Antimicrobials Flashcards
(34 cards)
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)
