rifampin and thiazolyl-blue

To compare the in vitro antibacterial efficacy of antistaphylococcal antibiotics in combination with fosfomycin or rifampicin, using a biofilm model.. The antibacterial activities of fusidic acid, linezolid, vancomycin, teicoplanin, rifampicin, minocycline, fosfomycin and tigecycline, individually and in fosfomycin or rifampicin combinations, were measured against planktonic or biofilm-embedded methicillin-resistant Staphylococcus aureus (MRSA) with susceptible and resistant breakpoint concentrations (SBCs and RBCs, respectively), using the MTT-staining method and by counting the number of cfu in the biofilms.. Linezolid alone at its SBC, and fosfomycin, linezolid, minocycline and tigecycline at their RBCs, exhibited killing effects on biofilm-embedded MRSA (P < 0.0001). Of the eight fosfomycin combinations studied, fosfomycin combined with linezolid, minocycline, vancomycin or teicoplanin at their respective SBCs, exhibited enhanced antibacterial activities (P < 0.0001) when compared with the control group, and outperformed rifampicin combinations (P < 0.01). The killing effects of fosfomycin combinations at their respective RBCs were better than those at their respective SBCs (P < 0.05). Significantly enhanced killing effects were observed with fosfomycin in combination with vancomycin or teicoplanin, compared with vancomycin or teicoplanin alone. For 10 randomly selected MRSA isolates, the results of colony counting in biofilms were comparable with those of the MTT-staining method.. Fosfomycin enhanced the activities of linezolid, minocycline, vancomycin and teicoplanin. These combinatorial treatments were even better than rifampicin combination regimens, and may provide therapeutic advantages in catheter-related or prosthetic joint infections.

Topics: Anti-Bacterial Agents; Biofilms; Drug Interactions; Fosfomycin; Humans; Methicillin-Resistant Staphylococcus aureus; Microbial Sensitivity Tests; Microbial Viability; Rifampin; Staining and Labeling; Tetrazolium Salts; Thiazoles

Rifampicin-induced hepatotoxicity has been well recognized in animals and patients. However, it is undetectable in cultured hepatocyte monolayers in vitro at the equivalent toxic concentration in vivo. This study investigated the rifampicin-induced toxicity on rat hepatocytes in gel entrapment vs. in monolayer culture. Thiazolyl tetrazolium reduction and albumin secretion were routinely detected to identify the toxic responses of rat hepatocytes to rifampicin, while reactive oxygen species (ROS) accumulation and intracellular glutathione (GSH) content were assayed as biomarkers of oxidative stress. In addition, Nile red staining and malondialdehyde (MDA) generation were, respectively, used as endpoints for lipid accumulation and peroxidation. After treatment of hepatocytes for 96 h at a serum rifampicin concentration (12 microM), gel-entrapped rat hepatocytes showed significant cellular damage indicated by alternations of all parameters indicated above, while hepatocyte monolayers did not show severe responses. In contrast to a lack of protections by cytochrome P 450 inhibitors, the ROS scavenger (glycyrrhizic acid) and thiol compounds (N-acetylcysteine and GSH) significantly reduced rifampicin toxicity in gel-entrapped hepatocytes. It appears that gel-entrapped rat hepatocytes reflected significant hepatotoxicity of rifampicin in vivo, and this toxicity was most possibly associated with oxidative stress and lipid accumulation.

Topics: Acetylcysteine; Albumins; Animals; Antitubercular Agents; Cell Culture Techniques; Cell Survival; Cells, Cultured; Chemical and Drug Induced Liver Injury; Cytochrome P-450 Enzyme Inhibitors; Drug Antagonism; Enzyme Inhibitors; Glutathione; Glycyrrhizic Acid; Hepatocytes; Lipid Metabolism; Male; Malondialdehyde; Oxidative Stress; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Rifampin; Tetrazolium Salts; Thiazoles

The aim of this study was the preparation of microparticles containing rifampicin using a biodegradable polymer poly(3-hydroxybutyrate-co-3-hydroxyvalerate) for oral administration produced by a bacteria. The poly(3-hydroxybutyrate-co-3-hydroxyvalerate) microparticles with and without rifampicin were prepared by the emulsification and solvent evaporation method, in which chloroform and polyvinyl alcohol are used as the solvent and emulsifier, respectively. Microparticles were obtained within a size range of 20-60 microm by changing the initial poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polyvinyl alcohol and rifampicin concentrations. An encapsulation efficiency value of 14% was obtained. The optimized total yield of 60% of the poly(3-hydroxybutyrate-co-3-hydroxyvalerate)/ rifampicin was obtained. A load of 0.035 mg/1 mg of PHBV was reached. Almost 90% of the drug loaded in the microparticles was released after 24 h. The size, encapsulation efficiency and ribampicin release of the microparticles varied as a function of the initial poly(3-hydroxybutyrate-co-3-hydroxyvalerate), polyvinyl alcohol and rifampicin concentrations. It was demonstrated that the microencapsulated rifampicin, although was not totally available in the medium, exhibited a similar inhibition value as free rifampicin at 24 h of incubation with S. aureus. Cytotoxicity assays demonstrated a reduction of the toxicity when rifampicin was microencapsulated in poly(3-hydroxybutyrate-co-3-hydroxyvalerate) while maintaining its antibacterial activity.

Topics: Animals; Antibiotics, Antitubercular; Cell Line; Cricetinae; Drug Compounding; Excipients; Microbial Sensitivity Tests; Microscopy, Electron, Scanning; Nanoparticles; Neutral Red; Nucleic Acid Synthesis Inhibitors; Particle Size; Polyesters; Rifampin; Staphylococcus aureus; Tetrazolium Salts; Thiazoles

Various types of rifampicin (RIF)-loaded microparticles were compared for their stability during nebulization. Poly(lactide-co-glycolide) (PLGA), chitosan (CHT) and PLGA/CHT microparticles (MPs) were prepared by emulsion or precipitation techniques. MPs ability to be nebulized (NE%) as well as stability during freeze-drying or/and nebulization (NEED%), were evaluated after RIF extraction from MPs and determination by light spectroscopy. MP mean diameters and zeta-potential values were measured by dynamic light scattering, morphology was assessed by SEM, cytotoxicity by MTT method and mucoadhesive properties by mucin association. In all cases, freeze-drying prior to nebulization did not affect EE%, NE or NEED%. In CHT, MPs RIF encapsulation efficiency (EE%) decreased with increasing CHT concentration (viscosity) and CHT-MP NEED% was higher when the polymer was crosslinked by glutaraldehyde. PLGA MPs, exhibited both higher RIF EE% and also higher nebulization ability and NEED%, compared to CHT ones, but also higher cytotoxicity. However, when the two polymers were combined in the PLGA/CHT MPs, EE%, NE% and NEED% increased with increasing MP CHT-content. PLGA/CHT MPs with 0.50% or 0.75% CHT exhibited highest EE% for RIF and also best nebulization ability and stability, compared to all other MP formulations studied. Additionally they had good mucoadhesive properties and comparably low cytotoxicity.

Topics: Adhesiveness; Administration, Inhalation; Antibiotics, Antitubercular; Cell Line; Chemical Phenomena; Chemistry, Physical; Chitosan; Diffusion; Drug Compounding; Drug Delivery Systems; Drug Stability; Electrochemistry; Emulsions; Humans; Lactic Acid; Microscopy, Electron, Scanning; Microspheres; Molecular Weight; Mucins; Mucous Membrane; Nebulizers and Vaporizers; Particle Size; Polyglycolic Acid; Polylactic Acid-Polyglycolic Acid Copolymer; Polymers; Pulmonary Alveoli; Rifampin; Solvents; Tetrazolium Salts; Thiazoles

Preparation of drug-loaded freeze-dried (FD) liposomes, designed for delivery to lungs after rehydration/nebulization was investigated. Rifampicin (RIF) incorporating multilamelar (MLV) and dried rehydrated vesicles (DRV); composed of phosphatidylcholine (PC), dipalmitoyloglycero-PC (DPPC) or distearoyloglycero-PC (DSPC), containing or not Cholesterol (Chol), were prepared. Vesicles were characterized for encapsulation efficiency (EE%), size distribution, zeta-potential, stability during freeze drying (FD) and nebulization (nebulization efficiency (NE%) and retention of RIF after nebulization (NER%)). Mucoadhesion and toxicity in A549 cells was measured. RIF EE% was not affected by liposome type but lipid composition was important; Synthetic lipid vesicles (DPPC and DSPC) had higher EE% compared to PC. As Chol increased EE% decreased. Freeze drying (FD) had no effect on EE%, however trehalose decreased EE% possibly due to RIF displacement. NER% was highly affected by lipid composition. Results of NE% and NER% for RIF-loaded liposomes show that DSPC/Chol (2:1) is the best composition for RIF delivery in vesicular form to lungs, by nebulization. Mucoadhesion and A549 cell toxicity studies were in line with this conclusion, however if mucoadhesion is required, improvement may be needed.

Topics: Adhesives; Adsorption; Aerosols; Antibiotics, Antitubercular; Calorimetry, Differential Scanning; Cell Survival; Cells, Cultured; Chemistry, Pharmaceutical; Cholesterol; Drug Compounding; Drug Delivery Systems; Excipients; Freeze Drying; Humans; Liposomes; Lung; Mucous Membrane; Nebulizers and Vaporizers; Particle Size; Pulmonary Alveoli; Rifampin; Surface Properties; Tetrazolium Salts; Thermodynamics; Thiazoles

Rapid, accurate and inexpensive methods are essential to detect drug-resistant Mycobacterium tuberculosis and allow timely application of effective treatment and precautions to prevent transmission. The proportion method, the MTT and Alamar Blue redox methods, and the D29 mycobacteriophage assay, were compared for their ability to detect resistance to isoniazid and rifampicin. When tested against a panel of known M. tuberculosis strains, the redox methods and the D29 assay showed good sensitivity and specificity compared to the proportion method, suggesting that they could be useful alternatives for identifying multidrug resistance in M. tuberculosis.

Topics: Antitubercular Agents; Costs and Cost Analysis; Drug Resistance, Bacterial; Isoniazid; Microbial Sensitivity Tests; Mycobacteriophages; Mycobacterium tuberculosis; Oxazines; Oxidation-Reduction; Rifampin; Sensitivity and Specificity; Tetrazolium Salts; Thiazoles; Xanthenes

Arsenic is an established human carcinogen. The role of aquaglyroporins (AQPs) in arsenic disposition was recently identified. In order to examine whether organic anion transporting polypeptide-C (OATP-C) also plays a role in arsenic transport, OATP-C cDNA was transfected into cells of a human embryonic kidney cell line (HEK-293). Transfection increased uptake of the model OATP-C substrate, estradiol-17beta-D-glucuronide, by 10-fold. In addition, we measured uptake and cytotoxicity of arsenate, arsenite, monomethylarsonate(MMA(V)), and dimethylarsinate (DMA(V)). Transfection of OATP-C increased uptake and cytotoxicity of arsenate and arsenite, but not of MMA(V) or DMA(V). Rifampin and taurocholic acid (a substrate of OATP-C) reversed the increased toxicity of arsenate and arsenite seen in OATP-C-transfected cells. The increase in uptake of inorganic arsenic was not as great as that of estradiol-17beta-D-glucuronide. Our results suggest that OATP-C can transport inorganic arsenic in a (GSH)-dependent manner. However, this may not be the major pathway for arsenic transport.

Topics: Arsenates; Arsenic; Arsenites; Biological Transport, Active; Cacodylic Acid; Cell Line; DNA Primers; DNA, Complementary; Estradiol; Humans; Immunoblotting; Lethal Dose 50; Liver-Specific Organic Anion Transporter 1; Reverse Transcriptase Polymerase Chain Reaction; Rifampin; Taurocholic Acid; Tetrazolium Salts; Thiazoles; Toxicity Tests; Transfection

Type 2 diabetes mellitus (T2DM) is characterized by an approximately 60% deficit in beta-cell mass, increased beta-cell apoptosis, and islet amyloid derived from islet amyloid polypeptide (IAPP). Human IAPP (hIAPP) forms oligomers, leading to either amyloid fibrils or toxic oligomers in an aqueous solution in vitro. Either application of hIAPP on or overexpression of hIAPP in cells induces apoptosis. It remains controversial whether the fibrils or smaller toxic oligomers induce beta-cell apoptosis. Rifampicin prevents hIAPP amyloid fibril formation and has been proposed as a potential target for prevention of T2DM. We examined the actions of rifampicin on hIAPP amyloid fibril and toxic oligomer formation as well as its ability to protect beta-cells from either application of hIAPP or endogenous overexpression of hIAPP (transgenic rats and adenovirus-transduced beta-cells). We report that rifampicin (Acocella G. Clin Pharmacokinet 3: 108-127, 1978) prevents hIAPP fibril formation, but not formation of toxic hIAPP oligomers (Bates G. Lancet 361: 1642-1644, 2003), and does not protect beta-cells from apoptosis induced by either overexpression or application of hIAPP. These data emphasize that toxic hIAPP oligomers, rather than hIAPP fibrils, initiate beta-cell apoptosis and that screening tools to identify inhibitors of amyloid fibril formation are likely to be less useful than those that identify inhibitors of toxic oligomer formation. Finally, rifampicin and related molecules do not appear to be useful as candidates for prevention of T2DM.

Topics: Adenoviridae; Amyloid beta-Protein Precursor; Animals; Apoptosis; Benzothiazoles; Blotting, Western; Cell Death; Coloring Agents; DNA, Complementary; Fluorescent Dyes; Humans; In Situ Nick-End Labeling; Insulin-Secreting Cells; Islets of Langerhans; Propidium; Rats; Rats, Sprague-Dawley; Rifampin; Tetrazolium Salts; Thiazoles

To study the performance of three rapid low cost methods for the detection of rifampicin resistance.. A panel of 20 coded Mycobacterium tuberculosis strains was tested blindly by the low cost methods: nitrate reductase, MTT and resazurin assays, and compared with the results obtained with the gold standard methods: the proportion method on Löwenstein-Jensen medium and the BACTEC TB 460 system. We have also tested two commercial tests: MGIT and INNO LiPA Rif.TB kit.. Complete agreement was observed among all methods.. These three simple methods might become inexpensive alternative procedures for rapid detection of rifampicin resistance in low-resource countries.

Topics: Antibiotics, Antitubercular; Colorimetry; Culture Media; DNA-Directed RNA Polymerases; Drug Resistance, Bacterial; Humans; Indicators and Reagents; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Nitrate Reductase; Nitrate Reductases; Oxazines; Oxidation-Reduction; Peru; Reagent Kits, Diagnostic; Rifampin; Tetrazolium Salts; Thiazoles; Tuberculosis; Xanthenes

We describe a test which uses the ability of viable cells to reduce 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) to detect resistance to a bactericidal drug, rifampin, in in vitro-cultured Mycobacterium tuberculosis. The assay shows a linear relationship between the number of viable bacteria and the ability to reduce MTT. Dead mycobacteria were unable to reduce MTT. Rifampin-sensitive M. bovis (BCG) and M. tuberculosis exposed to rifampin showed a rifampin concentration-dependent inhibition of the ability to reduce MTT, while the resistant strains were unaffected. The inhibition of MTT reduction after treatment with rifampin paralleled the reduction in the number of CFU. By using mixing experiments in which the population percentages of rifampin-sensitive and -resistant strains were varied, the assay could detect the presence of rifampin resistance in the mixture when at least 1% of the bacterial population was composed of drug-resistant strains. The assay is cheap, can be visually read, and requires less than 3 days to obtain susceptibility results. The total time required to obtain results, from the time sputum is received in the laboratory, is, in most cases, less than 4 to 5 weeks, which is the time required for primary culture of the bacteria. The MTT assay could, in combination with a test to detect resistance to isoniazid, be a cheap and rapid screening method for multidrug-resistant M. tuberculosis that is affordable even by low-income countries where tuberculosis is a major public health problem.

Topics: Antibiotics, Antitubercular; Colony Count, Microbial; Coloring Agents; Dose-Response Relationship, Drug; Drug Resistance, Microbial; Mycobacterium bovis; Mycobacterium tuberculosis; Rifampin; Tetrazolium Salts; Thiazoles; Tuberculosis, Multidrug-Resistant

The effect of the anti-tuberculosis drug rifampicin on pirarubicin activity was investigated in multidrug-resistant cells overexpressing P-glycoprotein. Rifampicin increased the sensitivity of pirarubicin to anthracycline-resistant mouse leukemic P388 cells and significantly enhanced the cytotoxicity and intracellular accumulation of pirarubicin in resistant cells, but had no effect in parent cells. By contrast, two other rifamycins, rifamycin B and SV, had no effect on pirarubicin accumulation in resistant cells. Rifampicin also enhanced pirarubicin-induced apoptosis and G2/M blockade on the cell cycle in resistant cells. These results show that rifampicin enhances the cytotoxic action of pirarubicin in resistant cells, at least partly via the inhibition of cellular pirarubicin efflux.

Topics: Animals; Antibiotics, Antineoplastic; Antibiotics, Antitubercular; Apoptosis; Cell Cycle; Doxorubicin; Drug Resistance, Multiple; Drug Synergism; Gene Expression Regulation, Neoplastic; Genes, MDR; Leukemia P388; Mice; Rifampin; Tetrazolium Salts; Thiazoles