In vitro activity of HMR 3004 (RU 64004) against 502 strains of anaerobic bacteria

The in vitro activity of HMR 3004 (RU 64004) was compared to azithromycin ( AZ), clarithromycin (CL), erythromycin (ER) and roxithromycin (RO). Anaerob es (n = 512) were tested using the NCCLS-approved Wadsworth brucella laked blood agar dilution method. Breakpoints for the inclusion of strains into t he susceptible/intermediate categories were 4 mu g/mL for all agents. Organ isms tested included Bacteroides fragilis group species (206), Campylobacte r gracilis (13), Bacteriodes species (13), Fusobacterium species (540 K), B ilophila wadsworthia (27), Peptostreptococcus (35), Porphyromonas sp. (12), Prevotella sp. (41), Sutterella wadsworthensis (16), Clostridium sp. (56) and Gram-positive non-sporeforming rods (29). HMR 3004 inhibited 78% of B. fragilis and 69% of B. fragilis groups species, respectively. Ninety-three percent of other Bacteroides were inhibited by HMR 3004, compared to 80% fo r AZ, 87% for ER, and 93% for CL and RO. HMR 3004 and AZ inhibited all Porp hyromonas species, compared to 93-94% for the other agents. HMR 3004 inhibi ted 98% of Prevotella compared to 91%, 93%, 93% and 95% for ER, AZ, RO and CL, respectively. Activity against Biophila wadsworthia (85-96%) was excell ent compared to poor or no activity for the other macrolides. All agents in hibited 100% of Clostridium perfringens and 50% of C. difficile and C. ramo sum. None of the agents had activity against the Fusobacterium mortiferum/v arium group. Approximately 90% of non-sporeforming Grampositive rods were i nhibited by all of the agents. Overall, HMR 3004 had the best activity agai nst anaerobes, inhibiting 77% compared to AZ (46%), CL (73%), ER (47%) and RO (46%). (C) 1999 Academic Press.