Antibacterial and anti-mycoplasma drugs are the go-to treatments for preventing and controlling diseases in livestock and poultry. With many types, different mechanisms, uses, and side effects, this guide breaks down their classifications, features, and precautions from a veterinary perspective to help ensure competent and safe use.
Classification and How Antibacterial Drugs Work
Based on how they work, antibacterial drugs fall into four main types:
- Bacteria-Killing Drugs (Type I): Like penicillins and cephalosporins, these block bacterial cell wall formation and are great for infections caused by fast-growing bacteria.
- Static Bacteria-Killing Drugs (Type II): These, such as aminoglycosides and polymyxins, disrupt bacterial cell membranes or protein production, targeting bacteria in a resting phase.
- Fast-acting bacteria-suppressing Drugs (Type III) include tetracyclines, chloramphenicol, and macrolides. They quickly stop bacterial protein production and can kill bacteria at high doses.
- Slow-Acting Bacteria-Suppressing Drugs (Type IV): Like sulfonamides, these slow down bacterial metabolism and take longer to work.
Effects of Combining Drugs
- Type I + Type II: Works better together
- Type I + Type III: May cancel each other out
- Type II + Type III: Works better together or adds up
- Type I + Type IV: Works better together
Main Types of Antibacterial Drugs and Their Uses
Here are the commonly used antibacterial drugs in livestock and poultry farming, with details on how they work, what they treat, and what to watch out for:
β-Lactams
How They Work: Contain a β-lactam ring that blocks bacterial cell wall formation and triggers enzymes that break down bacteria.
Subtypes: Penicillins, cephalosporins, atypical β-lactams, and β-lactamase inhibitors.
What They Target: Effective against Gram-positive (G+), Gram-negative (G-), and some anaerobic bacteria.
Uses: Widely used for respiratory, digestive, and soft tissue infections due to decisive action and low side effects, like swine streptococcal disease and avian colibacillosis (E. coli infections in poultry).
Precautions: Be cautious with animals allergic to penicillins; don’t mix with fast-acting bacteria-suppressing drugs to avoid weakening their effect.
Aminoglycosides
How They Work: Target the 30S ribosomal subunit to block protein production and damage cell membranes; these are dose-dependent bacteria-killers.
Common Drugs: Streptomycin, gentamicin, amikacin, and others.
What They Target: They work against aerobic G-bacilli (e.g., E. coli, Salmonella) and some G+ bacteria (e.g., Staphylococcus); they do not affect anaerobes.
Uses: Treat serious G- infections in pigs and poultry, like piglet yellow and white diarrhea and avian septicemia.
Precautions: Risk of ear and kidney damage; monitor kidney function and avoid long-term use.
Macrolides
How They Work: Target the 50S ribosomal subunit to stop protein production; usually fast-acting bacteria-suppressors but can kill at high doses.
Common Drugs:
First generation: Erythromycin, tylosin (less commonly used).
Second generation: Roxithromycin, clarithromycin, azithromycin.
Third generation: Telithromycin, quinupristin (less resistance).
First generation: Erythromycin, tylosin (less commonly used).
Second generation: Roxithromycin, clarithromycin, azithromycin.
Third generation: Telithromycin, quinupristin (less resistance).
What They Target: Effective against G+ bacteria, some G- bacteria, and atypical pathogens (e.g., Mycoplasma, Chlamydia).
Uses: Treat swine mycoplasma pneumonia and avian chronic respiratory disease (CRD).
Precautions: Resistance is increasing; choose drugs based on susceptibility tests.
Tetracyclines
How They Work: Target the 30S ribosomal subunit to block protein production.
Common Drugs: Tetracycline, doxycycline, minocycline.
What They Target: Broad-spectrum, effective against G+, G- bacteria, and Mycoplasma.
Uses: Treat avian cholera, swine respiratory disease, and bovine pasteurellosis.
Precautions: Resistance is common; don’t use dairy products (reduces absorption).
Fluoroquinolones
How They Work: Block bacterial DNA enzymes, stopping DNA replication.
Common Drugs: Enrofloxacin, ciprofloxacin, levofloxacin.
What They Target: Effective against G+ cocci, G- bacteria, Mycoplasma, and anaerobes.
Uses: Treat avian colibacillosis (E. coli infections in poultry) and swine respiratory infections.
Precautions: Use cautiously in young animals; may affect cartilage growth.
Glycylcyclines
Representative Drug: Tigecycline.
How They Work: Like tetracyclines, they block protein production.
What They Target: Effective against multidrug-resistant bacteria (e.g., MRSA, enterococci) and anaerobes.
Uses: Treat complex skin, soft tissue, and abdominal infections.
Precautions: Don’t use alone; save as a last-resort drug to limit resistance.
Glycopeptides
Common Drugs: Vancomycin, teicoplanin.
How They Work: Block cell wall formation; effective against G+ bacteria.
Uses: Treat resistant G+ infections, like MRSA-related swine skin infections.
Precautions: Monitor kidney function and hearing; don’t use for more than 14 days.
Nitroimidazoles
Common Drugs: Metronidazole, tinidazole.
How They Work: Damage bacterial DNA; broad-spectrum antibacterial action.
What They Target: Effective against anaerobes, spirochetes, and Mycoplasma.
Uses: Treat swine intestinal anaerobic infections and avian necrotic enteritis.
Precautions: Avoid alcohol during treatment to prevent severe reactions similar to those from mixing alcohol with certain drugs.
Precautions for Using Antibacterial Drugs
- Choose Wisely: Pick the right drug based on the type of bacteria, susceptibility tests, and animal species.
- Combination Therapy: Check how drugs work together or against each other to avoid combinations that don’t work.
- Dosage and Duration: Stick to recommended doses and treatment lengths to prevent resistance from overuse or underuse.
- Withdrawal Period: Follow withdrawal period rules (time before animals can be used for food) to avoid drug residues in food.
- Preventing Resistance: Rotate drug types regularly to reduce resistant bacteria.
Conclusion
Antibacterial and anti-mycoplasma drugs are vital for preventing and treating diseases in livestock and poultry, but they should be used carefully and based on science. Veterinarians should pick the best drug plan by examining clinical signs, lab tests, and drug properties to boost treatment success, lower resistance risks, and protect animal and public health.
