MULTICENTER COLLABORATIVE STUDY FOR THE IN-VITRO EVALUATION OF NEW MACROLIDES DIRITHROMYCIN AND ERYTHROMYCYLAMINE

A national study was conducted to determine the in vitro activity of 2 newer macrolides, dirithromycin and erythromycylamine compared with t hat of erythromycin, tetracycline and penicillin. Nineteen major teach ing hospitals participated in the study. Minimal Inhibitory Concentrat ions (MICs) were determined by agar dilution, mostly using Iso-Sensite st Agar and an inoculum of 10(4) cells per spot. 2284 clinically signi ficant strains were isolated in late 1991 and early 1992, comprising 1 736 Grampositive cocci, 355 Haemophilus influenzae, 97 Moraxella catar rhalis, 32 Listeria monocytogenes, 25 Neisseria meningitidis and 39 Ne isseria gonorrhoeae were tested. The study indicates that dirithromyci n and erythromycylamine possess antibacterial activity equivalent to t hat of erythromycin against most Grampositive cocci and M. catarrhalis . Strains resistant to erythromycin were also resistant to dirithromyc in and to erythromycylamine. Tetracycline was as active as the macroli des against both penicillin-resistant and penicillin-susceptible strai ns of Staphylococcus aureus. Coagulase-negative penicillin-resistant s taphylococci, compared with tetracycline, were relatively resistant to the macrolides. H. influenzae was less susceptible than the Gram-posi tive cocci.