In vitro activity of gemifloxacin (SB 265805) against anaerobes

Gemifloxacin mesylate (SB 265805), a new fluoronaphthyridone, was tested ag ainst 359 recent clinical anaerobic isolates by the National Committee for Clinical Laboratory Standards reference agar dilution method with supplemen ted brucella blood agar and an inoculum of 10(5) CFU/spot. Comparative anti mitrobials tested included trovafloxacin, levofloxacin, grepafloxacin, spar floxacin, sitafloxacin (DU-6859a), penicillin G, amoxicillin clavulanate, i mipenem, cefoxitin, clindamycin, and metronidazole. The MIG(50) and MIC90 ( MICs at which 50 and 90% of the isolates were inhibited) of gemifloxacin ag ainst various organisms with the number of strains tested in parentheses we re as follows tin micrograms per milliliter: for Bacteroides fragilis (28), 0.5 and 2; for Bacteroides thetaiotaomicron (24), 1 and 16; for Bacteroide s caccae (12), 1 and 16; for Bacteroides distasonis (12), 8 and >16; for Ba cteroides ovatus (12), 4 and >16; for Bacteroides stercoris (12), 0.5 and 0 .5; for Bacteroides uniformis (12), 1 and 4; for Bacteroides vulgatus (11), 4 and I; for Clostridium clostridioforme (15), 0.5 and 0.5; for Clostridiu m difficile (15), 1 and >16; for Clostridium innocuum (13), 0.125 and 2; fo r Clostridium perfringens (13), 0.06 and 0.06; for Clostridium ramosum (14) , 0.25 and 8; for Fusobacterium nucleatum (12), 0.125 and 0.25; for Fusobac terium necrophorum (11), 0.25 and 0.5; for Fusobacterium varium (13), 0.5 a nd 1; for Fusobacterium spp. (12), 1 and 2; for Peptostreptococcus anaerobi us (13), 0.06 and 0.06; for Peptostreptococcus asaccharolyticus (13), 0.125 and 0.1253 for Peptostreptococcus magnus (14), 0.03 and 0.03; for Peptostr eptococcus micros (12), 0.06 and 0.06; for Peptostreptococcus prevotii (14) , 0.06 and 0.25; for Porphyromonas asaccharolytica (11), 0.125 and 0.125; f or Prevotella bi,lia (10), 8 and 16; for Prevotella buccae (10), 2 and 2; f or Prevotella intermedia (10), 0.5 and 0.5; and for Prevotella melaninogeni ca (11), 1 and 1. Gemifloxacin mesylate (SB 265805) was 1 to 4 dilutions mo re active than trovafloxacin against fusobacteria and peptostreptococci, an d the two drugs were equivalent against clostridia and P. asaccharolytica. Gemifloxacin was equivalent to sitafloxacin (DU 6859a) against peptostrepto cocci, C. perfringens, and C. ramosum, and sitafloxacin was 2 to 3 dilution s more active against fusobacteria. Sparfloxacin, grepafloxacin, and levofl oxacin were generally less active than gemifloxacin against all anaerobes.