Lecture 36 Flashcards
What is selective toxicity?
This refers to an antibiotic targeting specific structures or metabolic features which are different between the pathogen and the host.
What is the definition of an antibiotic? What are three main types?
Substance produced by a microorganism that is antagonistic to the growth of other microorganisms in high dilution, The three major types are bacteriolytic: destroys the cell, bacteriocidal: kills the cells but doesn’t remove them and bacteriostatic: prevents growth.
What antibiotic types won’t work together and why?
Bacteriocidal and bacteriolytic antibiotics work during growth and as such won’t work with bacteriostatic antibiotics.
What two methods are used to measure antibiotic efficency?
Disk diffusion tests let us see the efficency of an antibiotic, the larger the inhibition zone the more efficent (this isn’t the only feature taken into account to decide the best antibiotic for an infection).
An Etest lets us see the minimum inhibitory concentration of an antibiotic. A patient will have roughly four times this amount kept as the blood concentration.
What are common antibacterial targets?
Cell wall, cytoplasmic membrane, protein synthesis (ribosomes), metabolic pathway, DNA synthesis or RNA synthesis.
How does penicillin work?
It interferes with the linking enzymes of the peptidoglycan cell wall, leading to NAM subunits remaining unattached to their neighbors but the cell will continue to grow, leading to the cell bursting from osmotic pressure.
What are some antibiotic resistance mechanisms?
Degrade the antibiotic enzymatically, change the antibiotic target, change the porins to decrease antibiotic uptake or pumping out the antibiotic faster.
How does antibiotic resistance arise?
The original resistance gene arises from mutation and the antibiotic rich environment gives this mutant a selective advantage these can then be spread to other species via conjugation, transduction or transformation.
What methods can be used to prevent development of antibiotic resistance?
- test the antibiotic sensitivity on target microorganism
- Use a sufficiently high concentration of the antibiotic
- Treat for a reasonable period (5-10 days).
- Complete the therapeutic regime.
- If a chronic infection treat with a combination of antibiotics.
What is our choice of antibiotics influenced by?
The nature of the infection (gram + or -), the source of infection (community/hospital), the resistance/susceptability profile (gotten from lab) or the site of infection (e.g skin, abscess, respiratory, gut or central nervous system).
What routes of administration are there?
Topical (e.g skin/eye), oral, suppository, intravenous (particularly for CNS or joint infection), intramuscular.
What are some side effects of antibiotics?
Toxicity, allergies, damage to normal microbiota and resistance development.
