g) 28-Oct-13 Flashcards
Two examples of atypical bacterial species
Rickettsia, mycoplasma, clamydia, borrelia, bartonella, mycobacterium.
Do not gram stain!
What are the 4 spectrums of the antimicroibial spectrum?
- Gram +ve aerobes
- Gram -ve aerobes
- Obligate anaerobes
- Penicillinase producing Staph
What are clues that might indicate bacterial infection?
Heat, pyrexia, neutrophillia.
BUT these can be produced by other things e.g. neoplasm, stres etc
Three examples that are commonly mistaken as having bacterial aetiology
- Vomiting without diarrhoea
- Haematouria in cat <10 years (too concentrated)
- Blood in faeces (no protective antimicrobials)
Two examples of antimicrobial classes that inhibit cell wall synthesis
Penicillin, Cephalosporin. (Both bacteriocidal)
What are the bacteriocidal drugs?
Penicillin, Cephalosporin, Aminoglycoside, Metronidazole, Fluroquinoles, Potentiated sulphonamides
What are the bacteriostatic drugs?
Tetracycline, Chloramphenicol, non-potentiated sulphonamides, macrolides, lincosamides
Example of an antimicrobial that inhibits cell membrane function
Polymyin, amphotericin B, imidazoles, nystalin
Examples of antimicrobials that inhibit protein synthesis
Chloramphinicol, macrolides, lincosamides, tetracycline (are bacteriostatic) and aminoglycosides (which is bacterocidal)
Why is it important to distinguish between time dependent and concentration dependent bacteriocidal drug?
Time dependent are SLOWLY bacteriocidal. o.e. the plasma levels should remain above the MIC for 80% of the time.
Concentration dependent drugs the peak concentration achieved predicts antimicrobial success
Examples of time dependent bacteriocidal drugs?
Penicillin, Cephalosporin, Potentiated sulphonamides
Examples of concentration dependent bacteriocidal drugs?
Metronidazole, Fluroquinolones, Aminoglycosides
Why can you not given bacteriocidal and bacteriostatic drugs together?
For bacteriocidal drugs to work the bacteria need to be multiplying.
What is the most common type of bacteria to infect the
a) UTI
b) Skin
c) Pyothorax
a) UTI = E-coli
b) Skin = Staphylococcus sp
c) Pyothroax = Obligate/ Faxulative anaerobes
Examples of sites that are difficult to penetrate
CNS (inc brain), eye, prostate, bronchus, mammary gland. The lipid membrane provides a barrier.
Also difficult to achieve in poorly perfused tissues i.e. extremities during shock
When might prophyalactin antibacterials be used in surgery?
-Patients with leucopemia, contaiminated surgury, where surgery lasts over 90minutes, where consequences would be disastrous (orthopaedic),
NEED TO BE ADMINISTERED BEFORE SURGURY SO ADEQUATE LEVELS AT TIME OF CONTAIMINA
What three antimicrobials have extensive activity against OBLIGATE ANAEROBIC (i.e. git flora)
Penicillins, Chloramphinicol ()
Lincosamides (bacteriostatic)
Which antimicrobials undergo extensive entero-heaptic recycling. When would this be advantageous?
Tetracyclines, Chloramphincol, Lincosamides.
Useful if you have to suppress endogenous GIT glora
Which penicillins are effective against gram +ve aerobes
Penicillin G (natural) is a narrow spectrum antimicrobial that is effective against gram + aerobes. It is SENSITIVE to beta lactamases. Aminopenicillins are BROAD spectrum but susceptible to beta-lactamases unless co-formulated with clavulanic acid
What are the differences between different generations of cephalosporins?
Second generation: Broadest spectrum included gram +ve (inc Staphylococci), good anaerobic activity and reasonable gram negative.
Third generation: Should be reserved for difficult gram -ve
When should third generation cephalosporins be used?
Difficult gram negative infections.
Example of a bacteriostatic drug that works by inhibiting protein synthesis. How is this group of drugs separated?
Tetracyclines. Separated into water soluble tetracyclines (oxytetracyclines) and lipid soluble
Example of a lipid soluble tetracyclines
Doxycycline. More lipid soluble so can penetrate prostate and blood bronchus barrier. Eliminated in faeces so safer in liver failure
What drug would you use for prostatitis in a patient with kidney disease
Needs to be lipid soluble and eliminated in faeces i.e. lipid soluble tetracycline = DOXACYCLINE
How do aminoglycosides work? What bacteria are they BEST against? Which bacteria do they have NO ACTION against?
Cause a mis-reading of mRNA is BACTERIOCIDAL. Concentration dependent.
Gram negative aerobic antibacterial actions. No action against anaerobes. NEED OXYGEN TO ENTER CELL.
Spectrum of macrolides/lincosamides
Narrow spectrum. Mainly Gram POSITIVE. Also good against mycoplasma.
Both are bacteriostatic and work by inhibiting protein synthesis
Sides effects of erythromycin
Vomiting in dogs
In which species does trimethoprine cause immune-mediated reactions?
Dobermanns, Pinschers. Trimethoprine is a potentiated sulphonamides (bacteriocidal) and has a short half life.
Is BROAD spectrum (not difficult gram -ve or serious anaerobic infections)
Which group do fluoroquinoles have NO action against
Anaerobes. Fluronquinoles can cross the BBB.
Should be reserved for difficult gram -ve
When should chloramphinicol be used? When is it contraindicated?
Bacteriostatic. Imbhibits bacterial protein synthesis.
Broad spectrum, including anaerobes. Excellent tissue penetration.
Do not use in animals with poor hepatic function as it causes irreversible hepatic enzyme inhibition.
Which group do fluoroquinoles have NO action against
Anaerobes. Fluronquinoles can cross the BBB.
Should be reserved for difficult gram -ve
When should chloramphinicol be used? When is it contraindicated?
Bacteriostatic. Imbhibits bacterial protein synthesis.
Broad spectrum, including anaerobes. Excellent tissue penetration.
Do not use in animals with poor hepatic function as it causes irreversible hepatic enzyme inhibition.
Why do we need to be careful of antimicrobial residues in food?
Some people have penicillin allergies = very dangerous.
Dairy wants no antibiotics in milk as affects cheese product (i.e. kills required natural bacteria)
Global antimicrobial resistance
Which bacteria do dairys want in the milk to aid cheese production
Lactococci, Lactobacilli or Streptococci. All gram positive
Two different types of mastitis tube
- Dry Cow Tube (MUCH LONGER LASTING)
Much LONGER withdrawal period - Lactating tubes
What does the cascade say are withdrawal times in milk and milk if not specifically specified?
Milk: 7 days
Meat: 28 days