In vitro antimicrobial activity of CP-99,219, a novel azabicyclo-naphthyridone.

CP-99,219 is a trifluoronaphthyridone with significant antibacterial activity that includes the family Enterobacteriaceae (MICs for 90% of the strains tested [MIC90s], < or = 0.015 to 0.5 micrograms/ml), Moraxella catarrhalis, Haemophilus influenzae, and gonococci (MICs, < or = 0.015 micrograms/ml). Legionella spp. were also CP-99,219 susceptible, with MICs of 0.008 to 0.12 micrograms/ml. CP-99,219 demonstrated activity greater than that of ciprofloxacin, ofloxacin, or enoxacin against Pseudomonas aeruginosa (MIC90, 1 microgram/ml), Xanthomonas maltophilia (MIC90, 2 micrograms/ml), Staphylococcus haemolyticus (MIC90, 0.5 micrograms/ml), Enterococcus faecalis (MIC90, 1 microgram/ml), and pneumococci (MIC90, 0.12 micrograms/ml). Numerous ciprofloxacin-resistant isolates were susceptible to CP-99,219, a new compound showing potential value for further in vivo trials.

Antimicrobial activities of two investigational fluoroquinolones (CI-960 and E4695) against over 100 Legionella sp. isolates.

The antimicrobial activities of two investigational fluoroquinolones (CI-960 and E4695) were compared with those of five similar compounds and four comparison drugs against 103 strains of Legionella pneumophila and five other Legionella species type strains. When concentrations inhibiting 90% of strains tested (MIC90s) for L. pneumophila were determined, CI-960 and temafloxacin emerged as the most active (0.015 microgram/ml) and were followed in potency by E4695 (0.03 microgram/ml). This activity was two- to fourfold greater than that of the reference drug, ciprofloxacin, and approached that of rifampin (MIC90, 0.008 microgram/ml). All fluoroquinolones studied were more active than erythromycin (MIC90, 0.5 microgram/ml). These two investigational fluoroquinolones appear well suited for further in vivo study of legionellosis therapy.

Antimicrobial activity of ten macrolide, lincosamine and streptogramin drugs tested against Legionella species.

RP59500, a semisynthetic pristinamycin combination, and 14 other antimicrobial agents were tested against 108 Legionella strains. Of the ten macrolide, lincosamine and streptogramin agents tested, the new streptogramin RP59500 ranked seventh in order of activity against Legionella pneumophila on the basis of MIC90 results as follows: clarithromycin = 14-OH clarithromycin (MIC90 0.12 mg/l) > roxithromycin > erythromycin = tylosin = virginiamycin > RP59500 (MIC90 1 mg/l) = azithromycin > dirithromycin > clindamycin (MIC90 8 mg/l). Of all 14 drugs tested in this study, rifampicin was the most potent with an MIC90 of 0.008 mg/l. In this retrospective study of Legionella strains (1981-1990 isolates), we observed no trend toward resistance to the agents investigated.

Interpretive criteria for disk diffusion tests using 5-microgram cefdinir disks with rapidly growing clinical isolates.

Preliminary interpretive zone diameter criteria were calculated for the 5-micrograms cefdinir disk diffusion test by using two potential MIC breakpoints (less than or equal to 0.5 and less than or equal to 1 micrograms/ml). The absolute agreement between tests ranged from 85.9 to 92.4%, and the false-susceptibility errors were principally contributed by the Enterobacter spp. (2.2% error). One proposed criterion was greater than or equal to 20-mm zone diameter (less than or equal to 1 micrograms/ml) for susceptibility and less than or equal to 16-mm zone diameter (greater than 2 micrograms/ml) for resistance to cefdinir. Clinical laboratory users of the disk diffusion method should be cautioned about the possibility of very major interpretive errors among enterobacter isolates.