PHARMACOLOGY - Antibiotics Flashcards
Which factors should you consider when selecting antibiotics in farm animal medicine?
Spectrum of activity
Location of bacteria
Bacteriostatic or bacteriocidal
Drug licensing
Withdrawal periods
Route of administration
Duration of action
Volume of administration
Cost
RUMA categorisation
What are the three main classifications of bacteria?
Gram positive
Gram negative
Mycoplasma
What is the difference between gram positive and gram negative bacteria?
Gram negative bacteria are surrounded by a thin peptidoglycan wall which is surrounded by an outer membrane containing lipopolysaccharide (LPS) which is also known as endotoxin. Gram positive bacteria lack an outer membrane however have a thicker peptidoglycan cells wall
What are the subdivisions of gram positive bacteria?
Non beta lactase producing bacteria
Beta lactamase producing bacteria
What are the subdivisions of gram negative bacteria?
Enteric bacteria
Fastiduous bacteria
What is enteric bacteria?
Enteric bacteria are bacteria which are a part of the gastrointestinal microbiome
What is fastiduous bacteria?
Fastiduous bacteria is bacteria which has complex nutritional requirements
Because of this, fastiduous bacteria is challenging to culture but easier to treat
When are bacteriocidal antibiotics preferential to bacteriostatic antibiotics?
Be aware in most situations either is fine
Bacteriocidal antibiotics are preferential in neonatal or immunosuppressed animals
When are bacteriostatic antibiotics preferential to bacteriocidal antibiotics?
Be aware in most situations either is fine
Bacteriostatic antibiotics are preferential in situations where killing the bacteria can cause harm such as endotoxic shock
Why is it so important to check the data sheet when choosing appropriate antibiotics for farm animals?
Ensure the drug and route of administration are licensed for use in this species, if not use the cascade if appropriate. Furthermore, always check withdrawal periods as these are food producing animals so this is critical!
When should the cascade be used?
The cascade should be used when there is not a sutiable licensed product available. Any time we are using an unlicensed product or using a licensed product NOT in accordance with the summary of produce characteristics this has to be done under the cascade and we have to be able to justify its use in regards to animal welfare
What are the additional regulations you must follow when prescribing drugs to food producing animals under the cascade?
- Maximum residue limit (MRL)
- Imported drugs must be authorised in a food producing species in the country of origin
- Apply minimum statutory withdrawal period
- Veterinarians must keep additional records for 3 years
- Applies to a single holding (can only be used on the premesis where it has be presribed for)
What is the minimum statutory withdrawal period for farm animal products?
Milk: 7 days
Eggs: 14 days
Meat/offal: 28 days
What are the RUMA categorisations of antibiotics in farm animals?
Category A - Avoid
Category B - Restrict (High Priority Critically Important Antibiotics)
Category C - Caution
Category D - Prudence
What is the mechanism of action of β-lactams?
β-lactams break down the bacterial peptidoglycan cell wall
What are the general characteristics of β-lactams?
Bacteriocidal
Renally excreted
Which β-lactams are in the prudent category?
Penicillin
Amoxicillin
What is the spectrum of activity for penicillin?
Gram positive, non beta lactamase producing bacteria
What is the spectrum of activity for amoxicillin?
Gram positive, non beta lactamase producing bacteria
Gram negative, enteric bacteria
Gram negative, fastiduous bacteria
Which β-lactams are in the caution category?
Potentiated Amoxicillin (Amoxicillin Clavulanic acid)
Cephalosporins (first and second generation)
What is clavulanic acid?
Clavulanic acid is a beta lactamase inhibitor
What is the spectrum of activity for potentiated amoxicillin?
Broad spectrum
Except mycoplasma as they don’t have a cell wall
Which β-lactams are in the restrict category?
Cephalosporins (third and fourth generation)
What is the spectrum of activity for cephalosporins?
Broad spectrum
Except mycoplasma as they don’t have a cell wall
Which RUMA categorisation are the tetracycline antibiotics?
Tetracyclines are in the prudent category
What is the mechanism of action of tetracyclines?
Tetracyclines inhibit bacterial protein synthesis
What are the general characteristics of tetracylcines?
Bacteriostatic
Broad spectrum
Variable activity agaisnt mycoplasma
Concentrate well in inflamed areas
Why should tetracyclines never be administered alongside β-lactams?
Tetracyclines are antagonistic to β-lactams
What are the two most common tetracylcines used in farm animals?
Oxytetracycline
Chlortetracycline
Which RUMA categorisation are the aminoglycoside antibiotics?
Aminoglycosides are in the caution category
What is the mechanism of action of aminoglycosides?
Aminoglycosides inhibit bacterial protein synthesis
What are the general characteristics of aminoglycosides?
Bacteriocidal
Effective against gram negative bacteria (enteric and fastiduous)
Little effect agaisnt mycoplasma
What is the formulation of aminoglycosides available in the UK?
Streptomycin combined with Penicillin (PenStrep)
Covers gram negative bacteria and gram positive, non betalactamase
Which bacteria is streptomycin particularly effective agaisnt?
Actinobacillus lignieresii (wooden tongue)
Which RUMA categorisation are sulphonamides (TMPS)?
Sulphonamides (TMPS) are in the prudent category
What is the mechanism of action of sulphonamides (TMPS)?
Sulphonamides (TMPS) inhibit bacterial folate synthesis
What are the general characteristics of sulphonamides (TMPS)?
Bacteriostatic but can be bacteriocidal in some instances
Broad spectrum (except mycoplasma)
Some activity agaisnt protozoa
Good intestinal penetration
Inhibited by pus
Which RUMA categorisation is florfenicol?
Florfenicol is in the caution category
What are the general characteristics of florfenicol?
Bacteriostatic but can be bacteriostatic in some instances
Broad spectrum
Effective against mycoplasma
Very good tissue penetration (joints, testicles, lungs, blood brain barrier)
Which RUMA categorisation are macrolides?
Macrolides are in the caution category
What is the mechanism of action of macrolides?
Macrolides inhibit bacterial protein synthesis
What are the general characteristics of macrolides?
Bacteriostatic
Effective agaisnt gram positive and fastiduous gram negative
Effective against mycoplasma
Concentrate well in inflamed areas (as can enter macrophages)
Long duration of action
Which macrolides are most commonly used in farm animals?
Gamithromycin
Tilmicosin
Tylosin
Which RUMA categorisation are lincosamides?
Lincosamides are in the caution category
What is the mechanism of action of lincosamides?
Lincosamides inhibit bacterial protein synthesis
What are the general characteristics of lincosamides?
Bacteriostatic
Effective agaisnt gram positive and fastiduous gram negative
Which RUMA categorisation are fluoroquinolones?
Fluoroquinolones are in the restrict category
What is the mechanisms of fluoroquinolones?
Fluoroquinolones inhibit bacterial protein synthesis
What are the general characteristics of fluoroquinolones?
Bacteriocidal
Broad spectrum
Effective agaisnt mycoplasma
