Pressure-dependent relaxation in the photoexcited mott insulator ET-F2TCNQ: influence of hopping and correlations on quasiparticle recombination rates

We measure the ultrafast recombination of photoexcited quasiparticles (holon-doublon pairs) in the one dimensional Mott insulator ET-F(2)TCNQ as a function of external pressure, which is used to tune the electronic structure. At each pressure value, we first fit the static optical properties and extract the electronic bandwidth t and the intersite correlation energy V. We then measure the recombination times as a function of pressure, and we correlate them with the corresponding microscopic parameters. We find that the recombination times scale differently than for metals and semiconductors. A fit to our data based on the time-dependent extended Hubbard Hamiltonian suggests that the competition between local recombination and delocalization of the Mott-Hubbard exciton dictates the efficiency of the recombination.

Synthesis and Antibacterial Activity of 1-(2-Fluorovinyl)-7-substituted-4-quinolone-3-carboxylic Acid Derivatives, Conformationally Restricted Analogues of Fleroxacin

The novel 1-(2-fluorovinyl)-4-quinolone-3-carboxylic acid derivatives Z-15a-c, E-15a-c, Z-16a-c, and E-16a-c, conformationally restricted analogues of fleroxacin (5), were synthesized, and their in vitro antibacterial activity was evaluated. A dehydrosulfenylation of a 2-fluoro-2-[(4-methoxyphenyl)sulfinyl]ethyl group was employed as a key step for the construction of a 2-fluorovinyl group at the N-1 position. It appeared evident that the Z-isomers Z-15a-c and Z-16a-c exhibited 2- to 32-fold more potent in vitro antibacterial activity than the corresponding E-isomers E-15a-c and E-16a-c. Furthermore, since Z-15b showed in vitro antibacterial activity and DNA gyrase inhibition comparable to that of 5, it was hypothesized that the conformation of Z-15b would be equivalent to the active conformer of 5. The results revealed that the antibacterial Z-1-(2-fluorovinyl)quinolone derivatives carry the novel N-1 substituent of the fluoroquinolones.

Effect of RO 23-9424, cefotaxime and fleroxacin on functions of human polymorphonuclear cells and cytokine production by human monocytes

The way in which an antibiotic interacts with host defences could influence the clinical outcome of many infectious diseases. The impact of RO 23-9424, a novel dual-action and extended-spectrum antibiotic, was studied on several functions of human polymorphonuclear neutrophils (PMNs). A significant (P < 0.05) increase of the superoxide (O2-) released by phorbol-myristate acetate (PMA) -stimulated PMN (10-100 mg/L) can be observed in the RO 23-9424 pre-treated cells. RO 23-9424, particularly at low dosages, showed an interesting but not statistically significant effect on PMN phagocytosis. Higher dosages of RO 23-9424 (50-200 mg/L) and fleroxacin (20-200 mg/L) significantly reduced PMN chemotaxis. Cytokine production by human monocytes were also evaluated after incubation with the antibiotic (100-200 mg/L) in both basal conditions and in response to endotoxin (lipopolysaccharide, LPS). In the LPS-treated cells, RO 23-9424 (100 mg/L) significantly (P < 0.05) enhanced the tumour necrosis factor-alpha (TNF-alpha) levels, compared with LPS controls after 4 h of incubation. RO 23-9424 (200 mg/L) was able to reduce in a dose-dependent way LPS-induced interleukin-1 beta (IL-1 beta) after 4 and 24 h of incubation. Interleukin-8 (IL-8) release was not significantly changed by RO 23-9424. Cefotaxime (200 mg/L) significantly (P < 0.05) increased the basal levels of IL-1 beta and reduced basal IL-8 concentration after 24 h of incubation. The lower concentration of cefotaxime reduced the LPS-stimulated IL-8 levels. Fleroxacin (100 mg/L) enhanced basal levels of IL-8. The potentiated PMN phagocytosis, the significantly enhanced O2- release by PMA-stimulated PMN and the dimetric changes of TNF-alpha and IL-1 beta appeared peculiar for RO 23-9424 and may have useful therapeutical implications.

Pharmacokinetics of fleroxacin after multiple oral dosing in patients receiving regular hemodialysis

The pharmacokinetic profile of fleroxacin was studied in eight noninfected patients receiving regular hemodialysis (four women and four men; mean age, 63 years; age range, 48 to 73 years). Dialysis clearances (mean +/- standard deviation) calculated from the amount of drug recovered in the dialysate exceeded those calculated from rates of extraction from plasma for fleroxacin (126 +/- 29 versus 73 +/- 11 ml/min) and its metabolite N-demethylfleroxacin (103 +/- 31 versus 72 +/- 15 ml/min) but not that for the metabolite fleroxacin N-oxide (100 +/- 25 versus 100 +/- 12 ml/min). Data were fitted to a two-compartment model over the total observation period of 8 days (six oral daily doses of 200 mg of fleroxacin on days 1 to 6 and hemodialysis treatments on day 1,3, and 6) by nonlinear mixed-effects modeling. The random variability of plasma fleroxacin concentrations was 13% about its prediction. The estimated metabolic clearance was 25 ml/min (coefficient of variation, 43%), and the calculated steady-state volume of distribution was 84 liters (coefficient of variation, 16%). The model was expanded for the two major metabolites by the addition of a two-compartment metabolite distribution. Formation clearances of N-demethylfleroxacin and fleroxacin N-oxide were estimated to be 54 and 33% of fleroxacin's metabolic clearance, respectively. The conclusions were as follows. Because of the slow metabolic clearance and intermittent dialysis treatment, steady-state conditions were not reached after 1 week of oral fleroxacin therapy, and there was relevant accumulation of fleroxacin as well as that of fleroxacin N-oxide in our patients with end-stage renal disease. We recommend that infected hemodialysis patients be treated with an initial oral dose of 400 mg of fleroxacin and then daily oral doses of 200 mg. One cannot recommend the treatment of this patient population with fleroxacin over prolonged time periods until more date about the levels of accumulation of fleroxacin and its metabolites in infected patients with renal disease are available.

The use of capillary electrophoresis to monitor the stability of a dual-action cephalosporin in solution

Ro 23-9424 is a broad-spectrum antibacterial agent consisting of a cephalosporin and a quinolone moiety which are held together by an ester linkage. This compound has limited solubility in water but is more soluble at alkaline pH. Such high pH values, however, lead to stability problems due to the lability of the ester linkage, and result in the formation of the free quinolone and cephalosporin moieties. The balance between solubility and stability presents a challenge in formulation development for this compound. Thus, it is important to effectively monitor the stability of Ro 23-9424 after it has been reconstituted in different solvent systems. In this manner, a diluent which does not lead to degradation of the drug can be identified. A capillary electrophoresis method was developed and validated to monitor the stability of Ro 23-9424. The method was found to meet acceptable criteria for method precision, system precision, linearity and limits of detection and quantitation. The method was used to monitor the stability and measure the half-life of Ro 23-9424 in water and in an L-arginine-sodium benzoate-saline diluent designed to mimic the drug delivery system. This work shows that capillary electrophoresis can be used to compare the stability of a drug in different solutions as an aid in formulation development.

Low-level resistance to the cephalosporin 3'-quinolone ester Ro 23-9424 in Escherichia coli

Four spontaneous, single-step mutants of Escherichia coli K-12 resistant to low levels of the cephalosporin 3'-quinolone ester Ro 23-9424 were isolated at a frequency of 10(-10) to 10(-11) mutants per CFU plated. The mutants were cross-resistant to both cephalosporin (cefotaxime) and quinolone (fleroxacin) components. Accordingly, they had altered porins and replicative DNA biosynthesis resistant to fleroxacin. There was no increase in beta-lactamase activity when tested with nitrocephin, and the penicillin-binding protein profiles were normal.

beta-Lactamase hydrolysis of cephalosporin 3'-quinolone esters, carbamates, and tertiary amines

The beta-lactam hydrolysis of five cephalosporin 3'-quinolones (dual-action cephalosporins) by three gram-negative beta-lactamases was examined. The dual-action cephalosporins tested were the ester Ro 23-9424; the carbamates Ro 25-2016, Ro 25-4095, and Ro 25-4835; and the tertiary amine Ro 25-0534. Also tested were cephalosporins with similar side chains (cefotaxime, desacetylcefotaxime, cephalothin, cephacetrile, and Ro 09-1227 [SR 0124]) and standard beta-lactams (penicillin G, cephaloridine). The beta-lactamases used were the plasmid-mediated TEM-1 and TEM-3 enzymes and the chromosomal AmpC. The cephacetrile-related compounds Ro 25-4095 and Ro 25-4835 were hydrolyzed by all three beta-lactamases with catalytic efficiencies (relative to penicillin G) ranging from approximately 5 (TEM-1, AmpC) to approximately 25 (TEM-3). The cephalothin-related Ro 25-2016 was also hydrolyzed by all three beta-lactamases, particularly the AmpC enzyme (relative catalytic efficiency, 110). The cefotaxime-related compounds Ro 25-0534 and Ro 23-9424 were hydrolyzed to any significant extent only by the TEM-3 enzyme (relative catalytic efficiencies, 1.2 and 4.7, respectively.

Antimicrobial activity of a new antipseudomonal dual-action drug, Ro 25-0534

Ro 25-0534, a tertiary amine-linked dual action combination (DAC) of a catechol cephalosporin and ciprofloxacin, was compared with a previously described DAC (Ro 23-9424), ciprofloxacin and cefotaxime. A total of 688 recent clinical isolates were tested and an additional collection of 110 Gram-negative bacilli possessing documented resistance to broad-spectrum antimicrobials were used. Ro 25-0534 was active against all tested species of Enterobacteriaceae (MIC90 range, 0.06-2 micrograms/ml), oxacillin-susceptible staphylococci, beta-hemolytic streptococci, and penicillin-susceptible pneumococci (MIC90 range, 1-2 micrograms/ml). Haemophilus influenzae (MIC90 range, 0.25-0.5 micrograms/ml), Moraxella catarrhalis (MIC90, 0.5 microgram/ml), and most nonenteric Gram-negative bacilli (MIC90 range, 2-4 micrograms/ml) such as Pseudomonas aeruginosa, Acinetobacter spp., and Xanthomonas maltophilia. Enterococci and Bacteroides fragilis isolates were resistant to Ro 25-0534. The Ro 25-0354 potency against most susceptible strains was generally severalfold less than that of Ro 23-9424 (except for Pseudomonas-Xanthomonas) or ciprofloxacin alone.

Anti-Brucella activity of Ro 23-9424, a dual-action antibacterial

The in vitro activity of dual-acting antibacterial Ro 23-9424 was determined by the agar dilution method against 126 clinical isolates of Brucella melitensis. It was compared with fleroxacin, ciprofloxacin and five conventional drugs. MIC50 and MIC90 for Ro 23-9424 were 1.0 and 4.0 mg/l, respectively, as compared with 0.25 and 0.5 mg/l for fleroxacin and ciprofloxacin. One strain which was resistant to other fluoroquinolones, with an MIC of > 8.0 mg/l, did not show cross-resistance to Ro 23-9424 and had an MIC of 4.0 mg/l. All the strains were susceptible to conventional drugs like gentamicin, streptomycin rifampicin, tetracycline and trimethoprim-sulfamethoxazole, with MICs ranging between 0.12 and 2.0 mg/l. Ro 23-9424 did not exhibit in vitro synergy with any of the conventional drugs.

Determination of a new antibacterial agent (Ro 23-9424) by multidimensional high-performance liquid chromatography with ultraviolet detection and direct plasma injection

Analysis of a new antibacterial agent, Ro 23-9424 (I), in plasma has been complicated by the fact that its metabolite, fleroxacin (II), is formed not only in vivo, but also nonenzymatically by the hydrolysis of the ester bond of I. In order to minimize sample preparation time and possible hydrolysis during sample preparation, a high-performance liquid chromatographic procedure was developed which features direct injection of plasma and multidimensional chromatography. The first dimension size-exclusion separation allows plasma proteins to elute with the column void volume. The second dimension reversed-phase column provides a high-resolution separation dependent upon the hydrophobicity of the sample species. With a 5-microliters injection, the limit of quantitation of the method is 0.35 microgram/ml for I and 0.27 microgram/ml for II. The method was used to determine steady state plasma vs. time profiles for I and II from 750 mg i.v. doses of I administered twice daily.

In vitro activity of Ro 23-9424, a dual-acting cephalosporin-quinolone antimicrobial agent

In vitro activity of new dual-acting antibacterial Ro 23-9429 was tested against 1294 bacterial isolates from patients in a major tertiary care referral hospital in Saudi Arabia. Its activity was compared with that of ciprofloxacin, fleroxacin, ampicillin, cephalothin, cefoxitin, cefotaxime, ceftazidime, piperacillin, oxacillin, gentamicin, amikacin, imipenem, and vancomycin. Of the 621 members of Enterobacteriaceae tested, every single isolate was inhibited by Ro 23-9429 at minimum inhibitory concentration ranging between < .03 and 8 micrograms/mL. No other antimicrobial tested was as active as this dual-acting cephalosporin-fluoroquinolone. Similarly, all of the 255 isolates of Acinetobacter, Aeromonas hydrophila, Pseudomonas aeruginosa, and Xanthomonas maltophilia were susceptible to Ro 23-9429. It inhibited all the 120 isolates of methicillin-resistant Staphylococcus aureus. Its in vitro activity against coagulase-negative staphylococci and enterococci was superior or comparable to that of other drugs that are commonly used in clinical practice.

Susceptibility of 170 penicillin-susceptible and penicillin-resistant pneumococci to six oral cephalosporins, four quinolones, desacetylcefotaxime, Ro 23-9424 and RP 67829

MICs of six oral cephalosporins (cefdinir, cefpodoxime, cefaclor, cefuroxime, cefixime and Ro 40-6890), four quinolones (ciprofloxacin, ofloxacin, OPC-17116 and fleroxacin), desacetylcefotaxime, Ro 23-9424 (a fused combination of fleroxacin + desacetylcefotaxime) and RP 67829 (a benzonaphthyridine) were determined for 49 penicillin-susceptible (S), 38 penicillin-intermediate (I), and 83 penicillin-resistant (R) strains of Streptococcus pneumoniae. All MICs were determined by a standardized agar dilution method utilizing Mueller-Hinton agar supplemented with sheep blood. MIC90s of OPC-17116 and RP 67829 were < or = mg/L, and were unaffected by penicillin-susceptibility. MICs of all beta-lactams increased with increasing penicillin-MICs, with cefdinir, cefpodoxime, cefuroxime and Ro 40-6890 being the most active compounds, followed by cefaclor and cefixime. MIC90s of ciprofloxacin and ofloxacin were 2 mg/L. MIC90s of Ro 23-9424 were lower than those of either parent compound (fleroxacin 8 mg/mL for all three groups; desacetylcefotaxime 0.5 mg/mL [S], 0.5 mg/mL [I], 4 mg/mL [R]; Ro 23-9424 0.125 mg/L [S], 0.25 mg/L [I], 0.5 mg/L [R]). The results indicated that several newly introduced and experimental antimicrobials have potential for the treatment of infections caused by resistant strains of S. pneumoniae.

RO 23-9424, a new cephalosporin 3'-quinolone: in-vitro antimicrobial activity and tentative disc diffusion interpretive criteria

The susceptibility of 410 clinical bacterial isolates to RO 23-9424, a novel cephalosporin 3'-quinolone, was determined. Overall, 97% of Enterobacteriaceae and 100% of staphylococci were inhibited by < or = 8.0 mg/L of RO 23-9424. Only 60% of Pseudomonas aeruginosa and 80-90% of Pseudomonas spp. and Xanthomonas maltophilia were inhibited by this concentration. Enterococci and Listeria monocytogenes were resistant to RO 23-9424. Clinical isolates of Moraxella catarrhalis, Streptococcus spp., and Corynebacterium jekeium were all susceptible to < or = 8.0 mg/L of RO 23-9424. This drug's antimicrobial activity was superior to that of its two components fleroxacin and desacetylcefotaxime against the organisms tested. Using < or = 8.0 mg/L and > or = 32 mg/L respectively as the susceptible and resistant MIC breakpoints for RO 23-9424, the regression analysis-derived disc diffusion zone diameter breakpoints for the 30 micrograms disc are: susceptible > or = 19 mm, intermediate 16-18 mm, and resistant < or = 15 mm.

In vitro activity of Ro 23-9424 against clinical isolates of Legionella species

Agar and broth microdilution MICs of Ro 23-9424 that inhibited 90% of 22 Legionella clinical isolates tested were 0.64 and 0.08 micrograms/ml, respectively; respective erythromycin values were 1.0 and 0.12 micrograms/ml. Ro 23-9424 (1 microgram/ml) was slightly more active than the same erythromycin concentration in a macrophage system, for both Legionella pneumophila strains studied.

In vitro activity of Ro 23-9424, a dual-action antibacterial agent, against bacterial isolates from cancer patients compared with those of other agents

The in vitro activity of Ro 23-9424 against bacterial isolates from patients with cancer was compared with those of fleroxacin, ciprofloxacin, cefoperazone, and ceftazidime. Ro 23-9424 inhibited the majority of the members of the family Enterobacteriaceae and all Aeromonas isolates at a concentration of less than or equal to 1.0 micrograms/ml. It was also active against Acinetobacter spp. and Haemophilus influenzae, including beta-lactamase-producing strains. The MIC for 90% of isolates (MIC90) of Pseudomonas aeruginosa was 16.0 micrograms/ml. All group A and B streptococci were inhibited by less than or equal to 0.25 micrograms/ml, and 90% of group G streptococci and Streptococcus pneumoniae were inhibited by 1.0 micrograms/ml. All methicillin-susceptible strains of Staphylococcus aureus and 60% of methicillin-resistant strains were susceptible to 2.0 micrograms of Ro 23-9424 per ml, whereas the MIC90 for Staphylococcus epidermidis and Staphylococcus hominis isolates was 4.0 micrograms/ml. Staphylococcus haemolyticus and Enterococcus spp. were less susceptible; MIC90s for them were 16.0 and 32.0 micrograms/ml. Ro 23-9424 has a broad antibacterial spectrum and potential utility for therapy of infections in cancer patients.

In vitro activity of Ro 23-9424, a dual-action cephalosporin, compared with activities of other antibiotics

The in vitro activity of Ro 23-9424, which is desacetyl-cefotaxime linked to fleroxacin, was compared with the activities of cefotaxime, desacetyl-cefotaxime, fleroxacin, ofloxacin, and ciprofloxacin. It inhibited the majority of members of the family Enterobacteriaceae, except for some Serratia marcescens, Citrobacter freundii, and Enterobacter cloacae strains, at less than or equal to 0.25 microgram/ml and had an MIC for 90% of strains tested (MIC90) of 8 micrograms/ml against Pseudomonas aeruginosa. Most group A, B, C, and G streptococci and Streptococcus pneumoniae were inhibited at less than or equal to 0.25 microgram/ml. Ninety percent of the staphylococci were inhibited at less than or equal to 4 micrograms/ml, except for some methicillin-resistant Staphylococcus aureus isolates. The MIC90S of Ro 23-9424 for Enterococcus faecalis and Listeria monocytogenes were greater than or equal to 16 micrograms/ml. Ninety percent of Clostridium perfringens isolates were inhibited by less than or equal to 2 micrograms/ml, whereas Bacteroides fragilis had an MIC90 of 32 micrograms/ml. There was a minimal inoculum size effect. The MICs and MBCs were either identical or within a twofold dilution. The MICs of Ro 23-9424 for Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Enterobacter cloacae, Citrobacter freundii, Pseudomonas aeruginosa, and Staphylococcus aureus increased 16- to 128-fold after 2 weeks of transfer in the presence of Ro 23-9424, showing that the presence of two agents does not prevent resistance.

Cephalosporin 3'-quinolone esters with a dual mode of action

According to the generally accepted mechanism by which bacterial enzymes react with cephalosporins, opening of the beta-lactam ring can lead to the expulsion of a 3'-substituent. A series of dual-action cephalosporins was prepared in which antibacterial quinolones were linked to the cephalosporin 3'-position through an ester bond in the expectation that, in addition to exerting their own beta-lactam activity, these cephalosporins would act as prodrugs for the second antibacterial agent. Compared to parent cephalosporins in which the 3'-substituent was acetoxy, the bifunctional cephalosporins exhibited a broadened antibacterial spectrum, suggesting that a dual mode of action may indeed be operative.

Mode of action of the dual-action cephalosporin Ro 23-9424

Ro 23-9424 is a broad-spectrum antibacterial agent composed of a cephalosporin and a quinolone moiety. Its biological properties were compared with those of its two components and structurally related cephalosporins and quinolones. Like ceftriaxone and cefotaxime but unlike its decomposition product, desacetyl cefotaxime, Ro 23-9424 bound at less than or equal to 2 micrograms/ml to the essential penicillin-binding proteins 1b and 3 of Escherichia coli and 1, 2, and 3 of Staphylococcus aureus. In E. coli, Ro 23-9424 produced filaments exclusively and decreased cell growth; cefotaxime produced both filaments and lysis. Like its decomposition product fleroxacin but unlike quinolone esters, Ro 23-9424 also inhibited replicative DNA biosynthesis in E. coli. In an E. coli strain lacking OmpF, growth continued after addition of Ro 23-9424, decreased after addition of cefotaxime, and stopped immediately after addition of fleroxacin. The results, together with the chemical stability of Ro 23-9424 (half-life, approximately 3 h at pH 7.4 and 37 degrees C), suggest that in E. coli the compound acts initially as a cephalosporin with intrinsic activity comparable to that of cefotaxime but with poorer penetration. Subsequent to the decomposition of Ro 23-9424 to fleroxacin and desacetyl cefotaxime, quinolone activity appears. The in vitro antibacterial activity reflects both mechanisms of action.

In vitro activities of a dual-action antibacterial agent, Ro 23-9424, and comparative agents

The in vitro activity of the dual-action antibacterial agent Ro 23-9424 was compared with those of cefotaxime, ceftazidime, ciprofloxacin, fleroxacin, imipenem, and amikacin against 358 aerobes and anaerobes. The MIC ranges, MICs for 50 and 90% of the strains (MIC50s and MIC90s), and percentage of strains susceptible for each agent at the recommended susceptible MIC breakpoint were determined for each genus. The MIC90s (micrograms per milliliter) of the agents against members of the family Enterobacteriaceae were as follows: ciprofloxacin, 0.063; Ro 23-9424, fleroxacin, and imipenem, 0.5; ceftazidime, 2; amikacin, 4; and cefotaxime, 16. The MIC90s (micrograms per milliliter) against Pseudomonas and Acinetobacter spp. were as follows: ciprofloxacin, 2; ceftazidime and imipenem, 8; Ro 23-9424, 16; fleroxacin, 32; amikacin, 64; and cefotaxime, 128. Against gram-positive bacteria, excluding the enterococci, the MIC90s (micrograms per milliliter) were as follows: ciprofloxacin, 1; imipenem, 4; Ro 23-9424 and fleroxacin, 8; amikacin, 64; and ceftazidime and cefotaxime, greater than 128. Against gram-positive bacteria, including the enterococci, the MIC90s changed only for the following agents: Ro 23-9424, 16 micrograms/ml; and amikacin, 128 micrograms/ml. Strains of Branhamella catarrhalis, Haemophilus influenzae, and Neisseria gonorrhoeae were 100% susceptible to Ro 23-9424, cefotaxime, ciprofloxacin, and fleroxacin, while the other three agents showed somewhat less activity only against N. gonorrhoeae. Against anaerobes, imipenem was the most effective agent, while the activities of the other six agents were variable.

In vitro activity of Ro 23-9424, ceftazidime, and eight other newer beta-lactams against 100 gram-positive blood culture isolates

One hundred Gram-positive bacteremia organisms from five important genus groups were tested against 10 newer beta-lactams. Ceftazidime was significantly less active (50% of strains at less than or equal to 8 micrograms/ml) compared to other cephalosporins. The penems (FCE-22101 and HRE-664) and imipenem were each superior to the cephalosporins with 92-93% inhibition of strains. A novel fused co-drug of fleroxacin and desacetyl-cefotaxime, Ro 23-9424, was 100% effective against these Gram-positive pathogens at less than or equal to 8 micrograms/ml. Several of these compounds should receive consideration for clinical trials for empiric therapy among neutropenic patient infections where Gram-positive pathogens may be more prevalent.