streptogramin streptogramin streptogramins are a class of antibiotics. streptogramins are effective in the treatment of vancomycin-resistant staphylococcus aureus (vrsa) and vancomycin-resistant enterococcus (vre), two of the most rapidly growing strains of multidrug-resistant bacteria. they fall into two groups: streptogramin a and streptogramin b. members include: quinupristin/dalfopristin pristinamycin virginiamycin nxl 103, an experimental streptogramin in clinical trials for the treatment of respiratory tract infections.