Antibiotics Flashcards
Saving commensals and overall population susceptibility (Bacterial Refugia) is achieved by what treatment approach
Specific
What is one of the best treatment approaches on finding an increase in fibrinogen, white cell count and presence on phagocytosed bacteria on microscopy?
Combination showing synergism/appropriate broad spectrum
Explain antibiotic combination antagonism
Static + cidal
For how long should antibiotic therapy be continued after the clinical symptoms disappear?
2 days
Name one factor that may increase the necessity of antibiotic use during surgical procedures.
Tissue handling
How does polar antibiotics (water soluble) antibiotics cross cell membranes?
Active/receptor assisted
Define Area Under the curve (AUC)
Amount of absorbed drug in blood stream
What is the half life of a drug?
Time to half concentration
Explain the mechanism of time dependent antibiotics.
Time above MIC 40-70%. Average of 50%
Name 1 factor which will influence the volume of distribution of an antibiotic.
Protein binding/charge/ size/ pH
How can the amount of free antibiotic in the blood be increased
Increase dose
Define bioavailability.
Amount of drug in blood measured by AUC
Name 3 factors that will influence bioavailability.
Dose, Injection site and volume
Define Volume of distribution.
(Total dose-bioavailability) – blood concentration= Vd example. Inject 100mg absorbed 60%. Total amount in body 60mg Blood concentration 20mg 60/20 = 3L/KG
Which group of antibiotics generally have a large volume of distribution?
Lipid soluble
What are the rules regarding ELDU in pet animals?
Does not apply. Need confirmation animal wont enter food chain.
Which are the major food producing species?
Cattle/swine/poultry
Where is the best location to give a sc injection in a small ruminant?
axilla
What is a side effect giving propylene glycol intravenously?
Lower blood pressure
Give an example of a time dependent antibiotic.
Tetracyclines
Give an example of an concentration dependent antibiotic.
Fluroquinolones. Depend on concentration. Does not equate to multiple dosing because of post antibiotic effect
AUC of penicillin would be affected if which organ fails?
Renal
What is the spectrum of penicillin?
Gram positive anerobe
Why is penicillin commonly used for the following wound infections, black leg and listeria?
Gram positive
In which production animals is the use of penicillin prohibited?
Lactating dairy cows and veal calves
You have a animal with a lymph adenopathy. There are phagocytosed bacteria in the lymphocytes. Culture show susceptibility to both procaine penicillin and Tulathromycin (macrolide). Which of the 2 antibiotics would you choose as a initial treatment and why?
Penicillin. Bactericidal preferred over intracellular
You have 2 antibiotics. One has a Vd of 10l/kg and the other 36L/kg which of the 2 antibiotics would you choose for a case of septic meningitis. Assume that the sensitivity of both for the infection is the same.
Vd 10L, bactericidal
Give 2 advantages of using synthetic penicillin over procaine penicillin.
Gram negative spectrum/can be used in lactating dairy cows and veal calves
Why is the meat withdrawal time for procaine penicillin problematic.
Because of variation in dose rates
For what type of antibiotic treatment is potassium penicillin often used.
Regional iv antibiosis
What is the indication of long acting ceftiofur?
Metaphylaxis. Treatment of Footrot,metritis,BRD
What part of the cephalosporin ELDU cannot be violated?
Dose, route, treatment schedule
From an antimicrobial perspective give 2 reasons why cephalosporin might give a better clinical response than ampicillin.
Less susceptible to penicillinase and wider gram negative spectrum
Under what circumstances would you have to use ampicillin rather than ceftiofur?
Lactating dairy cow and veal calf
Name a non-antibacterial effect of tetracycline.
Inhibits MMP’s (anti-inflammatory)
Oxytetracycline is not labeled to be used in lactating dairy cows but it is used topically for foot warts – Why?
Doesn’t get into the milk if used topically
What is the mechanism of action of oxytetracycline?
Reversible 30S ribosome binding. Relates to relapses as it is a time dependent antibiotic. bacteriostatic.
Define the extended spectrum of Oxytetracycline.
mycoplasma, richettsia, erlichia, protozoa, babesia
Name one of the mechanisms of bacterial resistance to oxytetracycline.
Formation of the efflux pump by the bacteria
In a time dependent antibiotic what needs to be done to increase the dose interval.
Increase the dose to extend the time
What effect of oxytet in the blood may make it go down?
Binding to ionized calcium
What are the absolute restrictions on the ceftiofur label
Dose,route,dose interval
You are asked to treat a septic joint caused by Ecoli in a veal calf. Which of the following antibiotics would you choose and give inclusion /exclusion criteria for each
Ampicillin: Gram –ve; small Vd; Polar; Bactericidal
Enrofloxacin: Gram-ve; Larger Vd; Lipid soluble; gram -ve ; intracellular; bactericidal; intracellular
What are 2 main indications of Danofloxacin
Treatment and control of BRD
What is a major problem using Tilmicosin
Can be lethal in humans and pigs
What is the main indication of Pirsue
Mastitis
Name 5 groups of organisms for which Macrolides are used
Gram +ve; Gram –ve; Spirochaetes; anerobes; mycoplasma
Name antibiotic groups specifically labeled for foot rot
Oxytetracyclines , macrolides, Florfenicol, Sulfadimethoxine, Excede
Some macrolides have extended dose intervals through what mechanism
Entero-hepatic cycle
Name 2 time dependent antibiotic groups with bactericidal capabilities
Florfenicol; Penicillins
What is the main indication of oral sulfas for calves
coccidiosis
What is the mechanism of action of Sulfonamides
Inhibit formation of folic acid necessary for the formation of bacterial RNA
What makes sulfas bactericidal
Addition of diaminopyridimidines (trimethoprim)
What does sulfas have in common with penicillins
Depend on rapid growth of the organism.
Not good for chronic infections
Why do the sulfonamides have a latent period
Bacteria use stored folic acid
What tissues are sulfonamides least active
Necrotic material and puss
