Infection: Macrolides Flashcards
Why are macrolides a good alternative for patients who are penicillin-allergic?
They have an antibacterial spectrum that is similar too but not identical to that of penicillin.
They are active against many-penicillin-resistant staphylococci, but some are now also resistant to the macrolides.
What are the main indications for macrolides? (3)
- Camplylobacter enteritis
- Respiratory infections (including pneumonia, whooping cough, Legionella, chlamydia, and mycoplasma infection).
- Skin infections
Erythromycin was the original macrolide isolated and is used in the treatment of what? (3)
- Early syphilis
- Uncomplicated genital chlamydial infection.
- Non-gonococcal urethritis.
What type of activity does Erythromycin have against haemophilus influenzae?
Poor.
What are the common side effects erythromycin can cause in some patients? How can these be avoided?
N, V + D which can be avoided in mild-moderate infection by giving a lower dose but if a more serious infections, such as Legionella pneumonia, is suspected then higher doses are needed.
How does azithromycin differ from erythromycin in terms of activity?
Azithromycin has slightly less activity than erythromycin against Gram-positive bacteria, but enhanced activity against some Gram-negative organisms like Haemophilus influenzae.
Why is once daily dosing with azithromycin recommended?
Plasma concentrations of azithromycin are very low, but tissue concentrations are much higher and it has a long tissue half life.
What macrolide is the best choice to treat an Haemophilus influenzae infection?
Azithromycin as although it has less activity than erythromycin against Gram-positive bacteria it has enhanced activity against some Gram-negative organisms like Haemophilus influenze.
How does clarithromycin relate to erythromycin in terms of structure and activity?
Clarithromycin is an erythromycin derivative with slightly greater activity than the parent compound. Tissue concentrations are higher than with erythromycin. It is given twice daily. Clarithromycin is also used in regimens for Helicobacter pylori eradication.
What macrolides is used in regimens for Helicobacter pylori eradication?
Clarithromycin is an erythromycin derivative with slightly greater activity than the parent compound. Tissue concentrations are higher than with erythromycin. It is given twice daily. Clarithromycin is also used in regimens for Helicobacter pylori eradication.
What macrolides have a role in the treatment of lyme disease?
Erythromycin, azithromycin, and clarithromycin have a role in the treatment of Lyme disease.
Spiramycin is also a macrolide which is used for the treatment of toxoplasmosis.
What macrolide is used for the treatment of toxoplasmosis?
Erythromycin, azithromycin, and clarithromycin have a role in the treatment of Lyme disease.
Spiramycin is also a macrolide which is used for the treatment of toxoplasmosis.
Where do macrolides exhibit their mechanism of action?
Bind - reversibily - to the P site on the 50s portion of the bacterial ribosome.
As a result of this binding, tRNA is dissociated from its translocation site, thereby perilously damaging the protein synthesis sequence
Macrolides are predominatly:
Bacteriostatic
OR
Bacteriocidal
Predominatly bacteriostatic.
Inhibit growth of bacteria but not themselves kill all bacteria.
Fidaxomicin is an exception: (USed for C. diff recurrence)
Why is Erythromycin given as an entetic-coated tablet or an ester prodrug?
It is destroyed at acid pH
