Effect of different nitroheterocyclic compounds on aerobic, microaerophilic, and anaerobic bacteria

Application of furazolidone in Helicobacter pylori infection eradication

Increasing antibiotic resistance is the primary reason for treatment failure of Helicobacter pylori (H. pylori) infection. To enhance the eradication rate, minimize the development of secondary resistance, and alleviate the socioeconomic burden, it is crucial to select H. pylori-sensitive antibiotics carefully. Furazolidone has been used for H. pylori eradication in developing countries for decades due to its affordability and low resistance rate. Numerous studies have demonstrated that furazolidone-containing regimens are more efficacious than those containing other antibiotics, as both first- and second-line therapies, and are also well tolerated. However, utility of furazolidone is restricted or not optimal in certain countries due to its infrequent but potentially severe adverse effects. The decision to discontinue usage of furazolidone because of concerns regarding adverse effects may be misguided. Here we comprehensively reviewed the studies on furazolidone at different dosages and treatment durations for H. pylori eradication. Further research on the mechanisms of action and clinical trials of furazolidone are of great practical importance.

Rabeprazole plus amoxicillin dual therapy is equally effective to bismuth-containing quadruple therapy for Helicobacter pylori eradication in central China: A single-center, prospective, open-label, randomized-controlled trial

BACKGROUND

Antibiotic resistance emerges as a major issue for Helicobacter pylori (H. pylori) treatment. High-dose dual therapy has recently shown encouraging results in H. pylori eradication, but it has yet to be validated in this H. pylori highly infected area; it is also not known if this concept can be extended to antibiotics other than amoxicillin, and factors that affect the eradication. We investigate if rabeprazole plus amoxicillin or furazolidone regimens could be a first-line therapy for H. pylori eradication, and factors that affect the curing rate.

METHODS

This is a single-center, prospective, open-label, randomized-controlled trial. Naive patients (n=292) were randomly treated with bismuth-containing quadruple therapy (BQT), rabeprazole plus amoxicillin (RADT), or furazolidone (RFDT) groups. RADT and FADT use three times daily regimens. H. pylori diagnosis and eradication were determined and confirmed by ¹³ C-urea breath test.

RESULTS

In per-protocol (PP) analysis, H. pylori eradication rate was 91.2% in BQT group, 89.6% in RADT, and 51.0% in RFDT group. In intention-to-treat (ITT) analysis, infection was eradicated in 86.7% of patients in BQT group, 85.8% in RADT, and 48.1% in RFDT groups, respectively. Noninferiority was confirmed between BQT and RADT groups. The incidence of side effects in BQT group was significantly higher than that in RADT group. Successful eradication was associated with lower body surface area (BSA) and low body mass index (BMI) in BQT group. Smoking and high BSA index reduced H. pylori eradication rate in RADT group.

CONCLUSIONS

Rabeprazole-amoxicillin dual therapy is equally effective to the bismuth-containing quadruple therapy for H. pylori eradication with fewer side effects and saves use of one antibiotic per each treatment. Successful eradication is also associated with low BSA and non-smoking condition, which deserves future stratified analysis for refinement and optimization.

Single- and Two-Electron Reduction of Nitroaromatic Compounds by Flavoenzymes: Mechanisms and Implications for Cytotoxicity

Nitroaromatic compounds (ArNO₂) maintain their importance in relation to industrial processes, environmental pollution, and pharmaceutical application. The manifestation of toxicity/therapeutic action of nitroaromatics may involve their single- or two-electron reduction performed by various flavoenzymes and/or their physiological redox partners, metalloproteins. The pivotal and still incompletely resolved questions in this area are the identification and characterization of the specific enzymes that are involved in the bioreduction of ArNO₂ and the establishment of their contribution to cytotoxic/therapeutic action of nitroaromatics. This review addresses the following topics: (i) the intrinsic redox properties of ArNO₂, in particular, the energetics of their single- and two-electron reduction in aqueous medium; (ii) the mechanisms and structure-activity relationships of reduction in ArNO₂ by flavoenzymes of different groups, dehydrogenases-electrontransferases (NADPH:cytochrome P-450 reductase, ferredoxin:NADP(H) oxidoreductase and their analogs), mammalian NAD(P)H:quinone oxidoreductase, bacterial nitroreductases, and disulfide reductases of different origin (glutathione, trypanothione, and thioredoxin reductases, lipoamide dehydrogenase), and (iii) the relationships between the enzymatic reactivity of compounds and their activity in mammalian cells, bacteria, and parasites.

Development and validation of LC-MS/MS method for determination of DNDI-VL-2098 in mouse, rat, dog and hamster blood

Aim: To develop a bioanalytical method to support pharmacokinetic evaluation of DNDI-VL-2098 in mouse, rat, dog and hamster following oral administration. Results & methodology: A robust LC-MS/MS bioanalytical method was developed to quantify DNDI-VL-2098. DNDI-VL-2098 showed time-dependent recovery loss in acetonitrile precipitated plasma in all species. Acid-lysed whole blood was identified as a matrix in which recovery was stable over time. A two-step extraction procedure was used, with protein precipitation followed by liquid-liquid extraction with methyl tert-butyl ether. The assay was validated in the dynamic range of 5-5000 ng/ml for mouse, rat and dog blood, and a fit-for-purpose method was developed for hamster. Conclusion: A specific LC-MS/MS assay for DNDI-VL-2098 was developed and validated in hemolyzed blood.

Effect of nitrofurans and NO generators on biofilm formation by Pseudomonas aeruginosa PAO1 and Burkholderia cenocepacia 370

Antibacterial drugs in the nitrofuran series, such as nitrofurazone, furazidin, nitrofurantoin and nifuroxazide, as well as the nitric oxide generators sodium nitroprusside and isosorbide mononitrate in concentrations that do not suppress bacterial growth, were shown to increase the capacity of pathogenic bacteria Pseudomonas aeruginosa PAO1 and Burkholderia cenocepacia 370 to form biofilms. At 25-100microg/ml, nitrofurans 2-2.5-fold enhanced biofilm formation of P. aeruginosa PAO1, and NO donors 3-6-fold. For B. cenocepacia 370, the enhancement was 2-5-fold (nitrofurans) and 4.5-fold (sodium nitroprusside), respectively.

Enzymes associated with reductive activation and action of nitazoxanide, nitrofurans, and metronidazole in Helicobacter pylori

Nitazoxanide (NTZ) is a redox-active nitrothiazolyl-salicylamide prodrug that kills Helicobacter pylori and also many anaerobic bacterial, protozoan, and helminthic species. Here we describe development and use of a spectrophotometric assay, based on nitroreduction of NTZ at 412 nm, to identify H. pylori enzymes responsible for its activation and mode of action. Three enzymes that reduce NTZ were identified: two related NADPH nitroreductases, which also mediate susceptibility to metronidazole (MTZ) (RdxA and FrxA), and pyruvate oxidoreductase (POR). Recombinant His-tagged RdxA, FrxA, and POR, overexpressed in nitroreductase-deficient Escherichia coli, each rapidly reduced NTZ, whereas only FrxA and to a lesser extent POR reduced nitrofuran substrates (furazolidone, nitrofurantoin, and nitrofurazone). POR exhibited no MTZ reductase activity either in extracts of H. pylori or following overexpression in E. coli; RdxA exhibited no nitrofuran reductase activity, and FrxA exhibited no MTZ reductase activity. Analysis of mutation to rifampin resistance (Rif(r)) indicated that NTZ was not mutagenic and that nitrofurans were only weakly mutagenic. Alkaline gel DNA electrophoresis indicated that none of these prodrugs caused DNA breakage. In contrast, MTZ caused DNA damage and was strongly mutagenic. We conclude that POR, an essential enzyme, is responsible for most or all of the bactericidal effects of NTZ against H. pylori. While loss-of-function mutations in rdxA and frxA produce a Mtz(r) phenotype, they do not contribute much to the innate susceptibility of H. pylori to NTZ or nitrofurans.

Genetic map of Salmonella typhimurium, edition VIII

We present edition VIII of the genetic map of Salmonella typhimurium LT2. We list a total of 1,159 genes, 1,080 of which have been located on the circular chromosome and 29 of which are on pSLT, the 90-kb plasmid usually found in LT2 lines. The remaining 50 genes are not yet mapped. The coordinate system used in this edition is neither minutes of transfer time in conjugation crosses nor units representing "phage lengths" of DNA of the transducing phage P22, as used in earlier editions, but centisomes and kilobases based on physical analysis of the lengths of DNA segments between genes. Some of these lengths have been determined by digestion of DNA by rare-cutting endonucleases and separation of fragments by pulsed-field gel electrophoresis. Other lengths have been determined by analysis of DNA sequences in GenBank. We have constructed StySeq1, which incorporates all Salmonella DNA sequence data known to us. StySeq1 comprises over 548 kb of nonredundant chromosomal genomic sequences, representing 11.4% of the chromosome, which is estimated to be just over 4,800 kb in length. Most of these sequences were assigned locations on the chromosome, in some cases by analogy with mapped Escherichia coli sequences.

Antibacterial activities of the antiparasitic drugs nifurtimox and benznidazole

Both nifurtimox and benznidazole, which are used for the treatment of Chagas' disease, also display marked antibacterial activities. Characteristically for nitroheterocyclic compounds, they are much more active against anaerobic and microaerophilic bacteria than against aerobic bacteria. Nitroreductase-deficient aerobes are completely resistant, whereas SOS-repair-deficient strains are moderately susceptible. Those strains are rapidly killed.