Self directed antibiotic module Flashcards
Revision
How do antibiotics that inhibit protein synthesis do so?
Antibiotics that inhibit protein synthesis do so by attaching to bacterial ribosomes, which are structurally different from mammalian ribosomes.
How do we know that most antibiotics that inhibit protein synthesis are bacteriostatic?
Usually protein synthesis can resume when the antibiotic is removed, so most of these antibiotics (macrolides, tetracyclines) are bacteriostatic.
What is the definition of bacteriostatic?
Inhibits growth but does not kill the bacteria. The bacteria are then killed by white blood cells.
What antibiotics that inhibits protein synthesis is the exception and is not bacteriostatic?
THe exception to this is the aminoglycoside group, where the binding of these antibiotics to the ribosome is lethal.
What is the role of Gentamicin (IV)?
It binds to ribosomes inhibiting protein synthesis, but bactericidal (kills bacteria).
Why must Gentamicin (IV) be given intravenously?
Not absorbed from the gut - must be given intravenously IV (occasionally intramuscularly, IM)
What is Gentamicin (IV) used for?
Active mainly against Gram negative aerobic organisms such as coliforms and Pseudomonas aeruginosa) and is used in hospital for treating serious (life-threatening) Gram negative infection.
Excreted in the urine.
How are Erythromycin, clarithromycin and azithromycin excreted from the body?
This group of antibiotics is excreted via the liver, biliary tract and into the gut (not excreted in urine).
What are Erythromycin, clarithromycin and azithromycin used for?
These antibiotics are lipophilic and pass through cell membranes easily. They are useful for treating certain infections where bacteria “hide” from the host’s immune system by getting into the host cells.
Erythromycin is safe in pregnancy (the others have not been trialled in pregnant women).
What are other antibiotics that inhibit protein synthesis?
Clindamycin
Chloramphenicol
Tetracyclines
(all of the above antibiotics are excreted via the liver and biliary system).
What is Clindamycin used for?
Used 2nd line to treat serious Staphylococcal and Streptococcal infection, particularly in penicillin-allergic patients.
Also active against the “true” anaerobes (organisms that will not grow in the presence of oxygen).
What is Chloramphenicol used for?
Mainly used as topical treatment for eye infections (as eye drops)
What is tetracyclines used for?
treating infections caused by bacteria that do not have a proper bacterial cell wall (atypical pneumonia organisms).
Treating some infections (chest, skin) in patients who are penicillin allergic.
How do tetracyclines work?
These antibiotics also inhibit bacterial protein synthesis by attaching to ribosomes and are bacteriostatic.
Excreted mainly via the liver and biliary system into the gut.
What type of tetracycline is used in Tayside?
Doxycycline (oral) is he tetracycline used in Tayside.
How does selection pressure affect resistance of bacteria?
Exposure of bacteria to antibiotics in the environment encourages resistance as small numbers of “resistant mutants” will survive whilst susceptible organisms die off (“survival of the fittest”).