Fluoroquinolone Compounds Research Articles

Culture and antibiotic susceptibility of Bartonella quintana in human erythrocytes.

Bartonella quintana, the agent of trench fever, has recently been implicated in various diseases, in particular, bacteremia and endocarditis in homeless people. The host cell of Bartonella spp. is believed to be the erythrocyte, and in the present study we demonstrate that B. quintana can be cultured in vitro in human erythrocytes. The bacteria were found to be intraerythrocytic by laser confocal microscopy with Bartonella species-specific monoclonal antibodies. Infections with B. quintana decreased the life span of erythrocytes in culture from 8.6 to 4.8 days. In the culture system we found that most of the antibiotics that we tested (doxycycline, fluoroquinolone compounds, and beta-lactams) were not bactericidal. Gentamicin was bactericidal at 4 micro g/ml, as was rifampin, but to a lesser extent. At this concentration, gentamicin has been shown to enter erythrocytes slowly and to reach a peak level of 0.26 micro g/ml after 24 h. At 0.26 micro g/ml, however, we found that gentamicin was not able to kill extracellular B. quintana, even after 96 h of incubation. We hypothesize that erythrocytes may be a reservoir for B. quintana and that the bactericidal activity of gentamicin that we observed occurs mainly when the bacteria emerge from the erythrocytes and are found extracellularly. It would appear that gentamicin should be administered for at least 5 days to cure patients infected with B. quintana.

Liquid chromatographic separation of the enantiomers of fluoroquinolone antibacterials on a chiral stationary phase based on a chiral crown ether

A chiral stationary phase (CSP) recently developed by bonding (diphenyl-substituted 1,1′-binaphthyl) crown ether to silica gel for the liquid chromatographic separation of enantiomers was applied to the resolution of investigational fluoroquinolone antibacterial agents including gemifloxacin (formerly LB20304a). All fluoroquinolone compounds used in this study were resolved quite well on the CSP. Especially, the resolution of gemifloxacin and its analogs on the CSP was excellent and even greater than that on the commercial Crownpak CR(+). The resolution was found to be dependent on the type and the content of organic, acidic, and inorganic modifiers added to the mobile phase and on the column temperature.

Pharmacokinetics and tolerability of gemifloxacin (SB-265805) after administration of single oral doses to healthy volunteers.

Gemifloxacin (known as SB-265805 or LB-20304) is a potent, novel fluoroquinolone compound with a broad spectrum of antibacterial activity. The pharmacokinetics and tolerability of oral gemifloxacin were characterized in healthy male volunteers after a single dose of 20, 40, 80, 160, 320, 600, or 800 mg. Multiple serum and urine samples were collected and analyzed for gemifloxacin using high-performance liquid chromatography with fluorescence detection. Safety assessments included vital signs, 12-lead electrocardiogram readings, hematology, clinical chemistry, urinalysis, and adverse-experience monitoring. Gemifloxacin was rapidly absorbed after all doses. Maximum concentrations of gemifloxacin in serum (C(max)) were achieved approximately 1 h after dosing, after which concentrations in serum declined in a biexponential manner. Values of C(max) and the area under the concentration-time curve in serum from 0 h to infinity (serum AUC(0-infinity)) increased linearly with dose. Serum AUC(0-infinity) values (mean +/- standard deviation) were 0.65+/-0.01, 1.28+/-0.22, 2.54+/-0.31, 5.48+/-1.24, 9.82+/-2.70, 24.4+/-7.1, and 31.4+/-7.6 microg. h/ml following 20-, 40-, 80-, 160-, 320-, 600-, and 800-mg doses, respectively. The terminal phase elimination half-life was independent of dose, with an overall mean of 7.4+/-2.0 h. The profiles indicated that the pharmacokinetic profile is suitable for a once-daily dosing regimen. Approximately 25 to 40% of the administered dose was excreted unchanged in the urine, and renal clearance (ca. 150 ml/min) was independent of dose. There were no significant changes in clinical chemistry, hematology, or urinalysis parameters, vital signs, or 12-lead electrocardiogram readings in subjects, irrespective of dose. The results of these studies support the further investigation of once-daily administration of gemifloxacin.

Direct liquid chromatographic enantiomer separation of new fluoroquinolones including gemifloxacin

The enantiomers of gemifloxacin mesylate (formerly LB20304a), a new fluoroquinolone compound with potent in vitro and in vivo antibacterial profile were resolved on a commercially available Crownpak CR chiral stationary phase (CSP). All of the fluoroquinolones, including gemifloxacin used in this study, were well enantioseperated on Crownpak CR(+) column. These results are the first reported for the direct separation of the enantiomers of quinolones on chiral crown ether coated Crownpak CR CSP. The behavior of chromatographic parameters by the change of mobile phase additives for the resolution of gemifloxacin was investigated. Also, the effect of structural change of gemifloxacin on chiral recognition was described.

Bactericidal Activity of Moxifloxacin Compared to Grepafloxacin and Clarithromycin against Streptococcus pneumoniae and Streptococcus pyogenes Investigated Using an In Vitro Pharmacodynamic Model

The aim of the present investigation was to study and compare the killing activity of two new fluoroquinolone compounds, moxifloxacin and grepafloxacin, and a new generation macrolide, clarithromycin, against three clinical isolates of Streptococcus pneumoniae (penicillin-susceptible, -intermediate and -resistant) and two Streptococcus pyogenes (erythromycin-suscepti-ble and -resistant) strains by simulating their human pharmacokinetics in a pharmacodynamic model. Results were achieved by measuring the reduction in viable bacterial count during the 24-h experimental period.All three antimicrobials led to a continuous reduction in the bacterial counts of penicillin-susceptible S. pneumoniae and erythromycin-susceptible S. pyogenes strains, the maximal reduction observed after 8-10 hours being 5-6 logs for moxifloxacin and 3 logs for grepafloxacin; clarithromycin exhibited a similar reduction of 5 logs only after 24 h. No regrowth was observed for any strain after 24 h with any of the antibiotics.The bactericidal activity of both the fluoroquinolones was not affected by penicillin resistance of S. pneumoniae and erythromycin resistance of S. pyogenes. In contrast, clarithromycin was not able to reduce the bacterial count of penicillin-resistant S. pneumoniae and erythromycin-resistant S. pyogenes strains.Moxifloxacin exhibited, within 24 h, higher and faster bactericidal activity than grepafloxacin and clarithromycin against S. pneumoniae, and was not affected by penicillin resistance. These results suggest that moxifloxacin is a promising new agent for treatment of streptococcal infections.

Comparative In Vitro Activity and Killing Effect of Trovafloxacin, DU-6859a, Levofloxacin and Sparfloxacin against Staphylococcus aureus

The predominance of quinolone resistance among methicillin-resistant Staphylococcus aureus (MRSA) isolates in the nosocomial environment led to the in vitro comparison of trovafloxacin (CP-99,219) and DU-6859a (which are novel fluoroquinolone compounds) with levofloxacin (the L-geometric isomer of ofloxacin) and Sparfloxacin against 152 S. aureus isolates, 104 of which were MRSA. At 2 mg/L trovafloxacin and DU-6859a inhibited 92.3 and 77.9% of MRSA isolates, respectively, possessing lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values than levofloxacin and Sparfloxacin, which inhibited 38.5 and 36.5% of isolates, respectively. In contrast, in the methicillin-susceptible population all tested fluoroquinolones had an equal intrinsic activity. Trovafloxacin possessed a superior killing effect compared with DU-6859a and Sparfloxacin, whereas levofloxacin was the least bactericidal quinolone. Indeed, the effect of trovafloxacin was mainly expressed at a quinolone concentration of 2 × MIC and after 24 hours of growth. However, in levofloxacin- and sparfloxacin-resistant MRSA isolates, DU-6859a had a superior killing effect compared with trovafloxacin. Trovafloxacin had a killing effect in only 20% of DU-6859a-, levofloxacin- and sparfloxacin-resistant isolates. Our findings support trovafloxacin and DU-6859a as highly active in vitro antistaphylococcal agents, especially in MRSA, which merit further clinical investigation.

Anti- Legionella activity of trovafloxacin compared with seven other antimicrobial agents including an intermethod evaluation

The activity of trovafloxacin, a new fluorinated naphtheridone, was tested against 61 Legionella spp. isolates and compared with that of 4 fluoroquinolones, 2 macrolides, and rifampin. Trovafloxacin MICs were determined by a reference agar dilution method and E-test (Solna, Sweden) strips on buffered charcoal yeast extract agar. Among the fluoroquinolone compounds, the rank order of activity (on the basis of MIC 90 results) determined with E-test strips was as follows: levofloxacin (MIC 90, 0.094 μg/ml) > trovafloxacin = sparfloxacin = ofloxacin (MIC 90, 0.19 μg/ml). Rifampin (MIC 90, 0.008 μg/ml) and clarithromycin (MIC 90, 0.032 μg/ml) were the most potent of all drugs tested, and erythromycin and ciprofloxacin were the least active. In this study, the E-test strips with trovafloxacin were validated (100% of results ± one log 2 dilution compared to the reference value) for susceptibility testing with Legionella isolates.

Intracellular organisms

The intracellular location of some microorganisms allow them to resist antibiotics with poor ability to penetrate eukaryotic cell membranes, such as the β-lactam compounds. Pharmacokinetic and pharmacodynamic properties of antibiotics within eukaryotic cells have been defined in the last two decades. Penetration but also subcellular localization of antibiotics within cells, as well as the possibility of their intracellular inactivation have to be considered. In vitro infected cell models have been useful to determine the activity of antibiotics against intracellular pathogens, although extrapolation of in vitro experimental data to the clinical situation remains hazardous. The pharmacokinetic properties and intracellular activity against a number of pathogens of the newer fluoroquinolone and macrolide compounds seems promising, but clinical data remain scarce.

DNA Gyrase and Topoisomerase IV on the Bacterial Chromosome: Quinolone-induced DNA Cleavage

DNA gyrase, the bacterial enzyme that supercoils DNA, is trapped on chromosomal DNA by the 4-quinolone compounds, as drug–gyrase complexes that contain DNA breaks. Examination of chromosomal DNA extracted from Escherichia coliindicated that bacteriostatic concentrations of oxolinic acid trap gyrase and block DNA synthesis without releasing broken DNA from gyrase–DNA complexes. Release, detected as free rotation of DNA in the presence of an intercalating dye, occurred only at high, bactericidal oxolinic acid concentrations. Release of DNA breaks and cell death were both blocked by chloramphenicol, an inhibitor of protein synthesis, suggesting that synthesis of additional protein activity is required to free the DNA ends. Ciprofloxacin, a more potent quinolone, released DNA breaks and killed cells even in the presence of chloramphenicol. It is proposed that this second, chloramphenicol-insensitive mode for release of DNA breaks and cell killing arises from dissociation of gyrase subunits. Ciprofloxacin also killed a gyrase ( gyrA) mutant resistant to the prototype of quinolone, nalidixic acid, and created complexes on DNA detected by DNA fragmentation. This lethal effect of ciprofloxacin was eliminated by additional mutations mapping in parC, one of the two genes encoding topoisomerase IV. Thus, the fluoroquinolone compounds have two intracellular targets. In the absence of the gyrAmutation, the parC(Cip R|1ru|) allele did not by itself confer resistance to ciprofloxacin, indicating that gyrase is the major quinolone target in E. coli. These findings provide a molecular explanation for quinolone action in bacteria and a new way to study topoisomerase IV–chromosome interactions.

Fluoroquinolones in paediatrics--1995.

The fluoroquinolones are characterised by a broad spectrum of antibacterial activity that includes many Mycobacterium, Chlamydia, Legionella, and Mycoplasma species as well as many multiply-resistant bacterial strains, good oral bioavailability, extensive tissue penetration, low protein binding and long elimination half-lives. Numerous clinical trials have shown that these compounds are effective and well tolerated in the treatment of adult patients with various infections, including urinary tract, respiratory tract, skin and soft tissue, bone and joint, and gynaecological infections, sexually transmitted diseases, infectious diarrhoea, infections in immunocompromised patients, and in surgical prophylaxis. Thus, there is increasing pressure to use this class of drugs in paediatric patients. However, concerns regarding adverse effects, particularly cartilage toxicity, have restricted development of the fluoroquinolone compounds for use in this population. Potential indications include Pseudomonas infections (mainly exacerbations of cystic fibrosis), urinary tract, gastrointestinal and central nervous system infections, infections in immunocompromised patients, certain otorhinolaryngological infections and infections caused by multiply-resistant pathogens. To date, clinical experience gained with fluoroquinolones in paediatric infections, which has been mainly on a compassionate-use basis, indicates that well-designed formal studies should be conducted to fully assess the efficacy and tolerability of these agents in specific indications in children.

In vitro activities of enoxacin, enrofloxacin, sparfloxacin, and ciprofloxacin against Escherichia coli strains isolated from diarrheic lambs and kids

The in vitro activities of four fluoroquinolone compounds were tested against 92 Escherichia coli strains of ovine and caprine origin under aerobic and anaerobic incubation conditions. The four fluoroquinolones proved to be highly effective against the E. coli isolates tested. When bacteria were cultured anaerobically, at least fourfold increases in the MICs of enoxacin for the strains occurred and no detectable changes in enrofloxacin, sparfloxacin, and ciprofloxacin MICs occurred.

Methods for testing the susceptibility of anaerobic bacteria to two fluoroquinolone compounds, PD 131628 and clinafloxacin.

The susceptibility of anaerobic bacteria to two new fluoroquinolones, PD 131628 (the bioactive form of PD 131112 or CI-990) and clinafloxacin (CI-960 or PD 127391), was determined with the agar dilution procedures and two media, and one broth microdilution procedure. Sparfloxacin and ciprofloxacin were also tested by the broth microdilution method. One hundred anaerobic isolates and four control strains were tested by the three methods which gave minimum inhibitory concentrations (MICs) that were essentially comparable, but not identical. With the broth microdilution method, the relative potency of the four fluoroquinolones was: clinafloxacin > PD 131628 > sparfloxacin > ciprofloxacin. For the latter three drugs but not clinafloxacin, the MIC values were often near the proposed interpretive breakpoint concentrations, and thus minor methodological differences frequently influenced the interpretive categories. Replicate agar dilution tests in five laboratories established MIC control limits for each of four control strains: those MIC limits could also be used to define the expected performance of the two alternative methods.

In vitro evaluation of WIN 57273, a new broad-spectrum fluoroquinolone

WIN 57273 is a new fluoroquinolone that has an expanded spectrum of activity against Staphylococcus spp. (MIC for 90% of isolates [MIC90], 0.008 microgram/ml), Enterococcus faecalis (MIC90, 0.06 microgram/ml), Bacillus spp. (MIC90, 0.03 micrograms/ml), Listeria monocytogenes (MIC90, 0.06 microgram/ml), Streptococcus spp. (MIC90, 0.03 microgram/ml), and Bacteroides fragilis group strains (MIC90, 0.5 microgram/ml). Like other fluoroquinolone compounds, WIN 57273 was active against members of the family Enterobacteriaceae (97% of strains inhibited by less than or equal to 2 micrograms/ml), Haemophilus, Branhamella, and Neisseria strains (100% susceptible), Acinetobacter spp. (100% susceptible), and Pseudomonas aeruginosa (68% susceptible). We observed that WIN 57273 was very active against cephalosporin- or aminoglycoside-resistant gram-negative strains but shared cross-resistance with other fluoroquinolones. Increasing inoculum concentrations had minimal effects on WIN 57273 MICs, and the drug was considered to be bactericidal based on reference MBC and kill curve analyses. Unlike most previously studied drugs in this class, WIN 57273 had increased activity (three- to fourfold) at low pH. Rates of mutation to WIN 57273 resistance at eight times its MIC were in the range of 5.6 x 10(-8) to greater than 1.4 x 10(-9). This new compound possesses a wide potential spectrum of use, and it should be evaluated further by in vitro and in vivo studies.

In vitro activity of the fluoroquinolone compounds

In vitro activity of the fluoroquinolone compounds

Bactericidal activities of ten different fluoroquinolones against selected enterobacteriaceae

Ten fluoroquinolone compounds and two other 4-quinolones were tested in a microdilution system. Minimal inhibitory concentrations and minimal bactericidal concentrations were determined with 1 × 10 7 and 5 × 10 5 colony forming units per milliliter. All 12 compounds were bactericidal. Continued inhibition by drug carried over in the subcultured samples was documented and that represents a potential source of technical error that needs to be controlled when determining minimal bactericidal concentrations for these extremely potent drugs.