The interaction of reduced metronidazole with DNA bases and nucleosides

The Effect of Subinhibitory Concentration of Metronidazole on the Growth and Biofilm Formation on Toxigenic Clostridioides difficile Strains Belonging to Different Ribotypes

Clostridioides difficile is a predominant nosocomial pathogen within the healthcare setting able to produce biofilms. Sub-minimum inhibitory concentrations (sub-MICs) of antibiotics trigger mechanisms affecting bacterial virulence, including increased adhesion and biofilm formation. The aim of this study was to investigate how sub-MICs of metronidazole affect the biofilm formation of C. difficile strains. We tested 14 reference and clinical C. difficile strains, including hypervirulent strains of RT027. The MICs of metronidazole for the tested strains were determined using the broth microdilution method. Biofilm formation was evaluated using confocal laser scanning microscopy. The C. difficile strains belonging to RT027 produced the highest amounts of biofilm. The results of confocal laser scanning microscopy showed that all the tested C. difficile strains developed larger biofilms with diversified architectures upon exposure to sub-MICs of metronidazole. In our study, we reveal that sub-MIC concentrations of metronidazole affect the biofilm formation of clinical and reference strains of C. difficile. Importantly, metronidazole induces biofilm formation via hypervirulent RT027 strains.

Metronidazole-Loaded Camphor-Based In Situ Forming Matrix for Periodontitis Treatment

Periodontitis is a widespread oral health problem caused by bacterial infections that lead to tooth loss and other systemic diseases. The aim of this study was to provide an alternative treatment for periodontitis by developing a metronidazole-loaded in situ forming matrix (ISM) using camphor as its matrix former. Five-percent w/w metronidazole dissolved in N-methyl pyrrolidone (NMP) with varying concentrations of camphor (30-50% w/w) and triacetin (0-25% w/w) were used. The physicochemical properties and antimicrobial activities of formulations were evaluated. Results showed that as the percentage of camphor increased, viscosity, density, contact angle, surface tension, and force of injection increased, while water tolerance decreased. The same trend was observed when increasing the triacetin concentration. The optimal metronidazole-loaded ISM was obtained at 40% w/w camphor and 5% w/w triacetin, which prolonged the release of metronidazole up to 6 days with Fickian diffusion release profile. The higher concentration of triacetin slowed down the phase inversion that led to an incomplete formation of the matrix and resulted in an inefficiently prolonged release of the metronidazole. Antimicrobial activities demonstrated that the developed formulation efficiently inhibited periodontitis-induced microorganisms including Porphyromonas gingivalis, Staphylococcus aureus, Escherichia coli, and Candida albicans. The metronidazole-loaded camphor-based ISM has potential as a new drug delivery system for periodontitis treatment.

Mass Spectrometry-Based Metabolomics Revealed Effects of Metronidazole on Giardia duodenalis

Giardia duodenalis is a significant protozoan that affects humans and animals. An estimated 280 million G. duodenalis diarrheal cases are recorded annually. Pharmacological therapy is crucial for controlling giardiasis. Metronidazole is the first-line therapy for treating giardiasis. Several metronidazole targets have been proposed. However, the downstream signaling pathways of these targets with respect to their antigiardial action are unclear. In addition, several giardiasis cases have demonstrated treatment failures and drug resistance. Therefore, the development of novel drugs is an urgent need. In this study, we performed a mass spectrometry-based metabolomics study to understand the systemic effects of metronidazole in G. duodenalis. A thorough analysis of metronidazole processes helps identify potential molecular pathways essential for parasite survival. The results demonstrated 350 altered metabolites after exposure to metronidazole. Squamosinin A and N-(2-hydroxyethyl)hexacosanamide were the most up-regulated and down-regulated metabolites, respectively. Proteasome and glycerophospholipid metabolisms demonstrated significant differential pathways. Comparing glycerophospholipid metabolisms of G. duodenalis and humans, the parasite glycerophosphodiester phosphodiesterase was distinct from humans. This protein is considered a potential drug target for treating giardiasis. This study improved our understanding of the effects of metronidazole and identified new potential therapeutic targets for future drug development.

New Pyrazolo-Benzimidazole Mannich Bases with Antimicrobial and Antibiofilm Activities

A new series of pyrazolo-benzimidazole hybrid Mannich bases were synthesized, characterized by ¹H-NMR, ¹³C-NMR, IR, UV-Vis, MS, and elemental analysis. In vitro cytotoxicity of the new compounds studied on fibroblast cells showed that the newly synthesized pyrazolo-benzimidazole hybrid derivatives were noncytotoxic until the concentration of 1 μM and two compounds presented a high degree of biocompatibility. The antibacterial and antibiofilm activity of the newly synthesized compounds was assayed on Gram-positive Staphylococcus aureus ATCC25923, Enterococcus faecalis ATCC29212, and Gram-negative Pseudomonas aeruginosa ATCC27853, Escherichia coli ATCC25922 strains. All synthesized compounds 5a–g are more active against all three tested bacterial strains Staphylococcus aureus ATCC25923, Enterococcus faecalis ATCC29212, and Escherichia coli ATCC25922 than reference drugs (Metronidazole, Nitrofurantoin), with the exception of compounds 5d and 5g, which are less active compared to Nitrofurantoin, and all synthesized compounds 5a–g are more active against Pseudomonas aeruginosa ATCC27853 compared to reference drugs (Metronidazole, Nitrofurantoin). Compound 5f showed the best activity against Staphylococcus aureus ATCC 25923, with a MIC of 150 μg/mL and has also inhibited the biofilm formed by all the bacterial strains, having an MBIC of 310 µg/mL compared to the reference drugs (Metronidazole, Nitrofurantoin).

Antimicrobial evaluation of the Cynara cardunculus extract in Helicobacter pylori cells using mid-infrared spectroscopy and chemometric methods

AIMS

The treatment effectiveness of gastric diseases caused by the bacteria Helicobacter pylori is failing due to high resistance to some antibiotics. Consequently, it is urgent to develop an accurate methodology to screen new antimicrobial agents.

METHODS AND RESULTS

A preliminary assay, using both therapeutic-based antibiotics (clarithromycin and metronidazole), was conducted to optimize experimental conditions in terms of the sensibility of the Fourier Transform Mid-Infrared spectroscopy (MIR-FTIR) associated with chemometric methods. Principal component analysis was applied to understand how the Cynara extract concentration acts differentially against H. pylori bacteria. The partial least squares model, characterized by R² = 0.98, and root mean square error cross-validation, 0.011, was developed for the spectral regions (3600 - 2500 cm^-1 , and 2000 - 698 cm^-1 ).

CONCLUSIONS

MIR-FTIR spectroscopy associated with chemometric methods can be considered a suitable approach to discover and analyze the promissory antimicrobial agents based on the biomolecular changes observed according to the Cynara extract.

SIGNIFICANCE AND IMPACT OF THE STUDY

MIR-FTIR spectroscopy and chemometric methods allowed to register the biomolecular changes due to the potential antimicrobial drugs at reduced concentrations comparatively to the conventional assay based on an agar-dilution method, being considered a useful approach to develop a platform to discover new bioactive molecules, allowing to reduce time and costs related to the exploratory step.

Clostridioides difficile: Current overview and future perspectives

The most common world-wide cause of antibiotic-associated infectious diarrhea and colitis is the toxin producing bacterium, Clostridioides difficile (C. difficile). Here we review the background and characteristics of the bacterium and the toxins produced together with the epidemiology and the complex pathogenesis that leads to a broad clinical spectrum of disease. The review describes the difficulties faced in obtaining a quick and accurate diagnosis despite the range of sensitive and specific diagnostic tools available. We also discuss the problem of disease recurrence and the importance of disease prevention. The high rates of infection recurrence mean that treatment strategies are constantly under review and we outline the diverse treatment options that are currently in use and explore the emerging treatment options of pulsed antibiotic use, microbial replacement therapies and the use of monoclonal antibodies. We summarize the future direction of treatment strategies which include the development of novel antibiotics, the administration of oral polyclonal antibody formulations, the use of vaccines, the administration of competitive non-toxigenic spores and the neutralization of antibiotics at the microbiota level. Future successful treatments will likely involve a combination of therapies to provide the most effective and robust approach to C. difficile management.

Binding preference of nitroimidazolic radiosensitizers to nucleobases and nucleosides probed by electrospray ionization mass spectrometry and density functional theory

Nitroimidazolic radiosensitizers are used in radiation therapy to selectively sensitize cancer cells deprived of oxygen, and the actual mechanism of radiosensitization is still not understood. Selecting five radiosensitizers (1-methyl-5-nitroimidazole, ronidazole, ornidazole, metronidazole, and nimorazole) with a common 5-nitroimidazolic ring with different substitutions at N1 and C2 positions of the imidazole moiety, we investigate here their binding to nucleobases (A, T, G, and C) and nucleosides (As, Td, Gs, and Cd) via the positive electrospray ionization mass spectrometry experiments. In addition, quantum chemical calculations at the M062x/6-311+G(d,p) level of theory and basis set were used to determine binding energies of the proton bound dimers of a radiosensitizer and a nucleobase. The positive electrospray ionization leads to the formation of proton bound dimers of all radiosensitizers except 1-methyl-5-nitroimidazole in high abundance with C and smaller abundance with G. Ronidazole and metronidazole formed less abundant dimers also with A, while no dimers were observed to be formed at all with T. In contrast to the case of the nucleoside Td, the dimer intensity is as high as that with Cd, while the abundance of the dimer with Gs is smaller than that of the former. The experimental results are consistent with the calculations of binding energies suggesting proton bound dimers with C and G to be the strongest bound ones. Finally, a barrier-free proton transfer is observed when protonated G or C approaches the nitroimidazole ring.

Synthesis, characterization, and anti-amoebic activity of N-(pyrimidin-2-yl)benzenesulfonamide derivatives

A new series of N-(pyrimidin-2-yl)benzenesulfonamide derivatives, 3a-3i and 4a-4i, was synthesized from pyrimidin-2-amines, 2a-2i, with the aim to explore their effects on in vitro growth of Entamoeba histolytica. The chemical structures of the compounds were elucidated by elemental analysis, FT-IR, (1) H- and (13) C-NMR, and ESI mass-spectral data. In vitro anti-amoebic activity was evaluated against HM1 : IMSS strain of Entamoeba histolytica. The IC50 values were calculated by using the double dilution method. The results were compared with the IC50 value of the standard drug 'metronidazole'. The selected compounds were tested for their cytotoxic activities by cell-viability assay using H9C2 cardiac myoblasts cell line, and the results indicated that all the compounds displayed remarkable >80% viabilities to a concentration of 100 μg/ml.

Formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine under anaerobic conditions by reductively activated nitro 5-deazaflavin derivatives

Electrolytically reduced 6- and 8-nitro-5-deazaflavin derivatives have been found to interact to react specifically with guanine base by means of cyclic voltammetry. Electrolytic reductions of 6- and 8-nitro-5-deazaflavin derivatives in the presence of the 2'-deoxyguanosine under anaerobic conditions resulted in prominent formation of 8-oxo-7,8-dihydro-2'-deoxyguanosine.

A comparison of the effects of methotrexate and misonidazole on the germinal cells of the subependymal plate of the rat

The cytotoxic effects of the drugs methotrexate (MTX) and misonidazole have been assessed in the rat brain by quantifying changes in the constituent cell populations of a glial cell progenitor layer, the subependymal plate (SEP). Three distinct cell types can be identified in the SEP on the basis of their nuclear morphology: cells with small dark (SD), small light (SL) or large light (LL) nuclei. The cells with SD nuclei may present pluripotential glial cell precursors. A reduction in the total nuclear density of the SEP, after the local ventricular administration of MTX, could be accounted for largely by a loss of cells with SD nuclei; to approximately 45% of control values 2 days after MTX followed by a full recovery in numbers by day 5. A further decline in the number of cells with SD nuclei occurred at 12 weeks after MTX administration. The pattern of changes in the cellularity of the SEP, after misonidazole administration, were similar to those observed after MTX treatment, although the magnitude of the response was reduced. It was concluded that both drugs, but MTX in particular, could have a potential additive effect on glial progenitor cells when used in combination with other forms of cancer therapy including radiation.

The reactivity of chloramphenicol reduction products with DNA bases

PURPOSE

The interaction between the constituent bases of deoxyribonucleic acid and the reduction products of the nitro-aromatic compound chloramphenicol and its nitroso derivative have been studied using an electrochemical system.

METHODS AND MATERIALS

The changes to the voltammetry of chloramphenicol and nitrosochloramphenicol upon addition of adenine, cytosine, guanine, and thymine at various concentrations have been measured. The biological implications of reductive activation of both chloramphenicol and nitrosochloramphenicol were examined using a phi X174 double transfection technique which measures biologically relevant deoxyribonucleic acid damage.

RESULTS

Measurement of the voltammetric response of chloramphenicol shows that the most noticeable change upon base addition is a decrease in the lifetime of the nitro radical anion in the following order of decreasing activity: adenine, thymine, and cytosine. No effect was observed with guanine. The reversible 2-electron nitrosochloramphenicol-hydroxychloramphenicol couple showed no interaction on the voltammetric timescale, although binding of the hydroxylamine to guanine was observed. Interaction of the azo derivative, formed as a consequence of further reduction plus chemical reaction of nitrosochloramphenicol was observed. Biological studies showed that no significant effect on deoxyribonucleic acid by chloramphenicol or nitrosochloramphenicol was observed under oxic conditions. Controlled reduction of nitrosochloramphenicol to the hydroxylamine gave considerably less damage than when nitrosochloramphenicol or chloramphenicol was completely reduced.

CONCLUSION

The chloramphenicol nitro radical anion reacts selectively with the bases of deoxyribonucleic acid. Reduction products of nitrosochloramphenicol beyond the 2-electron hydroxylamine are highly reactive to deoxyribonucleic acid.