Uptake and intracellular activity of trovafloxacin in human phagocytes and tissue-cultured epithelial cells

Pharmacokinetics in plasma and alveolar regions of a healthy calf intramuscularly administered a single dose of orbifloxacin

This study analyzed the pharmacokinetics of orbifloxacin (OBFX) in plasma, and its migration and retention in epithelial lining fluid (ELF) and alveolar cells within the bronchoalveolar lavage fluid (BALF). Four healthy calves received a single dose of OBFX (5.0 mg/kg) intramuscularly. Post-administration OBFX dynamics were in accordance with a non-compartment model, including the absorption phase. The maximum concentration (C_max) of plasma OBFX was 2.2 ± 0.1 μg/ml at 2.3 ± 0.5 hr post administration and gradually decreased to 0.3 ± 0.2 μg/ml at 24 hr following administration. The C_max of ELF OBFX was 9.3 ± 0.4 μg/ml at 3.0 ± 2.0 hr post administration and gradually decreased to 1.2 ± 0.1 μg/ml at 24 hr following administration. The C_max of alveolar cells OBFX was 9.3 ± 2.9 μg/ml at 4.0 hr post administration and gradually decreased to 1.1 ± 0.2 μg/ml at 24 hr following administration. The half-life of OBFX in plasma, ELF, and alveolar cells were 6.9 ± 2.2, 7.0 ± 0.6, and 7.8 ± 1.6 hr, respectively. The C_max and the area under the concentration-time curve for 0–24 hr with OBFX were significantly higher in ELF and alveolar cells than in plasma (P<0.05). These results suggest that OBFX is distributed and retained at high concentrations in ELF and alveolar cells at 24 hr following administration. Hence, a single intramuscular dose of OBFX (5.0 mg/kg) may be an effective therapeutic agent against pneumonia.

A New Criterion for Fluoroquinolone-Associated Disability Diagnosis: Functional Gastrointestinal Disorders

Background and Objectives: Fluoroquinolones (FQs) are a broad-spectrum class of antibiotics routinely prescribed for common bacterial infections despite recent recommendations to use them only for life-threatening cases. In addition to their antimicrobial properties, FQs act in the central nervous system as GABAA receptor inhibitors, which could potentially affect functionality of the vagus nerve at the forefront of gastrointestinal (GI) tract function. Alterations in neural control of digestion have been shown to be linked to Functional Gastrointestinal Disorders (FGIDs), which are usually diagnosed based on self-reported symptoms. The aim of this study was to assess the incidence of FGIDs following FQ use. Materials and Methods: Self-reports from the FDA Adverse Event Reporting System were analyzed together with ~300 survey responses from a social network derived sample to the Bowel Disease Questionnaire. Results: The results of this study suggested that six different FQs are associated with a wide range of GI symptoms not currently reported in the drugs’ labels. The responses from the survey suggested that ~70% of FQ users scored positive for FGID, with no positive correlation between drug type, duration of administration, dosage and frequency of administration. Conclusions: This study showed that GI disorders other than nausea, vomiting and diarrhea are more common than currently reported on the drug labels, and that FGIDs are possibly a common consequence of FQ use even after single use.

Fluoroquinolones-Associated Disability: It Is Not All in Your Head

Fluoroquinolones (FQs) are a broad class of antibiotics typically prescribed for bacterial infections, including infections for which their use is discouraged. The FDA has proposed the existence of a permanent disability (Fluoroquinolone Associated Disability; FQAD), which is yet to be formally recognized. Previous studies suggest that FQs act as selective GABAA receptor inhibitors, preventing the binding of GABA in the central nervous system. GABA is a key regulator of the vagus nerve, involved in the control of gastrointestinal (GI) function. Indeed, GABA is released from the Nucleus of the Tractus Solitarius (NTS) to the Dorsal Motor Nucleus of the vagus (DMV) to tonically regulate vagal activity. The purpose of this review is to summarize the current knowledge on FQs in the context of the vagus nerve and examine how these drugs could lead to dysregulated signaling to the GI tract. Since there is sufficient evidence to suggest that GABA transmission is hindered by FQs, it is reasonable to postulate that the vagal circuit could be compromised at the NTS-DMV synapse after FQ use, possibly leading to the development of permanent GI disorders in FQAD.

Pharmacokinetics in plasma and alveolar regions of healthy calves subcutaneously administered a single dose of enrofloxacin

This study aimed to analyze the pharmacokinetics of enrofloxacin (ERFX) and its metabolite ciprofloxacin (CPFX) in plasma, as well as their migration to, and retention in, the epithelial lining fluid (ELF) and alveolar cells within the bronchoalveolar fluid (BALF). Four healthy calves were subcutaneously administered a single dose of ERFX (5 mg/kg). ERFX and CPFX dynamics post-administration were analyzed via a non-compartment model, including the absorption phase. The Cmax of plasma ERFX was 1.6 ± 0.4 µg/ml at 2.3 ± 0.5 hr post-administration and gradually decreased to 0.14 ± 0.03 µg/ml at 24 hr following administration. The mean residence time between 0 and 24 hr (MRT_0–24) in plasma was 6.9 ± 1.0 hr. ERFX concentrations in ELF and alveolar cells peaked at 3.0 ± 2.0 hr and 4.0 ± 2.3 hr following administration, respectively, and gradually decreased to 0.9 ± 0.8 µg/ml and 0.8 ± 0.5 µg/ml thereafter. The plasma half-life (t1/2) of ERFX was 6.5 ± 0.7 hr, while that in ELF and alveolar cells was 6.5 ± 3.6 and 7.4 ± 4.3 hr, respectively. The Cmax and the area under the concentration-time curve for 0–24 hr for ERFX were significantly higher in alveolar cells than in plasma (P<0.05). These results suggest that ERFX is distributed at high concentrations in ELF and is retained at high concentrations in alveolar cells after 24 hr in the BALF region; hence, ERFX may be an effective therapeutic agent against pneumonia.

Treatment of the Fluoroquinolone-Associated Disability: The Pathobiochemical Implications

Long-term fluoroquinolone-associated disability (FQAD) after fluoroquinolone (FQ) antibiotic therapy appears in recent years as a significant medical and social problem, because patients suffer for many years after prescribed antimicrobial FQ treatment from tiredness, concentration problems, neuropathies, tendinopathies, and other symptoms. The knowledge about the molecular activity of FQs in the cells remains unclear in many details. The effective treatment of this chronic state remains difficult and not effective. The current paper reviews the pathobiochemical properties of FQs, hints the directions for further research, and reviews the research concerning the proposed treatment of patients. Based on the analysis of literature, the main directions of possible effective treatment of FQAD are proposed: (a) reduction of the oxidative stress, (b) restoring reduced mitochondrion potential ΔΨ_m, (c) supplementation of uni- and bivalent cations that are chelated by FQs and probably ineffectively transported to the cell (caution must be paid to Fe and Cu because they may generate Fenton reaction), (d) stimulating the mitochondrial proliferation, (e) removing FQs permanently accumulated in the cells (if this phenomenon takes place), and (f) regulating the disturbed gene expression and enzyme activity.

Targeted imaging of bacterial infections: advances, hurdles and hopes

Bacterial infections represent an increasing problem in modern health care, in particular due to ageing populations and accumulating bacterial resistance to antibiotics. Diagnosis is rarely straightforward and consequently treatment is often delayed or indefinite. Therefore, novel tools that can be clinically implemented are urgently needed to accurately and swiftly diagnose infections. Especially, the direct imaging of infections is an attractive option. The challenge of specifically imaging bacterial infections in vivo can be met by targeting bacteria with an imaging agent. Here we review the current status of targeted imaging of bacterial infections, and we discuss advantages and disadvantages of the different approaches. Indeed, significant progress has been made in this field and the clinical implementation of targeted imaging of bacterial infections seems highly feasible. This was recently highlighted by the use of so-called smart activatable probes and a fluorescently labelled derivative of the antibiotic vancomycin. A major challenge remains the selection of the best imaging probes, and we therefore present a set of target selection criteria for clinical implementation of targeted bacterial imaging. Altogether, we conclude that the spectrum of potential applications for targeted bacterial imaging is enormous, ranging from fundamental research on infectious diseases to diagnostic and therapeutic applications.

Intracellular penetration and activity of UB-8902 in human polymorphonuclear leukocytes

The intracellular penetration and activity of UB-8902 in human polymorphonuclear leukocytes was evaluated. Intracellular UB-8902 concentrations were 6-fold higher than extracellular levels. Uptake was rapid, reversible, saturable, and affected by external pH. UB-8902 showed intracellular activity against Staphylococcus aureus strains presenting mutations associated with fluoroquinolone resistance in the gyrA and/or grlA genes.

Intracellular penetration and activity of DX-619 in human polymorphonuclear leukocytes

The intracellular penetration and activity of DX-619 in human polymorphonuclear leukocytes have been evaluated. DX-619 reached intracellular concentrations 10 times higher than the extracellular concentrations reached. Uptake was rapid, reversible, nonsaturable, and affected by environmental temperature, some metabolic inhibitors, and a soluble membrane activator. DX-619 showed intracellular activity against Staphylococcus aureus.

Pharmacologic characteristics of prulifloxacin

Prulifloxacin, the prodrug of ulifloxacin, is a broad-spectrum oral fluoroquinolone antibacterial agent. After absorption, prulifloxacin is metabolized by esterases to ulifloxacin. The drug has a long elimination half-life, allowing once-daily administration. In vitro, ulifloxacin is generally more active than other fluoroquinolones against a variety of clinical isolates of Gram-negative bacteria, including community and nosocomial isolates of Escherichia coli, Klebsiella spp., Proteus, Providencia and Morganella spp., Moraxella catarrhalis, Haemophilus spp., and Pseudomonas aeruginosa. Gram-positive organisms, including methicillin- or oxacillin-susceptible Staphylococcus aureus, Enterococcus spp. and Streptococcus pneumoniae, are susceptible to ulifloxacin. In well-designed clinical trials, prulifloxacin showed good clinical and bacteriological efficacy (similar to that of ciprofloxacin) and was generally well tolerated, demonstrating a similar tolerability profile to that of ciprofloxacin. In conclusion, the in vitro inhibitory and bactericidal activities exhibited by ulifloxacin and the favorable characteristics shown by its prodrug (prulifloxacin) in clinical trials, particularly indicate this drug for the treatment of lung and urinary infections.

Effect of recombinant murine granulocyte colony-stimulating factor with or without fluoroquinolone therapy on mixed-infection abscesses in mice

The aim of the study was to determine if immunomodulation of host defense with recombinant murine granulocyte colony-stimulating factor (G-CSF) improves the efficacy of trovafloxacin or moxifloxacin in abscesses containing Bacillus fragilis ATCC 23745 and different Escherichia coli strains varying in virulence. Treatment of mice inoculated with 10(7) CFU B. fragilis and 10(5) CFU low-virulence E. coli with either trovafloxacin (150 mg/kg/day every 24 hours, days 3 to 7) or moxifloxacin (96 mg/kg/day every 12 hours, days 3 to 7), significantly reduced the number of B. fragilis to 6.9 +/- 0.35 and 5.8 +/- 0.10 and that of E. coli to 4.9 +/- 0.09 and 4.2 +/- 0.07 log CFU/abscess for trovafloxacin and moxifloxacin, respectively, compared to controls (B. fragilis 8.7 and E. coli 7.4 log CFU/abscess) on day 8. Also, moxifloxacin was more potent than trovafloxacin. Addition of G-CSF prophylaxis (1 mug once on day -1) or therapy (1 mug/day on days 3 to 7) to fluoroquinolone treatment did not improve the efficacy of fluoroquinolone therapy alone. The effect of moxifloxacin with or without G-CSF prophylaxis on abscesses with a virulent hemolytic E. coli strain was also studied. In moxifloxacin-treated mice, 75% survived infection compared to 10% of controls. Combining moxifloxacin with G-CSF prophylaxis significantly decreased survival (30%) compared to moxifloxacin alone. In addition, G-CSF prophylaxis resulted in a threefold (E. coli) to 100-fold (B. fragilis) increased outgrowth in the abscesses of surviving mice. In conclusion, the addition of G-CSF to a fluoroquinolone is not advisable since, depending on the virulence of the E. coli strains, this might detrimentally influence the outcome of therapy.

Fluoroquinolones and tendon disorders

Fluoroquinolones are the most potent oral antibiotics in clinical use today. Increasingly, these drugs are being prescribed for relatively benign infections and for new categories of patients, including paediatric patients. As their use becomes more frequent, so will the adverse events. This review focuses on a rare but debilitating adverse reaction, the fluoroquinolone-associated tendinopathy. Despite many published case reports and approximately 3500 cases reported to the World Health Organization Collaborating Centre for Drug Monitoring, little is known about the mechanisms behind this fluoroquinolone-specific toxicity. Data on chemical properties, mode of action, pharmacokinetic features, clinical presentation and risk factors in relation to tendon toxicity are discussed and the literature reviewed. As long as the musculoskeletal toxicity cannot be predicted by in vitro or in vivo models and this class of antibiotics is one of the most commonly linked to selection of resistant bacteria, a more prudent use of fluoroquinolones is warranted.

Comparative activity of quinolones (ciprofloxacin, levofloxacin, moxifloxacin and garenoxacin) against extracellular and intracellular infection by Listeria monocytogenes and Staphylococcus aureus in J774 macrophages

OBJECTIVES

Quinolones accumulate in eukaryotic cells and show activity against a large array of intracellular organisms, but systematic studies aimed at examining their pharmacodynamic profile against intracellular bacteria are scarce. The present work aims at comparing intracellular-to-extracellular activities in this context.

METHODS

We assessed the activities of ciprofloxacin, levofloxacin, moxifloxacin and garenoxacin against the extracellular (broth) and intracellular (infected J774 macrophages) forms of Listeria monocytogenes (cytosolic infection) and Staphylococcus aureus (phagolysosomal infection) using a range of clinically meaningful extracellular concentrations (0.06-4 mg/L).

RESULTS

All four quinolones displayed concentration-dependent bactericidal activity against extracellular and intracellular L. monocytogenes and S. aureus for extracellular concentrations in the range 1-4-fold their MIC. Compared at equipotent extracellular concentrations, intracellular activities against L. monocytogenes were roughly equal to those that were extracellular, but were 50-100 times lower against S. aureus. Because quinolones accumulate in cells (ciprofloxacin, approximately 3 times; levofloxacin, approximately 5 times; garenoxacin, approximately 10 times, moxifloxacin, approximately 13 times), these data show that, intracellularly, quinolones are 5-10 times less potent against L. monocytogenes (P=0.065 [ANCOVA]), and at least 100 times less potent (P < 0.0001) against S. aureus. Because of their lower MICs and higher accumulation levels, garenoxacin and moxifloxacin were, however, more active than ciprofloxacin and levofloxacin when compared at similar extracellular concentrations.

CONCLUSIONS

Quinolone activity is reduced intracellulary. This suggests that either only a fraction of cell-associated quinolones exert an antibacterial effect, or that intracellular activity is defeated by the local environment, or that intracellular bacteria only poorly respond to the action of quinolones.

Quantitative analysis of gentamicin, azithromycin, telithromycin, ciprofloxacin, moxifloxacin, and oritavancin (LY333328) activities against intracellular Staphylococcus aureus in mouse J774 macrophages

Using J774 macrophages, the intracellular activities of gentamicin, azithromycin, telithromycin, ciprofloxacin, moxifloxacin, and oritavancin (LY333328) against Staphylococcus aureus (strain ATCC 25923) have been quantitatively assessed in a 24-h model. S. aureus was positively localized in phagolysosomes by confocal and electron microscopy, and extracellular growth was prevented with 0.5 mg of gentamicin/liter (1x MIC) in controls. When tested at extracellular concentrations equivalent to their maximum concentrations in human serum, all antibiotics except azithromycin caused a significant reduction of the postphagocytosis inoculum within 24 h, albeit to markedly different extents (telithromycin [2 mg/liter], 0.60 log; ciprofloxacin [4.3 mg/liter], 0.81 log; gentamicin [18 mg/liter], 1.21 log; moxifloxacin [4 mg/liter], 1.51 log; oritavancin [25 mg/liter], 3.49 log). Intracellular activities were not systematically related to drug accumulation (apparent cellular-to-extracellular concentration ratios in infected cells: ciprofloxacin, 3.2; gentamicin, 6.8; telithromycin, 8.7; moxifloxacin, 13.4; azithromycin, 50; oritavancin, 348). Intracellular activity was not directly correlated to extracellular activity as measured in broth. Conditions of pH 5 (i.e., mimicking that of phagolysosomes) markedly reduced the activity of gentamicin, azithromycin, and telithromycin (>or=32 x) and fairly extensively reduced that of ciprofloxacin and moxifloxacin (>or=4 x) but did not affect oritavancin activity. We conclude that the cellular accumulation of antibiotics is not the only parameter to take into account for intracellular activity but that local environmental conditions (such as pH) and other factors can also prove critical.

Uptake and intracellular activity of linezolid in human phagocytes and nonphagocytic cells

The intracellular penetration and activity of linezolid in human polymorphonuclear leukocytes and tissue-cultured cells (McCoy) were evaluated. Linezolid reached intracellular concentrations slightly greater than extracellular ones in both types of cell. The uptake was rapid and not saturable and was affected by environmental temperature and cell viability. Linezolid showed slight intracellular activity against Staphylococcus epidermidis at high extracellular concentrations.

Accumulation of ciprofloxacin and minocycline by cultured human gingival fibroblasts

Through a mechanism that is unclear, systemic fluoroquinolones and tetracyclines can attain higher levels in gingival fluid than in blood. We hypothesized that gingival fibroblasts take up and accumulate these agents, thereby enhancing their redistribution to the gingiva. Using fluorescence to monitor transport activity, we characterized the accumulation of fluoroquinolones and tetracyclines in cultured human gingival fibroblast monolayers. Both were transported in a concentrative, temperature-dependent, and saturable manner. Fibroblasts transported ciprofloxacin and minocycline with K(m) values of 200 and 108 micro g/mL, respectively, at maximum velocities of 4.62 and 14.2 ng/min/ micro g cell protein, respectively. For both agents, transport was most efficient at pH 7.2 and less efficient at pH 6.2 and 8.2. At steady state, the cellular/extracellular concentration ratio was > 8 for ciprofloxacin and > 60 for minocycline. Thus, gingival fibroblasts possess active transporters that could potentially contribute to the relatively high levels these agents attain in gingival fluid.

An in vitro model of ciprofloxacin and minocycline transport by oral epithelial cells

BACKGROUND

Fluoroquinolones and tetracyclines can penetrate epithelial cells, but the mechanism by which they cross the plasma membrane is unclear. In this study, a cell line derived from oral epithelium was used as a model to demonstrate a role for active transport.

METHODS

Transport of ciprofloxacin and minocycline by confluent cell monolayers was assayed by measuring the increase in cell-associated fluorescence.

RESULTS

Uptake of both agents was saturable and was inhibited at low temperatures. At 37 degrees C, the cells transported ciprofloxacin and minocycline with Km values of 351 and 133 microg/ml, respectively, and maximum velocities of 5.11 and 13.4 ng/min/microg cell protein, respectively. When ciprofloxacin and minocycline were removed from the extracellular medium, the intracellular levels of both agents decreased. Ciprofloxacin efflux from loaded cells occurred more rapidly than with minocycline. Cells accumulated intracellular drug levels that were at least 8-fold higher than extracellular levels for ciprofloxacin and at least 40-fold higher for minocycline. Transport of ciprofloxacin and minocycline was significantly influenced by pH and was most favorable at pH 7.7 and 7.2, respectively. While ciprofloxacin transport was Na+ independent, minocycline transport was strongly inhibited when sodium in the medium was replaced with choline. Transport of both agents was inhibited by a variety of organic cations, but the pattern of inhibition was different. Papaverine, phenylephrine, and doxycycline competitively inhibited minocycline transport, but inhibited ciprofloxacin transport by a non-competitive mechanism.

CONCLUSIONS

Epithelial cells take up ciprofloxacin and minocycline via different active transport systems. These transporters may play an important role in enhancing the effectiveness of these agents against invasive pathogens.

Determination of Intracellular Concentrations of Free and Two Types of Liposome-Encapsulated Enrofloxacin in Anatolian Shepherd Dog Monocytes

In this study, it was evaluated the accumulation of free and two types of liposome-encapsulated enrofloxacin (LEE) at the doses of 0.25, 0.5 and 1 microg/ml, which were clinically relevant concentrations into monocytes of healthy Anatolian shepherd dogs. Enrofloxacin was encapsulated with two different types of liposome in multilamellar large vesicles (MLV). Type A MLV composed of 15 mg egg phosphatidylcholine and 35 mg cholesterol, Type B MLV composed of phosphatidylcholine (PC), cholesterol and enrofloxacin, in a molar ratio of 1 : 1 : 1. The mean sizes of Type A and Type B liposome were found to be 7.65 and 4.27 microm, respectively. However, the mean encapsulation rate determined of Type A (13 +/- 2%) was found lower than Type B liposome (44 +/- 3%). The amounts of intracellular enrofloxacin concentrations were determined by high performance liquid chromatography. Type B LEE accumulated significantly higher level into monocytes when compared to free drug or Type A liposome. This study showed that Type B LEE markedly concentrated within monocytes and may improve the antibacterial efficacy of the antibiotic.

Discrepancy between uptake and intracellular activity of moxifloxacin in a Staphylococcus aureus-human THP-1 monocytic cell model

The correlation between uptake of moxifloxacin by THP-1, a continuous line of monocytic cells devoid of intrinsic bactericidal properties, and its activity against Staphylococcus aureus ATCC 25923, a susceptible reference strain (MIC and minimal bactericidal concentration of moxifloxacin, 0.1 mg/liter), was studied in a 5-h assay. The uptake of the drug, added to the culture medium at 0.2 to 32 mg/liter, was evaluated by high-performance liquid chromatography. The ratio of the cellular to extracellular concentration of moxifloxacin reached, at equilibrium, 4.36 +/- 0.39 in uninfected cells and 6.25 +/- 0.41 in infected cells. The intracellular activity of moxifloxacin, introduced into the extracellular fluid at 0.06 to 8 mg/liter, was determined by the enumeration of viable bacteria. At concentrations < or =0.2 mg/liter, the drug inhibited only the intracellular bacterial growth, while at concentrations > or =0.5 mg/liter, it decreased the bacterial inoculum by less than 1 log(10) unit, with a maximum effect at 3 to 4 h, followed by regrowth of surviving bacteria to 80 to 120% of the original level at 5 h. In contrast, when killing curves were determined by using Mueller-Hinton broth with a similar inoculum (10(7) CFU/ml), moxifloxacin at concentrations > or =0.2 mg/liter reduced the inoculum by at least 3 log(10) units at 3 to 4 h, leaving < or =0.1% survival at 24 h. Persisters exhibited a fluoroquinolone susceptibility identical to that of S. aureus ATCC 25923. Our data indicate that moxifloxacin at therapeutic extracellular concentrations accumulates approximately sixfold in infected THP-1 cells and remains active intracellularly, but significantly less active than under in vitro conditions.

Uptake of quinolones by in-vitro human monocyte derived macrophages

We have developed an in-vitro model of monocyte-derived macrophage (MDMphi) to compare fluoroquinolone uptake in monocytes and derived macrophages. Monocyte-derived macrophages were obtained in-vitro by cultivating freshly isolated monocytes for seven days in RPMI 1640 medium, containing foetal calf serum and Rhu granulocyte-macrophage colony stimulating factor. Final suspensions contained 95% viable cells and 63% macrophages. Intramacrophagic accumulation of ciprofloxacin, ofloxacin or sparfloxacin was measured at equilibrium after 30-min incubation in the presence of 16-18 microg mL(-1) antibiotic. The results revealed low intracellular accumulation of ofloxacin in MDMphi (intracellular/extracellular ratio: IC/EC = 1.7). Ciprofloxacin and sparfloxacin uptake was significantly higher. The IC/EC ratios were only slightly increased in macrophages when compared with monocytes under the same experimental conditions. These results suggest that maturation of monocyte to macrophage has only a limited effect on basal quinolone uptake. Monocytic maturation cannot explain the important differences between fluoroquinolone accumulation in monocytes and tissue macrophages. Cell activation may be a greater determinant.

Differential uptake of grepafloxacin by human circulating blood neutrophils and those exudated into tissues

The uptake of the antimicrobial quinolone agent, grepafloxacin, both by human circulating blood neutrophils and by those exudated into tissues, was evaluated in vitro by comparing the intracellular drug concentrations. In circulating blood neutrophils, the uptake of grepafloxacin was rapid and saturable at 37 degrees C. The uptake of grepafloxacin into circulating blood neutrophils was reduced by lowering the environmental temperature or by the presence of metabolic inhibitors, suggesting the involvement of an active transport mechanism. Furthermore, the uptake of grepafloxacin by tissue (salivary) neutrophils was also partially temperature-dependent and was significantly greater than that by circulating blood neutrophils, i.e. exudation of neutrophils into tissue results in a markedly enhanced transport mechanism for grepafloxacin. This phenomenon may be related to the higher defense activity against infection seen in exudated tissue neutrophils.

Effects of continuous or pulsed exposure to rifabutin and sparfloxacin on the intracellular growth of Staphylococcus aureus and Mycobacterium tuberculosis

The time-kinetics of the intracellular bioactivity and intracellular post-antibiotic effect (PAE) of rifabutin and sparfloxacin against Staphylococcus aureus and Mycobacterium tuberculosis, grown in human monocytes, were evaluated. Intracellular bactericidal activity against staphylococci was shown in the presence of extracellular drug concentrations equal or superior to 1/10 plasma Cmax. The bactericidal activity of rifabutin was dependent on both its extracellular concentrations and the exposure time. In contrast, the pattern of the intracellular activity of sparfloxacin was characterized by a minimal concentration dependent killing. Both antibiotics (from 1/10 to the expected lung Cmax) showed intracellular bioactivity against M. tuberculosis H37Ra and H37Rv strains. A long intracellular PAE on staphylococci (>4 hours) was demonstrated when drugs were removed from the infected monocytes after 1 h treatment. Our findings suggest that rifabutin and sparfloxacin may be useful in the treatment of lower respiratory tract infections due to intracellular pathogens.

Comparison of antimycobacterial activity of grepafloxacin against Mycobacterium avium with that of levofloxacin: accumulation of grepafloxacin in human macrophages

The bactericidal activity of two new quinolones, grepafloxacin and levofloxacin, against five strains of Mycobacterium avium was investigated in vitro. The minimum inhibitory concentrations (MICs) of these two quinolones, determined by the broth microdilution method, were comparable for all strains tested. In contrast, grepafloxacin suppressed the intracellular growth of all the strains in monocyte-derived macrophages more strongly than levofloxacin, when the cells infected with these strains were incubated for 7 days in the presence of various concentrations of the two new quinolones. To find the reason for the strengthened intracellular killing activity of grepafloxacin, we determined the ratio of the concentration of the new quinolones in the cells to that in the medium (C/M concentration ratio). The C/M concentration ratio of grepafloxacin was increased to 34.7 by 7 days, whereas that of levofloxacin at 7 days was only 12.3. These data suggested that a higher level of intraphagocytic accumulation of grepafloxacin endows it with greater mycobactericidal activity.

Intracellular penetration and activity of gemifloxacin in human polymorphonuclear leukocytes

The intracellular penetration and activity of gemifloxacin in human polymorphonuclear leukocytes (PMN) were evaluated. Gemifloxacin reached intracellular concentrations eight times higher than extracellular concentrations. The uptake was rapid, reversible, and nonsaturable and was affected by environmental temperature, cell viability, and membrane stimuli. At therapeutic extracellular concentrations, gemifloxacin showed intracellular activity against Staphylococcus aureus.

Effects of trovafloxacin on the IL-1-dependent activation of E-selectin in human endothelial cells in vitro

E-selectin is an endothelial-specific surface protein, which is transiently expressed in response to inflammatory cytokines and plays an important role in the recruitment of leukocytes to the site of infection. The effect of two fluoroquinolones, ciprofloxacin (cipro) and trovafloxacin (trova), on the interleukin-1 (IL-1)-dependent activation of E-Selectin was studied on human umbilical vein endothelial cells (HUVEC) in vitro. Trova, at 80 microg/ml, affected the transient expression of E-selectin mRNA after pro-inflammatory stimulation with IL-1 leading to a sustained expression over 24 h. Surface expression of E-selectin remained upregulated after 24 h in a higher percentage of cells when they were activated in the presence of trova, as determined by flow cytometry analysis. Moreover, the concentration of shedded soluble E-selectin (sE-selectin) in the cell supernatant increased by 3.5 fold compared to those stimulated in the presence of cipro or without fluoroquinolones. Analogously, the antiproliferative effect of trova on endothelial cells was found to be more pronounced compared to cipro leading to an accumulation of cells arrested in G1-phase. These data provide evidence that accumulation of high concentration of trova in vivo in inflamed tissue might alter inflammatory responses.

Double-blind comparison of trovafloxacin and doxycycline in the treatment of uncomplicated Chlamydial urethritis and cervicitis. Trovafloxacin Chlamydial Urethritis/Cervicitis Study Group

BACKGROUND

Chlamydia trachomatis is among the most common sexually transmitted bacteria worldwide. With excellent activity against C. trachomatis and Neisseria gonorrhoeae and prolonged elimination half-life allowing once-daily dosage, the fluoroquinolone trovafloxacin has potential advantages in the treatment of uncomplicated chlamydial infection.

GOAL OF THIS STUDY

This study compared the efficacy of trovafloxacin with that of doxycycline for the treatment of uncomplicated chlamydial infection.

STUDY DESIGN

In a double-blind, multicenter trial, trovafloxacin 200 mg was administered once daily for 5 days and doxycycline 100 mg was administered twice daily for 7 days to patients with uncomplicated chlamydial urethritis or cervicitis. Follow-up visits were conducted 10, 21, and 35 days after enrollment.

RESULTS

Of the 970 patients (403 men, 567 women) observed, 511 were microbiologically evaluable and 360 were clinically evaluable. C. trachomatis eradication rates in the trovafloxacin and doxycycline groups were equivalent in women (95% and 97%, respectively), but not in men (89% and 99%). Similarly, rates of clinical success (cure plus improvement) demonstrated equivalence of trovafloxacin and doxycycline in women (96% and 94%), but not in men (94% and 100%). The most frequent treatment-related adverse events were dizziness, nausea, and headache in patients given trovafloxacin, and nausea, vomiting, and headache in patients given doxycycline. Treatment-related discontinuations were comparable between the drug groups.

CONCLUSION

Trovafloxacin given once daily for 5 days was clinically and bacteriologically equivalent to doxycycline given twice daily for 7 days in women with uncomplicated chlamydial cervicitis. This equivalence was not demonstrated in men with uncomplicated chlamydial urethritis.

Effects of enrofloxacin on porcine phagocytic function

The interaction between enrofloxacin and porcine phagocytes was studied with clinically relevant concentrations of enrofloxacin. Enrofloxacin accumulated in phagocytes, with cellular concentration/extracellular concentration ratios of 9 for polymorphonuclear leukocytes (PMNs) and 5 for alveolar macrophages (AMs). Cells with accumulated enrofloxacin brought into enrofloxacin-free medium released approximately 80% (AMs) to 90% (PMNs) of their enrofloxacin within the first 10 min, after which no further release was seen. Enrofloxacin affected neither the viability of PMNs and AMs nor the chemotaxis of PMNs at concentrations ranging from 0 to 10 microg/ml. Enrofloxacin (0.5 microg/ml) did not alter the capability of PMNs and AMs to phagocytize fluorescent microparticles or Actinobacillus pleuropneumoniae, Pasteurella multocida, and Staphylococcus aureus. Significant differences in intracellular killing were seen with enrofloxacin at 5x the MIC compared with that for controls not treated with enrofloxacin. PMNs killed all S. aureus isolates in 3 h with or without enrofloxacin. Intracellular S. aureus isolates in AMs were less susceptible than extracellular S. aureus isolates to the bactericidal effect of enrofloxacin. P. multocida was not phagocytosed by PMNs. AMs did not kill P. multocida, and similar intra- and extracellular reductions of P. multocida isolates by enrofloxacin were found. Intraphagocytic killing of A. pleuropneumoniae was significantly enhanced by enrofloxacin at 5x the MIC in both PMNs and AMs. AMs are very susceptible to the A. pleuropneumoniae cytotoxin. This suggests that in serologically naive pigs the enhancing effect of enrofloxacin on the bactericidal action of PMNs may have clinical relevance.

Intracellular activity of trovafloxacin against Staphylococcus aureus

The effect of trovafloxacin on Staphylococcus aureus ingested by human granulocytes or monocytes was compared with that on S. aureus in cell-free medium. Maximum growth inhibition (E(R,max)) by the antibiotic was 0.530 log10/h for S. aureus within granulocytes, 0.912 log10/h for S. aureus within monocytes, and 1.830-1.916 log10/h for S. aureus in medium. EC50, the concentration at which 50% of the maximum growth inhibition is achieved, did not differ significantly under the conditions investigated. After inhibition of intracellular killing by granulocytes with sodium fluoride, the intracellular antibacterial activity of trovafloxacin was still less than that in medium. A 3.4 times higher concentration was needed to achieve the same effect on phagocytosed S. aureus as in cell-free medium. Trovafloxacin binds more strongly to granulocytes than to monocytes, the respective cellular concentrations being 10 and four times higher than that in medium. In conclusion, the activity of trovafloxacin against S. aureus ingested by human granulocytes or monocytes is less than that against S. aureus in cell-free medium and is not related to the cell-associated concentration. Intracellular conditions are not favourable for the antibacterial activity of trovafloxacin.

Mechanism underlying levofloxacin uptake by human polymorphonuclear neutrophils

The mechanism of radiolabeled levofloxacin ([3H]levofloxacin) uptake by human polymorphonuclear neutrophils (PMNs) was investigated by a classical velocity centrifugation technique. PMNs were incubated with levofloxacin for 5 to 180 min under various conditions before centrifugation through an oil cushion. Radioactivity was measured in the cell pellet to determine the amount of cell-associated drug. The uptake of levofloxacin was moderate with a cellular concentration/extracellular concentration ratio of about 4 to 6. Levofloxacin accumulated in PMNs parallel to the extracellular concentration, without saturation, over the range of 2.5 to 200 mg/liter (linear regression analysis: r = 0.92; P < 0.001). The activation energy was low (36 +/- 7.2 kJ/mol). Levofloxacin uptake was increased in Ca(2+)-depleted, EGTA-containing medium by approximately 33% (P = 0.022), while Ni2+, a Ca2+ channel inhibitor, inhibited it in a concentration-dependent manner, with the concentration that inhibited 50% of control uptake being approximately 2.65 mM. Verapamil (an L-type Ca2+ channel inhibitor) and other pharmacologic agents which modify Ca2+ homeostasis did not modify levofloxacin uptake. Interestingly, Ca2+ and Mg2+ inhibited levofloxacin uptake in a concentration-dependent manner. EGTA, Ni2+, and verapamil did not modify levofloxacin efflux; thapsigargin, a Ca2+ pool-releasing agent, modestly increased the intracellular retention of levofloxacin. In addition, contrary to other fluoroquinolones, probenecid at 1 to 10 mM did not modify either levofloxacin uptake or efflux. These data are consistent with a mechanism of passive accumulation of levofloxacin in PMNs. Extracellular Ca2+ and Mg2+ may influence the structural conformation of levofloxacin or the lipophilicity of PMN membranes, thus explaining their effect on levofloxacin uptake.

Uptake and intracellular activity of moxifloxacin in human neutrophils and tissue-cultured epithelial cells

The penetration by moxifloxacin of human neutrophils (polymorphonuclear leukocytes [PMN]) and tissue-cultured epithelial cells (McCoy cells) was evaluated by a fluorometric assay. At extracellular concentrations of 5 mg/liter, the cellular-to-extracellular concentration ratios (C/E) of moxifloxacin in PMN and McCoy cells were 10.9 +/- 1.0 and 8.7 +/- 1.0, respectively (20 min; 37 degrees C). The uptake of moxifloxacin by PMN was rapid, reversible, nonsaturable (at extracellular concentrations ranging from 1 to 50 microg/ml), and not affected by cell viability. The uptake of moxifloxacin was affected by external pH and the environmental temperature. The incubation of PMN in the presence of sodium fluoride, sodium cyanide, and carbonyl cyanide m-chlorophenylhydrazone significantly decreased the C/E of this agent. Neither PMN stimulation nor phagocytosis of opsonized Staphylococcus aureus significantly affected the uptake of moxifloxacin by human PMN. This agent, at concentrations of 0.5, 1, and 5 mg/liter, induced a significant reduction in the survival of intracellular S. aureus in human PMN. In summary, moxifloxacin reaches much higher intracellular concentrations within phagocytic and nonphagocytic cells than extracellular ones, remaining active inside the neutrophils.

Trovafloxacin: a new fluoroquinolone

OBJECTIVE

To review the pharmacology, antimicrobial activity, pharmacokinetics, clinical efficacy, and safety of trovafloxacin.

DATA SOURCES

A MEDLINE search (January 1966-April 1998) was conducted for relevant literature using the terms CP-99,219, CP-116,519, trovafloxacin, and alatrofloxacin. Abstracts published by the American Society of Microbiology during 1995-1997 meetings were also reviewed.

STUDY SELECTION AND DATA EXTRACTION

All in vitro, animal, and human studies were reviewed for the antimicrobial activity, pharmacokinetics, efficacy, and safety of trovafloxacin.

DATA SYNTHESIS

Trovafloxacin is a new fluoroquinolone with enhanced activity against gram-positive and anaerobic microorganisms. The oral bioavailability under fasting conditions is approximately 88%. The elimination half-life of trovafloxacin is approximately 10 hours. Less than 10% of trovafloxacin is eliminated unchanged in the urine. Trovafloxacin is effective in the treatment of community-acquired pneumonia and nosocomial pneumonia with cure rates of > 90% and 77%, respectively. Trovafloxacin is comparable with ceftriaxone in the treatment of meningococcal meningitis in children; each produces a cure rate of approximately 90%. In treatment of uncomplicated urinary tract infection, both ciprofloxacin and trovafloxacin achieve an eradication rate of > or = 93%. Trovafloxacin is similar to ofloxacin in the treatment of urogenital Chlamydia trachomatis and acute exacerbations of chronic bronchitis, with clinical success in 97% of patients with each drug. The common adverse effects of trovafloxacin include dizziness, headache, and gastrointestinal intolerance.

CONCLUSIONS

The advantages of once-daily dosing and enhanced activity of trovafloxacin against gram-positive and anaerobic organisms may expand its use over available fluoroquinolones. Further studies are needed to define its role in the treatment of various infectious diseases.

Pharmacokinetics and metabolism of single oral doses of trovafloxacin

Trovafloxacin, a new fluoronaphthyridone derivative related to fluoroquinolone antimicrobial drugs, has demonstrated the following characteristics: significant gram-positive and gram-negative activity; significant activity against anaerobes and atypical respiratory pathogens; approximately 11-hour elimination half-life, permitting once-daily administration; and good tissue penetration. Because <10% of an orally administered dose is recovered in urine as unchanged drug, the predominant route of trovafloxacin elimination appears to be nonrenal. The two studies described in this review examined the metabolism and excretion of trovafloxacin and compared the time course and concentrations of trovafloxacin and its metabolites in bile to those in serum. In the first study, four healthy male volunteers received a single, oral 200-mg dose of radiolabeled trovafloxacin. In the second study, three patients with indwelling nasobiliary tubes received a single 200-mg dose of trovafloxacin. Samples of blood, urine, bile, and feces were collected. Trovafloxacin in urine and serum was analyzed by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection and in bile by HPLC-mass spectroscopy (MS). Levels of the N-acetyl metabolite in bile were determined by HPLC/UV/MS. Metabolites in serum, urine, and feces were determined by reverse-phase HPLC/MS, and radioactivity in these samples was assayed by liquid scintillation counting. In the first study, 63.3% and 23.1% of total radioactivity were recovered in feces and urine, respectively, with most of the radioactivity in urine in the form of the ester glucuronide metabolite (12.8%) and unchanged trovafloxacin (5.9%). Unchanged drug, the N-acetyl metabolite, and the N-sulfate of trovafloxacin accounted for 43.2%, 9.2%, and 3.9%, respectively, of the radioactivity in feces. In the second study, biliary trovafloxacin concentrations were highest between 1.5 and 10 hours postdose, and the maximum concentrations ranged from 18.9 to 37.9 microg/mL. The mean bile:serum ratio of trovafloxacin was 14.9, and the biliary concentration of parent drug was higher than that of its N-acetyl metabolite. In both studies, trovafloxacin was well tolerated, with no discontinuations due to adverse events. The pharmacokinetic profile of trovafloxacin in serum was consistent in healthy subjects and in individuals who had undergone recent hepatobiliary surgery. Trovafloxacin is metabolized primarily by the liver, through phase II metabolism (glucuronidation 13.2%, N-acetylation 10.4%, and N-sulfoconjugation 4.1%); minimal oxidative metabolism was detected. Renal elimination accounted for <10% of the administered dose. The high bile to serum ratio and higher trovafloxacin concentrations relative to metabolite concentrations are consistent with nonrenal elimination. These pharmacokinetic and pharmacodynamic results, together with a broad antimicrobial spectrum, long 11-hour elimination half-life, and low drug-interaction potential, suggest that trovafloxacin may be particularly appropriate for use in the surgical setting.

Intracellular accumulation, subcellular distribution, and efflux of tilmicosin in chicken phagocytes

Tilmicosin is a semi-synthetic macrolide antibiotic, currently approved for veterinary use in cattle and swine respiratory disease, and is in development for use in poultry mycoplasma air sacculitis. In order to provide an understanding of clinical efficacy, the in vitro interaction of tilmicosin with three types of chicken phagocytes (MQ-NCSU macrophages, monocyte-macrophages, and heterophils) was evaluated. After incubation with radiolabeled tilmicosin, uptake was determined and expressed as the ratio of the cellular (Cc) to the extracellular (Ce) drug concentration (Cc:Ce). Tilmicosin was avidly accumulated by heterophils (Cc: Ce 138 at 4 h incubation vs 32 and 66, respectively, in MQ-NCSU and monocyte-macrophages) with 61 to 88% localized in the lysosomes. Uptake was dependent on cell viability, temperature, and pH, but was not influenced by metabolic inhibitors. However, phagocytosis of Pasteurella multocida and lipopolysaccharide exposure increased tilmicosin uptake by the chicken phagocytes. Upon removal of extracellular tilmicosin, 50% of the intracellular tilmicosin was effluxed within the first 30 min, but after 4 h of incubation in antibiotic-free medium, 30% remained cell-associated. Opsonized P. multocida significantly enhanced the release of tilmicosin from all three types of chicken phagocytes. Tilmicosin uptake was observed to increase lysosomal enzyme (acid phosphatase, lysozyme, avidin, and beta-glucuronidase) production. Finally, neutrophils were shown to transport and efflux bioactive tilmicosin in a test system measuring both neutrophil chemotaxis under agarose and a bioassay measuring inhibition of bacterial growth in the presence of antibiotic in agar. These in vitro observations of cellular pharmacology suggest a complex interaction between phagocytes and tilmicosin that contribute to clinical efficacy.

Intracellular accumulation, subcellular distribution and efflux of tilmicosin in swine phagocytes

Tilmicosin is a semi-synthetic macrolide antibiotic, currently approved for veterinary use in cattle and swine respiratory disease. As the concentrations of tilmicosin are generally low in swine lung tissue, the interaction of tilmicosin with three types of swine phagocytes (monocyte-macrophages, alveolar macrophages, and neutrophils) was evaluated to provide an understanding of clinical efficacy. After incubation with radiolabelled tilmicosin, uptake was determined and expressed as the ratio of the intracellular (Ci) to the extracellular (Ce) drug concentration (Ci/Ce). Tilmicosin was avidly accumulated by the swine phagocytes (Ci/Ce 48-69 at 4 h incubation) with 51 to 85% localized in the lysosomes. Uptake was dependent on cell viability, temperature and pH, but was not influenced by the metabolic inhibitors, sodium cyanide or potassium fluoride. However, lipopolysaccharide (LPS) exposure increased tilmicosin uptake by the swine phagocytes. In neutrophils, upon removal of extracellular tilmicosin, 60% of the intracellular tilmicosin was effluxed within the first 30 min, but after 4 h of incubation in drug-free medium, 25% remained cell-associated. In contrast, after 4 h of incubation in drug-free medium, 60% and 45% of tilmicosin remained cell-associated, within alveolar macrophages and monocyte-derived macrophages, respectively. Tilmicosin uptake was observed to increase lysosomal enzyme (acid phosphatase, lysozyme and beta-glucuronidase) production. Finally, neutrophils were shown to transport and efflux bioactive tilmicosin in a test system measuring both neutrophil chemotaxis under agarose and a bioassay measuring inhibition of bacterial growth in the presence of antibiotic in agar. These in vitro interactions of tilmicosin with swine phagocytes suggest an integral role in effecting clinical efficacy.

In vitro extracellular and intracellular activity of two newer and two earlier fluoroquinolones against Listeria monocytogenes

Two new fluoroquinolones (trovafloxacin and sparfloxacin) with enhanced activity against gram-positive pathogens and two earlier compounds (ciprofloxacin and ofloxacin) were tested for their in vitro inhibitory and bactericidal activity against 80 strains of Listeria monocytogenes. All strains were uniformly highly susceptible to trovafloxacin, the MIC90 being 0.25 mg/l. Resistance to sparfloxacin was not detected, however the MIC90 of sparfloxacin was eight times that of trovafloxacin. A few strains were resistant to ciprofloxacin and ofloxacin (MIC90 4 mg/l for both drugs). MBCs usually exceeded MICs by 2 to 4 times. The MBC90 of trovafloxacin (1 mg/l) was lower than that of the other three drugs (8 mg/l). After checking their ability to enter and grow within human enterocyte-like Caco-2 cells, four strains were used to study the intracellular activity and eradicating power of the four quinolones. Trovafloxacin was more active than sparfloxacin and the earlier fluoroquinolones in terms of both intracellular killing and inhibition of a cytopathogenic effect. The uniform high-level activity of trovafloxacin against Listeria monocytogenes isolates in conventional in vitro assays and its extracellular and intracellular killing of invasive strains suggest that this and maybe other new fluoroquinolones should be further investigated as possible anti-listerial agents.