In-vitro activity of moxifloxacin against fluoroquinolone-resistant strains of aerobic gram-negative bacilli and Enterococcus faecalis.
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MICs of the new fluoroquinolone, moxifloxacin, and those of ciprofloxacin, ofloxacin and sparfloxacin for 19 genetically characterized fluoroquinolone-resistant strains were determined by the agar dilution method. The MICs of moxifloxacin for Escherichia isolates with one mutation in gyrA (corresponding to Ser83-->Leu or Asp87-->Gly substitution) were 0.25-0.5 mg/L, while those of ciprofloxacin, ofloxacin and sparfloxacin were 0.06-0.25, 1 and 0.12-0.5 mg/L, respectively. These values were four- to 16-fold higher than those of the same antibiotics for the wild-type strain, E. coli KL16. Similar results were observed with clinical isolates of Salmonella spp. harbouring one mutation in gyrA leading to the substitution of Ser83 by Phe or Tyr. In the presence of two mutations in the E. coli gyrA gene, the MICs of moxifloxacin ciprofloxacin, ofloxacin and sparfloxacin were 2, 0.5, 4 and 1 mg/L, respectively; these were 32 times higher than the MICs of these agents for E. coli KL16. The MICs of the four quinolones for triple mutants with two mutations in gyrA and one in parC were even higher, i.e. 8, 8, 16 and 8-16 mg/L, respectively. The MICs of moxifloxacin for Campylobacter coli and Campylobacter jejuni strains with a gyrA mutation leading to Thr86-->Ile substitution ranged from 1 to 2 mg/L, while the MICs of ciprofloxacin, ofloxacin and sparfloxacin were 16-32 mg/L, 8-16 and 4-8 mg/L, respectively. For high-level ciprofloxacin-resistant (MICs of 32 mg/L) clinical isolates of Enterococcus faecalis with one substitution at position 83 in GyrA (E. coli coordinates), the MICs of moxifloxacin, ofloxacin and sparfloxacin were 8-16, > or = 128 and 32 mg/L respectively. In conclusion, moxifloxacin and other fluoroquinolones exhibit cross-resistance against aerobic gram-negative bacilli and enterococci. The in-vitro activity of moxifloxacin was greater than that of ofloxacin and slightly less than that of ciprofloxacin and sparfloxacin against Enterobacteriaceae, but greater than those of the three other compounds tested against Campylobacter spp and E. faecalis. (+info)
The in-vitro activity of moxifloxacin against Legionella species and the effects of medium on susceptibility test results.
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The in-vitro activities of moxifloxacin, ciprofloxacin, erythromycin and rifampicin against 49 Legionella spp. isolates were determined by an agar dilution method with buffered charcoal yeast extract agar containing alpha-ketoglutarate. Because the inhibitory effects of charcoal in the test media were pronounced (92% for quinolones, 90.5% for rifampicin and 92.5% for erythromycin), the MICs were corrected for the charcoal-bound fraction of the antibiotics. The corrected geometric mean MICs were 0.018 mg/L for moxifloxacin, 0.02 mg/L for ciprofloxacin, 0.27 mg/L for erythromycin and 0.005 mg/L for rifampicin. (+info)
The effect of moxifloxacin on its target topoisomerases from Escherichia coli and Staphylococcus aureus.
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The effect of moxifloxacin on its target enzymes was evaluated by three different approaches: (i) the MICs of moxifloxacin and nine other fluoroquinolones were determined for mutants of Escherichia coli (n = 13) and Staphylococcus aureus (n = 5) carrying different combinations of resistance mutations; (ii) the activity of moxifloxacin on isolated targets was determined as IC50 values for wild-type and mutant type II topoisomerases from E. coli; and (iii) the mutation frequencies were determined for two single-step mutants (MI with a Ser83-->Leu mutation in gyrA and WT-4 with a Ser80-->Ile mutation in parC) and their parent strain (WT). Of the quinolones tested, moxifloxacin was the only one showing an equivalent high activity against both targets. This is reflected by a comparable high susceptibility of the test strains of E. coli and S. aureus and by the IC50 values of moxifloxacin which were 50-90% lower than those of ciprofloxacin, norfloxacin and sparfloxacin for the wild-type and single mutant enzymes of gyrase and topoisomerase IV. However, double mutant GyrA was significantly more sensitive to moxifloxacin than to the other fluoroquinolones tested, while wild-type topoisomerase IV was two-fold more refractory. Mutation rates of WT, MI and WT-4 for ciprofloxacin and moxifloxacin were 5 x 10(-8) vs 4 x 10(-10); <6 x 10(-11) vs <6 x 10(-11); and 2 x 10(-6) vs 5 x 10(-7), respectively. These data indicate an equivalent high inhibitory activity of moxifloxacin on DNA gyrase and topoisomerase IV of E. coli. (+info)
Antimicrobial activity and accumulation of moxifloxacin in quinolone-susceptible bacteria.
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The antibacterial activity of moxifloxacin, compared with that of ciprofloxacin, was determined for five strains of Staphylococcus aureus, including one NorA-overproducing strain, two quinolone-susceptible strains of Streptococcus pneumoniae, four quinolone-susceptible strains of Haemophilus influenzae, and one strain each of quinolone-susceptible Escherichia coli, Pseudomonas aeruginosa and Moraxella catarrhalis. In addition, the accumulation of moxifloxacin and ciprofloxacin by the NCTC type strain of S. pneumoniae, H. influenzae, S. aureus, E. coli and P. aeruginosa was determined by a fluorescence method. For all strains, moxifloxacin accumulated to a lower concentration than ciprofloxacin. The concentrations of moxifloxacin accumulated ranged from 12 to 44 ng/mg dry cells. The lowest concentration was accumulated by S. pneumoniae NCTC 7465 and the highest concentration by S. aureus NCTC 8532. Increased expression of norA in S. aureus had no effect on the accumulation of moxifloxacin. Despite differences in the concentration of moxifloxacin accumulated by the different species, there was little difference between the MICs of this agent for each strain (0.06-0.5 mg/L), suggesting that the concentration accumulated by wild-type bacteria has little effect on the MIC. (+info)
Bactericidal properties of moxifloxacin and post-antibiotic effect.
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The time-kill kinetics and post-antibiotic effect (PAE) of moxifloxacin were studied for strains of Streptococcus pneumoniae, Streptococcus pyogenes, Haemophilus influenzae, Staphylococcus aureus and Escherichia coli. Moxifloxacin had a bactericidal effect against all strains tested, with the least rapid bactericidal effect being against S. pyogenes and the most rapid effect against S. aureus and E. coli. The PAE of moxifloxacin was similar to that of other fluoroquinolones and increased with increasing concentration. No association was found between the bactericidal effect of moxifloxacin and the duration of PAE. Gram-positive and gram-negative organisms were also exposed to concentrations of moxifloxacin, sparfloxacin and amoxycillin that simulated the drug concentrations obtained in human serum after standard oral dosing schedules. Simulation of moxifloxacin concentrations in human serum reduced viable counts more effectively and more rapidly than shown in time-kill experiments; in contrast, sparfloxacin and amoxycillin were less effective than when constant concentrations of these antibacterials were used. (+info)
Pharmacokinetics of the 8-methoxyquinolone, moxifloxacin: tissue distribution in male rats.
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BAY 12-8039 (moxifloxacin-HCl) and 14C-labelled BAY 12-8039 were administered to male rats as single i.v. and oral doses of 4.6 and 5.0 mg/kg bodyweight respectively. The distribution of substance-associated radioactivity in the body was investigated by whole-body autoradiography. The concentrations of the unchanged compound in plasma, skin suction blister fluid and lung tissue were determined by HPLC. Whole-body autoradiography revealed distinctly higher concentrations of radioactivity in the gastrointestinal tract, urinary bladder and in most organs and tissues (e.g. kidneys, liver, spleen, lungs, various glands, cartilaginous tissues and in melanin-containing structures located in the eye, meninges and hair follicles of pigmented skin) than in blood. Radioactivity crossed the blood-brain barrier only to a small extent. The results show a high tissue affinity and a rapid and homogeneous distribution of radioactivity from blood to organs or tissues. No relevant difference in the distribution of radioactivity was found following i.v. and oral administration. After i.v. and oral dosing similar concentrations of the unchanged compound were determined in skin suction blister fluid and plasma. The concentrations of the unchanged compound in lung tissue were about three times higher than those in plasma following both i.v. and oral administration. The concentration-time courses for moxifloxacin in plasma and lung tissue were parallel. (+info)
Pharmacokinetics of the 8-methoxyquinolone, moxifloxacin: a comparison in humans and other mammalian species.
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The pharmacokinetics of moxifloxacin was investigated in NMRI mice, Wistar rats, rhesus monkeys, beagle dogs, Gottingen minipigs and healthy human volunteers after i.v. and oral administration of moxifloxacin-HCl (single doses of moxifloxacin 9.2 mg/kg bodyweight) in animals and 100 mg moxifloxacin (1.4 mg/kg bodyweight p.o. and 1.2 mg/kg bodyweight i.v.) in humans. The plasma concentration vs time courses of the unchanged compound (determined by HPLC) and the derived pharmacokinetic parameters were used to evaluate the absorption process, to compare the pharmacokinetics in these species and to perform an interspecies scaling. The results of the pharmacokinetic investigations indicate a clear dependence on the species. Moxifloxacin is absorbed quickly (rats, dogs, humans > monkeys): the major portion of the dose reached the systemic circulation within the first 2 h. In the minipig absorption was slower. Bioavailability was high to moderate (91-52%) in all species. Protein binding (f(u)) was low (55-71%) in all species. The volume of distribution at steady state (Vss) was medium to large (2.0-4.9 L/kg) in all species. There were considerable differences in maximum concentrations (C(max,norm), 0.430-0.070 kg/L) and in AUCnorm values (oral, 6.18-0.184 kg x h/L; i.v., 7.51-0.237 kg x h/L). Total body clearance (CL) decreased with increasing bodyweight (4.21-0.132 L/(h x kg)). The mean residence time (MRT) decreased with decreasing bodyweight (15-0.88 h). The half-life (t(1/2)) decreased with decreasing bodyweight (oral, 12-1.3 h, i.v., 13-0.93 h). There was moderate to low renal excretion (i.v., 20-6.2%), the renal clearance, (CL(R)) was in the range 0.615-0.0222 L/(h x kg). Regarding the pharmacokinetic parameters determined after oral administration, the dog was most similar to the human in terms of Cmax, AUC and t(1/2). There was good correlation between bodyweight and CL (coefficient of correlation (r) = 0.959), Vss (r = 0.990) and MRT (r = 0.943). On the basis of preclinical studies a terminal half-life appropriate for once-daily dosing in humans was predicted and confirmed by Phase I data. (+info)
Fluoroquinolone phototoxicity: a comparison of moxifloxacin and lomefloxacin in normal volunteers.
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Moxifloxacin, a broad-spectrum fluoroquinolone with the methoxy group at position 8 of the quinolone structure that is believed to confer reduced phototoxicity, was investigated in 32 healthy human male volunteers by a randomized double-blind placebo and positive control (lomefloxacin) phototest technique. A comparison of pre- and on-drug photosensitivity levels tested with an irradiation monochromator using relevant sunlight wavelengths, failed to demonstrate phototoxicity after administration of either placebo or moxifloxacin (200 mg or 400 mg/day) for 7 days. As expected, lomefloxacin (400 mg/day) phototoxicity was revealed at the UVA wavebands 335 +/- 30 nm and 365 +/- 30 nm (maximal at 24 h), with a phototoxic index of 3-4. The susceptibility to this effect rapidly normalized within 48 h of stopping the drug. No special protection from UVA wavelengths is necessary for those taking moxifloxacin. (+info)