antibioticsbooks

Streptogramins
15
Agent: quinupristin/dalfopristin
The increase in resistance to antibiotics among
staphylococci and enterococci led to pharmaceutical
companies increasing the development of drugs
to combat these resistant infections. One of the
first of the newer drugs to treat VRE and MRSA
infections was quinupristin/dalfopristin. These
drugs are two different streptogramins given in a
combined formulation. Though each separate streptogramin
is bacteriostatic, when given together
they act synergistically to give bactericidal activity
against some Gram-positive cocci; hence the
brand name of this drug: Synercid. Quinupristin/
dalfopristin initially enjoyed frequent use, particularly
to treat VRE infections, but its use has
lessened as other agents have come on the market.
Other streptogramins have been developed and are
used in animals as growth promoters, a questionable
but common practice in modern agriculture
(where .50% of U.S. antibiotics are used).
Mechanism of Action
Quinupristin and dalfopristin bind to different
sites on the 50S subunit of the bacterial ribosome
to prevent bacterial protein synthesis.