Combination of Streptogramin B quinupristin with Streptogramin A dalfopristin in a 30:70 ratio From fermentation of Streptomyces pristinaspiralis Largely gram positive bacteria BINDS TO 50S subunit RESERVED TREATMENT FOR SERIOUS INFECTIONS CAUSED BY MULTI DRUG RESISTANT GRAM POSITIVE ORGANISMS SUCH AS VANCOMYCIN-RESISTANT ENTEROCOCCUS FAECIUM