Introduction:Avian colibacillosis is a bacterial infectious disease that seriously harms the poultry industry and causes huge economic losses. With the restricted use and ban of antibiotics in poultry farming, the incidence of this disease has increased, threatening poultry health. Therefore, there is an urgent need to develop new technologies and products to replace antibiotics. This article outlines the harm caused by avian colibacillosis and focuses on the efficacy and mechanisms of action of feed antibiotic alternatives in preventing and controlling the disease, providing a reference for developing non-antibiotic prevention and control measures.
1. Characteristics and harm of avian colibacillosis
Avian colibacillosis is caused by infection with certain serotypes of avian pathogenic Escherichia coli (APEC) and is an opportunistic disease. Routes of infection include the mucosa, digestive tract, and respiratory tract; the disease is often triggered by co-infections or adverse environmental conditions, and its symptoms vary. APEC is prone to mutation and has many serotypes, which limits vaccine development. Although antibiotics were once effective, their use has led to the emergence of multidrug-resistant bacteria. APEC also poses a zoonotic risk, making the development of antibiotic alternatives urgent.
2. Research progress on the prevention and treatment of the disease using non-antibiotic substances
2.1 Organic acids
Organic acids (such as formic acid, propionic acid, and acetic acid) have antimicrobial functions. They can improve growth performance and immune function in chickens infected with APEC, stimulate intestinal mucosal growth, promote intestinal villus development, improve ileal morphology, increase the number of lactic acid bacteria in the cecum, and reduce the number of Escherichia coli.
2.2 Plant extracts
Plant extracts (such as plant essential oils, polyphenols, and alkaloids) have antibacterial, antiviral, antifungal, and antioxidant properties. Plant essential oils such as oregano oil, rosemary extract, and star anise oil can enhance the antioxidant capacity of infected broiler chickens and alleviate intestinal and liver damage. Plant polyphenols (such as tannins and resveratrol) inhibit the proliferation of Escherichia coli by suppressing its motility and biofilm formation.
2.3 Bacteriophages
Bacteriophages are viruses that can infect bacteria and treat APEC infections by lysing the target bacteria. Studies have shown that bacteriophage mixtures are more effective in treating APEC infections and can significantly reduce mortality and lesions in broiler chickens.
2.4 Probiotics
Probiotics (such as Lactobacillus and Bacillus) inhibit pathogen adhesion to the intestinal mucosa through competitive exclusion and produce antimicrobial compounds, thereby inhibiting pathogen colonization in the host. Probiotics can improve growth performance and immune function in chickens infected with APEC and improve intestinal morphology and microbial community composition.
2.5 Antimicrobial peptides
Antimicrobial peptides kill bacteria by disrupting the integrity of bacterial cell membranes and are unlikely to induce bacterial resistance. They can be used either as an alternative to antibiotics to treat APEC infection or as an adjunct to enhance the efficacy of antibiotics.
2.6 Prebiotics
Prebiotics (such as mannan oligosaccharides and fructooligosaccharides) can regulate the gut microbiota and selectively promote the metabolism and proliferation of beneficial bacteria. Prebiotics can improve the growth performance of chickens infected with APEC, improve gut microbial composition, and enhance the antioxidant capacity of the intestinal mucosa.
2.7 Yolk antibodies
Yolk antibodies are specific immunoglobulins produced by laying hens after stimulation by foreign antigens such as vaccines, and they significantly inhibit the growth of Escherichia coli K88. Yolk antibodies have potential for treating avian colibacillosis, but related research is limited.
2.8 Other substances
Enzyme preparations, vitamins, and certain amino acids also have inhibitory effects on APEC infection. Vitamins E and A can enhance humoral immunity and phagocytic capacity in broiler chickens and promote antibody production.
3. Summary and outlook
APEC is a major bacterial pathogen that threatens the poultry industry, and antibiotic resistance is a serious problem. There is an urgent need to find new alternatives to antibiotics for preventing and treating avian colibacillosis. Non-antibiotic substances (such as organic acids, plant extracts, bacteriophages, probiotics, antimicrobial peptides, and prebiotics) have shown good effects in preventing and controlling APEC infections. However, further research into their mechanisms of action and safety is needed to gradually achieve their widespread promotion and application in actual production.
Source of literature: https://doi.org/10.12418/CJAN2024.412.