Antimicrobials Flashcards
Beta Lactam (B-Lactam) Members of the Family
- Penicillins, (Ampicillin, Amoxicilling, Ticracillin)
- Cephalosporins (1st, 2nd, 3rd, 4th Generations)
- Sublactams
- Carbapenems (Imipenem)
- Monobactams (Aztreonam)
Beta Lactam (B-Lactam) Mechanism of action
Inhibit Cell wall synthesis (peptidoglycan synthesis).
Stimulate autolysins which degrade peptidoglycan
Beta Lactam (B-Lactam)
- All have a B-Lactam Ring
- Differ in teir spectrum of activities
- Some are effective against both Gram Negatives and Gram Positives
- Some are effective against only Gram Negative than Gram positives or vice versa
- Vary in their absorption, toxicity, and their ability to penetrate tissues or the BBB
- Bactericidal antimicrobials
- Excretion through kidneys
- Time dependant killing
Beta Lactam (B-Lactam) Resistance mechanisms
- B-Lactamase (enzyme which cleaves B lactam ring) production
- Extended spectrum B lactamase
- Alteration in penicillin binding proteins
Beta Lactam (B-Lactam) Synergism
- Use in combination with Beta Lactamase inhibitors such as Clavulinic acid, sublactam, Tazobactam
- Aminoglycoside + B lactams facilitates entry in to bacterial cells
- Do not mix aminoglycosides with penicillin in the same syringe
- Ticarcillin + quinolones in pseudomonas infections
Beta Lactam (B-Lactam) Antagonism
- Tetracycline and chloramphenicol
- Anaphylactic reaction (type I hypersensitivity)
- Penicillin can act as a hapten
Tetracyclines
- A broad spectrum antibiotic (active against Gram Positive, Gram negative, Mycoplasma, Chlamydia, Ehrlichia, Rickettsia, Anaplasma, Mycobacterium and protozoan parasites)
- Widely used in ruminants and swine
- Inhibit protein synthesis (bind to 30s ribo)
- Bacteriostatic
- Time dependant antimicrobials
Tetracyclines Members of the Family
Oxytetracycline, Chlortetracycline, Doxycycline, Minocycline
Tetracyclines Resistance mechanisms
- Energy dependant efflux
- Ribosomal protection
- Chemical modification and catalysis by enzymes
Tetracycline Notable Facts
- Chelating agents
- Cross placental barrier
- Secreted in milk
- Anti-inflammatory, Neuroprotective and immunomodulant effects
Tetracycline Toxicity and adverse effects
- Irritant
- Cardiovascular effects
- Tooth discoloration
- Alternation of intestinal flora and enterocolitis (Horses)
- Intravenous administration of Doxycycline in horses; cardiovascular collapse
- Nephrotoxicosis
Aminoglycosides Members of the Family
-Gentamicin, Tobramycin, Streptomycin, Kanamycin, Neomycin, Spectinomycin, Amikacin
Aminoglycosides Mechanism of Action
- Inhibit protein synthesis (30s ribosome)
- Bactericidal
- Concentration dependant antimicrobial
Aminoglycosides
- Oxygen dependant uptake by th emicrobes
- Purulent debris inactive aminoglycosides
- Prolonged post antibiotic effect
- Need parenteral administration
- Renal excretion
- Does not penetrate BBB
Aminoglycosides Synergism
With Beta-lactams but physically incompatible with B-lactams
Aminoglycosides Toxicity
- Nephrotoxicity (acute tubular necrosis)
- Calcium supplementation and high protein diet
- Ototoxicity/Cranial nerve VIII toxicity/vestibular or cochlear damage (cats more susceptible)
Aminoglycosides Resistance Mechanisms
Are by plasmid mediated enzymes which inactivate aminoglycosides
Fluoroquinolones
- Synthetic anitmicrobial agents
- Entrofloxacin, Ciprofloxacin
- Inhibit DNA gyrase (DNA replication)
- Oral absorption, extended half-life
- Concentration dependant killing
- High intracellular concentration in phagocytes
- Bactericidal
- Prolonged Post antibiotic effect
- Excreted through urine
- Rapid resistance development
Fluoroquinolones Resistance
- Not very effective against anaerobes
- By modification or protection of target, decreased permeability, efflux pump
Fluoroquinolones Synergism
With beta-lactams, amionglycosides
Fluoroquinolones Toxicity
- Generally safe
- Articular cartilage degeneration in juvenile dogs, retinal degeneration in cats (high enrofloxacin dose)
- Neurotoxic effect, tendon rupture (humans)
- Canine toxic shock syndrome; S. canis infection and Fluoroquinolone monotherapy (bacteriophage induced lysis of S. canis)
Sulfa or Potentiated Sulfa Drugs Members of the Family
- Sulfonamide
- Sulfamethoxazole
- Sulfadiazine etc.
Sulfa or Potentiated Sulfa Drugs
- Oral absorption - good
- Excreted through bile feces, urine
- Broad spectrum antimicrobial agent (bacteria and protozoa)
Sulfa or Potentiated Sulfa Drugs Synergism
Synergistic with diaminopyrimidines (Trimethoprim, Pyrimethamine)
Sulfa or Potentiated Sulfa Drugs Toxicity
Allergic reactions in dogs (Doberman Pinschers)
Sulfa or Potentiated Sulfa Drugs Resistance
By impaired drug penetration, altered enzymes
Macrolides, Azalides, Ketolides Members or Groups
-Erythromycin, Azithromycin, Clarithromycin, (Tulathromycin, Tilmicosin, Tylosin)
Macrolides, Azalides, Ketolides
Intracellular accumulation in phagocytes
Macrolides, Azalides, Ketolides
- Intracellular accumulation in phagocytes
- Inhibit protein synthesis
- Bacteriostatic
- Immunomodulatory effect
Macrolides, Azalides, Ketolides Resistance
Target site modification, active efflux, enzymatic inactivation
Macrolides, Azalides, Ketolides - Chloramphenicol
- Cloramphenicol, Thaimphenicol, florfenicol
- Inhibit protein synthesis
- Bacteriostatic
Macrolides, Azalides, Ketolides - Lincosamides
- Clindamycin, Lincomycin
- Inhibit protein synthesis
- Do not combine with macrolides
- Bacteristatic
Macrolides, Azalides, Ketolides - Rifampin
- Inhibit RNA polymerase
- Bactericidal against intracellular and extracellular bacteria
Macrolides, Azalides, Ketolides - Peptide Antibiotics
Glycopeptides (Vancomycin), Polymyxins, Bacitracin
