Antibiotics, Pt. 3 Flashcards
Mechanisms of action of antibacterial drugs:
What are the 2 drug classes that inhibit membrane function? What are their targets?
- Polymyxin B - LPS, inner and outer membranes of G- bacteria
- Lipopeptides - LPS, inner and outer membranes of G+ bacteria
What 2 types of Polymixin B are commonly used? What are their therapeutic uses? How do they affect bacteria?
- Polymyxin B - G- bacterial infections of the skin, eye, ear, and GIT; endotoxicosis
- Colistin - GI infections (E. coli, Salmonella), IV dosing to treat serious infections caused by MDR
G- bactericidal
What is Polymyxin B commonly combined with for broad-spectrum action?
Bacitracin
- in horses
What Lipopeptide is commonly used? What is its therapeutic use? How does it affect bacteria?
Daptomycin (experimental in rabbits) - complicated skin and soft tissue infections, bacteremia (MRSA)
G+ bactericidal
What 2 drug classes inhibit nucleic synthesis? What are their targets?
- Rifamycin - targets RNA synthesis by blocking bacterial RNA polymerase
- Fluoroquinolones - targets DNA synthesis by blocking DNA gyrase (topo II) activity
What is the therapeutic use of Rifampin? What specific infection does it treat?
broad spectrum bactericidal that can target anaerobes resistant to Florfenicol
Rhodococcus equi infections
What is Rifampin commonly combined with? How is this combo used?
Erythromycin
fungal infections in dogs and cats
What 6 Fluoroquinolones are commonly used? What are their therapeutic uses?
- Enrofloxacin - skin and systemic infections in dogs, cats, birds, and cows
- Danofloxacin - respiratory infections
- Difloxacin - dermal, respiratory, UTI in dogs
- Orbifloxacin - dermal, respiratory, UTI in dogs and cats
- Marbofloxacin - dermal, respiratory, UTI in dogs and cats
- Pradofloxacin
broad spectrum bactericidal against anaerobes resistant to Florfenicol
What Fluoroquinolone is used to treat bovine respiratory infections?
Danofloxacin
What new Fluoroquinolone is considered safer? Why?
Pradofloxacin - non-retinotoxic
What are 2 causes of Fluoroquinolone resistance?
- mutations in genes encoding DNA gyrase and topoisomerase
- subtherapeutic levels may allow the growth of mutants
What adverse effects are possible in Fluoroquinolone use in puppies, dogs, and cats?
chondrotoxicity
seizures in epileptic dogs - Enrofloxacin!
retinal degeneration
What 2 uses of Fluoroquinolones are prohibited?
- extra-label use in food animals
- use in poultry
What is the mechanism of action of antimetabolite antibiotics? What are 3 drug classes that do this?
block bacterial biosynthesis of folic acid essential for purine and DNA synthesis by targeting a folic acid synthesis enzyme
- Sulfonamides
- Trimethoprim
- Ormethoprim
What are Sulfonamides? How do they act as antimetabolites? How does Trimethoprim work?
structural analogs of para-aminobenzoic acid (PABA), an early intermediate in folic acid synthesis
inhibits the enzyme involved in the production of dihydrofolic acid
inhibits the enzyme involved in the production of tetrahydrofolic acid
What is the overall therapeutic use of Sulfonamides? What 5 are most commonly used?
broad spectrum bacteriostatic
- Sulfamethazine - prevention and treatment of local/systemic infections
- Sulfachlorpyridazine - respiratory and enteric infections
- Sulfamethoxazole - UTIs
- Sulfacetamide - ophthalmic infections
- Sulfasalazine - colitis and IBD
What Sulfonamide is used to treat pink eye?
Sulfacetamide
What are potentiated Sulfonamides? What is their purpose?
fixed combination of Sulfonamides with Trimethoprim
broader spectrum, less common resistance, becomes bactericidal
What causes Sulfonamide resistance? What are 4 common adverse effects?
increased PABA production, decreased binding to synthase, and bacterial metabolism
- keratoconjunctivitis sicca in dogs*
- arthritis in Dobermans*
- renal crystalluria
- thrombocytopenia and anemia
What miscellaneous antibacterial may cause dermatitis in pigs? What is its mechanism of action? Spectrum?
Tiamulin
blocks protein synthesis
bacteriostatic against G+ cocci, Mycoplasma, and G-
What is the mechanism of action of Vancomycin and Bacitracin? What are their spectrum? Toxicity?
blocks cell wall synthesis
VANCOMYCIN = bactericidal against G+ - ototoxicity, nephrotoxicity, resistance
BACITRACIN ‘ bactericidal against G+ and spirochetes - no systemic toxicity
Miscellaneous Antibacterials:
What are the 4 major benefits that antibacterial usage has achieved?
- alleviating pain and suffering
- ensures food security
- protects livelihoods
- reduce zoonotic disease spread
What are the 2 general uses of antibacterials?
- THERAPEUTIC - relating to disease and under veterinary supervision; treatment, control spread of illness, prevent illness in healthy animals
- NON-THERAPEUTIC - relating to production; growth promotion
