Antibiotics I Flashcards
What does penicillin inhibit?
Cell wall peptidoglycan synthesis
What happens when disruption of the peptidoglycan wall occurs?
Osmotic lysis of the bacterium
What causes ‘Hotspot’ in dogs?
Staphylococcus
Beta lactam antibiotics …
Contain a beta lactam ring in their molecular structures. Inhibits cell wall biosynthesis in the bacterial organism.
Beta lactams are hydrophilic, they do not like crossing membranes.
Targeting bacterial peptidoglycan is an example of what?
Selective Toxicity
What is the most commonly used beta-lactamase inhibitor?
Clavulanic acid eg amoxycillin
Beta-Lactam Antibiotics
What are natrual penicillins predominatly active against?
Gram +ves and anaerobes, but some very important gram -ves also
incl pasteurella, streptococcus, and clostridia
Beta-Lactam Antibiotics
What are aminopenicillins active against?
predom G+ve & anaerones, some important G-ve’s
Same as penicillin, but with better penetration (pKA related) into tissues/bacteria. eg amoxycillin.
Beta-lactam Antibiotics
What are first gen cephalosporons active against?
Gram +ive, successive generations have increased activity against Gram-negative bacteria.
Beta-Lactam Antibiotics
Why does first gen cephalosporins have excellent activity against staphylococcus
/
B-lactam ring is structually resistant to B lactamase.
Beta-Lactam Antibiotics
Third gen cephalosporins active against?
Further improved gram neg but reduced gram pos activity.
What is the t1/2 of B-lactams?
approx 1hr
How safe is B-lactamans in regards to toxicity and what can it be used in?
Verysafe.
Geriatrics, juveniles, pregnancy and during lactation.
What are the side effects of B-lactams and how do they come about?
Usually come about through a dysbiosis
- killing good bacteria
- recolonisation by a monomorphic population
- toxins
- GIT signs
Diarrhoahea, vomitting most common side effects
A bit about Procaine Penicillin?
- Kills streptococcus, clostridia and pasteurella
- Excellent anaerobic efficacy
- Does not work against b-lactamase producing bacteria
- Convient dosing (sid)
- Never IV
- Low LD50 esp in horses
- Prescribed commonly
What is the procaine used for in penicillin?
An insoluble salt
What can procaine do to a horse’s brain?
Inhibits neural conduction in inhibitory inter-neurons
A bit about amoxicillin - clavulanic acid
- excellent anaerobic efficiacy
- works against b-lactamase producing bacteria
- convient dosing (sid or bid)
- good distribution to most tissues
- not good for abcesses, pneumonia and mastitis
- Never IV
What happens if you give a small animal oral beta lactam?
Destroys normal gut flora, overgrowth of clostridum difficile, toxin production.
Give a summary of Aminoglycosides
- 30S ribosome target
- Gram neg mostly
- Doesnt kill anaerobes
- SID dosing
- Synergy with b-lactams
- Poor oral absorption
- Vestibular ototoxicity
- Nephrotoxicity
What is one of, if not the most commonly used antibiotic classes for production animals?
Tetracyclines
What is the mechanism of action of the ocytetracycline?
Binds to ribosomes and inhibits protein synthesis
A bit about tetracyclines?
- broad spectrum
- long t1/2 (12hrs)
- excellent distribution
- 50:50 hepatic: renal metabolism
- out of date solutions are toxic
- large animal use mostly
Name the two classes of beta lactams
- penicillins
- cephalosporins (more resistant to breakage)
