MARIDOMYCIN, A NEW MACROLIDE ANTIBIOTIC. II

Maridomycin has been found to have a strong in vitro antibacterial activity against Gram-positive bacteria and some Gram-negative bacteria such as Neisseria gonorrhoeae and Vibrio cholerae. The antibiotic was more active at pH9 than pH6. The antibacterial activity was enhanced by decrease in bacterial inoculum size, but not influenced by the presence of horse serum. The in vitro bacterial resistance to maridomycin was enhanced stepwise by serial transfer, and cross resistance was observed between maridomycin and each of macrolide antibiotics tested. This antibiotic, however, was effective against clinically isolated macrolide-resistant group B and C staphylococci. Furthermore, maridomycin demonstrated bacteriostatic activity and its protein binding ratio examined by cellophane bag dialysis method was found to be low. Maridomycin was as effective as leucomycin on Gram-positive bacterial infection in mice by subcutaneous, intraperitoneal or intravenous administration.