Showing papers by "Paul M. Tulkens published in 2014"

Comparison of the Antibiotic Activities of Daptomycin, Vancomycin, and the Investigational Fluoroquinolone Delafloxacin against Biofilms from Staphylococcus aureus Clinical Isolates

Abstract: Biofilm-related infections remain a scourge. In an in vitro model of biofilms using Staphylococcus aureus reference strains, delafloxacin and daptomycin were found to be the most active among the antibiotics from 8 different pharmacological classes (J. Bauer, W. Siala, P. M. Tulkens, and F. Van Bambeke, Antimicrob. Agents Chemother. 57:2726-2737, 2013, doi:10.1128/AAC.00181-13). In this study, we compared delafloxacin to daptomycin and vancomycin using biofilms produced by 7 clinical strains (S. aureus epidemic clones CC5 and CC8) in order to rationalize the differences observed between the antibiotics and strains. The effects of the antibiotics on bacterial viability (resazurin reduction assay) and biomass (crystal violet staining) were measured and correlated with the proportion of polysaccharides in the matrix, the local microenvironmental pH (micro-pH), and the antibiotic penetration in the biofilm. At clinically meaningful concentrations, delafloxacin, daptomycin, and vancomycin caused a ≥25% reduction in viability against the biofilms formed by 5, 4, and 3 strains, respectively. The antibiotic penetration within the biofilms ranged from 0.6 to 52% for delafloxacin, 0.2 to 10% for daptomycin, and 0.2 to 1% for vancomycin; for delafloxacin, this was inversely related to the polysaccharide proportion in the matrix. Six biofilms were acidic, explaining the high potency of delafloxacin (lower MICs at acidic pH). Norspermidine and norspermine (disassembling the biofilm matrix) drastically increased delafloxacin potency and efficacy (50% reduction in viability for 6 biofilms at clinically meaningful concentrations) in direct correlation with its increased penetration within the biofilm, while they only modestly improved daptomycin efficacy (50% reduction in viability for 2 biofilms) and penetration, and they showed marginal effects with vancomycin. Delafloxacin potency and efficacy against biofilms are benefited by its penetration into the matrix and the local acidic micro-pH.

Tedizolid Phosphate for the Management of Acute Bacterial Skin and Skin Structure Infections: Safety Summary

Abstract: The novel oxazolidinone tedizolid phosphate is in late-stage clinical development. In an effort to improve efficacy and safety, the adverse event profile and safety aspects of tedizolid phosphate have been evaluated in several preclinical animal models and through ongoing clinical trials. Early dose-ranging studies demonstrated a favorable overall adverse event profile and low thrombocytopenia rates, which have been consistently confirmed in phase 2 and 3 clinical trials. Pharmacokinetic modeling suggests a lower potential for monoamine oxidase interaction, and animal and human subject testing has confirmed these predictions. Studies in special patient populations showed a consistent and predictable pharmacokinetic profile across age groups and comorbid conditions, without evidence of increased incidence of adverse effects over matched controls. The favorable safety profile makes tedizolid phosphate an important new option for the management of serious Gram-positive infections, including those caused by methicillin-resistant Staphylococcus aureus.

Antibiotic activity against naive and induced Streptococcus pneumoniae biofilms in an in vitro pharmacodynamic model.

Abstract: Biofilms play a role in the pathogenicity of pneumococcal infections. A pharmacodynamic in vitro model of biofilm was developed that allows characterization of the activity of antibiotics against viability and biomass by using in parallel capsulated (ATCC 49619) and noncapsulated (R6) reference strains. Naive biofilms were obtained by incubating fresh planktonic cultures for 2 to 11 days in 96-well polystyrene plates. Induced biofilms were obtained using planktonic bacteria collected from the supernatant of 6-day-old naive biofilms. Biomass production was more rapid and intense in the induced model, but the levels were similar for both strains. Full concentration responses fitting sigmoidal regressions allowed calculation of maximal efficacies and relative potencies of drugs. All antibiotics tested (amoxicillin, clarithromycin, solithromycin, levofloxacin, and moxifloxacin) were more effective against young naive biofilms than against old or induced biofilms, except macrolides/ketolides, which were as effective at reducing viability in 2-day-old naive biofilms and in 11-day-old induced biofilms of R6. Macrolides/ketolides, however, were less potent than fluoroquinolones against R6 (approximately 5- to 20-fold-higher concentrations needed to reduction viability of 20%). However, at concentrations obtainable in epithelial lining fluid, the viabilities of mature or induced biofilms were reduced 15 to 45% (amoxicillin), 17 to 44% (macrolides/ketolides), and 12 to 64% (fluoroquinolones), and biomasses were reduced 5 to 45% (amoxicillin), 5 to 60% (macrolides/ketolides), and 10 to 76% (fluoroquinolones), with solithromycin and moxifloxacin being the most effective and the most potent agents (due to lower MICs) in their respective classes. This study allowed the ranking of antibiotics with respect to their potential effectiveness in biofilm-related infections, underlining the need to search for still more effective options.

Pharmacological Characterization of 7-(4-(Piperazin-1-yl)) Ciprofloxacin Derivatives: Antibacterial Activity, Cellular Accumulation, Susceptibility to Efflux Transporters, and Intracellular Activity

Abstract: Purpose To evaluate pharmacological properties (antibacterial activity; accumulation in phagocytic cells; activity against intracellular bacteria; susceptibility to fluoroquinolone efflux transporters) of ciprofloxacin derivatives modified at C-7 of the piperazine ring.

Study of Macrophage Functions in Murine J774 Cells and Human Activated THP-1 Cells Exposed to Oritavancin, a Lipoglycopeptide with High Cellular Accumulation

Abstract: Oritavancin, a lipoglycopeptide antibiotic in development, accumulates to high levels in the lysosomes of eukaryotic cells. We examined specific functions of macrophages (phagocytic capacity, lysosomal integrity, metabolic activity, and production of reactive oxygen species [ROS]) in correlation with the cellular accumulation of the drug, using J774 mouse macrophages and THP-1 human monocytes differentiated into macrophages using phorbol 12-myristate 13-acetate. Oritavancin did not affect Pseudomonas aeruginosa phagocytosis, lysosomal integrity, or metabolic activity in cells incubated for 3 h with extracellular concentrations ranging from 5 to 50 μg/ml. At extracellular concentrations of ≥25 μg/ml, oritavancin reduced latex bead phagocytosis by approximately 50% and doubled ROS production in J774 macrophages only. This may result from the fact that the cellular accumulation of oritavancin was 15 times higher in J774 cells than in activated THP-1 cells at 3 h. Human pharmacokinetic studies estimate that the concentration of oritavancin in alveolar macrophages could reach approximately 560 μg/ml after administration of a cumulative dose of 4 g, which is below the cellular concentration needed in the present study to impair latex bead phagocytosis (1,180 μg/ml) or to stimulate ROS production (15,000 μg/ml) by J774 cells. The data, therefore, suggest that, in spite of its substantial cellular accumulation, oritavancin is unlikely to markedly affect macrophage functions under the conditions of use investigated in current phase III trials (a single dose of 1,200 mg).

Study the expression of mexab-oprm pump genes in clinical isolates of pseudomonas aeruginosa using rt-pcr method

Abstract: Pseudomonas aeruginosa is an opportunistic bacterium that is intrinsically resistant to different antimicrobial substances. One reason for this resistance is the expression of multiple drug efflux pumps, such as MexAB-OprM. Analysis of expression of the MexAB–OprM pump such as mexA with RT-PCR especially with commercial kit can largely aid in selection of suitable antibiotic treatment. Thus, the aim of this investigation was to study the expression of mexA and oprM genes using RT-PCR in clinical isolates. Materials & Methods: Following the extraction of RNA from 17 clinical isolates and synthesis of cDNA, the relative quantification of mexA and oprM genes were determined by RT- PCR with and without commercial kit, respectively. Results: Over-expression of both mexA and oprM genes were seen in eight clinical isolates. This overexpression corresponded to 2-4 fold increase in MIC for carbenicillin.. Conclusion: The convergence between results obtained from using and not using the kit. Moreover, the convergence between only MIC for carbenicillin among several antibiotics used in phenotypic method and the expression of MexAB-OprM pump was found in all clinical isolates. Therefore, the application of phenotypic method and analysis of gene expression using RT- PCR with commercial kit, due to its ease of working, simultaneously is recommended

Comparison of genotypic method of mexx gene expression and phenotypic method of minimum inhibitory concentration in clinical isolates of pseudomonas aeruginosa

Abstract: i Background: The MexXY-OprM efflux pump contributes to the intrinsic resistance to various antimicrobial agents in Pseudomonas aeruginosa isolated from patients. Detection of the expression of genes encoding components of the MexXY-OprM efflux pump such as mexX using real time polymerase chain reaction (PCR) can be helpful in selecting suitable antibiotic treatment. Objective: The aim of this study was to compare the genotypic method of mexX gene expression and the phenotypic method of minimum inhibitory concentration in clinical isolates of Pseudomonas aeruginosa. Methods: This descriptive-laboratory study was conducted in University of Catholique de Louvain in 2012. After RNA extraction from 16 clinical isolates and cDNA synthesis, expression of mexX was detected by real time PCR using P. aeruginosa mex Q-TesT. According to the mex Q-TesT guideline, which is based on student T-test with 95% confidence interval and P<0.05, values equal or greater than 5 were considered as overexpression. Findings: Only 7 out of 11 clinical isolates with increased minimum inhibitory concentration for aminoglycosides showed overexpression of mexX. There was not any relationship between the pump expression and the increase in minimum inhibitory concentration values for various antibiotics. Conclusion: Since the results of the gene expression and the antimicrobial resistance data are not consistent in all cases, simultaneous use of both genotypic and phenotypic methods is recommended.