Polyvinyl Alcohol/Chitosan Single-Layered and Polyvinyl Alcohol/Chitosan/Eudragit RL100 Multi-layered Electrospun Nanofibers as an Ocular Matrix for the Controlled Release of Ofloxacin: an In Vitro and In Vivo Evaluation.

A novel nanofiber insert was prepared with a modified electrospinning method to enhance the ocular residence time of ofloxacin (OFX) and to provide a sustained release pattern by covering hydrophilic polymers, chitosan/polyvinyl alcohol (CS/PVA) nanofibers, with a hydrophobic polymer, Eudragit RL100 in layers, and by glutaraldehyde (GA) cross-linking of CS-PVA nanofibers for the treatment of infectious conjunctivitis. The morphology of the prepared nanofibers was studied using scanning electron microscopy (SEM). The average fiber diameter was found to be 123 ± 23 nm for the single electrospun nanofiber with no cross-linking (OFX-O). The single nanofibers, cross-linked for 10 h with GA (OFX-OG), had an average fiber diameter of 159 ± 30 nm. The amount of OFX released from the nanofibers was measured in vitro and in vivo using UV spectroscopy and microbial assay methods against Staphylococcus aureus, respectively. The antimicrobial efficiency of OFX formulated in cross-linked and non-cross-linked nanofibers was affirmed by observing the inhibition zones of Staphylococcus aureus and Escherichia coli. In vivo studies using the OFX nanofibrous inserts on a rabbit eye confirmed a sustained release pattern for up to 96 h. It was found that the cross-linking of the nanofibers by GA vapor could reduce the burst release of OFX from OFX-loaded CS/PVA in one layer and multi-layered nanofibers. In vivo results showed that the AUC0-96 for the nanofibers was 9-20-folds higher compared to the OFX solution. This study thus demonstrates the potential of the nanofiber technology is being utilized to sustained drug release in ocular drug delivery systems.

In Vivo Bioluminescent Monitoring of Therapeutic Efficacy and Pharmacodynamic Target Assessment of Antofloxacin against Escherichia coli in a Neutropenic Murine Thigh Infection Model.

Antimicrobial resistance among uropathogens has increased the rates of infection-related morbidity and mortality. Antofloxacin is a novel fluoroquinolone with broad-spectrum antibacterial activity against urinary Gram-negative bacilli, such as Escherichia coli This study monitored the in vivo efficacy of antofloxacin using bioluminescent imaging and determined pharmacokinetic (PK)/pharmacodynamic (PD) targets against E. coli isolates in a neutropenic murine thigh infection model. The PK properties were determined after subcutaneous administration of antofloxacin at 2.5, 10, 40, and 160 mg/kg of body weight. Following thigh infection, the mice were treated with 2-fold-increasing doses of antofloxacin from 2.5 to 80 mg/kg administered every 12 h. Efficacy was assessed by quantitative determination of the bacterial burdens in thigh homogenates and was compared with the bioluminescent density. Antofloxacin demonstrated both static and killing endpoints in relation to the initial burden against all study strains. The PK/PD index area under the concentration-time curve (AUC)/MIC correlated well with efficacy (R2 = 0.92), and the dose-response relationship was relatively steep, as observed with escalating doses of antofloxacin. The mean free drug AUC/MIC targets necessary to produce net bacterial stasis and 1-log10 and 2-log10 kill for each isolate were 38.7, 66.1, and 147.0 h, respectively. In vivo bioluminescent imaging showed a rapid decrease in the bioluminescent density at free drug AUC/MIC exposures that exceeded the stasis targets. The integration of these PD targets combined with the results of PK studies with humans will be useful in setting optimal dosing regimens for the treatment of urinary tract infections due to E. coli.

In Vivo Pharmacokinetic and Pharmacodynamic Profiles of Antofloxacin against Klebsiella pneumoniae in a Neutropenic Murine Lung Infection Model.

Antofloxacin is a novel broad-spectrum fluoroquinolone under development for the treatment of infections caused by a diverse group of bacterial species. We explored the pharmacodynamic (PD) profile and targets of antofloxacin against seven Klebsiella pneumoniae isolates by using a neutropenic murine lung infection model. Plasma and bronchopulmonary pharmacokinetic (PK) studies were conducted at single subcutaneous doses of 2.5, 10, 40, and 160 mg/kg of body weight. Mice were infected intratracheally with K. pneumoniae and treated using 2-fold-increasing total doses of antofloxacin ranging from 2.5 to 160 mg/kg/24 h administered in 1, 2, 3, or 4 doses. The Emax Hill equation was used to model the dose-response data. Antofloxacin could penetrate the lung epithelial lining fluid (ELF) with pharmacokinetics similar to those in plasma with linear elimination half-lives over the dose range. All study strains showed a 3-log10 or greater reduction in bacterial burden and prolonged postantibiotic effects (PAEs) ranging from 3.2 to 5.3 h. Dose fractionation response curves were steep, and the free-drug area under the concentration-time curve over 24 h (AUC0-24)/MIC ratio was the PD index most closely linked to efficacy (R2 = 0.96). The mean free-drug AUC0-24/MIC ratios required to achieve net bacterial stasis, a 1-log10 kill, and a 2-log10 kill for each isolate were 52.6, 89.9, and 164.9, respectively. When integrated with human PK data, these PD targets could provide a framework for further optimization of dosing regimens. This could make antofloxacin an attractive option for the treatment of respiratory tract infections involving K. pneumoniae.

Plasma drug activity in patients on treatment for multidrug-resistant tuberculosis.

Little is known about plasma drug concentrations relative to quantitative susceptibility in patients with multidrug-resistant tuberculosis (MDR-TB). We previously described a TB drug activity (TDA) assay that determines the ratio of the time to detection of plasma-cocultured Mycobacterium tuberculosis versus control growth in a Bactec MGIT system. Here, we assess the activity of individual drugs in a typical MDR-TB regimen using the TDA assay. We also examined the relationship of the TDA to the drug concentration at 2 h (C2) and the MICs among adults on a MDR-TB regimen in Tanzania. These parameters were also compared to the treatment outcome of sputum culture conversion. Individually, moxifloxacin yielded superior TDA results versus ofloxacin, and only moxifloxacin and amikacin yielded TDAs equivalent to a -2-log killing. In the 25 patients enrolled on a regimen of kanamycin, levofloxacin, ethionamide, pyrazinamide, and cycloserine, the C2 values were found to be below the expected range for levofloxacin in 13 (52%) and kanamycin in 10 (40%). Three subjects with the lowest TDA result (<1.5, a finding indicative of poor killing) had significantly lower kanamycin C2/MIC ratios than subjects with a TDA of ≥1.5 (9.8 ± 8.7 versus 27.0 ± 19.1; P = 0.04). The mean TDAs were 2.52 ± 0.76 in subjects converting to negative in ≤2 months and 1.88 ± 0.57 in subjects converting to negative in >2 months (P = 0.08). In Tanzania, MDR-TB drug concentrations were frequently low, and a wide concentration/MIC range was observed that affected plasma drug activity ex vivo. An opportunity exists for pharmacokinetic optimization in current MDR-TB regimens, which may improve treatment response.

Contribution of moxifloxacin or levofloxacin in second-line regimens with or without continuation of pyrazinamide in murine tuberculosis.

RATIONALE: High-dose levofloxacin (L) (1,000 mg) was as active as moxifloxacin (M) (400 mg) in an early bactericidal activity trial, suggesting these fluoroquinolones could be used interchangeably. Whether pyrazinamide (Z) contributes sterilizing activity beyond the first 2 months in fluoroquinolone-containing second-line regimens remains unknown. OBJECTIVES: We compared the efficacy of M and high-dose L alone or in combination with ethionamide (Et), amikacin (A), and Z given for 2 or 7 months. METHODS: A pharmacokinetic study was performed to determine the L dose equivalent to 1,000 mg in humans. Treatment started 2 weeks after aerosol infection with Mycobacterium tuberculosis H37Rv. Mice received M or L alone or in combination with 2 months of EtZA followed by 5 months of Et or EtZ. MEASUREMENTS AND MAIN RESULTS: After 2 months of treatment, lung colony-forming unit (CFU) counts were similar in mice receiving either fluoroquinolone alone, but, after 4 and 5 months, CFU counts were 2 log10 lower in mice receiving M. Mice receiving 2MEtZA/3MEt and 2LEtZA/3LEt had 1.0 and 2.7 log10 lung CFUs, respectively. When Z was given throughout, both regimens rendered mice culture negative by 5 months, and most mice did not relapse after 7 months of treatment, with fewer relapses observed in the M group after 6 and 7 months of treatment. CONCLUSIONS: In murine tuberculosis, M had superior efficacy compared with L despite lower serum drug exposures and may remain the fluoroquinolone of choice for second-line regimens. Z contributed substantial sterilizing activity beyond 2 months in fluoroquinolone-containing second-line regimens, largely compensating for L's weaker activity.

Optimization of anti-pseudomonal antibiotics for cystic fibrosis pulmonary exacerbations: III. fluoroquinolones.

This review is the third installment in a comprehensive State of the Art series and aims to evaluate the use of fluoroquinolones in the management of P. aeruginosa infection in both children and adults with cystic fibrosis (CF). Oral and intravenous ciprofloxacin have been shown to be well-tolerated in the treatment of acute pulmonary exacerbations (APE) secondary to P. aeruginosa. Older literature supports an oral dosing regimen of 40 mg/kg/day divided every 12 hr, up to 2 g/day, and intravenous (IV) ciprofloxacin 30 mg/kg/day divided every 8 hr, maximum 1.2 g/day in children, and 750 mg administered orally twice a day or 400 mg IV every 8 hr in adults. However, a recent pharmacodynamic (PD) modeling study shows that the literature, U.S. Food and Drug Administration (FDA)-approved, and Cystic Fibrosis Foundation (CFF) guideline dosing regimens may be suboptimal for the treatment of P. aeruginosa in APE. Further study is warranted to determine if higher doses of ciprofloxacin are needed. Limited pharmacokinetic (PK), PK/PD, and efficacy studies involving levofloxacin exist in adult patients with CF. No pediatric data exists for levofloxacin in CF patients. Further study is needed to determine the tolerability and efficacy of levofloxacin in APE. At this time, the routine use of levofloxacin in the treatment of APE in pediatric and adult patients cannot be recommended.

Dose findings of antofloxacin hydrochloride for treating bacterial infections in an early clinical trial using PK-PD parameters in healthy volunteers.

AIM: To find an appropriate dose regimen of the novel antibacterial agent antofloxacin for a phase II clinical trial using a population pharmacokinetic (PPK) study in healthy volunteers and the minimum inhibitory concentration (MIC) as pharmacodynamic (PD) parameters. METHODS: Twenty-four healthy volunteers were enrolled in a double-blind crossover study and received antofloxacin (200 or 400 mg/d, po) for consecutive 5 d with 10 d washout between two separate periods. Blood concentrations were analyzed using HPLC with a UV-Vis detector. The values of area under the curve (AUC) with covariates were obtained from a PPK model, and the MICs came from the previous in vitro studies. The dose regimen was determined for the phase II clinical trial according to the ratio (>20) of AUC/MIC, and the efficacy of the dose was evaluated by the trial. RESULTS: A two-compartment model best described the time-concentration data with first-order absorption. The PPK parameter estimates for CL, V(c), Q, V(p) and K(A) are 8.34 L/h, 142 L, 15.9 L/h, 52.2 L and 4.64 1/h, respectively. The covariates sex for K(A), weight for CL, weight for V(c) and interoccasion variability were included in the final model. The AUC/MIC was calculated based on the PPK model and the MIC of antofloxacin for Escherichia coli, Klebsiella pneumonia, Staphylococcus aureus and Staphylococcus epidermidis were determined in previous researches. The 400 mg loading dose with 200 mg/d maintenance dose was recommended and confirmed by the phase II trial. CONCLUSION: The ratio of AUC from the PPK model vs MIC as the PD parameter can be applied in a dose-finding trial of antofloxacin in treatment of bacterial infections. The PPK model suggests that sex and body weight may be considerations in regards to individual therapy, which should be investigated in larger clinical trials and serve as a potential reference for clinical therapies.

Application of organogels as oral controlled release formulations of hydrophilic drugs.

We previously demonstrated that organogels prepared from soybean oil using 12-hydroxy stearic acid as a gelator can slowly release ibuprofen, a model lipophilic drug. In this study, we investigated the applicability of organogels as controlled release formulations of hydrophilic drugs. The release rates of theophylline and ofloxacin, which are used as model hydrophilic drugs, were significantly slower than those of ibuprofen and antipyrine (model lipophilic drugs). Furthermore, no erosion was noted during drug release from organogels. Lipophilic drug molecules are released after diffusion in organogels because all molecules fully dissolve in the gel. On the other hand, hydrophilic drug molecules need to be dissolved before they diffuse in the organogel, prior to their release from the gel. Therefore, it is speculated that the release rates of hydrophilic drugs are slower than those of lipophilic drugs. To confirm the usefulness of organogels in controlled release formulations in vivo, organogels containing ibuprofen, ofloxacin, theophylline or antipyrine were intraduodenally administered to rats. All drugs used in this study were rapidly absorbed when administered in aqueous suspensions. In contrast, the drug concentrations in plasma after administration in organogels were lower; however, the lower concentrations of drugs sustained for 10 h after administration. With organogel administration, the mean residence time of drugs was longer than that with aqueous suspension administration. In conclusion, organogels are potential candidates for controlled release formulations of not only lipophilic drugs, but also hydrophilic drugs.

Population pharmacokinetics and pharmacodynamics of ofloxacin in South African patients with multidrug-resistant tuberculosis.

Despite the important role of fluoroquinolones and the predominant use of ofloxacin for treating multidrug-resistant tuberculosis in South Africa, there are limited data on ofloxacin pharmacokinetics in patients with multidrug-resistant tuberculosis, no ofloxacin pharmacokinetic data from South African patients, and no direct assessment of the relationship between ofloxacin pharmacokinetics and the MIC of ofloxacin of patient isolates. Our objectives are to describe ofloxacin pharmacokinetics in South African patients being treated for multidrug-resistant tuberculosis and assess the adequacy of ofloxacin drug exposure with respect to the probability of pharmacodynamic target attainment (area under the time curve/MIC ratio of at least 100). Sixty-five patients with multidrug-resistant tuberculosis were recruited from 2 hospitals in South Africa. We determined the ofloxacin MICs for the Mycobacterium tuberculosis isolates from baseline sputum specimens. Patients received daily doses of 800 mg ofloxacin, in addition to other antitubercular drugs. Patients underwent pharmacokinetic sampling at steady state. NONMEM was used for data analysis. The population pharmacokinetics of ofloxacin in this study has been adequately described. The probability of target attainment expectation in the study population was 0.45. Doubling the dose to 1,600 mg could increase this to only 0.77. The currently recommended ofloxacin dose appeared inadequate for the majority of this study population. Studies to assess the tolerability of higher doses are warranted. Alternatively, ofloxacin should be replaced with more potent fluoroquinolones.

Fluoroquinolones in the management of community-acquired pneumonia in primary care.

A literature search was conducted to evaluate the pharmacokinetic and pharmacodynamic profile of the respiratory fluoroquinolones (gemifloxacin, levofloxacin and moxifloxacin) and their efficacy and safety in the management of community-acquired pneumonia (CAP). Data show that CAP is a common presentation in primary care practice, and is associated with high rates of morbidity and mortality, particularly in the elderly. Although the causative pathogens differ depending on treatment setting and patient factors, Streptococcus pneumoniae is the primary pathogen in all treatment settings. As a class, the respiratory fluoroquinolones have a very favorable pharmacokinetic and pharmacodynamic profile. Pharmacodynamic criteria suggest that moxifloxacin and gemifloxacin are more potent against S. pneumoniae, which may have the added benefit of reducing resistance selection and enhancing bacterial eradication. The respiratory fluoroquinolones are also generally well tolerated, and are first-line options for outpatient treatment of CAP in patients with comorbidities or previous antibiotic use.

Sensitivity and proportionality assessment of metabolites from microdose to high dose in rats using LC-MS/MS.

BACKGROUND: The objective of this study was to evaluate the sensitivity requirement for LC-MS/MS as an analytical tool to characterize metabolites in plasma and urine at microdoses in rats and to investigate proportionality of metabolite exposure from a microdose of 1.67 µg/kg to a high dose of 5000 µg/kg for atorvastatin, ofloxacin, omeprazole and tamoxifen. RESULTS: Only the glucuronide metabolite of ofloxacin, the hydroxylation metabolite of omeprazole and the hydration metabolite of tamoxifen were characterized in rat plasma at microdose by LC-MS/MS. The exposure of detected metabolites of omeprazole and tamoxifen appeared to increase in a nonproportional manner with increasing doses. Exposure of ortho- and para-hydroxyatorvastatin, but not atorvastatin and lactone, increased proportionally with increasing doses. CONCLUSION: LC-MS/MS has demonstrated its usefulness for detecting and characterizing the major metabolites in plasma and urine at microdosing levels in rats. The exposure of metabolites at microdose could not simply be used to predict their exposure at higher doses.

Novel mucoadhesive polysaccharide isolated from Bletilla striata improves the intraocular penetration and efficacy of levofloxacin in the topical treatment of experimental bacterial keratitis.

OBJECTIVES: The objective of the present study was to evaluate a novel mucoadhesive polymer extracted from Bletilla striata for ocular delivery of 0.5% levofloxacin in rabbits, and to determine its improved efficacy against experimental keratitis. METHODS: B. striata polysaccharide (BsP) was subjected to cell cytotoxicity and ferning tests. The pharmacokinetics and bioavailability of topically applied 0.5% levofloxacin-BsP eye drops was investigated and compared with 0.5% levofloxacin eye drops (Cravit). Experimental Staphylococcus aureus keratitis was induced and treated with levofloxacin or levofloxacin-BsP eye drops. KEY FINDINGS: BsP markedly increased the proliferative capacity of a human corneal epithelial [corrected] cell line. The ferning test showed that BsP exhibited optimal performance as a tear fluid. The polysaccharides significantly increased intra-aqueous penetration and corneal accumulation in rabbits. Treatment with levofloxacin-BsP reduced the number of organisms more significantly than eye drops containing levofloxacin alone. CONCLUSIONS: BsP appears to be a promising candidate as a vehicle for topical ophthalmic drug delivery, especially for antibiotics.

Levofloxacin in the treatment of community-acquired pneumonia.

Levofloxacin is a fluoroquinolone that has a broad spectrum of activity against several causative bacterial pathogens of community-acquired pneumonia (CAP). The efficacy and tolerability of levofloxacin 500 mg once daily for 10 days in patients with CAP are well established. Furthermore, a high-dose (750 mg), short-course (5 days) of once-daily levofloxacin has been approved for use in the USA in the treatment of CAP, acute bacterial sinusitis, acute pyelonephritis and complicated urinary tract infections. Levofloxacin can be used as a monotherapy in patients with CAP, however, levofloxacin combination therapy with anti-pseudomonal beta-lactam (or aminoglycoside) should be considered if Pseudomonas aeruginosa is the causative pathogen of the respiratory infection. The high-dose, short-course levofloxacin regimen maximizes its concentration-dependent antibacterial activity, decreases the potential for drug resistance and has better patient compliance. Oral levofloxacin is rapidly absorbed and is bioequivalent to the intravenous formulation and the patients can switch between these formulations, which results in more options with respect to the therapeutic regimens. Furthermore, levofloxacin is generally well tolerated, has good tissue penetration and adequate concentrations can be maintained at the site of infections.

[Levofloxacin (Tavanic) in complex therapy of tuberculosis].

Preclinical and clinical investigations of levofloxacin in complex with antituberculosis drugs of the main and reserve groups in 152 patients with newly diagnosticated drug resistant pulmonary tuberculosis demonstrated its efficacy and safety. The adverse events due to levofloxacin (8.6% of the cases) disappeared after discontinuation of the drug use without any affection of the patient's organs. Levofloxacin is applicable in antituberculosis therapy of patients with extended, acute progressing or polycavernous tuberculosis of the lungs. It provides significant clinical improvement and if necessary allows to prepare the patient in a short period for surgical operation.

Efficacy of aerosol MP-376, a levofloxacin inhalation solution, in models of mouse lung infection due to Pseudomonas aeruginosa.

Progressive respiratory failure due to Pseudomonas aeruginosa is the leading cause of morbidity and mortality in patients with cystic fibrosis. The pulmonary delivery of antimicrobial agents provides high concentrations of drug directly to the site of infection and attains pharmacokinetic-pharmacodynamic indices exceeding those which can be achieved with systemic dosing. MP-376 is a new formulation of levofloxacin that enables the safe aerosol delivery of high concentrations of drug to pulmonary tissues. In vivo studies were conducted to demonstrate the efficacy of MP-376 in models of mouse pulmonary infection. The superiority of aerosol dosing over systemic dosing was demonstrated in models of both acute and chronic lung infection. In a model of acute lung infection, aerosol treatment with MP-376 once or twice daily reduced the lung bacterial load to a greater extent than aerosol tobramycin or aztreonam did when they were administered at similar or higher doses. The bacterial killing by aerosol MP-376 observed in the lung in the model of acute pulmonary infection translated to improved survival (P < 0.05). In a model of chronic pulmonary infection, aerosol MP-376 had antimicrobial effects superior to those of aztreonam (P < 0.05) and effects similar to those of tobramycin (P > 0.05). In summary, these data show that aerosol MP-376 has in vivo activity when it is used to treat acute and chronic lung infections caused by P. aeruginosa.

Efficacy of fluoroquinolones against pathogenic oral bacteria.

This article reviews the characteristics of the main fluoroquinolones used in dentistry (ciprofloxacin, levofloxacin and moxifloxacin), including pharmacokinetic/ pharmacodynamic parameters, susceptibility profiles of oral bacteria and clinical trials on their efficacy in dental practice. It seems that some of these antibiotics might represent a safe alternative in patients with allergy, intolerance, or lack of response to beta-lactams.

High doses of levofloxacin vs moxifloxacin against staphylococcal experimental foreign-body infection: the effect of higher MIC-related pharmacokinetic parameters on efficacy.

OBJECTIVES: Since levofloxacin at high doses was the best therapy in staphylococcal tissue-cage model of foreign-body infection, we hypothesized that moxifloxacin with higher ratio of area under the concentration-time curve to the MIC (AUC/MIC) would provide better results. METHODS: MICs, MBCs, MPCs (mutant prevention concentration) and 24h kill-curves were determined in the log and stationary phases. Using the aforementioned model, we tested the efficacy of levofloxacin 100mg/kg/d, moxifloxacin 40mg/kg/d and moxifloxacin 80mg/kg/d; they were equivalent to human levels for 1000mg/d, 400mg/d and 800mg/d, respectively. We screened for the appearance of resistant strains. RESULTS: MICs and MBCs in logarithmic and stationary phases and MPCs of levofloxacin were 0.5, 1 and 4, 0.8microg/ml, respectively, and those of moxifloxacin 0.12, 0.25 and 2, 0.25microg/ml. AUC/MIC were 234 (levofloxacin), 431 (moxifloxacin 40) and 568 (moxifloxacin 80). Bacterial counts decreases in tissue-cage fluids (means of logCFU/ml) were -1.81 (n=25), -1.31 (23), and -1.46 (20), respectively; for controls it was 0.24 (22). All groups were better than controls (p<0.05); no differences between them existed. CONCLUSIONS: Moxifloxacin with higher AUC/MIC ratio did not improve the efficacy of high doses of levofloxacin.

Novel in vitro pharmacodynamic model simulating ofloxacin pharmacokinetics in the treatment of Pseudomonas aeruginosa biofilm-associated infections.

OBJECTIVES: The conventional in vitro models simulate pharmacodynamics of antibiotics in the treatment of planktonic Pseudomonas aeruginosa. In this study, we propose a novel pharmacodynamic model of ofloxacin activity in the treatment of P. aeruginosa biofilm. METHODS: P. aeruginosa biofilm carrying coupons were suspended in a continuous flow central compartment bioreactor (CCB). In the CCB, the pharmacokinetics of different ofloxacin dosing regimens were simulated. Samples from the coupons and the CCB were assessed for viability of the biofilm and the shedding planktonic cells, respectively, over 24h. In addition, ofloxacin concentrations were assessed in each sample withdrawn for the CCB using bioassay method. RESULTS: The microbiological outcomes on P. aeruginosa biofilm and the shedding planktonic cells in response to different ofloxacin dosing regimens were not parallel and this may explain the non-coincidence of microbiological and clinical outcomes with biofilm associated infections. CONCLUSION: The current study has introduced unprecedented novel dynamic model for the assessment of the microbiological outcome on both biofilm and shedding planktonic cells of P. aeruginosa in response to different dosing regimens of ofloxacin which in turn can simulate the clinical outcomes in biofilm associated infections of P. aeruginosa, e.g. cystic fibrosis. Furthermore, different scenarios of antibiotic dosing regimens against biofilm related infections can be mimicked using such model.

Activity of ciprofloxacin and levofloxacin in experimental pneumonia caused by Klebsiella pneumoniae deficient in porins, expressing active efflux and producing QnrA1.

The objective of this study was to evaluate the activities of ciprofloxacin and levofloxacin in a murine model of pneumonia caused by Klebsiella pneumoniae C2 (with altered GyrA, deficient in porins and expressing active efflux of quinolones) and the transconjugant C2pMG252 derived from it and expressing the qnrA1 determinant. MICs and MBCs of the two quinolones were determined according to CLSI guidelines. Time-kill curves (at 1x and 4x MIC) were also performed to assess bactericidal activity. An experimental model of pneumonia in mice was evaluated. Groups of 15 mice were infected with either strain and treated with ciprofloxacin (80 mg/kg/day) or levofloxacin (100 mg/kg/day). Control non-treated animals were also evaluated. In the case of strain C2, log(10) CFU/g of lung in non-treated animals was 9.16 +/- 2.16. This value was reduced to 3.53 +/- 1.04 (p <0.001) and 3.38 +/- 0.46 (p <0.001) in animals treated with ciprofloxacin or levofloxacin, respectively. Percentages of surviving mice were 26.7% (control group) and 100% (both ciprofloxacin and levofloxacin; p <0.001 vs. controls). Bacterial counts (log(10) CFU/g) in lungs of animals infected with strain C2pMG252 were 9.65 +/- 2.49 in non-treated animals and 7.74 +/- 2.67 and 7.57 +/- 3.84 for those treated with ciprofloxacin or levofloxacin, respectively (p >0.05 vs. control group). Of non-treated animals infected with strain C2pMG252, 14.3% survived. Ciprofloxacin and levofloxacin improved the survival in these mice (53.3% for both antimicrobials, p 0.03). In conclusion, the expression of qnrA1 in K. pneumoniae with additional mechanisms of resistance causes decreased efficacy of fluoroquinolones in a pneumonia model in mice.

Use of pharmacodynamic endpoints for the evaluation of levofloxacin for the treatment of acute maxillary sinusitis.

Sinusitis remains 1 of the most common reasons for antimicrobial prescriptions in the United States, with health care costs approaching $4 billion annually. We utilized the serial sinus aspirate sampling (SSAS) technique to obtain daily specimens to evaluate the time course of drug effect in patients with acute maxillary sinusitis. Eighteen patients with a radiologically confirmed acute maxillary sinusitis were enrolled into a study evaluating the relationship between levofloxacin exposure and the time course of antimicrobial effect using SSAS. SSAS was performed daily during therapy for bacteriologic evaluation. Six steady-state levofloxacin concentrations were obtained. Levofloxacin plasma and sinus aspirate concentrations were modeled using Monte Carlo Parametric Expectation Maximization algorithm implemented in S-ADAPT 1.53. Endpoints evaluated included time to resolution of signs and symptoms and time to sinus sterilization. Among the 18 enrolled patients, 15 were clinically evaluable. From these, 1 Streptococcus pneumoniae, 3 Haemophilus influenzae, 1 Moraxella catarrhalis, 1 Corynebacterium spp., and 1 coagulase-negative Staphylococcus organisms were isolated, with the latter 2 organisms being likely contaminants. For the pathogens, levofloxacin MIC values ranged from 0.03 to 2 mg/L. All pathogens were eradicated by the 4th day of therapy. The median and mean time to sinus sterilization (pathogens only) was 1 and 1.4 days, respectively. The median time to resolution of each sign and symptom ranged from 1.5 to 12-19 days, with the 83% of total signs and symptoms resolved by the end of therapy (day 5). The mean plasma area under the concentration-time curve (AUC) (mg x h/L) was 100.1 (n = 14, %CV = 27). Plasma AUC/MIC ratios ranged from 33.9 to 1696 for isolated pathogens. In this pilot SSAS study, levofloxacin rapidly eradicated isolated pathogens from the maxillary sinus.