Streptogramin Antibiotics and Oxazolidinone Antimicrobial Agents Flashcards
Synercid is a mixture containing?
30% quinupristin and 70% dalfopristin
Are quinupristin and dalfopristin useful on their own?
No, each of these compounds is bacteriostatic alone, but bactericidal in combination
Dalfopristin MOA
directly interferes with the peptidyl transferase-catalyzed step
What reaction does peptidyl transferase (ribosomal RNA) catalyze?
catalyzes the formation of a peptide bond between the two amino acids present in the ribosome
Quinupristin MOA
binds in the ribosomal tunnel and causes blockage of the tunnel
Syncercid is used IV for treatment of:
- Vancomycin-resistant Enterococcus faecium bacteremia
- Skin infections caused by MRSA
- Vancomycin-resistant Enterococcus faecium urinary tract infections
Most common resistance to quinupristin is due to?
adenine methylation of A2058 in the 23S rRNA as in the case of erythromycin and clindamycin
What can resistance to Streptogramin also be caused by?
resistance can also be due to efflux and enzymatic inactivation (metabolism) by resistant bacteria
What is Streptogramin likely to be reserved for?
reserved for serious life-threatening infections caused by gram (+) organisms
Mild side effects of synercid?
inflammation and pain at the site of injection, nausea, diarrhea, muscle weakness and rash
Drug interactions of Streptogramins
Streptogramins inhibit cytochrome CYP3A4
CYP3A4 metabolizes
warfarin, diazepam, astemizole, terfenadine, cisapride, non-nucleoside reverse transcriptase inhibitors and cyclosporine
Oxazolidinones are a novel class of antimicrobials that act by
inhibiting protein synthesis
MOA of linezolid?
acts early by potent interaction with 50S ribosomal subunit
In the initiation step of bacterial translation, the 50S subunit associates with?
associates with fMet-tRNA and a complex composed of the 30S ribosomal subunit and mRNA to form the functional 70S initiation complex
What does linezolid have affinity for?
the 50S subunit - no affinity to the 30S subunit
Linezolid interaction with the 50S subunit does what?
prevents the formation of the 70S initiation complex
Which rRNA does linezolid specifically interact with?
the 23S rRNA
Linezolid is used to treat:
- Vancomycin-resistant Enterococcus faecium
- Nosocomial pneumonia caused by methacillin - resistant strains of Staphylococcus aureus
- Skin infections caused by methicillin-resistant strains of Staphylococcus aureus
Emergence of linezolid resistant has been reported in which species?
Enterococcus species, MRSA, and E. coli
Other mild reported side effects of linezolid?
headache, tongue discoloration and oral Monilia (Candida) infections
More serious side effects of linezolid?
thrombocytopenia, GI bleeding and anemia
Long-term treatment of linezolid resulted in?
fully reversible myelosuppression and linezolid-induced neuropathy
What should be monitored weekly in patients receiving linezolid?
complete blood counts
Linezolid is a reversible, nonselective inhibitor of
monoamine oxidase
Patients taking linezolid should not consume large quantities of?
food or beverages that are rich in tyramine (cheese, red wine) in order to avoid a significant pressor response
Because of drug interactions, linezolid has the potential for interaction with?
adrenergic and serotonergic agents
What has been observed when linezolid is administered to normotensive subjects?
a reversible potentiation of pressor response to pseudoepherine
