Imidazolium salts as alternative compounds to control diseases caused by plant pathogenic bacteria.

AIMS: To evaluate the inhibitory effect of five structurally different imidazolium salts on the in vitro growth of plant pathogenic bacteria that belong to divergent taxonomic genera as well as their ability to reduce the severity of common bacterial blight of common bean caused by Xanthomonas axonopodis pv. phaseoli and bacterial speck of tomato caused by Pseudomonas syringae pv. tomato. METHODS AND RESULTS: Growth inhibition of Xanthomonas, Pseudomonas, Erwinia, Pectobacterium and Dickeya strains by imidazolium salts was assessed in vitro by radial diffusion on agar medium and by ressazurin reduction in liquid medium. The reduction of common bacterial blight and bacterial speck symptoms and the area under de disease progress curves were determined by spraying two selected imidazolium salts on healthy plants 48 h prior to inoculation with virulent strains of the bacterial pathogens. All imidazolium salts inhibited the growth of all plant pathogenic bacteria when tested by radial diffusion on agar medium. The strength of inhibition differed among imidazolium salts when tested on the same bacterial strain and among bacterial strains when tested with the same imidazolium salt. In liquid medium, most imidazolium salts presented the same minimum inhibitory concentration (MIC) and minimum bactericidal concentration values (200 µmol l-1 ), the most notable exception of which was the MIC (at least 1000 µmol l-1 ) for the dicationic MImC10 MImBr2 . The imidazolium salts C16 MImBr and C16 MImCl caused significant reductions in the severity of common bacterial blight symptoms when compared with nontreated plants. CONCLUSION: Imidazolium salts inhibit the in vitro growth of plant pathogenic bacteria and reduce plant disease symptoms to levels comparable to an authorized commercial antibiotic product. SIGNIFICANCE AND IMPACT OF THE STUDY: New compounds exhibiting broad-spectrum antibacterial activity with potential use in agriculture were identified.

Assessing an imidazolium salt's performance as antifungal agent on a mouthwash formulation.

AIMS: This study demonstrates the development of a mouthwash formulation containing the imidazolium salt (IMS) 1-n-hexadecyl-3-methylimidazolium chloride (C16 MImCl), considering its stability and efficacy against Candida sp. Biofilm formation. METHODS AND RESULTS: A variety of in vitro test methods were applied, assessing contaminated acrylic resin strip specimens before and after applying the mouthwash formulations. The formulation using C16 MImCl presented a similar antibiofilm activity to cetylpyridinium chloride one and a commercial mouthwash, but at a 10 times lower concentration. Scanning electron microscopy imaging demonstrated that the selected mouthwash preparation fully destroys the biofilm cells, while with the hypoallergenicity test no irritant effect was observed in ex vivo model. CONCLUSIONS: The results presented herein indicate a high potential for imidazolium salts application as mouthwash agents that can eliminate Candida biofilm growth at very low concentrations. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates a new and effective antibiofilm formulation containing the IMS C16 MImCl. These findings suggest the IMS' use as mouthwash formulations active ingredient against Candida biofilms on oral surfaces, as it outperforms the often used cetylpyridinium chloride at a 10 times lower concentration.

Imidazolium salts with antifungal potential for the control of head blight of wheat caused by Fusarium graminearum.

AIMS: Evaluate the in vitro effect of imidazolium salts (IMS) on the conidia germination and mycelial growth of Fusarium graminearum and their in vivo efficacy for suppressing the symptoms of the disease and infection of kernels in wheat plants. METHODS AND RESULTS: The minimum inhibitory concentrations (MIC) of three IMS (C16 MImCl, C16 MImMeS and C16 MImNTf2 ) were determined for four F. graminearum isolates using serial broth dilution method. The MICs found for all IMS were either 3·12 or 6·25 µg ml(-1) across the isolates, with the former as the most frequent. In the mycelial growth assay on potato dextrose agar media, only the C16 MImCl among the IMS reduced 50% of mycelial growth of one isolate at an estimated concentration of 0·32 mg ml(-1) . The time-kill curves showed a strong fungicidal effect starting 1 h after incubation at a concentration of 12·5 µg ml(-1) , representing a fourfold increase in the most frequent MIC. The C16 MImCl sprayed onto the spikes of potted wheat plants during the flowering stage reduced disease intensity at levels comparable to the commercial fungicide when applied preventatively (1 h prior to fungal inoculation), rather than curatively, and at the higher dosage (2 mg ml(-1) ) rather than lower dosage (0·5 mg ml(-1) ). CONCLUSIONS: C16 MImCl proved to be a potent inhibitor of F. graminearum growth and provided good levels of control of the disease at levels comparable to a commercial fungicide, in wheat plants treated prior to fungal infection during flowering stages. SIGNIFICANCE AND IMPACT OF THE STUDY: This study suggests the potential of using IMS as alternative to the hazardous standard fungicides in the management of Fusarium head blight of wheat.

1-n-Hexadecyl-3-methylimidazolium methanesulfonate and chloride salts with effective activities against Candida tropicalis biofilms.

UNLABELLED: Although the use of catheters in critically ill patients is mostly inevitable, this invasive procedure comes together with several health risks. Within this context, the contamination with Candida tropicalis is a primary concern as this highly prevalent pathogenic yeast can develop an extensive polymeric matrix that hinders the drugs' penetration and its effective treatment. This study addresses the potential for the 1-n-hexadecyl-3-methylimidazolium methanesulfonate (C16 MImMeS) and chloride (C16 MImCl) salts for eliminating the viable cells of biofilms of Candida tropicalis, compared to the performance of chlorhexidine (CHX) and fluconazole (FLZ). The minimum concentration required of C16 MImMeS, C16 MImCl, CHX and FLZ for elimination of the biofilm's viable cells (MBEC) was evaluated through microtitre plate biofilm exposure with different concentrations of these substances. These concentrations were determined at 80% of effective activity against the biofilm's viable cells by using the MTT reduction assay. C16 MImMeS and C16 MImCl were able to eliminate the viable cells at much lower concentrations (15·6 and 0·45 µg ml(-1) respectively) than CHX (1250 µg ml(-1) ) and FLZ (resistance of the viable cells). This demonstrates the high potential of these substances for nosocomial infections control. SIGNIFICANCE AND IMPACT OF THE STUDY: The 1-n-hexadecyl-3-methylimidazolium methanesulfonate (C16 MImMeS) and chloride (C16 MImCl) salts are extremely effective in eliminating the viable cells of Candida tropicalis biofilms, which allows the use of much lower concentrations than with the antimicrobial of choice (chlorhexidine) in hospital practices. These findings indicate these imidazolium salts as high-potential candidates for asepsis of medical environments and materials, including implants.

Imidazolium salts with antifungal potential against multidrug-resistant dermatophytes.

AIMS: To investigate the antidermatophytic action of a complementary set imidazolium salts (IMS), determining structure-activity relationships and characterizing the IMS toxicological profiles. METHODS AND RESULTS: The susceptibility evaluation of 45 dermatophytic clinical isolates, treated in vitro with eleven different IMS (ionic compounds) and commercial antifungals (nonionic compounds), was performed by broth microdilution, following the standard norm of CLSI M38-A2. All dermatophytes were inhibited by IMS, where the lowest minimum inhibitory concentration (MIC) values were observed for salts with n-hexadecyl segment in the cation side chain, containing either the chloride or methanesulfonate anion. 1-n-Hexadecyl-3-methylimidazolium chloride (C16 MImCl) and 1-n-hexadecyl-3-methylimidazolium methanesulfonate (C16 MImMeS) acted as fungicides, even in extremely low concentrations, wherein C16 MImMeS exerted this effect on 100% of the tested dermatophytes. Some of these IMS provoked evident alterations on the fungi cell morphology, causing a total cell damage of ≥ 70%. Importantly, none of the screened IMS were cytotoxic, mutagenic or genotoxic to human leucocyte cells. CONCLUSIONS: This report demonstrates for the first time the strong antifungal potential of IMS against multidrug-resistant dermatophytes, without presenting toxicity to human leucocyte cells at MIC. SIGNIFICANCE AND IMPACT OF THE STUDY: The expressive antifungal activity of IMS, combined with the in vitro nontoxicity, makes them promising compounds for the safe and effective treatment of dermatophytoses, mainly when this skin mycosis is unresponsive to conventional drugs.

Imidazolium salts as antifungal agents: strong antibiofilm activity against multidrug-resistant Candida tropicalis isolates.

UNLABELLED: The in vitro activity of the imidazolium salt C16 MImCl against planktonic and biofilm cells of multidrug-resistant isolates of Candida tropicalis was evaluated, both in solution and applied on a commercial catheter surface. This was determined by inhibition and susceptibility assays of biofilm and planktonic cells. In both cases, C16 MImCl prevented in vitro biofilm formation of C. tropicalis strains, including multidrug-resistant ones. Outstanding performances were observed, even at extremely low concentrations. Furthermore, this is the first report of the antifungal lock property of C16 MImCl, using a tracheal catheter as the test specimen to mimic a clinical in vivo condition. As such, C16 MImCl has been identified as a promising antimicotic pharmaceutical candidate for the treatment of candidiasis infections. SIGNIFICANCE AND IMPACT OF THE STUDY: The imidazolium salt 1-n-hexadecyl-3-methylimidazolium chloride (C16 MImCl) strongly prevents, in concentrations as low as 0·028 µg ml(-1) , the biofilm formation of multidrug-resistant Candida tropicalis isolates, either in solution or applied on the surface of commercial catheters. This presents an effective antimicotic candidate and alternative for invasive clinical procedure toolset asepsis.