Promising Anti-Biofilm Agents and Phagocytes Enhancers for the Treatment of Candida albicans Biofilm–Associated Infections

Evaluation of antifungal spectrum of Cupferron against Candida albicans

Candida albicans is an opportunistic yeast accounting for about 50-90 % of all cases of candidiasis in humans, ranging from superficial to systemic potentially life-threatening infections. The presence of several virulence factors, including biofilm, hyphal transition, and proteolytic enzymes production, worsens the fungal infections burden on healthcare system resources. Hence, developing new bioactive compounds with antifungal activity is a pressing urgence for the scientific community. In this perspective, we evaluated the anti-Candida potential of the N-Nitroso-N-phenylhydroxylamine ammonium salt (cupferron) against standard and clinical C. albicans strains. Firstly, the in vitro cytotoxicity of cupferron was checked in the range 400-12.5 μg/mL against human microglial cells (HMC-3). Secondly, its antifungal spectrum was explored via disk diffusion test, broth-microdilution method, and time-killing curve analysis, validating the obtained results through scanning electron microscopy (SEM) observations. Additionally, we evaluated the cupferron impact on the main virulence determinants of Candida albicans. At non-toxic concentrations (100-12.5 μg/mL), the compound exerted interesting anti-Candida activity, registering a minimum inhibitory concentration (MIC) between 50 and 100 μg/mL against the tested strains, with a fungistatic effect until 100 μg/mL. Furthermore, cupferron was able to counteract fungal virulence at MIC and sub-MIC values (50-12.5 μg/mL). These findings may propose cupferron as a new potential antifungal option for the treatment of Candida albicans infections.

Fighting Emerging Caspofungin-Resistant Candida Species: Mitigating Fks1-Mediated Resistance and Enhancing Caspofungin Efficacy by Chitosan

Invasive candidiasis poses a worldwide threat because of the rising prevalence of antifungal resistance, resulting in higher rates of morbidity and mortality. Additionally, Candida species, which are opportunistic infections, have significant medical and economic consequences for immunocompromised individuals. This study explores the antifungal potential of chitosan to mitigate caspofungin resistance in caspofungin-resistant Candida albicans, C. krusei, and C. tropicalis isolates originating from human and animal sources using agar well diffusion, broth microdilution tests, and transmission electron microscope (TEM) analysis of treated Candida cells. Reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) was performed to assess the expression of SAGA complex genes (GCN5 and ADA2) and the caspofungin resistance gene (FKS) in Candida species isolates after chitosan treatment. The highest resistance rate was observed to ketoconazole (80%) followed by clotrimazole (62.7%), fluconazole (60%), terbinafine (58%), itraconazole (57%), miconazole (54.2%), amphotericin B (51.4%), voriconazole (34.28%), and caspofungin (25.7%). Nine unique FKS mutations were detected, including S645P (n = 3 isolates), S645F, L644F, S645Y, L688M, E663G, and F641S (one isolate in each). The caspofungin minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values before chitosan treatment ranged from 2 to 8 µg/mL and 4 to 16 µg/mL, respectively. However, the MIC and MFC values were decreased after chitosan treatment (0.0625-1 µg/mL) and (0.125-2 µg/mL), respectively. Caspofungin MIC was significantly decreased (p = 0.0007) threefold following chitosan treatment compared with the MIC values before treatment. TEM analysis revealed that 0.5% chitosan disrupted the integrity of the cell surface, causing irregular morphologies and obvious aberrant changes in cell wall thickness in caspofungin-resistant and sensitive Candida isolates. The cell wall thickness of untreated isolates was 0.145 μm in caspofungin-resistant isolate and 0.125 μm in sensitive isolate, while it was significantly lower in chitosan-treated isolates, ranging from 0.05 to 0.08 μm when compared with the cell wall thickness of sensitive isolate (0.03 to 0.06 μm). Moreover, RT-qPCR demonstrated a significant (p < 0.05) decrease in the expression levels of histone acetyltransferase genes (GCN5 and ADA2) and FKS gene of caspofungin-resistant Candida species isolates treated with 0.5% chitosan when compared with before treatment (fold change values ranged from 0.001 to 0.0473 for GCN5, 1.028 to 4.856 for ADA2, and 2.713 to 12.38 for FKS gene). A comparison of the expression levels of cell wall-related genes (ADA2 and GCN5) between caspofungin-resistant and -sensitive isolates demonstrated a significant decrease following chitosan treatment (p < 0.001). The antifungal potential of chitosan enhances the efficacy of caspofungin against various caspofungin-resistant Candida species isolates and prevents the development of further antifungal resistance. The results of this study contribute to the progress in repurposing caspofungin and inform a development strategy to enhance its efficacy, appropriate antifungal activity against Candida species, and mitigate resistance. Consequently, chitosan could be used in combination with caspofungin for the treatment of candidiasis.

Genomic epidemiology of antifungal resistance in human and avian isolates of Candida albicans: a pilot study from the One Health perspective

Stress-induced genomic changes in Candida albicans contribute to the adaptation of this species to various environmental conditions. Variations of the genome composition of animal-origin C. albicans strains are largely unexplored and drug resistance or other selective pressures driving the evolution of these yeasts remained an intriguing question. Comparative genome analysis was carried out to uncover chromosomal aneuploidies and regions with loss of heterozygosity (LOH), two mechanisms that manage genome plasticity. We detected aneuploidy only in human isolates. Bird-derived isolates showed LOH in genes commonly associated with antifungal drug resistance similar to human isolates. Our study suggests that environmental fungicide usage might exert selective pressure on C. albicans infecting animals, thus contributing to the spread of potentially resistant strains between different hosts.

Combating Cariogenic Streptococcus mutans Biofilm Formation and Disruption with Coumaric Acid on Dentin Surface

Streptococcus mutans, the primary cause of dental caries, relies on its ability to create and sustain a biofilm (dental plaque) for survival and pathogenicity in the oral cavity. This study was focused on the antimicrobial biofilm formation control and biofilm dispersal potential of Coumaric acid (CA) against Streptococcus mutans on the dentin surface. The biofilm was analyzed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) viability assay, microtiter plate assay, production of extracellular polymeric substances (EPSs), florescence microscopy (surface coverage and biomass μm2) and three-dimensional (3D) surface plots. It was observed that CA at 0.01 mg/mL reduced bacterial growth by 5.51%, whereases at 1 mg/mL, a significant (p < 0.05) reduction (98.37%) was observed. However, at 1 mg/mL of CA, a 95.48% biofilm formation reduction was achieved, while a 73.45% biofilm dispersal (after 24 h. treatment) was achieved against the preformed biofilm. The MTT assay showed that at 1 mg/mL of CA, the viability of bacteria in the biofilm was markedly (p < 0.05) reduced to 73.44%. Moreover, polysaccharide (EPS) was reduced to 24.80 μg/mL and protein (EPS) to 41.47 μg/mL. ImageJ software (version 1.54 g) was used to process florescence images, and it was observed that the biofilm mass was reduced to 213 (μm2); the surface coverage was reduced to 0.079%. Furthermore, the 3D surface plots showed that the untreated biofilm was highly dense, with more fibril-like projections. Additionally, molecular docking predicted a possible interaction pattern of CA (ligand) with the receptor Competence Stimulating Peptide (UA159sp, PDB ID: 2I2J). Our findings suggest that CA has antibacterial and biofilm control efficacy against S. mutans associated with dental plaque under tested conditions.

The growth inhibitory and apoptotic effects of umbelliprenin in a mouse model of systemic candidiasis

AIMS

Umbelliprenin has shown promising biological activities, including immunoregulatory, anti-inflammatory, and anti-cancer effects. The present study investigated the growth inhibitory and apoptotic effects of umbelliprenin against Candida albicans in a BALB/c mice model of disseminated candidiasis.

METHODS AND RESULTS

First, an antimicrobial assay via microdilution sensitivity test was performed. Then, twenty-five 6-week-old female BALB/c mice (20 ± 12 g) were divided into five groups of five mice, including one control group (no umbelliprenin treatment) and four experimental groups: C. albicans-infected mice treated with umbelliprenin at the doses of 5, 10, 20, and 40 mg kg -1. The brain, lung, kidney, spleen, and liver tissues were examined for fungal infection and histological lesions, and TUNEL staining was performed to assess apoptosis. The β-1, 3-glucan synthase assay was used to evaluate enzymatic activity, and gene expression analysis was also performed to investigate the transcriptional changes of ERG11, CDR1, ALS1, and HWP1 genes. The MIC of umbelliprenin was 1.5 mg mL-1. Our results showed that at the 40 mg kg -1 dose, umbelliprenin was able to eradicate fungal infection in BALB/c mice. The percentage of apoptotic cells in umbelliprenin-treated groups increased in a concentration-dependent manner. Umbelliprenin (40 mg kg -1) also inhibited the expression of β-1, 3-glucan synthase, and the genes involved in antifungal resistance (CDR1 and ERG11), as well as the expression of the genes encoding adhesins (ALS1 and HWP1).

CONCLUSION

Our results showed that umbelliprenin could promote antifungal effects, partly via inducing apoptosis.

Antibiotic Resistance: Challenges and Strategies in Combating Infections

From a broader perspective, antibiotic or antimicrobial resistance is still evolving and spreading internationally. Infectious diseases have become more complex and often impossible to cure, increasing morbidity and mortality. Despite the failure of conventional, standard antimicrobial therapy, no new class of antibiotics has been developed in the last 20 years, which results in various cutting-edge and other tactics that can be used to encounter these disease-causing microorganisms with antibiotic resistance. In the continued fight against bacterial infections, there is an urgent requirement for new antibiotics and other antimicrobials. Antibiotic resistance is inevitable, and pharmaceutical companies consistently show little interest in funding novel antibiotic research. Some methods are being used as a possible replacement for conventional antibiotics. Combination therapy, methods that target the proteins or enzymes that cause antimicrobial resistance and bacterial resistance, systems for delivery of the drug, physicochemical approaches, and informal ways, such as the CRISPR-Cas system, are some of these approaches. These various approaches influence how multi-drug-resistant organisms are handled in human clinical settings.

Molecular epidemiology of Candida albicans infections revealed dominant genotypes in waterfowls diagnosed with esophageal mycosis

Fungal infections of animals could yield significant economic losses, especially in the poultry industry, due to their adverse effects on growth, feed intake, digestion, and reproduction. Previous investigations showed that Candida albicans plays the main etiological role in the esophageal mycosis of birds. In this study, we used multilocus sequence typing (MLST) to determine the population structure and molecular epidemiology of C. albicans isolated from geese and ducks in Hungary. Interestingly, only three known genotypes were identified among investigated flocks, namely, diploid sequence type (DST) 840, DST 656, and DST 605, suggesting the intra-species transmission of these genotypes. Additionally, two novel allele combinations (new DSTs) were found that have not been previously submitted to the MLST database. Phylogenetic analysis of isolates revealed a close relationship between DST 656 and DST 605 as well as between the two newly identified genotypes (designated DST 3670 and DST 3671). Although isolates from birds belonged to minor clades in contrast with most human isolates, no species-specificity was observed. Poultry-derived isolates were group founders or closely related to group founders of clonal complexes, suggesting that C. albicans is exposed to lesser selective pressure in animal hosts. The increasing number of genetic information in the C. albicans MLST database could help to reveal the epidemiological characteristics and evolutionary pathways that are essential for disease prevention strategies.

Biotechnological applications of biofilms formed by osmotolerant and halotolerant yeasts

Many microorganisms are capable of developing biofilms under adverse conditions usually related to nutrient limitation. They are complex structures in which cells (in many cases of different species) are embedded in the material that they secrete, the extracellular matrix (ECM), which is composed of proteins, carbohydrates, lipids, and nucleic acids. The ECM has several functions including adhesion, cellular communication, nutrient distribution, and increased community resistance, this being the main drawback when these microorganisms are pathogenic. However, these structures have also proven useful in many biotechnological applications. Until now, the most interest shown in these regards has focused on bacterial biofilms, and the literature describing yeast biofilms is scarce, except for pathological strains. Oceans and other saline reservoirs are full of microorganisms adapted to extreme conditions, and the discovery and knowledge of their properties can be very interesting to explore new uses. Halotolerant and osmotolerant biofilm-forming yeasts have been employed for many years in the food and wine industry, with very few applications in other areas. The experience gained in bioremediation, food production and biocatalysis with bacterial biofilms can be inspiring to find new uses for halotolerant yeast biofilms. In this review, we focus on the biofilms formed by halotolerant and osmotolerant yeasts such as those belonging to Candida, Saccharomyces flor yeasts, Schwannyomyces or Debaryomyces, and their actual or potential biotechnological applications. KEY POINTS: • Biofilm formation by halotolerant and osmotolerant yeasts is reviewed. • Yeasts biofilms have been widely used in food and wine production. • The use of bacterial biofilms in bioremediation can be expanded to halotolerant yeast counterparts.

Biofilm Formation and Phospholipase and Proteinase Production in Cryptococcus neoformans Clinical Isolates and Susceptibility towards Some Bioactive Natural Products

Background. Cryptococcosis is one of the most common fungal infections in immunocompromised patients, which is caused by Cryptococcus neoformans. However, relatively little is known about the virulence factors of C. neoformans and the incidence of antifungal drug resistance in C. neoformans is rapidly increasing. This study was undertaken to investigate the virulence factors in C. neoformans, thymol, curcumin, piperine, gallic acid, eugenol, and plumbagin for their potential antimicrobial activity against C. neoformans. Methods. The production of phospholipase and proteinase was detected using standard methods. Biofilm formation was determined using the microtiter plate method. The broth microdilution method was used to determine the antifungal activity. The antibiofilm activity was assessed using the safranin staining method. Results. All isolates of C. neoformans produced biofilms with optical density values ranging from 0.16 to 0.89. A majority of C. neoformans isolates that were tested exhibited strong phospholipase (7/8) and proteinase (5/8) production. Plumbagin (with minimum inhibitory concentration values ranging from 4 to 16 μg/mL) showed the highest antifungal activity followed by thymol (with minimum biofilm inhibitory concentration values ranging from 8 to 64 μg/mL). In addition, plumbagin showed the highest antibiofilm activity with minimum biofilm inhibitory concentration and minimum biofilm eradication concentration values ranging from 4 to 16 μg/mL and 32 to 256 μg/mL, respectively. Conclusion. Plumbagin, compared to other natural products studied, was the most efficient in terms of antifungal and antibiofilm activities. Hence, plumbagin could be used in combination with antifungals for the development of new anticryptococcal drugs.

Bioactive metabolites of Streptomyces misakiensis display broad-spectrum antimicrobial activity against multidrug-resistant bacteria and fungi

Background

Antimicrobial resistance is a serious threat to public health globally. It is a slower-moving pandemic than COVID-19, so we are fast running out of treatment options.

Purpose

Thus, this study was designed to search for an alternative biomaterial with broad-spectrum activity for the treatment of multidrug-resistant (MDR) bacterial and fungal pathogen-related infections.

Methods

We isolated Streptomyces species from soil samples and identified the most active strains with antimicrobial activity. The culture filtrates of active species were purified, and the bioactive metabolite extracts were identified by thin-layer chromatography (TLC), preparative high-performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) spectroscopy, and gas chromatography-mass spectrometry (GC-MS). The minimum inhibitory concentrations (MICs) of the bioactive metabolites against MDR bacteria and fungi were determined using the broth microdilution method.

Results

Preliminary screening revealed that Streptomyces misakiensis and S. coeruleorubidus exhibited antimicrobial potential. The MIC₅₀ and MIC₉₀ of S. misakiensis antibacterial bioactive metabolite (ursolic acid methyl ester) and antifungal metabolite (tetradecamethylcycloheptasiloxane) against all tested bacteria and fungi were 0.5 μg/ml and 1 μg/mL, respectively, versus S. coeruleorubidus metabolites: thiocarbamic acid, N,N-dimethyl, S-1,3-diphenyl-2-butenyl ester against bacteria (MIC₅₀: 2 μg/ml and MIC₉₀: 4 μg/mL) and fungi (MIC₅₀: 4 μg/ml and MIC₉₀: 8 μg/mL). Ursolic acid methyl ester was active against ciprofloxacin-resistant strains of Streptococcus pyogenes, S. agalactiae, Escherichia coli, Klebsiella pneumoniae, and Salmonella enterica serovars, colistin-resistant Aeromonas hydrophila and K. pneumoniae, and vancomycin-resistant Staphylococcus aureus. Tetradecamethylcycloheptasiloxane was active against azole- and amphotericin B-resistant Candida albicans, Cryptococcus neoformans, C. gattii, Aspergillus flavus, A. niger, and A. fumigatus. Ursolic acid methyl ester was applied in vivo for treating S. aureus septicemia and K. pneumoniae pneumonia models in mice. In the septicemia model, the ursolic acid methyl ester-treated group had a significant 4.00 and 3.98 log CFU/g decrease (P < 0.05) in liver and spleen tissue compared to the infected, untreated control group. Lung tissue in the pneumonia model showed a 2.20 log CFU/g significant decrease in the ursolic acid methyl ester-treated group in comparison to the control group. The haematological and biochemical markers in the ursolic acid methyl ester-treated group did not change in a statistically significant way. Moreover, no abnormalities were found in the histopathology of the liver, kidneys, lungs, and spleen of ursolic acid methyl ester-treated mice in comparison with the control group.

Conclusion

S. misakiensis metabolite extracts are broad-spectrum antimicrobial biomaterials that can be further investigated for the potential against MDR pathogen infections. Hence, it opens up new horizons for exploring alternative drugs for current and reemerging diseases.

Antibiotic resistance: The challenges and some emerging strategies for tackling a global menace

Background

Antibiotic resistance is currently the most serious global threat to the effective treatment of bacterial infections. Antibiotic resistance has been established to adversely affect both clinical and therapeutic outcomes, with consequences ranging from treatment failures and the need for expensive and safer alternative drugs to the cost of higher rates of morbidity and mortality, longer hospitalization, and high‐healthcare costs. The search for new antibiotics and other antimicrobials continues to be a pressing need in humanity's battle against bacterial infections. Antibiotic resistance appears inevitable, and there is a continuous lack of interest in investing in new antibiotic research by pharmaceutical industries. This review summarized some new strategies for tackling antibiotic resistance in bacteria.

Methods

To provide an overview of the recent research, we look at some new strategies for preventing resistance and/or reviving bacteria's susceptibility to already existing antibiotics.

Results

Substantial pieces of evidence suggest that antimicrobials interact with host immunity, leading to potent indirect effects that improve antibacterial activities and may result in more swift and complete bactericidal effects. A new class of antibiotics referred to as immuno‐antibiotics and the targeting of some biochemical resistance pathway components including inhibition of SOS response and hydrogen sulfide as biochemical underlying networks of bacteria can be considered as new emerging strategies to combat antibiotic resistance in bacteria.

Conclusion

This review highlighted and discussed immuno‐antibiotics and inhibition of SOS response and hydrogen sulfide as biochemical underlying networks of bacteria as new weapons against antibiotic resistance in bacteria.