Antibiotic Resistance in Poultry Industry: History & Background
Antibiotic resistance in poultry is a global health crisis exacerbated by the extensive use of antimicrobials in animal agriculture. Poultry farming, especially chicken production, is widespread globally due to its affordability and lack of cultural or religious barriers to consumption. Antimicrobials are widely used in poultry farming for disease prevention, treatment, and growth promotion, many of which are critically or highly important for human medicine. This widespread use of antimicrobials in poultry farming contributes to the emergence of antimicrobial resistance (AMR) in both pathogens and commensal organisms. Concerns include the presence of antimicrobial residues in meat and eggs, economic setbacks from ineffective antimicrobial use, and the toll of untreated poultry ailments. This blog will delve into the origins, classification, mechanism, and resistance of antibiotics.
Origins of Antibiotics
- Antibiotics, medicines that kill bacteria, revolutionized medicine in the 1900s, changing how doctors treat diseases and improve health.
- Antibiotics, medicines that kill bacteria, revolutionized medicine in the 1900s, changing how doctors treat diseases and improve health.
- Alexander Fleming’s discovery of penicillin in 1928 marked the beginning of modern antibiotics, connecting ancient practices with contemporary medicine.
- The “golden era” of antibiotic discovery after World War II led to the identification of many antibiotics still used today.
- Despite initial optimism about antibiotics’ ability to handle infections, bacterial resistance emerged, prompting the development of new antibiotics and strategies to combat resistance.
- Ongoing efforts include exploring phage therapy, combining antibiotics, and using precision medicine to address drug-resistant bacteria.
Antibiotics and Poultry industry
- Antibiotic use in the poultry industry began in the mid-20th century, initially for treating bacterial infections.
- Antibiotics were later used routinely in poultry feed and water as growth promoters and for disease prevention, improving poultry health and productivity.
- Widespread antibiotic use contributed to increased production efficiency and lower mortality rates among poultry birds.
- Concerns about antibiotic resistance and their impact on human health and the environment have led to calls for more judicious use and stricter regulations in many countries.
Antibiotics Class and Mode of Action
Beta-Lactams
The ß-lactam ring is part of the core structure of several antibiotic families, the principal ones being the penicillins, cephalosporins, carbalpenems, and monobactams, which are, therefore, also called ß- lactam antibiotics. Nearly all these antibiotics work by inhibiting bacterial cell wall biosynthesis. This has a lethal effect on bacteria.
Mode of Action:
Inhibit bacterial cell wall synthesis by binding irreversibly to penicillin-binding proteins (PBPs), leading to cell wall weakening and lysis.
Examples: Penicillins (e.g., amoxicillin), cephalosporins (e.g., cephalexin), carbapenems (e.g., imipenem).
Glycopeptides
The glycopeptide antibiotics are a class of antimicrobial agents that share a similar, macromolecular structure and basic mechanism of action.
Mode of Action:
Bind to the D-Ala-D-Ala terminus of peptidoglycan precursors, preventing their incorporation into the cell wall and leading to cell death.
Examples: Vancomycin, teicoplanin.
Sulphonamides
Sulphonamides are the antibiotics that have structural similarity with p-aminobenzoic acid (PABA) containing sulphonamide (S02NH2) groups in their chemical structure. They have bacteriostatic action against gram +ve & gram —ve bacteria.
Mode of Action:
Inhibit bacterial folic acid synthesis by competitively inhibiting the enzyme dihydropteroate synthase.
Examples: Sulfadimethoxine, sulfamethoxazole, sulfadiazine.
Fluoroquinolones
The fluoroquinolones are a family of broad spectrum, systemic antibacterial agents that have been used widely as therapy of respiratory and urinary tract infections. Fluoroquinolones are active against a wide range of aerobic gram-positive and gram-negative organisms.
Mode of Action:
Inhibit bacterial DNA gyrase and topoisomerase IV, preventing DNA replication and transcription, ultimately leading to cell death.
Examples: Enrofloxacin, ciprofloxacin, danofloxacin.
Macrolides
Mode of Action:
Bind to the 50S ribosomal subunit of bacteria, inhibiting protein synthesis and leading to bacterial cell death.
Examples: Erythromycin, tylosin, azithromycin, clarithromycin.
Tetracyclines
Tetracyclines (tetracycline, doxycycline, minocycline, tigecycline) are a class of medication used to manage and treat various bacterial infections. Tetracyclines classify as protein synthesis inhibitor antibiotics and are broad-spectrum.
Mode of Action:
Bind to the bacterial ribosome, inhibiting protein synthesis and disrupting bacterial membrane integrity.
Examples: Oxytetracycline, chlortetracycline, doxycycline.
Aminoglycosides
Aminoglycosides are called bactericidal antibiotics because they kill bacteria directly. They accomplish this by stopping bacteria from producing proteins needed for their survival.
Mode of Action:
Bind to the 30S ribosomal subunit of bacteria, causing misreading of mRNA and inhibition of protein synthesis.
Examples: Gentamicin, neomycin, streptomycin.
Lincosamides
Mode of Action:
Bind to the 50S ribosomal subunit, inhibiting protein synthesis.
Examples: Lincomycin, clindamycin.
Ionophores
(Greek) iov =ion, (phero) = carry (Greek)
Ionophores can be literally called as “Charge carriers / charge bearers.” The word ionophore was coined by Pressman in 1964. Ionophores, initially called ion complexers were discovered in 1950’s and first used as anti-coccidial agents.
They are molecules that act as membrane shuttles for ions across the lipid membranes without expenditure of energy.
Mode of Action:
Disrupt bacterial cell membrane potential, leading to ion leakage and cell death.
Examples: Monensin, salinomycin.
Conclusion
- Antibiotic resistance occurs when bacteria can withstand the effects of antibiotics meant to kill or inhibit their growth.
- Bacteria develop resistance through natural genetic variation or by acquiring resistance genes from other bacteria.
- Resistance mechanisms include changes to cell wall structure, production of enzymes that break down antibiotics, and pumping antibiotics out of bacterial cells.
- Overuse and misuse of antibiotics have accelerated the development of antibiotic resistance, making infections harder to treat.
- Antibiotic resistance is a global health problem, leading to increased rates of illness and death.
- Scientists are researching ways to combat antibiotic resistance, including modifying antibiotics and targeting bacterial enzymes in poultry and replacing antibiotics with phytogenic feed additives.
- Genetic modification and the spread of resistance genes among bacteria contribute to antibiotic resistance.
- Antibiotic resistance genes can originate from natural sources and spread through various mechanisms, with increased antibiotic use hastening this process.
