STREPTOGRAMINS - A UNIQUE CLASS OF ANTIBIOTICS

Streptogramin antibiotics represent a unique class of antibacterials i n that each member of the class consists of at least 2 structurally un related molecules: group A streptogramins (macrolactones) and group B streptogramins (cyclic hexadepsipeptides). Both group A and group B st reptogramins inhibit protein synthesis at the ribosomal level, and the y act synergistically against many isolates, their combination generat ing bactericidal activities and reducing the possibility of emergence of resistant strains. The mechanisms of acquired resistance to group B streptogramins are similar to those induced by erythromycin, but grou p A streptogramins remain unaffected by target modifications and activ e efflux. The pharmacokinetic parameters of group A and group B strept ogramins in blood are quite similar. In addition, both the A and B gro ups penetrate and accumulate in macrophages and in the bacterial veget ations of experimental endocarditis. There are important structural an d biological differences between the streptogramins and the macrolides . The main differentiating features are the rapid antibacterial killin g of streptogramins and the rarity of cross-resistance between the 2 g roups of antibiotics.