Streptogramins

Streptogramins are a type of antibiotic that inhibit protein synthesis in bacteria by binding to the 50S ribosomal sub-unit, in a similar way to macrolides and lincosamides.

They are produced naturally by certain subspecies of Streptomyces bacteria. Streptogramins include two structurally unrelated components, streptogramin group A (dalfopristin) and streptogramin group B  (quinupristin). A mixture of group A and group B causes a 10 to 100-fold greater bacterial growth inhibition than the individual components given alone, and the combination is considered bactericidal. Streptogramins are mostly only effective against gram-positive bacteria.

Quinupristin and dalfopristin are marketed in a fixed 30:70 ratio as Synercid which is administered by injection. Side effects may include severe stomach pain, diarrhea that is watery or bloody; pain, bruising, swelling, or severe irritation around the IV needle site; jaundice (yellowing of the skin or eyes); seizures (convulsions); an irregular heart rate; sudden numbness or weakness; severe headache; slurred speech; or problems with balance.