers in broilers (Zhang et al., 2022).

Conclusion

In conclusion, nutrition plays a vital role in controlling Salmonella and E. coli infections in poultry production, offering proactive solutions at the farm level. Nutritional additives like probiotics, prebiotics, organic acids, and phytobiotics can reduce pathogen colonization, enhance gut health, and bolster the immune system. By managing these infections at the source, the reliance on antibiotics is lessened, thereby mitigating the risk of antimicrobial resistance. This targeted approach not only improves poultry health and performance but also significantly contributes to producing safer food products by reducing contamination during processing. Therefore, strategic nutritional interventions are crucial for a sustainable and responsible poultry industry.

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