Mechanism of action of lomefloxacin

The anticoccidial activity of the fluoroquinolone lomefloxacin against experimental Eimeria tenella infection in broiler chickens

Coccidiosis is a crucial parasitic disease of the poultry industry. As a result of the enormous global economic losses and the increased resistance to the conventional anticoccidial agents, there is a continuous need to find new anticoccidials. Here, the anticoccidial effect of the fluoroquinolone lomefloxacin versus diclazuril in experimentally infected broilers was tested for the treatment of Eimeria tenella infection. Ninety 14-day-old Cobb strain broiler chickens were allocated into five groups, each with 18 chicks. Group 1 (G1) was separated as an uninfected negative control and received no treatment; group 2 (G2), infected untreated (positive control); group 3 (G3), infected and treated with lomefloxacin at a dose rate of 100 ppm in drinking water; group 4 (G4), infected and treated with diclazuril at a dose rate of 2.5 ppm in drinking water; group 5 (G5), infected and treated with lomefloxacin at a dose rate of 100 ppm plus diclazuril at dose rate of 2.5 ppm in drinking water. Clinical signs, mortality rates, number of oocysts per gram of faeces (OPG), growth performance parameters (weight gain: WG and feed conversion ratio: FCR), lesion scoring, haematological and serum biochemical analyses, antioxidant biomarkers and histopathologic inspection of the caeca were used as evaluation criteria for the anticoccidial efficacy of both lomefloxacin and diclazuril. The findings herein showed that administration of lomefloxacin and/or diclazuril improved growth performance parameters (WG, FCR) and significantly (P ≤ 0.05) reduced OPG, and diminished the severity of bloody diarrhoea and mortalities. Additionally, haematological indices and serum biochemical parameters such as ALT, AST, ALP, creatinine, uric acid, total proteins, albumin and globulin were improved. Finally, a significant elevation in the levels of the antioxidant biomarkers was observed in the chicks of G3, G4 and G5 as compared with those of G2.

Cultivation in Space Flight Produces Minimal Alterations in the Susceptibility of Bacillus subtilis Cells to 72 Different Antibiotics and Growth-Inhibiting Compounds

Past results have suggested that bacterial antibiotic susceptibility is altered during space flight. To test this notion, Bacillus subtilis cells were cultivated in matched hardware, medium, and environmental conditions either in space flight microgravity on the International Space Station, termed flight (FL) samples, or at Earth-normal gravity, termed ground control (GC) samples. The susceptibility of FL and GC samples was compared to 72 antibiotics and growth-inhibitory compounds using the Omnilog phenotype microarray (PM) system. Only 9 compounds were identified by PM screening as exhibiting significant differences (P < 0.05, Student's t test) in FL versus GC samples: 6-mercaptopurine, cesium chloride, enoxacin, lomefloxacin, manganese(II) chloride, nalidixic acid, penimepicycline, rolitetracycline, and trifluoperazine. Testing of the same compounds by standard broth dilution assay did not reveal statistically significant differences in the 50% inhibitory concentrations (IC₅₀s) between FL and GC samples. The results indicate that the susceptibility of B. subtilis cells to a wide range of antibiotics and growth inhibitors is not dramatically altered by space flight.IMPORTANCE This study addresses a major concern of mission planners for human space flight, that bacteria accompanying astronauts on long-duration missions might develop a higher level of resistance to antibiotics due to exposure to the space flight environment. The results of this study do not support that notion.

Development of a UPLC-MS/MS method for the determination of lomefloxacin in rabbit aqueous humor and its application to a pharmacokinetic study

Lomefloxacin is a kind of synthetic fluoroquinolone antibiotic, which is used for the treatment of infectious diseases. In this study, a rapid and efficient liquid chromatography-tandem mass spectrometric assay was developed to determine the concentration of lomefloxacin in rabbit aqueous humor quantitatively. Aqueous humor samples were extracted by protein precipitation. Ofloxacin was chosen as internal standard. The chromatographic separation was achieved on a Kinetex C18 (50mm×2.10mm, 2.6μm, Phenomenex Corp, USA) column, with a gradient of methanol (0.1% formic acid) and water (0.1% formic acid). Multiple reaction monitoring (MRM) with positive ionization mode was used for the mass analysis. The validation of this method was based on the European Medicines Agency (2011) [1] and US FDA Guidelines (2001) [2]. The calibration range of aqueous humor samples was 5-1200ng/mL with r=0.9990 (n=6). For all QC samples, Inter-and intra-run precisions were less than 15% and accuracies were between 80%-120%. In conclusion, the assay was rapid, sensitive and able to determinate the lomefloxacin in rabbit aqueous humor accurately. At the same time, this method was successfully applied to study the pharmacokinetics of lomefloxacin hydrochloride eye drops and lomefloxacin hydrochloride ophthalmic gel in rabbit aqueous humor.

Determination of antibiotic EC50 using a zero-flow microfluidic chip based growth phenotype assay

Current existing assay systems for evaluating antimicrobial activity suffer from several limitations including excess reagent consumption and inaccurate concentration gradient preparation. Recently, microfluidic systems have been developed to provide miniaturized platforms for antimicrobial susceptibility assays. However, some of current microfluidic based assays require continuous flows of reagents or elaborate preparation steps during concentration preparation. In this study, we introduce a novel microfluidic chip based growth phenotype assay that automatically generates a logarithmic concentration gradient and allows observing the growth of pathogenic bacteria under different concentrations of antibiotics in nanoliter batch culture reactors. We chose pathogen bacterium Pseudomonas aeruginosa as a model strain and evaluated the inhibitory effects of gentamicin and ciprofloxacin. We determined the EC50 values and confirmed the validity of the present system by comparing the EC50 values obtained through conventional test tube method. We demonstrated that the EC50 values acquired from present assay are comparable to those obtained from conventional test tube cultures. The potential application of present assay system for investigating combinatorial effects of antibiotics on multidrug resistant pathogenic bacteria is discussed and it can be further used for systematic evaluation of antifungal or antiviral agents.

Efficacy and safety of lomefloxacin on bacterial extraocular disease in the horse

Lomefloxacin is a broad-spectrum fluoroquinolone antibiotic used for the treatment of bacterial extraocular disease. This study investigated the efficacy and safety of lomefloxacin eye drops for bacterial extraocular disease in horses. Lomefloxacin ophthalmic solution (0.3%) was instilled three times daily for 2–5 days in 65 horses diagnosed with bacterial extraocular disease based on clinical findings. Clinical observations and bacteriological examinations were performed at the start of treatment, 2 and 5 days after the start of treatment, and at the discontinuation or termination of treatment. Of the 65 horses, 64 were positive for bacteria, and 22 bacterial genera and 47 bacterial species were identified. The efficacy of lomefloxacin was evaluated in 63 horses; one horse with a negative culture and another with suspected bacterial contamination were excluded. Lomefloxacin was considered to be clinically effective in 54 horses. The major bacterial species identified were Staphylococcus aureus, Streptococcus equi subsp. zooepidemicus, Acinetobacter lwoffii, Staphylococcus xylosus, Staphylococcus vitulinus, Enterobacter agglomerans, Flavimonas oryzihabitans and Staphylococcus sciuri, with a cumulative disappearance rate of 80% or more at the termination of instillation. Excluding one horse that did not undergo a bacteriological examination, the remaining 62 horses were assessed for bacteriological outcome. Full or partial bacterial clearance was detected in 95% or more of the 62 horses. One of the 65 horses reported adverse events that had no causal relation with the eye drops. Our results showed that lomefloxacin is safe and effective for the treatment of bacterial extraocular disease in horses.

Synthesis and antibacterial activity of N-(5-benzylthio-1,3,4-thiadiazol-2-yl) and N-(5-benzylsulfonyl-1,3,4-thiadiazol-2-yl)piperazinyl quinolone derivatives

A series of N-(5-benzylthio-1,3,4-thiadiazol-2-yl) and N-(5-benzylsulfonyl-1,3,4-thiadiazol-2-yl) derivatives of piperazinyl quinolones was synthesized and evaluated for antibacterial activity against Gram-positive and Gram-negative microorganisms. Some of these derivatives exhibit high activity against Gram-positive bacteria; Staphylococcus aureus and Staphylococcus epidermidis, comparable or more potent than their parent N-piperazinyl quinolones norfloxacin and ciprofloxacin as reference drugs. The SAR of this series indicates that both the structure of the benzyl unit and the S or SO(2) linker dramatically impact antibacterial activity.

Determination of lipophilicity of two quinolone antibacterials, ciprofloxacin and grepafloxacin, in the protonation equilibrium

The objective of this study was to compare protonation equilibrium and lipophilicity of two quinolone antibacterials, grepafloxacin (GPFX) and ciprofloxacin (CPFX), in order to give an insight into effects on the physicochemical properties by slight structural motifs. The protonation equilibrium was investigated by a spectrophotometry. Macro- and micro-dissociation constants were simultaneously determined, based on nonlinear regression analysis using the MULTI program, and then microspecies distribution could be described accordingly. Zwitterionic microspecies predominated at isoelectrical point (pI) for both drugs, and the concentration ratio of neutral to zwitterionic forms was near 4-fold greater for GPFX than that for CPFX. The apparent partition coefficient (D(O/B,pH)) versus pH profiles had the shape of a parabolic curve in an n-octanol/buffer system, and reached the maximum around pI for both, respectively. Moreover, two introduced methyl groups in GPFX increased not only intrinsic lipophilicity but also neutral microspecies fraction relative to CPFX, and D(O/B,pH) of GPFX was consequently far higher than that of CPFX. The results emphasized that there were significant differences in protonation equilibrium and lipophilicity between GPFX and CPFX, which conduced to explaining their different behavior in terms of antibacterial activities and pharmacokinetics.

Lomefloxacin clinical pharmacokinetics

Lomefloxacin is a quinolone antibiotic with chemical and microbiological properties similar to most commercially available agents of this class. There are differences, however, between lomefloxacin and other quinolones in activity against specific micro-organisms, a situation that is typical of most antibiotic classes. The pharmacokinetics of lomefloxacin support once- or twice-daily dosage, depending on the pathogen or site of infection. This is a result of its relatively high serum concentrations and long half-life. The outstanding pharmacokinetic features of lomefloxacin are its high degree of tissue distribution, lack of significant metabolism (and, therefore, no competitive drug interactions with other metabolised drugs showing a common metabolic pathway), and good oral absorption. Like most fluoroquinolones, lomefloxacin can chelate with heavy metals. However, this interaction can be eliminated by administering lomefloxacin 2h before the cation-containing products. Dosage adjustments are required in patients with renal dysfunction. However, patients with liver disease do not require alterations in lomefloxacin dosage regimens. The safety profile, lack of significant drug interactions and convenience of administration make lomefloxacin a useful agent in specific clinical settings.

Uncomplicated urinary tract infections: lomefloxacin versus trimethoprim/sulphamethoxazole

Data were collected from 14 French centres which participated in a randomized study to compare the safety and efficacy of 400 mg lomefloxacin taken orally once daily by 62 patients with 160/800 mg trimethoprim/sulphamethoxazole (TMP/SMX) taken orally twice daily by 64 patients with uncomplicated urinary tract infections. Most patients were infected with Escherichia coli at baseline (72.4% in the lomefloxacin group and 69.0% in the TMP/SMX group) and all patients were treated for 5 days. At 5-9 days post-treatment, lomefloxacin had eradicated the causative organism of infection in 100% of evaluable patients treated with lomefloxacin compared with 86.7% of those treated with TMP/SMX. At 4-6 weeks post-treatment, there were no marked differences in eradication rates between the two treatment groups: 83.3% and 80.0% for the lomefloxacin and TMP/SMX groups, respectively. Clinical cure rates showed no marked differences between treatment groups at 5-9 days or at 4-6 weeks post-treatment. At 5-9 days post-treatment, lomefloxacin achieved a clinical cure rate of 78.6% compared with 86.7% for TMP/SMX evaluable patients. At 4-6 weeks post-treatment, the clinical cure rates were 66.7% and 86.7% for the evaluable lomefloxacin- and TMP/SMX-treated patients, respectively. Both treatment regimens were well tolerated with a low incidence of adverse events. In conclusion, once-daily oral dosing with lomefloxacin is a safe and efficacious alternative to twice-daily dosing with TMP/SMX in the treatment of uncomplicated urinary tract infections.

Lomefloxacin: microbiologic assessment and unique properties

In comparative studies, lomefloxacin, a new difluorinated quinolone, exhibits broad antibacterial activity in vitro, similar or superior to that of other quinolones (enoxacin, ofloxacin, pipemidic acid, nalidixic acid, and norfloxacin) but less than that of ciprofloxacin. Lomefloxacin inhibited Neisseria gonorrhoeae, Moraxella (Branhamella) catarrhalis, Haemophilus influenzae, Pseudomonas aeruginosa, Staphylococcus aureus, and the majority of aerobic gram-negative rods, including nosocomial isolates, at concentrations readily achievable in biologic fluids and tissues. Lomefloxacin was less active against obligate anaerobes and streptococci. Organisms resistant to methicillin, penicillin, or the aminoglycosides were susceptible to lomefloxacin. No significant lomefloxacin resistance was identified in 18 countries in which in vitro studies were conducted, with the exception of a small number of strains tested in France. The frequency with which spontaneous single-step resistance to lomefloxacin develops in vitro is low.

Comparison of the safety and efficacy of lomefloxacin and trimethoprim/sulfamethoxazole in the treatment of uncomplicated urinary tract infections: results from a multicenter study

Lomefloxacin, a new difluorinated quinolone, and trimethoprim/sulfamethoxazole (TMP/SMX) were compared in the treatment of adults with uncomplicated urinary tract infections. The study was conducted as a multicenter, controlled, prospectively randomized, single-blind study in five countries (Argentina, Belgium, Brazil, Mexico, and Venezuela). A total of 254 patients were enrolled: 129 in the lomefloxacin group and 125 in the TMP/SMX group. Patients received either 400 mg lomefloxacin orally once daily or 160 mg/800 mg TMP/SMX orally twice daily for 7-10 days. Escherichia coli and Proteus mirabilis were the pathogens most frequently isolated. At 5-9 days post-therapy, satisfactory bacteriologic results were noted in 98.4% of patients treated with lomefloxacin and in 95.8% of patients in the TMP/SMX group (p = 0.2153). Clinical success 5-9 days post-therapy was noted in 99.2% of patients in the lomefloxacin group and in 98.3% of patients in the TMP/SMX group (p = 0.5138). Adverse events probably related to treatment occurred in 6% of those treated with lomefloxacin and in 7% of patients treated with TMP/SMX. Once-daily oral lomefloxacin is a well-tolerated and effective treatment of uncomplicated urinary tract infections caused by susceptible pathogens.

The U.S. clinical experience with lomefloxacin, a new once-daily fluoroquinolone

Lomefloxacin is a new fluoroquinolone antimicrobial agent that has undergone extensive worldwide clinical evaluation. This report summarizes the safety and efficacy of lomefloxacin in the treatment of uncomplicated urinary tract infections, complicated urinary tract infections, acute exacerbations of chronic bronchitis, and for prophylaxis during urinary tract surgery. The clinical data presented are an overview of all clinical studies conducted in the United States to date. The results have been derived from multiple studies in which patients received lomefloxacin or a comparative agent in either blinded or open-label studies. During the course of the clinical program in the United States, lomefloxacin has been compared with oral norfloxacin, ciprofloxacin, and cefaclor, as well as parenteral cefotaxime. In all instances, the once-daily oral administration of lomefloxacin was either equally effective or statistically significantly superior in clinical and/or bacteriologic efficacy to these comparative agents. In addition, the comparators were administered either two or three times per day, except in the surgical prophylaxis studies, in which single doses of each antibiotic were administered preoperatively. These results attest to the value of the convenience and simplicity of the oral dosing regimen for lomefloxacin. During the course of the clinical program, lomefloxacin was well tolerated, with most adverse events of mild to moderate severity. In general, the incidence of adverse events for patients and subjects receiving lomefloxacin was comparable to that observed in patients treated with comparator drugs. The most common adverse events were related to the gastrointestinal tract (nausea and diarrhea), the skin and appendages (photosensitivity), and the central nervous system (dizziness and headache). A sub-analysis of adverse events in the respiratory studies demonstrated that concomitant administration of lomefloxacin and theophylline does not increase the incidence of adverse events when compared to lomefloxacin alone. An additional sub-analysis also showed that the incidence of adverse events in elderly patients was similar to that in younger patients. The results of the U.S. clinical program indicate that lomefloxacin administered orally once daily is effective and well tolerated in a variety of infections of bacterial origin.

Lomefloxacin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

The antibacterial efficacy of oral lomefloxacin has been investigated in a wide variety of infections, including respiratory and uncomplicated and complicated urinary tract infections, obstetric, gynaecological, joint, skin, oral, ear, nose, throat and eye infections. It has also been used as an otic solution in patients with otitis media and as an ophthalmic solution in the treatment of eye infections. In clinical trials its efficacy is equivalent to that of other quinolones and it is at least as effective as other antibacterial drugs ordinarily used in these infections. Lomefloxacin offers certain advantages compared with other quinolone antibacterial drugs in that it may be conveniently administered once daily and theophylline dosage adjustment does not appear to be necessary in patients receiving this bronchodilator concomitantly. Thus, orally administered lomefloxacin should prove a useful broad spectrum antibacterial drug for a wide variety of clinical infections.

Mechanism of action of sparfloxacin against and mechanism of resistance in gram-negative and gram-positive bacteria

The inhibition of DNA synthesis by sparfloxacin; accumulation of sparfloxacin into members of the family Enterobacteriaceae, Pseudomonas aeruginosa, and staphylococci; induction of recA in Escherichia coli; and the optimum bactericidal concentration (OBC) were measured, and killing kinetics at the OBC were estimated. The OBC and maximum recA-inducing concentration in E. coli were both 1 microgram of sparfloxacin per ml. Accumulation was rapid; two- to threefold more sparfloxacin than ciprofloxacin accumulated in staphylococci and more sparfloxacin accumulated in staphylococci than in gram-negative bacteria. Laboratory mutants with decreased susceptibilities to quinolones alone or multiply resistant were selected from the Enterobacteriaceae and Staphylococcus aureus by using sparfloxacin.

Inhibition by quinolones of DNA gyrase from Staphylococcus aureus

In order to clarify the mechanism of action of quinolones against Staphylococcus aureus, the subunit A and B proteins of DNA gyrase were separately purified from a crude extract of S. aureus FDA 209-P. The reconstituted enzyme exhibited ATP-dependent DNA supercoiling activity. The inhibitory effects of quinolones on the supercoiling activity of the purified enzyme were measured by the quantitative electrophoresis method (17), using plasmid DNA, pBR322 or pUB110, as substrates and expressed as the 50% inhibitory concentrations (IC50s). The IC50s of ofloxacin, DR-3355 (l-ofloxacin), ciprofloxacin, tosufloxacin, sparfloxacin, and DS-4524, a new quinolone derivative, for pBR322 were 63.0, 37.8, 30.5, 46.0, 28.5, and 3.2 micrograms/ml, respectively. These values were closely correlated with antibacterial activity (MIC), with correlation coefficients of 0.953 for pBR322 and 0.938 for pUB110. These results indicate that, in S. aureus, as in gram-negative bacteria, DNA gyrase is likely to be a major target enzyme of quinolones.

Mode of action of the new quinolones: new data

New details of the molecular interactions of quinolones with their target DNA gyrase and DNA have come from the nucleotide sequences of the gyrA genes from resistant mutants of Escherichia coli and wild-type strains of other bacteria and studies of gyrase A tryptic fragments, all suggesting the importance of an amino-terminal domain in quinolone action. Alterations in DNA supertwisting were also associated with altered quinolone susceptibility, possibly by indirect effects on DNA gyrase expression. Specific binding of relevant concentrations of norfloxacin to a complex of DNA gyrase and DNA in the presence of ATP, the cooperativity of DNA binding, and the crystalline structure of nalidixic acid have led to a model in which quinolones bind cooperatively to a pocket of single-strand DNA created by DNA gyrase. Quinolones vary in their relative activity against DNA gyrase and its eukaryotic homolog topoisomerase II, and in some assays increased action against the eukaryotic enzyme was associated with genotoxicity. Inhibition of bacterial DNA synthesis by quinolones may correlate with MICs in some species, but comparisons of drug accumulation and inhibition of DNA synthesis in permeabilized cells among species have been difficult to interpret. The specific factors necessary for bacterial killing by quinolones in addition to interaction with DNA gyrase have remained elusive, but include oxygen and new protein synthesis. The coordinate expression of the SOS proteins appears not to be necessary for quinolone lethality. Two independent mutants with selective reduced killing by quinolones and beta-lactams indicate overlap in the pathways of bactericidal activity of these classes of agents with distinct targets.