title: Susceptibilities of 428 gram-positive and -negative anaerobic bacteria to Bay y3118 compared with their susceptibilities to ciprofloxacin, clindamycin, metronidazole, piperacillin, piperacillin-tazobactam, and cefoxitin.
abstract: The susceptibilities of 428 gram-negative and gram-positive anaerobes (including selected cefoxitin-resistant strains) to Bay y3118 (a new fluoroquinolone), ciprofloxacin, clindamycin, metronidazole, cefoxitin, piperacillin, and piperacillin-tazobactam were tested. Organisms comprised 115 Bacteroides fragilis group, 116 non-B. fragilis Bacteroides, Prevotella, and Porphyromonas spp., 40 fusobacteria, 58 peptostreptococci, 48 gram-positive non-spore-forming rods, and 51 clostridia. beta-Lactamase production was demonstrated in 87% of the gram-negative rods but in none of the gram-positive organisms. Overall, Bay y3118 was the most active agent, with all organisms inhibited at an MIC of < or = 2.0 micrograms/ml (MICs for 50% [MIC50] and 90% [MIC90] of strains tested, 0.125 and 0.5 microgram/ml, respectively). By contrast, ciprofloxacin was much less active, with only 42% of strains susceptible at a breakpoint of 2.0 micrograms/ml (MIC50, 4.0 micrograms/ml; MIC90, 16.0 micrograms/ml). Metronidazole was active against all gram-negative rods, but 7% of peptostreptococci, 83% of gram-positive non-spore-forming rods, and 4% of non-Clostridium perfringens, non-Clostridium difficile clostridia were resistant to this agent (MICs, > 16.0 micrograms/ml). Clindamycin was active against 94% of Bacteroides, Prevotella, and Porphyromonas spp., 91% of peptostreptococci, and 100% of gram-positive non-spore-forming rods, but was active against only 70% of fusobacteria and 53% of clostridia. Cefoxitin was active against > or = 90% of all groups except the B. fragilis group and non-Propionibacterium acnes gram-positive non-spore-forming rods (both 85%) and C. difficile (20%). Significant enhancement of piperacillin by tazobactam was seen in all beta-lactamase-positive strains (99% susceptible; MIC90, 8.0 micrograms/ml), and all beta-lactamase-negative strains were susceptible to piperacillin (MIC90, 8.0 micrograms/ml). Clinical studies are required to delineate the role of Bay y3118 in the treatment of anaerobic infections.
authors.affiliation: Department of Pathology (Clinical Microbiology), Hershey Medical Center, Pennsylvania 17033.
authors.forename: G A
authors.initials: GA
authors.lastname: Pankuch
authors.forename: M R
authors.initials: MR
authors.lastname: Jacobs
authors.forename: P C
authors.initials: PC
authors.lastname: Appelbaum
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001421:Bacteria, Anaerobic / Q000187:drug effects* / Q000201:enzymology; D002440:Cefoxitin / Q000494:pharmacology*; D002939:Ciprofloxacin / Q000494:pharmacology*; D002981:Clindamycin / Q000494:pharmacology*; D004359:Drug Therapy, Combination / Q000494:pharmacology; D024841:Fluoroquinolones; D006089:Gram-Negative Anaerobic Bacteria / Q000187:drug effects* / Q000201:enzymology; D006094:Gram-Positive Bacteria / Q000187:drug effects* / Q000201:enzymology; D008795:Metronidazole / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010878:Piperacillin / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis
chemical_list: D000890:Anti-Infective Agents; D024841:Fluoroquinolones; D008795:Metronidazole; C079807:Bay Y3118; D002981:Clindamycin; D002939:Ciprofloxacin; D002440:Cefoxitin; D001618:beta-Lactamases; D010878:Piperacillin