Nitroimidazole Drugs Research Articles

Boosting the Sustained Release Performance of Metronidazole and Ornidazole with MIL-53(Fe) Derived Spherical Porous Carbon.

Metal-organic framework (MOF) derived spherical porous carbon (SPC) has potential application value in the field of adsorption and sustained release of nitroimidazole drugs. This work used MIL-53(Fe) as a precursor and prepared spherical 3-aminophenol-formaldehyde resin containing MIL-53(Fe) crystals using the advanced Stöber method, followed by the successful preparation of MIL-53(Fe) derived SPC (MSPC) with a structure containing both micropores and mesopores through high-temperature carbonization. The effects of the doping amount of MIL-53(Fe) on the sphericity and particle size of MSPC were investigated. The drug uptake capacity and sustained release performances of MSPC for metronidazole (MNZ) and ornidazole (ONZ) were assessed through batch tests, along with an investigation into the impact of varying pH levels on the sustained release performances. The experimental findings revealed that the drug loading of MNZ and ONZ onto MSPC achieved 111 and 120 mg/g, respectively, with a sustained release time of up to 24 h. The drug loading process adhered to the Langmuir isotherm adsorption model and conformed to the pseudo-second-order kinetics model, whereas the sustained release mechanism was consistent with the Korsmeyer-Peppas model. Furthermore, cytotoxicity and cyclic drug loading experiments indicated that MSPC exhibited good biocompatibility and stability. Therefore, this study provides new ideas for the development of SPC drug carriers.

Distinct substrate specificities of the three catalytic subunits of the Trichomonas vaginalis proteasome.

The protozoan parasite Trichomonas vaginalis (Tv) causes trichomoniasis, the most common non-viral sexually transmitted infection in the world. Although Tv has been linked to significant health complications, only two closely related 5-nitroimidazole drugs are approved for its treatment. The emergence of resistance to these drugs and lack of alternative treatment options poses an increasing threat to public health, making development of novel anti-Trichomonas compounds an urgent need. The proteasome, a critical enzyme complex found in all eukaryotes has three catalytic subunits, β1, β2, and β5 and has been validated as a drug target to treat trichomoniasis. With the goal of developing tools to study the Tv proteasome, we isolated the enzyme complex and identified inhibitors that preferentially inactivate either one or two of the three catalytic subunits. Using a mass spectrometry-based peptide digestion assay, these inhibitors were used to define the substrate preferences of the β1, β2 and β5 subunits. Subsequently, three model fluorogenic substrates were designed, each specific for one of the catalytic subunits. This novel substrate profiling methodology will allow for individual subunit characterization of other proteasomes of interest. Using the new substrates, we screened a library of 284 peptide epoxyketone inhibitors against Tv and determined the subunits targeted by the most active compounds. The data show that inhibition of the Tv β5 subunit alone is toxic to the parasite. Taken together, the optimized proteasome subunit substrates will be instrumental for understanding the molecular determinants of proteasome specificity and for accelerating drug development against trichomoniasis.

CRISPR Screening and Comparative LC-MS Analysis Identify Genes Mediating Efficacy of Delamanid and Pretomanid against Mycobacterium tuberculosis.

Tuberculosis (TB), the leading cause of death from bacterial infections worldwide, results from infection with Mycobacterium tuberculosis (Mtb). The antitubercular agents delamanid (DLM) and pretomanid (PMD) are nitroimidazole prodrugs that require activation by an enzyme intrinsic to Mtb; however, the mechanism(s) of action and the associated metabolic pathways are largely unclear. Profiling of the chemical-genetic interactions of PMD and DLM in Mtb using combined CRISPR screening reveals that the mutation of rv2073c increases susceptibility of Mtb to these nitroimidazole drugs both in vitro and in infected mice, whereas mutation of rv0078 increases drug resistance. Further assays show that Rv2073c might confer intrinsic resistance to DLM/PMD by interfering with inhibition of the drug target, decaprenylphophoryl-2-keto-b-D-erythro-pentose reductase (DprE2), by active nicotinamide adenine dinucleotide (NAD) adducts. Characterization of the metabolic pathways of DLM/PMD in Mtb using a combination of chemical genetics and comparative liquid chromatography-mass spectrometry (LC-MS) analysis of DLM/PMD metabolites reveals that Rv0077c, which is negatively regulated by Rv0078, mediates drug resistance by metabolizing activated DLM/PMD. These results might guide development of new nitroimidazole prodrugs and new regimens for TB treatment.

Anti-Microbial Drug Metronidazole Promotes Fracture Healing: Enhancement in the Bone Regenerative Efficacy of the Drug by a Biodegradable Sustained-Release In Situ Gel Formulation.

Nitroimidazoles comprise a class of broad-spectrum anti-microbial drugs with efficacy against parasites, mycobacteria, and anaerobic Gram-positive and Gram-negative bacteria. Among these drugs, metronidazole (MTZ) is commonly used with other antibiotics to prevent infection in open fractures. However, the effect of MTZ on bone remains understudied. In this paper, we evaluated six nitroimidazole drugs for their impact on osteoblast differentiation and identified MTZ as having the highest osteogenic effect. MTZ enhanced bone regeneration at the femur osteotomy site in osteopenic ovariectomized (OVX) rats at the human equivalent dose. Moreover, in OVX rats, MTZ significantly improved bone mass and strength and improved microarchitecture compared to the vehicle-treated rats, which was likely achieved by an osteogenic mechanism attributed to the stimulation of the Wnt pathway in osteoblasts. To mitigate the reported neurological and genotoxic effects of MTZ, we designed an injectable sustained-release in situ gel formulation of the drug that improved fracture healing efficacy by 3.5-fold compared to oral administration. This enhanced potency was achieved through a significant increase in the circulating half-life and bioavailability of MTZ. We conclude that MTZ exhibits osteogenic effects, further accentuated by our sustained-release delivery system, which holds promise for enhancing bone regeneration in open fractures.

Drug resistance patterns and genotype associations of Trichomonas gallinae in meat pigeons (Columba livia): insights from Guangdong Province, China.

Avian trichomoniasis, caused by the protozoan parasite Trichomonas gallinae, is a prevalent and economically significant disease in pigeons. This study investigated the drug resistance of T. gallinae isolates in Guangdong Province, China. The results revealed that 25.3% (20/79) of the isolates were resistant to one or more of the four nitroimidazole drugs tested, namely, metronidazole, dimetridazole, secnidazole, and tinidazole. Secnidazole elicited the highest resistance rate (19.0%; 15/79), followed by tinidazole (17.7%; 14/79), metronidazole (17.7%; 14/79), and dimetridazole (13.9%; 11/79). An enormous majority of the resistant isolates (70.0%; 14/20) exhibited resistance to multiple drugs. Additionally, the resistance rate was significantly higher in isolates from birds aged < 30 days (53.3%; 8/15) than in those from older birds (23.1%; 12/52). Moreover, no drug resistance was detected in female pigeons. The genotype of the isolated strain was also associated with drug resistance. Specifically, 50.0% (15/30) of ITS-B genotypes exhibited resistance to drugs, while only 10.2% (5/49) of ITS-A genotypes demonstrated resistance. This study also found the growth characteristics of different Trichomonas isolates to be influenced by their genotypes and initial inoculum concentrations. These findings underscore the urgent need for effective measures to control and prevent drug-resistant T. gallinae infections in pigeons, thus ensuring the stable development of the pigeon industry.

Metronidazole pharmacokinetics in geese (Anser anser domesticus) after intravenous and oral administrations.

Metronidazole (MTZ) is a 5-nitroimidazole anti-bacterial and anti-protozoal drug. In human and companion animal medicine, MTZ remains widely used due to its effectiveness against anaerobic bacteria and protozoa. In farm animals, however, MTZ is currently prohibited in several countries due to insufficient data on nitroimidazoles. The purpose of this study was to assess its pharmacokinetics (PK) in geese after single intravenous (IV) and oral (PO) administrations. Fifteen-month old healthy male geese (n = 8) were used. Geese were subjected to a two-phase, single-dose (10 mg/kg IV, 50 mg/kg PO), open, longitudinal study design with a two-week washout period between the IV and PO phases. Blood was drawn from the left wing vein to heparinized tubes at 0, 0.085 (for IV only), 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 6, 8, 10, 24, and 48 h. Plasma MTZ concentrations were measured using HPLC coupled to an UV detector, and the data were pharmacokinetically analyzed using PKanalix™ software with a non-compartmental approach. MTZ was still quantifiable and well above the LLOQ at 24 h after both routes of administration. Following IV administration, terminal elimination half-life, volume of distribution, and total clearance were 5.47 h, 767 mL/kg, and 96 mL/h/kg, respectively. For the PO route, the bioavailability was high (85%), and the mean peak plasma concentration was 60.27 μg/mL at 1 h. When parameters were normalized for the dose, there were no statistically significant differences for any of the PK parameters between the two routes of administration. The study shows that oral administration of MTZ seems to be promising in geese, although comprehensive research on its pharmacodynamics and multiple-dose studies are necessary before its adoption in geese can be further considered.

Physicochemical considerations in the formulation development of silicone elastomer vaginal rings releasing 5-nitroimidazole drugs for the treatment of bacterial vaginosis

Bacterial vaginosis (BV) is a common dysbiosis of the human vaginal microbiota characterized by depletion of hydrogen peroxide and lactic acid-producing Lactobacillus bacteria and an overgrowth of certain facultative anaerobic bacteria. Although short-term cure rates following treatment with frontline antibiotics (most notably oral metronidazole (MNZ), clindamycin vaginal cream, and MNZ vaginal gel) are generally high, longer-term recurrence rates are an issue. The development of vaginal formulations offering continuous/sustained administration of antibiotic drugs over one or more weeks might prove useful in reducing recurrence. Here, we report the manufacture and preclinical testing of matrix-type vaginal rings offering sustained release of four 5-nitroimidazole antimicrobial drugs either being used clinically or having potential in treatment of BV – MNZ, tinidazole (TNZ), secnidazole (SNZ) and ornidazole (ONZ). All four drugs showed good compatibility with a medical-grade addition-cure silicone elastomer based upon thermal analysis experiments, and matrix-type rings containing 250 mg (3.125 %w/w) of each drug were successfully manufactured by reaction injection molding. 28-day in vitro drug release studies demonstrated root-time kinetics, with daily release rates of 25, 22, 9 and 6 mg/day½ for SNZ, ONZ, MNZ and TNZ, respectively. The rank order of drug release from rings correlated with the simple molecular permeability parameter S/V, where S is the measured drug solubility in silicone fluid and V is the drug molecular volume. The relative merits of SNZ and ONZ over MNZ (the current reference treatment) are discussed. The data support development of vaginal rings for sustained release of 5-nitroimidazole compounds for treatment of BV.

Boosted sustained-release with iron-based MOF-derived mesoporous-carbon-spheres as a nitroimidazole drugs carrier

Metal-organic framework (MOF) with a buildable internal structure has aroused great interest focus as self-sacrificing precursors of porous carbon (PC). However, as a drug carrier, the MOF-derived PC developed thus far are generally composed of irregular powder shape due to their crystalline nature, which consequently causing the cerebral infarction, cerebral thrombosis, and other blood diseases. In this article, we propose a novel approach to constructing amorphous carbon microspheres (ACMs) by distorting the topological network through hydrothermal treatment precursors of MIL-101(Fe). Then, a distinctive MIL-101(Fe)-derived spherical porous carbons (MSPC) is achieved through high temperature calcination toward ACMs. Effects of the glucose initial concentration and hydrothermal treatment time on the sphericity of the as-prepared mesoporous MSPC were investigated in depth. And the loading capacities and sustained-release performances of nitroimidazole drugs over MSPC through simulation internal environment of human body at different pH values was systematically evaluated. The nitroimidazole drugs loading rate and release time of MSPC are 10% and 17 h under preferred process. Furthermore, the MSPC exhibited very low toxicity on Hela cells and 293T cells at the concentrations tested (10–800 μg mL−1). This study, therefore, supports the potential of the mesoporous carbon spheres as a carrier for nitroimidazole drug delivery.

Identification of Fungus-Derived Natural Products as New Antigiardial Scaffolds.

There is an unmet need for effective therapies for treating diseases associated with the intestinal parasite Giardia lamblia. In this study, a library of chemically validated purified natural products and fungal extracts was screened for chemical scaffolds that can inhibit the growth of G. lamblia. The phenotypic screen led to the identification of several previously unreported classes of natural product inhibitors that block the growth of G. lamblia. Hits from phenotypic screens of these naturally derived compounds are likely to possess a variety of mechanisms of action not associated with clinically used nitroimidazole and thiazolide compounds. They may therefore be effective against current drug-resistant parasite strains. IMPORTANCE There is a direct link between widespread prevalence of clinical giardiasis and poverty. This may be one of the reasons why giardiasis is a significant contributor to diarrheal morbidity, stunting, and death of children in resource-limited communities around the world. FDA-approved treatments for giardiasis include metronidazole, related nitroimidazole drugs, and albendazole. However, a substantial number of clinical infections are resistant to these treatments. The depth of the challenge is partly exacerbated by a lack of investment in the discovery and development of novel agents for treatment of giardiasis. Applicable interventions must include new drug development strategies that will result in the identification of effective therapeutics, particularly those that are inexpensive and can be quickly advanced to clinical uses, such as products from nature. This study identified novel chemical scaffolds from fungi that can form the basis of future medicinal chemistry optimization of novel antigiardial agents.

N,N-Dimethylaniline and Zno nanoparticles mediated photochemical transformation of metronidazole

The present study evaluates the photochemical behavior of a nitroimidazole derivative drug metronidazole in presence of N,N dimethylaniline and ZnO nanoparticles. The photochemical behavior was examined in a photochemical reactor by irradiating with a light of 254 and 310 nm. After completion of reaction one photoproduct was obtained. The photoproduct was isolated by using column chromatography and the structure of the isolated photoproduct was established by different spectroscopic techniques. This study provides the probable mechanism of the photochemical transformation of metronidazole in presence of an electron donor and in presence of ZnO NPs. During the photochemical transformation the nitro group of metronidazole was reduced in the amine group by a series of electron transfer processes. The ZnO nanoparticles are very efficient catalysts, and they degrade almost 90% metronidazole in the 60 min of UV irradiation. The photocatalytic mechanism of the ZnO nanoparticles is also discussed.

A survey on the anti-Trichomonas vaginalis effect of the hydroalcoholic extract of various medicinal plants in vitro

Background and aims: Trichomoniasis is the most common non-viral sexually transmitted infection worldwide; although it is treated by a 5-nitroimidazole drug family such as metronidazole (MTZ) with numerous side effects, and in this regard, alternative new drugs are required. Therefore, this study examined the anti-Trichomoniasis effect of the hydroalcoholic extract of some traditional medicinal plants of Iran in vitro. Methods: In this experimental study, the hydroalcoholic extracts of medicinal plants were prepared by maceration at a stock concentration of 20 mg/mL in the saline solution and then used for in vitro anti-trichomonas experiments. Trichomonas vaginalis trophozoites were isolated from the patient and cultured in a Trypticase Yeast extract Iron-Serum-33 medium. In addition, 200 μL of the culture medium containing 5×104 trophozoites was diluted in plate wells, and 10 doses were separately added on trophozoites for each extract serially diluted between 0.12 and 16 mg/mL in triplicate. The plates were incubated for 48 hours at 37 ° C with 5% CO2 . The number of trophozoites was counted with a hemocytometer and Trypan blue staining. Finally, the half maximal inhibitory concentration (IC50) was calculated by probit analysis. Results: Among the tested plants, Eugenia caryophyllata, Camellia sinensis, and Terminalia chebula Retz showed the best anti-trichomonal activity with IC50 values of 1.21, 1.62, and 1.66 mg/mL, respectively. All tested extracts had more IC50 than MTZ (IC50 100 mg/mL), an antiprotozoal drug used as a positive control. Conclusion: According to the results of this study, E. caryophylata, C. sinensis and T. chebula Retz affected the growth of T. vaginalis. Thus, it is recommended that other studies use this plant for the treatment of trichomoniasis infection.

A Questionnaire Based Survey with Physicians for Effectiveness and Tolerability of Secnidazole in Periodontitis at Sri Lanka

Background: Periodontitis is a chronic inflammatory disease affecting supportive gingival tissue. Since most of periodontal infections causes orofacial infections, the prescribing of antimicrobials by physician has become important in dental practice. Antimicrobials are the mainstay of the treatment of periodontitis. Objective: To conduct questionnaire-based survey among physicians in Sri Lanka for the effectiveness and tolerability of secnidazole in periodontitis. Methodology: A prospective observational study was conducted for six months with physicians based in Sri Lanka. A questionnaire was prepared in consultation with key opinion leaders, including ten questions which focused on effectiveness and tolerability of 2gm secnidazole in patients with periodontitis. Physician’s voluntary consent was taken for their participation in the survey. Results: A total of forty-one responses were received from physicians, it was observed that 90.2% physicians prescribed antibacterial followed by antiprotozoal in dental infections. Most common symptom for the prescription of secnidazole was in periodontal pus 53.7% accompanied by inflammatory symptoms 46.3%, and bleeding gums. Secnidazole 2gm single dose was preferred by 87.8% physicians for its convenient dosing over the metronidazole, tinidazole and ornidazole. Physicians found secnidazole was good to excellent for effectiveness in 97.6% and tolerability in 97.6% for periodontitis. Conclusion: Secnidazole 2gm single dose was found effective and tolerable in the treatment of periodontitis. It is preferred over the other nitroimidazole drugs like metronidazole, tinidazole and ornidazole for its convenient dosing. From the survey it is observed that, physicians were in favor of Secnidazole for treatment of periodontitis.

Initial expression levels of nimA are decisive for protection against metronidazole in Bacteroides fragilis

ObjectivesIn the genus Bacteroides, the nim genes are resistance determinants for metronidazole, a nitroimidazole drug widely used against anaerobic pathogens. The Nim proteins are considered to act as nitroreductases. However, data from several studies suggest that the expression levels of Nim do not increase with increasing resistance which is conflicting with this notion. The impact of Nim protein levels on low-level metronidazole resistance, however, representing the early stage of induced resistance in the laboratory, has not been assessed as yet. MethodsThe nimA gene was cloned into two different plasmids and introduced into B. fragilis strain 638R. Expression levels of nimA mRNA were measured by RT-qPCR and compared to those in strain 638R harbouring plasmid pI417, the original clinical plasmid harbouring IS element IS1168 with the nimA gene. Further, metronidazole susceptibility was assessed by Etest and the activity of pyruvate:ferredoxin oxidoreductase (PFOR) was measured in all strains after induction of high-level metronidazole resistance. ResultsThe level of protection against metronidazole by nimA correleated with the level of expression of nimA mRNA. Further, the activity of PFOR in highly-resistant B. fragilis 638R was only preserved when expression levels of nimA were high. ConclusionsAlthough the development of high-level metronidazole resistance in B. fragilis strains with a nimA gene is not caused by an increase of nimA expression as compared to the less resistant parent strains, nimA expression levels might be of decisive importance in the early stage of resistance development. This has potential implications for metronidazole resistance in clinical isolates.

In Vitro Effect of 5-Nitroimidazole Drugs against Trichomonas vaginalis Clinical Isolates.

ABSTRACTInfections with the sexually transmitted parasite Trichomonas vaginalis are normally treated with metronidazole, but cure rates are suboptimal and recurrence rates following treatment are high. Therefore, our objective was to assess the in vitro antitrichomonas activities of three other 5-nitroimidazole drugs and compare them with metronidazole. T. vaginalis isolates (n = 94) isolated from South African women presenting with vaginal discharge syndrome at two sexually transmitted disease clinics in KwaZulu-Natal were grown from frozen stock. Twofold serial dilutions (16 to 0.25 mg/L) of metronidazole, tinidazole, ornidazole, and secnidazole were prepared in Diamond’s broth. The MICs were read after 48 h of anaerobic incubation at 37°C. An MIC of <2 mg/L was defined as susceptible, an MIC of 2 mg/L was defined as intermediate, and an MIC of >2 mg/L was defined as resistant. Sixty-one percent (57/94) of the T. vaginalis isolates were susceptible to metronidazole, 80% (75/94) were susceptible to tinidazole, 75% (71/94) were susceptible to secnidazole, and 89% (84/94) were susceptible to ornidazole. Resistance levels were 11%, 2%, and 1% for metronidazole, tinidazole, and secnidazole, respectively, while no resistance was observed for ornidazole. Intermediate scores were 28% for metronidazole, 18% for tinidazole, 24% for secnidazole, and 11% for ornidazole. Isolates from a proportion of women with bacterial vaginosis (BV) had higher MICs, and no isolates from women coinfected with another sexually transmitted infectious organism were resistant to any of the antimicrobials tested. This study showed that among T. vaginalis isolates in KwaZulu-Natal, there is no in vitro resistance to ornidazole. Of the 5-nitroimidazoles, metronidazole showed the highest level of resistance. The very low levels of resistance for the other three antimicrobials indicate that all three are viable options as a replacement for metronidazole if these in vitro findings are found to correlate with clinical outcomes.IMPORTANCE Trichomonas vaginalis is the most common nonviral sexually transmitted infection associated with reproductive sequelae and HIV acquisition risk worldwide. Despite its role in reproductive health, a high prevalence in South Africa, and the reported metronidazole resistance worldwide, no alternative regimens have been tested against T. vaginalis in our setting. This study compared the susceptibility patterns of three other 5-nitroiminazoles (secnidazole, tinidazole, and ornidazole), which are active against T. vaginalis with metronidazole in vitro. Metronidazole, the drug of choice for the treatment of trichomoniasis, showed the highest level of resistance, while the three regimens showed very low levels of resistance. These data indicate that all three are viable options as a replacement for metronidazole if these in vitro findings are found to correlate with clinical outcomes.

Effect of the Symbiosis with Mycoplasma hominis and Candidatus Mycoplasma Girerdii on Trichomonas vaginalis Metronidazole Susceptibility.

Trichomoniasis, the most common non-viral sexually transmitted infection worldwide, is caused by the protozoon Trichomonas vaginalis. The 5- nitroimidazole drugs, of which metronidazole is the most prescribed, are the only effective drugs to treat trichomoniasis. Resistance against metronidazole is increasingly reported among T. vaginalis isolates. T. vaginalis can establish an endosymbiosis with two Mycoplasma species, Mycoplasma hominis and Candidatus Mycoplasma girerdii, whose presence has been demonstrated to influence several aspects of the protozoan pathobiology. The role of M. hominis in T. vaginalis resistance to metronidazole is controversial, while the influence of Ca. M. girerdii has never been investigated. In this work, we investigate the possible correlation between the presence of Ca. M. girerdii and/or M. hominis and the in vitro drug susceptibility in a large group of T. vaginalis isolated in Italy and in Vietnam. We also evaluated, via RNA-seq analysis, the expression of protozoan genes involved in metronidazole resistance in a set of syngenic T. vaginalis strains, differing only for the presence/absence of the two Mycoplasmas. Our results show that the presence of M. hominis significantly increases the sensitivity to metronidazole in T. vaginalis and affects gene expression. On the contrary, the symbiosis with Candidatus Mycoplasma girerdii seems to have no effect on metronidazole resistance in T. vaginalis.

Modulation of Iron Import and Metronidazole Resistance in Bacteroides fragilis Harboring a nimA Gene

Bacteroides fragilis is a commensal of the human gut but can also cause severe infections when reaching other body sites, especially after surgery or intestinal trauma. Bacteroides fragilis is an anaerobe innately susceptible to metronidazole, a 5-nitroimidazole drug that is prescribed against the majority of infections caused by anaerobic bacteria. In most of the cases, metronidazole treatment is effective but a fraction of B. fragilis is resistant to even very high doses of metronidazole. Metronidazole resistance is still poorly understood, but the so-called nim genes have been described as resistance determinants. They have been suggested to encode nitroreductases which reduce the nitro group of metronidazole to a non-toxic aminoimidazole. More recent research, however, showed that expression levels of nim genes are widely independent of the degree of resistance observed. In the search for an alternative model for nim-mediated metronidazole resistance, we screened a strain carrying an episomal nimA gene and its parental strain 638R without a nim gene for physiological differences. Indeed, the 638R daughter strain with the nimA gene had a far higher pyruvate-ferredoxin oxidoreductase (PFOR) activity than the parental strain. High PFOR activity was also observed in metronidazole-resistant clinical isolates, either with or without a nim gene. Moreover, the strain carrying a nimA gene fully retained PFOR activity and other enzyme activities such as thioredoxin reductase (TrxR) after resistance had been induced. In the parental strain 638R, these were lost or very strongly downregulated during the development of resistance. Further, after induction of high-level metronidazole resistance, parental strain 638R was highly susceptible to oxygen whereas the daughter strain with a nimA gene was hardly affected. Ensuing RT-qPCR measurements showed that a pathway for iron import via hemin uptake is downregulated in 638R with induced resistance but not in the resistant nimA daughter strain. We propose that nimA primes B. fragilis toward an alternative pathway of metronidazole resistance by enabling the preservation of normal iron levels in the cell.

Structure‐activity relationships for several series of fragment‐based inhibitors that target Trichomonas vaginalis nucleoside ribohydrolase enzymes

Trichomoniasis, the most common sexually transmitted infection in the world, is caused by the parasitic protozoan Trichomonas vaginalis. Upon infection, T. vaginalis has been known to cause a variety of adverse effects as well as predisposition to other illnesses. Trichomoniasis is commonly treated with 5‐nitroimidazole drugs; however, some strains have developed resistance to these drugs and novel treatments are needed. Since T. vaginalis cannot synthesize nucleobases de novo, it relies on nucleoside ribohydrolases within its pyrimidine and purine salvage pathways in order to acquire nucleobases from its host. Nucleoside ribohydrolases, such as adenosine/guanosine preferring nucleoside ribohydrolase (AGNH) and uridine nucleoside ribohydrolase (UNH), cleave the N‐glycosidic bond of purine and pyrimidine nucleosides resulting in the formation of a nucleobase and a ribose sugar. Inhibiting the AGNH or UNH enzymes would block the salvage pathway resulting in parasite cell death. Fragment screening of AGNH and UNH identified ligand‐efficient scaffolds to serve as medicinal chemistry starting points for drug design. A variety of phenyl pyridine, phenyl pyrimidine, and phenyl pyrazine compounds were then synthesized and screened for inhibitory properties. 1H and 19F NMR‐based activity assays were employed, using adenosine and 5‐fluorouridine as substrates for AGNH and UNH, respectively. It was found that compounds containing a hydroxyl group at the 2‐position resulted in lower IC50 values for AGNH, and that the UNH IC50 was lower for compounds with hydroxy or methoxy functional groups at the 2’ and 3’ positions. With the enzyme inhibition data at hand structure‐activity relationships are being derived and will be used in combination with molecular modeling to design the next generation of compounds to be synthesized. Structural data is also being pursued for both enzymes to guide compound design. Highly purified AGNH and UNH, including selenomethionine‐AGNH, have been prepared for crystallography collaborations.

Efficacy of secnidazole in the treatment of trichomoniasis and vaginal dysbiosis

Introduction. Trichomoniasis is a vaginal infectious and inflammatory disease, which falls into the category of sexually transmissible nosological entities. It is the profile of vaginal microecosystem changes in trichomoniasis that determines the vector of transformation of the vaginal microbiome towards the formation of bacterial vaginosis (BV), namely, a hypercolonized community of anaerobic microorganisms with underlying suppression of the dominant presence of the resident acidophilic microflora.Aim. To evaluate the clinical and bacteriological efficacy of 5-nitroimidazole drugs secnidazole and metronidazole in the therapy of acute trichomoniasis and concomitant vaginal dysbacteriosis.Materials and methods. As a comparison object, we used the therapy regimens for acute trichomoniasis with the 5-nitroimidazole drugs secnidazole and metronidazole, involving 2 grams (g) once as a single dose. The study included 64 patients diagnosed with acute trichomoniasis. The average age of the patients was 34 ± 7 years (95% CI 32–37). The patients were divided into two groups: group 1 (n = 32) used Secnidazole, group 2 (n = 32) used Secnidazole 2 g once as a single dose. Metronidazole was used at a dose of 500 mg 2 times a day for 5 days. Patients were observed by a doctor during two visits, and a follow-up assessment of the treatment results was carried out by way of remote interrogation.Results. The use of the drug therapy ensured removal of Trichomonas from the vagina. Both groups showed relief of clinical symptoms from B1 to B2: discomfort, itching, burning, dyspareunia, hyperemia of the mucosa with underlying tendency towards normalization of laboratory findings of the vaginal microbiocenosis condition. At the same time, it should be noted that the therapy efficiency was higher in group 1 (secnidazole).Conclusion. Thus, the administration of secnidazole provided greater therapeutic efficacy as compared with the use of the similar therapeutic dose and frequency of metronidazole to treat Trichomonas and, in combination with rehabilitation therapy, determined a more pronounced tendency towards normalization of the composition of the vaginal microflora.

Anti-Trichomonas vaginalis activity and chemical analysis of metabolites produced by marine-associated fungi.

Trichomoniasis is the most common non-viral sexually transmitted infection worldwide and it may have serious consequences, especially for women. Currently, 5-nitroimidazole drugs are the treatment of choice for trichomoniasis, although presenting adverse effects and reported cases of drug resistance. Metabolites isolated from marine fungi have attracted considerable attention due to their unique chemical structures with diverse biological activities, including antiprotozoal activity. In this study, we showed the anti-Trichomonas vaginalis activity of fractions obtained from marine fungi and the chemical composition of the most active fraction was determined. Ethyl acetate fractions of the fungus Aspergillus niger (EAE03) and Trichoderma harzianum/Hypocrea lixii complex (EAE09) were active against T. vaginalis. These samples, EAE03 and EAE09, were also effective against the fresh clinical isolate metronidazole-resistant TV-LACM2R, presenting MIC values of 2.0mg/mL and 1.0mg/mL, respectively. The same MIC values were found against ATCC 30,236T. vaginalis isolate. In vitro cytotoxicity revealed only the fraction named EAE03 with no cytotoxic effect; however, the active fractions did not promote a significant hemolytic effect after 1-h incubation. Already, the in vivo toxicity evaluation using Galleria mellonella larvae demonstrated that none of the tested samples caused a reduction in animal survival. The fraction EAE03 was followed for purification steps and analyzed by LC-DAD-MS. Eleven compounds were annotated, including butyrolactone, butanolide, and atromentin. Overall, the range of activities reported confirms the potential of marine fungi to produce bioactive molecules.

Biochemical and structural characterization of Haemophilus influenzae nitroreductase in metabolizing nitroimidazoles.

Nitroheterocycle antibiotics, particularly 5-nitroimidazoles, are frequently used for treating anaerobic infections. The antimicrobial activities of these drugs heavily rely on the in vivo bioactivation, mainly mediated by widely distributed bacterial nitroreductases (NTRs). However, the bioactivation can also lead to severe toxicities and drug resistance. Mechanistic understanding of NTR-mediated 5-nitroimidazole metabolism can potentially aid addressing these issues. Here, we report the metabolism of structurally diverse nitroimidazole drug molecules by a NTR from a human pathogen Haemophilus influenzae (HiNfsB). Our detailed bioinformatic analysis uncovered that HiNfsB represents a group of unexplored oxygen-insensitive NTRs. Biochemical characterization of the recombinant enzyme revealed that HiNfsB effectively metabolizes ten clinically used nitroimidazoles. Furthermore, HiNfsB generated not only canonical nitroreduction metabolites but also stable, novel dimeric products from three nitroimidazoles, whose structures were proposed based on the results of high resolution MS and tandem MS analysis. X-ray structural analysis of the enzyme coupled with site-directed mutagenesis identified four active site residues important to its catalysis and broad substrate scope. Finally, transient expression of HiNfsB sensitized an E. coli mutant strain to 5-nitroimidazoles under anaerobic conditions. Together, these results advance our understanding of the metabolism of nitroimidazole antibiotics mediated by a new NTR group and reinforce the research on the natural antibiotic resistome for addressing the antibiotic resistance crisis.