Treatment of vaginitis caused by non-albicans Candida species

INTRODUCTION

In the face of increased frequency of non-albicans Candida vulvovaginitis (VVC) reported worldwide, there is a paucity of effective oral and topical antifungal drugs available. Drug selection is further handicapped by an absence of data of clinical efficacy of available antifungal drugs for these infections.

AREAS COVERED

In this review, attention is directed at the cause of drug shortage as well as increased frequency of non-albicans Candida (NAC) vulvovaginitis. There is widespread recognition of reduced in vitro azole drug susceptibility in NAC species. Moreover, antifungal susceptibility tests have not been standardized or validated for NAC isolates, hence clinicians rely on an element of empiricism especially given the absence of randomized controlled comparative studies targeting NAC species. Clinical spectrum of NAC species isolates is highly variable with ongoing difficulty in determining a causal role in symptomatic patients.

EXPERT OPINION

We have entered the era of demand for Candida species-specific therapy and although consensus treatment guidelines are emerging, new antifungal agents that target these multiple-azole resistant or relatively resistant vaginal NAC species are urgently needed.

MALDI-TOF mass spectrometry identification and antifungal susceptibility testing of yeasts causing vulvovaginal candidiasis (VVC) in Tebessa (Northeastern Algeria)

Vulvovaginal candidiasis (VVC) alongside with antifungal resistance are becoming a major clinical problem in recent years. A prospective study aimed to evaluate the diversity of yeast strains associated with VVC in Tebessa city (northeastern Algeria) and investigate their susceptibility patterns. Over two months, yeasts were isolated on chromogenic medium from twenty-nine non-pregnant women with symptomatic VVC. The isolates were characterized with MALDI-TOF MS and antifungal susceptibility testing was performed for nine antifungal drugs using SensititreTM YeastOneTM YO10. Twenty-nine non-duplicate yeasts were recovered and the mass spectrometry profiles showed reliable scores of which four genera and five different species were identified. Candida albicans accounted for 65.5 % (n = 19) of the total number of isolates, followed by C. glabrata with 20.7% (n = 6). For the remaining non-albicans Candida (NCA) species, Kluyveromyces marxianus with 6.9% (n = 2), Pichia kudriavzevii and Saccharomyces cerevisiae with one isolate each. The antifungal susceptibilities showed wild type MICs of C. albicans to amphotericin B, azoles and echinocandins. In addition, four C. albicans isolates were resistant to flucytosine. For C. glabrata isolates, 100% non-WT phenotype was found for both posaconazole and itraconazole. For the very first time, the obtained outcomes bring out new data concerning the epidemiology of yeasts causing VVC in Algeria and their antimicrobial susceptibility profiles.

Similarity searching for anticandidal agents employing a repurposing approach

Fungal infections caused by Candida are still a public health concern. Particularly, the resistance to traditional chemotherapeutic agents is a major issue that requires efforts to develop new therapies. One of the most interesting approaches to finding new active compounds is drug repurposing aided by computational methods. In this work, two databases containing anticandidal agents and drugs were studied employing cheminformatics and compared by similarity methods. The results showed 36 drugs with high similarities to some candicidals. From these drugs, trimetozin, osalmid and metochalcone were evaluated against C. albicans (18804), C. glabrata (90030), and miconazole-resistant strain C. glabrata (32554). Osalmid and metochalcone were the best, with activity in the micromolar range. These findings represent an opportunity to continue with the research on the potential antifungal application of osalmid and metochalcone as well as the design of structurally related derivatives.

Inhibitors of 3-Hydroxy-3-methylglutaryl Coenzyme A Reductase Decrease the Growth, Ergosterol Synthesis and Generation of petite Mutants in Candida glabrata and Candida albicans

Candida glabrata and Candida albicans, the most frequently isolated candidiasis species in the world, have developed mechanisms of resistance to treatment with azoles. Among the clinically used antifungal drugs are statins and other compounds that inhibit 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR), resulting in decreased growth and ergosterol levels in yeasts. Ergosterol is a key element for the formation of the yeast cell membrane. However, statins often cause DNA damage to yeast cells, facilitating mutation and drug resistance. The aim of the current contribution was to synthesize seven series of compounds as inhibitors of the HMGR enzyme of Candida ssp., and to evaluate their effect on cellular growth, ergosterol synthesis and generation of petite mutants of C. glabrata and C. albicans. Compared to the reference drugs (fluconazole and simvastatin), some HMGR inhibitors caused lower growth and ergosterol synthesis in the yeast species and generated fewer petite mutants. Moreover, heterologous expression was achieved in Pichia pastoris, and compounds 1a, 1b, 6g and 7a inhibited the activity of recombinant CgHMGR and showed better binding energy values than for α-asarone and simvastatin. Thus, we believe these are good candidates for future antifungal drug development.

Cinnamaldehyde Loaded Poly(lactide-co-glycolide) (PLGA) Microparticles for Antifungal Delivery Application against Resistant Candida albicans and Candida glabrata

Researchers have explored natural products to combat the antibiotic resistance of various microorganisms. Cinnamaldehyde (CIN), a major component of cinnamon essential oil (CC-EO), has been found to effectively inhibit the growth of bacteria, fungi, and mildew, as well as their production of toxins. Therefore, this study aimed to create a delivery system for CIN using PLGA microparticles (CIN-MPs), and to compare the antifungal activity of the carried and free CIN, particularly against antibiotic-resistant strains of Candida spp. The first part of the study focused on synthesizing and characterizing the PLGA MPs, which had no toxic effects in vivo and produced results in line with the existing literature. The subsequent experiments analyzed the antifungal effects of MPs-CIN on Candida albicans and Candida glabrata, both resistant (R) and sensitive (S) strains and compared its efficacy with the conventional addition of free CIN to the culture medium. The results indicated that conveyed CIN increased the antifungal effects of the product, particularly towards C. albicans R. The slow and prolonged release of CIN from the PLGA MPs ensured a constant and uniform concentration of the active principle within the cells.

Anti-Candidal Activity of Reboxetine and Sertraline Antidepressants: Effects on Pre-Formed Biofilms

Reboxetine (REB) and sertraline (SER) are antidepressants. The antifungal potential of these drugs against planktonic Candida has been recently reported with limited data about their effects on Candidal biofilms. Biofilms are self-derived extracellular matrixes produced by the microbial population that is attached to biotic surfaces, such as vaginal and oral mucosa, or abiotic surfaces, such as biomedical devices, resulting in persistent fungal infections. The commonly prescribed antifungals, azoles, are usually less effective when biofilms are formed, and most of the prescribed antifungals are only fungistatic. Therefore, the current study investigates the antifungal potentials of REB and SER, alone and in combination with fluconazole (FLC) and itraconazole (ITR) against Candidal biofilms. Using proper controls, Candida species (Candida albicans, C. albicans; Candida krusei, C. krusei; and Candida glabrata, C. glabrata) were used to form biofilms in 96-well microplates. Serial dilutions corresponding to concentrations ranging from 2 to 4096 µg/mL of the target drugs (REB, SER, FLC, ITR) were prepared and added to the plates. Impairment of the biofilm biomass and biofilm metabolic viability was detected using the crystal violet (CV) assay and 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay, respectively. In the checkerboard assay, the sessile fractional inhibitory concentration index (SFICI) was calculated to evaluate the effects of drug combinations. SER was more effective in reducing the biomass than REB for C. albicans and C. glabrata, but both were equal for C. krusei. For the reduction in metabolic activity in C. albicans and C. glabrata, SER had a slight advantage over REB. In C. krusei, REB was slightly more potent. Overall, FLC and ITR were almost equal and produced more significant reductions in metabolic activity when compared to SER and REB, except for C. glabrata, where SER was almost equal to FLC. Synergism was detected between REB + FLC and REB + ITR against biofilm cells of C. albicans. Synergism was detected between REB + ITR against biofilm cells of C. krusei. Synergism was detected between REB + FLC and REB + ITR against biofilm cells of C. albicans, C. krusei, and C. glabrata. The results of the present study support the potential of SER and REB as anti-Candidal biofilm agents that are beneficial as a new antifungal to combat Candidal resistance.

Commiphora wildii Merxm. Essential Oil: Natural Heptane Source and Co-Product Valorization

As an alternative to fossil volatile hydrocarbon solvents used nowadays in perfumery, investigation on essential oil of Commiphora wildii Merxm. oleo gum resin as a source of heptane is reported here. Heptane, representing up to 30 wt-% of this oleo gum resin, was successfully isolated from the C. wildii essential oil, using an innovative double distillation process. Isolated heptane was then used as a solvent in order to extract some noble plants of perfumery. It was found that extracts obtained with this solvent were more promising in terms of sensory analysis than those obtained from fossil-based heptane. In addition, in order to valorize the essential oil depleted from heptane, chemical composition of this oil was found to obtain, and potential biological activity properties were studied. A total of 172 different compounds were identified by GC-MS in the remaining oil. In vitro tests-including hyaluronidase, tyrosinase, antioxidant, elastase and lipoxygenase, as well as inhibitory tests against two yeasts and 21 bacterial strains commonly found on the skin-were carried out. Overall, bioassays results suggest this heptane-depleted essential oil is a promising active ingredient for cosmetic applications.

Evaluation of the Post-Antifungal Effect of Rezafungin and Micafungin against Candida albicans, Candida parapsilosis, and Candida glabrata

BACKGROUND

Rezafungin, a new echinocandin with an extended half-life, exhibits potent activity against Candida spp. Aside from the MIC, specific interactions between antifungal and isolate, including the duration of anti-infective activity, may impact dose interval choices and infection outcome.

OBJECTIVES

We evaluated rezafungin and micafungin post-antifungal effect (PAFE) against C. albicans, C. parapsilosis, and C. glabrata.

METHODS

Six Candida spp. isolates were tested, including 2 of each species, C. albicans, C. parapsilosis, and C. glabrata. Antifungal susceptibility testing was performed using the CLSI reference broth microdilution method. Antifungal concentrations of 1X, 4X, and 16X the baseline MIC were used for PAFE determinations. Colony counts were performed at T0 (pre-exposure), after the 1-h drug exposure, after the cell wash (T1), and at T2, T4, T8, T12, T24, and T48 hours.

RESULTS

Rezafungin PAFE results were equivalent to micafungin PAFE values for one C. albicans (>14.9 h and both C. glabrata (>40 h) isolates for all concentrations tested. The rezafungin and micafungin PAFEs could not be determined against one C. albicans isolate. Prolonged PAFE results were also noted for rezafungin (range, 18.4 h to >40 h) against both C. parapsilosis isolates at all concentrations, while no micafungin PAFE or a short PAFE (range, 1.8 h to 7.4 h) was observed against these organisms, except at 16X bMIC.

CONCLUSIONS

Rezafungin showed sustained growth inhibition following drug removal and displayed equivalent or longer PAFE values than micafungin against all tested Candida spp.

Elucidating the lactic acid tolerance mechanism in vaginal clinical isolates of Candida glabrata

Incidence of vulvovaginal candidiasis are strikingly high and treatment options are limited with nearly 50% Candida glabrata cases left untreated or experience treatment failures. The vaginal microenvironment is rich in lactic acid, and the adaptation of C. glabrata to lactic acid (LA) is the main reason for clinical treatment failure. In the present study, C. glabrata and its vaginal clinical isolates were comprehensively investigated for their growth response, metabolic adaptation and altered cellular pathway to LA using different biochemical techniques, metabolic profiling and transcriptional studies. C. glabrata shown considerable variations in its topological and biochemical features without compromising growth in LA media. Chemical profiling data highlighted involvement of cell wall/membrane, ergosterol and oxidative stress related pathways in mediating adaptative response of C. glabrata towards LA. Further, one dimensional proton (1H) NMR spectroscopy based metabolic profiling revealed significant modulation in 19 metabolites of C. glabrata cells upon growth in LA. Interestingly myo-inositol, xylose, putrescine and betaine which are key metabolites for cell growth and viability were found to be differentially expressed by clinical isolates. These observations were supported by the transcriptional expression study of selected genes evidencing cell wall/membrane re-organisation, altered oxidative stress, and reprogramming of carbon metabolic pathways. Collectively, the study advances our understanding on adaptative response of C. glabrata in vaginal microenvironment to lactic acid for survival and virulence.

Amphotericin B Polymer Nanoparticles Show Efficacy against Candida Species Biofilms

Purpose: Chronic infections of Candida albicans are characterised by the embedding of budding and entwined filamentous fungal cells into biofilms. The biofilms are refractory to many drugs and Candida biofilms are associated with ocular fungal infections. The objective was to test the activity of nanoparticulate amphotericin B (AmB) against Candida biofilms. Methods: AmB was encapsulated in the Molecular Envelope Technology (MET, N-palmitoyl-N-monomethyl-N,N-dimethyl-N,N,N-trimethyl-6-O-glycolchitosan) nanoparticles and tested against Candida biofilms in vitro. Confocal laser scanning microscopy (CLSM) imaging of MET nanoparticles’ penetration into experimental biofilms was carried out and a MET-AmB eye drop formulation was tested for its stability. Results: MET-AmB formulations demonstrated superior activity towards C. albicans biofilms in vitro with the EC50 being ~30 times lower than AmB alone (EC50 MET-AmB = 1.176 μg mL⁻¹, EC50 AmB alone = 29.09 μg mL⁻¹). A similar superior activity was found for Candida glabrata biofilms, where the EC50 was ~10× lower than AmB alone (EC50 MET-AmB = 0.0253 μg mL⁻¹, EC50 AmB alone = 0.289 μg mL⁻¹). CLSM imaging revealed that MET nanoparticles penetrated through the C. albicans biofilm matrix and bound to fungal cells. The activity of MET-AmB was no different from the activity of AmB alone against C. albicans cells in suspension (MET-AmB MIC90 = 0.125 μg mL⁻¹, AmB alone MIC90 = 0.250 μg mL⁻¹). MET-AmB eye drops were stable at room temperature for at least 28 days. Conclusions: These biofilm activity findings raise the possibility that MET-loaded nanoparticles may be used to tackle Candida biofilm infections, such as refractory ocular fungal infections.

A Systematic Study of the Antibacterial Activity of Basidiomycota Crude Extracts

The excessive consumption of antibiotics in clinical, veterinary and agricultural fields has resulted in tremendous flow of antibiotics into the environment. This has led to enormous selective pressures driving the evolution of antimicrobial resistance genes in pathogenic and commensal bacteria. In this context, the World Health Organization (WHO) has promoted research aiming to develop medical features using natural products that are often competitive with synthetic drugs in clinical performance. Fungi are considered an important source of bioactive molecules, often effective against other fungi and/or bacteria, and thus are potential candidates in the search of new antibiotics. Fruiting bodies of sixteen different fungal species of Basidiomycota were collected in the Italian Alps. The identification of fungal species was performed through Internal Transcribed Spacer (ITS) sequencing. Most species belong to genera Cortinarius, Mycena and Ramaria, whose metabolite contents has been scarcely investigated so far. The crude extracts obtained from the above mushrooms were tested for their inhibition activity against five human pathogens: Candida albicans ATCC 14053, C. glabrata ATCC 15126, Staphylococcus aureus NCTC 6571, Pseudomonas aeruginosa ATCC 27853 and Klebsiella pneumoniae ATCC 13883. Twelve crude extracts showed activity against P. aeruginosa ATCC 27853. Highest activity was shown by some Cortinarius species, as C. nanceiensis.

Clonal evolution of Candida albicans, Candida glabrata and Candida dubliniensis at oral niche level in health and disease

Background:Candida species have long been recognised as aetiological agents of opportunistic infections of the oral mucosa, and more recently, as players of polymicrobial interactions driving caries, periodontitis and oral carcinogenesis.

Methods: We studied the clonal structure of Candida spp. at oral niche resolution in patients (n = 20) with a range of oral health profiles over 22 months. Colonies from oral micro-environments were examined with multilocus sequencing typing.

Results:Candida spp. identified were C. albicans, C. glabrata and C. dubliniensis. Increased propensity for micro-variations giving rise to multiple diploid strain types (DST), as a result of loss of heterozygosity, was observed among C. albicans clade 1 isolates compared to other clades. Micro-variations among isolates were also observed in C. dubliniensis contra to expectations of stable population structures for this species. Multiple sequence types were retrieved from patients without clinical evidence of oral candidosis, while single sequence types were isolated from oral candidosis patients.

Conclusion: This is the first study to describe the clonal population structure, persistence and stability of Candida spp. at oral niche level. Future research investigating links between Candida spp. clonality and oral disease should recognise the propensity to micro-variations amongst oral niches in C. albicans and C. dubliniensis identified here.

In Vitro Characterization of Twenty-One Antifungal Combinations against Echinocandin-Resistant and -Susceptible Candida glabrata

This study was designed to analyze the interaction of 21 antifungal combinations consisting of seven major antifungal agents against 11 echinocandin- susceptible and six-resistant C. glabrata isolates. The combinations were divided into five major groups and were evaluated by checkerboard, disc diffusion, and time-killing assays. Synergy based on the fractional inhibitory concentration index of ≤0.50 was observed in 17.65-29.41% of the cases for caspofungin combinations with azoles or amphotericin B. Amphotericin B combination with azoles induced synergistic interaction in a range of 11.76-29.41%. Azole combinations and 5-flucytosine combinations with azoles or amphotericin B did not show synergistic interactions. None of the 21 combinations showed antagonistic interactions. Interestingly, 90% of the detected synergism was among the echinocandin-resistant isolates. Disk diffusion assays showed that the inhibition zones produced by antifungal combinations were equal to or greater than those produced by single drugs. The time-killing assay showed the synergistic action of caspofungin combination with fluconazole, voriconazole, and posaconazole, and the amphotericin B-5-flucytosine combination. Furthermore, for the first time, this assay confirmed the fungicidal activity of caspofungin-voriconazole and amphotericin B-5-flucytosine combinations. The combination interactions ranged from synergism to indifference and, most importantly, no antagonism was reported and most of the synergistic action was among echinocandin-resistant isolates.

Development of Polythiourethane/ZnO-Based Anti-Fouling Materials and Evaluation of the Adhesion of Staphylococcus aureus and Candida glabrata Using Single-Cell Force Spectroscopy

The attachment of bacteria and other microbes to natural and artificial surfaces leads to the development of biofilms, which can further cause nosocomial infections. Thus, an important field of research is the development of new materials capable of preventing the initial adhesion of pathogenic microorganisms. In this work, novel polymer/particle composite materials, based on a polythiourethane (PTU) matrix and either spherical (s-ZnO) or tetrapodal (t-ZnO) shaped ZnO fillers, were developed and characterized with respect to their mechanical, chemical and surface properties. To then evaluate their potential as anti-fouling surfaces, the adhesion of two different pathogenic microorganism species, Staphylococcus aureus and Candida glabrata, was studied using atomic force microscopy (AFM). Our results show that the adhesion of both S. aureus and C. glabrata to PTU and PTU/ZnO is decreased compared to a model surface polydimethylsiloxane (PDMS). It was furthermore found that the amount of both s-ZnO and t-ZnO filler had a direct influence on the adhesion of S. aureus, as increasing amounts of ZnO particles resulted in reduced adhesion of the cells. For both microorganisms, material composites with 5 wt.% of t-ZnO particles showed the greatest potential for anti-fouling with significantly decreased adhesion of cells. Altogether, both pathogens exhibit a reduced capacity to adhere to the newly developed nanomaterials used in this study, thus showing their potential for bio-medical applications.

Effects of Storage Temperature and pH on the Antifungal Effects of Commercial Oral Moisturizers against Candida Albicans and Candida Glabrata

Background and objectives: Oral moisturizers have been used to treat dry mouth. This study aimed to investigate the effects of storage temperature and pH on the antifungal effects of oral moisturizers against Candida albicans and Candida glabrata. Materials and Methods: Thirty-one oral moisturizers and amphotericin B (AMPH-B) were stored at 25 and 37 °C for 1 week. Subsequently, they were added to cylindrical holes in 50% trypticase soy agar plates inoculated with C. albicans and C. glabrata (10⁷ cells/ml). The antifungal effects were evaluated based on the sizes of the growth-inhibitory zones formed. Two-way analysis of variance was used to determine the effects of storage temperature and pH on the growth-inhibitory zones. Results: Significant differences in the effects of storage temperature and pH of the moisturizers were observed against C. albicans and C. glabrata. The growth-inhibitory zones of samples stored at 37 °C and with neutral pH were significantly larger than those stored at 25 °C and with acidic pH, respectively. The sizes of the zones formed by most of the oral moisturizers were larger than those formed by AMPH-B (concentration, 0.63 µg/ml). Conclusion: The antifungal effects of oral moisturizers against C. albicans and C. glabrata were affected by their storage temperature and pH.

Genetic Basis of Azole and Echinocandin Resistance in Clinical Candida glabrata in Japan

Infections caused by Candida glabrata have caused worldwide concern, especially when they are associated with increasing echinocandin and azole resistance. In this study, we analyzed the molecular mechanisms of azole and echinocandin resistance in C. glabrata isolates obtained from hospitalized patients in Japan from 1997 to 2019. All isolates were checked phenotypically for resistance and genotypically for mutations in PDR1, ERG11, hot spot 1 (HS1), HS2, and HS3 of FKS1, and HS1 and HS2 of FKS2, and all isolates were genotyped by multilocus sequence typing (MLST). Interestingly, 32.6% of the isolates were resistant to caspofungin, and 4.7% were resistant to micafungin. The isolates showed low rates of resistance to azoles, ranging from 2.3% to 9.3%, and only 4.7% of the isolates were non-wild type for flucytosine susceptibility. For the first time in Japan, 4.7% of the isolates were identified as multidrug-resistant strains. Nonsynonymous mutations in PDR1, including two novel mutations associated with azole resistance, were identified in 39.5% of the isolates, and a single nonsynonymous mutation was identified in ERG11 Nine isolates from the same patient harbored nonsynonymous mutations in HS1 of FKS2, and a single isolate harbored a single nonsynonymous mutation in HS1 of FKS1 MLST genotyping revealed 13 different sequence types (STs), with 3 new STs, and ST7 was the most prevalent among the patients (35%) and was associated with high resistance rates. Our results are of crucial clinical concern, since understanding the molecular mechanisms underlying fungal resistance is imperative for guiding specific therapy for efficient patient treatment and promoting strategies to prevent epidemic spread.

Functional characteristics of Svl3 and Pam1 that are required for proper cell wall formation in yeast cells

In the budding yeast Saccharomyces cerevisiae, Svl3 and Pam1 proteins work as functional homologues. Loss of their function causes increased levels of chitin deposition in the cell wall and temperature sensitivity, suggesting their involvement in cell wall formation. We found that the N- and C-termini of these proteins have distinctive and critical functions. They contain an N-terminal part that has a probable 2-dehydropantoate 2-reductase domain. In Svl3, this part can be replaced with the yeast 2-dehydropantoate 2-reductase, Pan5, suggesting that Svl3 and its homologues may be able to mediate 2-dehydropantoate 2-reductase function. On the other hand, Svl3 is recruited to the bud tip and bud neck via multiple localization signals in the C-terminal part. One of such signals is the lysine-rich region located in the C-terminal end. The function and localization of Svl3 are significantly disrupted by the loss of this lysine-rich region; however, its localization is not completely abolished by the mutation because another localization signal enables appropriate transport. Svl3 and Pam1 orthologues are found in cells across fungal species. The Svl3 orthologues of Candida glabrata can complement the loss of Svl3 and Pam1 in S. cerevisiae. C. glabrata cells lacking the SVL3 and PAM1 orthologue genes exhibit phenotypes similar to those observed in svl3∆pam1∆ S. cerevisiae cells. Thus, Svl3 homologues may be generally required for the assembly of the cell wall in fungal cells.

High diversity of Candida glabrata in a tertiary hospital-Mwanza, Tanzania

Candida glabrata is a genetically diverse human pathogenic yeast, whose subpopulations have been documented to vary geographically. Here, we report MLST genotypes and antifungal drug susceptibility of C. glabrata isolates from Africa. Among 47 mostly urogenital isolates, we found 13 sequence types, amounting to a 27% genetic population difference. More than half of the isolates were of novel sequence types. ST18 was most predominant and had reduced susceptibility to fluconazole. There was clear segregation of STs between urine and vaginal specimen. In Tanzania, the C. glabrata population is genetically diverse, and divergent from those seen in other countries.

Anidulafungin Susceptibility Testing of Candida glabrata Isolates from Blood Cultures by the MALDI Biotyper Antibiotic (Antifungal) Susceptibility Test Rapid Assay

Echinocandins are the recommended first-line antifungals for treatment of invasive candidiasis. The increasing number of Candida glabrata strains resistant against echinocandins is an emerging health care concern. The rapid detection of resistant C. glabrata isolates is an urgent requirement for clinical laboratories. In this study, we developed the MALDI Biotyper antibiotic (antifungal) susceptibility test rapid assay (MBT ASTRA) for the rapid detection of anidulafungin-resistant C. glabrata isolates directly from positive blood cultures. Of 100 C. glabrata strains, MBT ASTRA classified 69 as susceptible and 29 as resistant. Microdilution assays performed according to the Clinical and Laboratory Standards Institute (CLSI) guidelines, used as a standard reference, identified 65 susceptible, 9 intermediate, and 26 resistant isolates. Sequencing of hot spot 1 and hot spot 2 regions of the FKS1 and FKS2 genes classified 86 susceptible and 14 resistant isolates. The MBT ASTRA had sensitivity and specificity of 80% and 95%, respectively, compared to the microdilution method. Positive and negative agreement of MBT ASTRA was calculated at 100% and 80%, respectively, compared with the molecular sequencing approach. Together, these results revealed a high accuracy of MBT ASTRA compared to microdilution according to the CLSI and PCR analysis, resulting in a categorical agreement of 90% and 83%, respectively. The validity of MBT ASTRA was 98%. Importantly, MBT ASTRA provided antifungal susceptibility testing (AFST) within 6 h that was both accurate and reliable compared to the other two approaches, which require at least 24 h or are costly. Therefore, this method has the potential to facilitate clinical AFST rapidly at low sample costs for clinical labs already equipped with matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS).

Adherence and Cytotoxicity of Candida spp. to HaCaT and A549 cells

Candida species are opportunistic fungal pathogens that cause superficial or invasive infections. Recently, the incidence of infection by non-Candida albicans species, especially Candida glabrata, has increased. In this study, we analyzed the adhesion and cytotoxicity of various Candida spp. that are part of the normal human microbiota. C. albicans adheres well to cell culture plates and to cultured cells. C. glabrata selectively adheres to epithelial cells rather than to cell culture plates. Candida parapsilosis insufficiently adheres to confluent monolayers of human lung epithelial A549 and keratinocyte HaCaT cells. We then analyzed the cytotoxicity of C. albicans and C. glabrata, which adhered well to epithelial cells. C. glabrata has been found to cause more damage to A549 cells than to HaCaT cells, suggesting that resident Candida spp. have distinct cytotoxic effects in different tissues. It is important to clarify the properties of Candida spp. as there is evidence that normal microbiota can cause infections. Our data suggest that it is necessary to use appropriate cell lines for characterizing the adherence and cytotoxicity of Candida spp.

Inhibition of recombinant enzyme 3-hydroxy-3-methylglutaryl-CoA reductase from Candida glabrata by α-asarone-based synthetic compounds as antifungal agents

Due to increasing resistance of Candida species to antifungal drugs, especially azoles, new drugs are needed. The proposed compounds 3 and 4 are analogous to α-asarone (2), a naturally occurring potent inhibitor of HMGR with hypolipidemic and antifungal activity. We used the recombinant enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase of Candida glabrata (CgHMGR) as a model to test the effectiveness of the test compounds. Compounds 3 and 4 demonstrated inhibitory kinetics, having lower IC₅₀ values (42.65 μM and 28.77 μM, respectively) than compound 2 (>100 μM). The docking studies showed better binding energies for compounds 3 and 4 (-5.35 and -6.1 kcal/mol, respectively) than for compound 2 (-4.53 kcal/mol). These findings suggest that the tested compounds are better than their natural analogue. Plaque assays were performed on the C. glabrata strain CBS138 by applying ergosterol or cholesterol to evaluate the possible reversal of the inhibition induced by compounds 2, 3 and 4. Inhibition was easily suppressed in all three cases, recovering the viability of C. glabrata. These results reveal that the CgHMGR model is excellent for testing antifungals. Compound 4 produced the best effect and is herein proposed as a new potent antifungal agent.

Moonlighting proteins induce protection in a mouse model against Candida species

In recent years, C. albicans and C. glabrata have been identified as the main cause of candidemia and invasive candidiasis in hospitalized and immunocompromised patients. In order to colonize the human host, these fungi express several virulence factors such as the response to oxidative stress and the formation of biofilms. In the expression of these virulence factors, the cell wall of C. albicans and C. glabrata is of fundamental importance. As the outermost structure of the yeast, the cell wall is the first to come in contact with the reactive oxygen species (ROS) generated during the respiratory outbreak, and in the formation of biofilms, it is the first to adhere to organs or medical devices implanted in the human host. In both processes, several cell wall proteins (CWP) are required, since they promote attachment to human cells or abiotic surfaces, as well as to detoxify ROS. In our working group we have identified moonlighting CWP in response to oxidative stress as well as in the formation of biofilms. Having identified moonlighting CWP in Candida species in response to two virulence factors indicates that these proteins may possibly be immunodominant. The aim of the present work was to evaluate whether proteins of this type such as fructose-bisphosphate aldolase (Fba1), phosphoglycerate kinase (Pgk) and pyruvate kinase (Pk), could confer protection in a mouse model against C. albicans and C. glabrata. For this, recombinant proteins His₆-Fba1, His₆-Pgk and His₆-Pk were constructed and used to immunize several groups of mice. The immunized mice were infected with C. albicans or C. glabrata, and subsequently the liver, spleen and kidney were extracted and the number of CFU was determined. Our results showed that Pk confers immunity to mice against C. albicans, while Fba1 to C. glabrata. This data allows us to conclude that the moonlighting CWP, Fba1 and Pk confer in vivo protection in a specific way against each species of Candida. This makes them promising candidates for developing specific vaccines against these pathogens.

The phosphorelay signal transduction system in Candida glabrata: an in silico analysis

Signaling systems allow microorganisms to sense and respond to different stimuli through the modification of gene expression. The phosphorelay signal transduction system in eukaryotes involves three proteins: a sensor protein, an intermediate protein and a response regulator, and requires the transfer of a phosphate group between two histidine-aspartic residues. The SLN1-YPD1-SSK1 system enables yeast to adapt to hyperosmotic stress through the activation of the HOG1-MAPK pathway. The genetic sequences available from Saccharomyces cerevisiae were used to identify orthologous sequences in Candida glabrata, and putative genes were identified and characterized by in silico assays. An interactome analysis was carried out with the complete genome of C. glabrata and the putative proteins of the phosphorelay signal transduction system. Next, we modeled the complex formed between the sensor protein CgSln1p and the intermediate CgYpd1p. Finally, phosphate transfer was examined by a molecular dynamic assay. Our in silico analysis showed that the putative proteins of the C. glabrata phosphorelay signal transduction system present the functional domains of histidine kinase, a downstream response regulator protein, and an intermediate histidine phosphotransfer protein. All the sequences are phylogenetically more related to S. cerevisiae than to C. albicans. The interactome suggests that the C. glabrata phosphorelay signal transduction system interacts with different proteins that regulate cell wall biosynthesis and responds to oxidative and osmotic stress the same way as similar systems in S. cerevisiae and C. albicans. Molecular dynamics simulations showed complex formation between the response regulator domain of histidine kinase CgSln1 and intermediate protein CgYpd1 in the presence of a phosphate group and interactions between the aspartic residue and the histidine residue. Overall, our research showed that C. glabrata harbors a functional SLN1-YPD1-SSK1 phosphorelay system.

Evolution of reduced co-activator dependence led to target expansion of a starvation response pathway

Although combinatorial regulation is a common feature in gene regulatory networks, how it evolves and affects network structure and function is not well understood. In S. cerevisiae, the phosphate starvation (PHO) responsive transcription factors Pho4 and Pho2 are required for gene induction and survival during phosphate starvation. In the related human commensal C. glabrata, Pho4 is required but Pho2 is dispensable for survival in phosphate starvation and is only partially required for inducing PHO genes. Phylogenetic survey suggests that reduced dependence on Pho2 evolved in C. glabrata and closely related species. In S. cerevisiae, less Pho2-dependent Pho4 orthologs induce more genes. In C. glabrata, its Pho4 binds to more locations and induces three times as many genes as Pho4 in S. cerevisiae does. Our work shows how evolution of combinatorial regulation allows for rapid expansion of a gene regulatory network’s targets, possibly extending its physiological functions.

The diversity of life on Earth has intrigued generations of scientists and nature lovers alike. Research over recent decades has revealed that much of the diversity we can see did not require the invention of new genes. Instead, living forms diversified mostly by using old genes in new ways – for example, by changing when or where an existing gene became active. This kind of change is referred to as “regulatory evolution”.

A class of proteins called transcription factors are hot spots in regulatory evolution. These proteins recognize specific sequences of DNA to control the activity of other genes, and so represent the “readers” of the genetic information. Small changes to how a transcription factor is regulated, or the genes it targets, can lead to dramatic changes in an organism. Before we can understand how life on Earth evolved to be so diverse, scientists must first answer how transcription factors evolve and what consequences this has on their target genes.

So far, most studies of regulatory evolution have focused on networks of transcription factors and genes that control how an organism develops. He et al. have now studied a regulatory network that is behind a different process, namely how an organism responds to stress or starvation. These two types of regulatory networks are structured differently and work in different ways. These differences made He et al. wonder if the networks evolved differently too.

The chemical phosphate is an essential nutrient for all living things, and He et al. compared how two different species of yeast responded to a lack of phosphate. The key difference was how much a major transcription factor known as Pho4 depended on a so-called co-activator protein named Pho2 to carry out its role. Baker’s yeast (Saccharomyces cerevisiae), which is commonly used in laboratory experiments, requires both Pho4 and Pho2 to activate about 20 genes when inorganic phosphate is not available in its environment. However, in a related yeast species called Candida glabrata, Pho4 has evolved to depend less on Pho2. He et al. went on to show that, as well as being less dependent on Pho2, Pho4 in C. glabrata activates more than three times as many genes as Pho4 in S. cerevisiae does in the absence of phosphate. These additional gene targets for Pho4 in C. glabrata are predicted to extend the network’s activities, and allow it to regulate new process including the yeast’s responses to other types of stress and the building of the yeast’s cell wall.

Together these findings show a new way that regulatory networks can evolve, that is, by reducing its dependence on the co-activator, a transcription factor can expand the number of genes it targets. This has not been seen for regulatory networks related to development, suggesting that different networks can indeed evolve in different ways. Lastly, because disease-causing microbes are often stressed inside their hosts and C. glabrata sometimes infects humans, understanding how this yeast’s response to stress has evolved may lead to new ways to prevent and treat this infection.

Identification of Components of the SUMOylation Machinery in Candida glabrata: ROLE OF THE DESUMOYLATION PEPTIDASE CgUlp2 IN VIRULENCE

Regulation of protein function by reversible post-translational modification, SUMOylation, is widely conserved in the eukaryotic kingdom. SUMOylation is essential for cell growth, division, and adaptation to stress in most organisms, including fungi. As these are key factors in determination of fungal virulence, in this study, we have investigated the importance of SUMOylation in the human pathogen, Candida glabrata We identified the enzymes involved in small ubiquitin-like modifier conjugation and show that there is strong conservation between Saccharomyces cerevisiae and C. glabrata We demonstrate that SUMOylation is an essential process and that adaptation to stress involves changes in global SUMOylation in C. glabrata Importantly, loss of the deSUMOylating enzyme CgUlp2 leads to highly reduced small ubiquitin-like modifier protein levels, and impaired growth, sensitivity to multiple stress conditions, reduced adherence to epithelial cells, and poor colonization of specific tissues in mice. Our study thus demonstrates a key role for protein SUMOylation in the life cycle and pathobiology of C. glabrata.

Diversity and antifungal susceptibility of Norwegian Candida glabrata clinical isolates

Background

Increasing numbers of immunocompromised patients have resulted in greater incidence of invasive fungal infections with high mortality. Candida albicans infections dominate, but during the last decade, Candida glabrata has become the second highest cause of candidemia in the United States and Northern Europe. Reliable and early diagnosis, together with appropriate choice of antifungal treatment, is needed to combat these challenging infections.

Objectives

To confirm the identity of 183 Candida glabrata isolates from different human body sites using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) and VITEK^®2, and to analyze isolate protein profiles and antifungal susceptibility. The minimum inhibitory concentration (MIC) of seven antifungal drugs was determined for the isolates to elucidate susceptibility.

Design

A total of 183 C. glabrata isolates obtained between 2002 and 2012 from Norwegian health-care units were analyzed. For species verification and differentiation, biochemical characterization (VITEK^®2) and mass spectrometry (MALDI–TOF) were used. MIC determination for seven antifungal drugs was undertaken using E-tests^®.

Results

Using VITEK^®2, 92.9% of isolates were identified as C. glabrata, while all isolates (100%) were identified as C. glabrata using MALDI-TOF. Variation in protein spectra occurred for all identified C. glabrata isolates. The majority of isolates had low MICs to amphotericin B (≤1 mg/L for 99.5%) and anidulafungin (≤0.06 mg/L for 98.9%). For fluconazole, 18% of isolates had MICs >32 mg/L and 82% had MICs in the range ≥0.016 mg/L to ≤32 mg/L.

Conclusions

Protein profiles and antifungal susceptibility characteristics of the C. glabrata isolates were diverse. Clustering of protein profiles indicated that many azole resistant isolates were closely related. In most cases, isolates had highest susceptibility to amphotericin B and anidulafungin. The results confirmed previous observations of high MICs to fluconazole and flucytosine. MALDI-TOF was more definitive than VITEK^®2 for C. glabrata identification.

Biocatalytic reduction of racemic 2-arenoxycycloalkanones by yeasts P. glucozyma and C. glabrata: one way of achieving chiral 2-arenoxycycloalcohols

Chiral β-aryloxy alcohols are interesting building blocks that form part of drugs like β adrenergic antagonists. Acquiring cyclic rigid analogs to obtain more selective drugs is interesting. Thus, we used whole cells of yeast strains Pichia glucozyma and Candida glabrata to catalyze the reduction of several 2-arenoxycycloalkanones to produce chiral 2-arenoxycycloalcohols with good/excellent enantioselectivity. In both cases, the alcohol configuration that resulted from the carbonyl group reduction was S. Yeast P. glucozyma allowed the conversion of both enantiomers of the starting material to produce 2-arenoxycycloalcohols with configuration (1S, 2R) and (1S, 2S). The reaction with C. glabrata nearly always allowed the kinetic resolution of the starting ketone, recovering 2-arenoxycycloalkanone with configuration S and (1S, 2R)-2-arenoxycycloalcohol.All the four possible stereoisomers of 2-phenoxycyclohexanol and the two enantiomers of 2-phenoxycyclohexanone were obtained by combining the biocatalyzed reaction with the oxidation/reduction of the chiral compounds with standard reagents. This is a simple approach for the synthesis of the rigid chiral moiety 2-arenoxycycloalcohols contained in putative β-blockers 2-arenoxycycloalkanepropanolamines.

Secretion of the acid trehalase encoded by the CgATH1 gene allows trehalose fermentation by Candida glabrata

The emergent pathogen Candida glabrata differs from other yeasts because it assimilates only two sugars, glucose and the disaccharide trehalose. Since rapid identification tests are based on the ability of this yeast to rapidly hydrolyze trehalose, in this work a biochemical and molecular characterization of trehalose catabolism by this yeast was performed. Our results show that C. glabrata consumes and ferments trehalose, with parameters similar to those observed during glucose fermentation. The presence of glucose in the medium during exponential growth on trehalose revealed extracellular hydrolysis of the sugar by a cell surface acid trehalase with a pH optimum of 4.4. Approximately ∼30% of the total enzymatic activity is secreted into the medium during growth on trehalose or glycerol. The secreted enzyme shows an apparent molecular mass of 275 kDa in its native form, but denaturant gel electrophoresis revealed a protein with ∼130 kDa, which due to its migration pattern and strong binding to concanavalin A, indicates that it is probably a dimeric glycoprotein. The secreted acid trehalase shows high affinity and activity for trehalose, with Km and Vmax values of 3.4 mM and 80 U (mg protein)(-1), respectively. Cloning of the CgATH1 gene (CAGLOK05137g) from de C. glabrata genome, a gene showing high homology to fungal acid trehalases, allowed trehalose fermentation after heterologous expression in Saccharomyces cerevisiae.

In vivo Candida glabrata biofilm development on foreign bodies in a rat subcutaneous model

OBJECTIVES

Biofilm studies have been mostly dedicated to the major human fungal pathogen Candida albicans, whereas much less is known about this virulence factor in Candida glabrata, certainly under in vivo conditions. This study provides a deeper understanding of the biofilm development of C. glabrata, its architecture and susceptibility profile to fluconazole and echinocandins.

METHODS

In vitro and in vivo C. glabrata biofilms were developed inside serum-coated triple-lumen catheters placed in 24-well polystyrene plates or implanted subcutaneously in the back of a rat, respectively. Scanning electron microscopy and confocal scanning laser microscopy were used to visualize the biofilm architecture. Quantitative real-time PCR was used to demonstrate the expression profile of EPA1, EPA3, EPA6 and AWP1-AWP7 during in vivo biofilm formation.

RESULTS

Mature biofilms were observed within the first 48 h and the amount of biofilm reached its maximum by 6 days. Architecturally, mature C. glabrata biofilms consisted of a thick network of yeast cells embedded in an extracellular matrix. Moreover, in vivo biofilms were susceptible to echinocandin drugs, whereas fluconazole remained ineffective. Gene expression profiling revealed that EPA3, EPA6, AWP2, AWP3 and AWP5 were up-regulated in in vivo biofilms compared with in vitro biofilms.

CONCLUSIONS

C. glabrata is a unique microorganism, which, despite the lack of transition to the hyphal form, formed thick biofilms inside foreign bodies in vivo. To our knowledge, this is the first study that has described in vivo C. glabrata biofilm development and its architectural changes in detail and provides an insight into the susceptibility profile, as well as the gene expression machinery, of biofilm-associated infections.

Evaluation of possibilities in identification and susceptibility testing for Candida glabrata clinical isolates with the Integral System Yeast Plus (ISYP)

The aim of this study was to evaluate possibilities of correct identification and susceptibility testing of C. glabrata clinical isolates with Integral System Yeast Plus (ISYP). For species identification, as the reference method, API Candida test and species-specific PCR reactions were used. The potential of antifungal susceptibility testing by the ISYP test was compared with the Sensititre Yeast One. Whilst the reference methods confirmed that the received population (n = 65 isolates) represented only C. glabrata, identification with the ISYP system showed correct data only in the case of 18 strains tested (27.7%). Species identification of the other 47 strains with the ISYP test was not possible at all. Significant differences were also observed for drug susceptibility testing carried out by the ISYP and the Sensititre Yeast One. The highest level of disagreement in classifying strains as resistant or susceptible estimated, as 73.9% and 40.0%, was observed for itraconazole and amphotericin B, respectively. Satisfactory results were only obtained for 5-fluorocytosine with 93.8% agreement between both methods. In our opinion the idea of the ISYP system is certainly good. The combination of identification ability and drug susceptibility testing in one test is very important, especially from a clinical point of view. However, the current version of the ISYP has many disadvantages. We would like to encourage the manufacturer to make an effort and develop a new, more accurate version of the test.

Prevalence and epidemiological characteristics of vaginal candidiasis in the UAE

Vaginal candidiasis (VC) continues to be a health problem to women worldwide. Although the majority of VC cases are caused by Candida albicans (C. albicans), non-albicans Candida spp. like C. glabrata and C. tropicalis are emerging as important and potentially resistant opportunistic agents of VC. The objective of this study was to evaluate the prevalence and epidemiology of VC in the UAE through retrospective analysis of pertinent data compiled by the microbiology and infection control unit at Latifa Hospital, Dubai between 2005 and 2011. The incidence of VC significantly increased from 10.76% in 2005 to 17.61% in 2011; average prevalence was 13.88%. C. albicans occurred at a frequency of 83.02%, C. glabrata at 16.5% and C. tropicalis at 1.2%. A single C. dubliniensis isolate was identified in the sample population. The percentage of C. albicans significantly decreased from 83.02% in the sample population as a whole to 60.8% in subjects over 45 years of age (P < 0.01) and that of C. glabrata, C. tropicalis and C. krusei significantly increased from 13.88%, 0.9% and 0.03% to 29.7%, 6.7% and 1.4% (P < 0.05) respectively. The incidence of VC in the UAE is on the rise and the frequency of non-albicans Candida spp. is noticeably increasing especially in postmenopausal women.

Prevalence of Candida co-infection in patients with pulmonary tuberculosis

BACKGROUND

Candida species are emerging as a potentially pathogenic fungus in patients with broncho-pulmonary diseases. The synergistic growth promoting association of Candida and Mycobacterium tuberculosis has raised increased concern for studying the various Candida spp . and its significance in pulmonary tuberculosis patients during current years.

AIMS

This study was undertaken with the objective of discovering the prevalence of co-infection caused by different Candida species in patients with pulmonary tuberculosis.

METHOD

A total of 75 patients with pulmonary tuberculosis diagnosed by sputum Ziehl-Neelsen staining were included in the study. Candida co-infection was confirmed using the Kahanpaa et al. criteria. Candida species were identified using gram stain morphology, germ tube formation, morphology on cornmeal agar with Tween-80, sugar fermentation tests and HiCrome Candida Agar.

RESULTS

Candida co-infection was observed in 30 (40%) of patients with pulmonary tuberculosis. Candida albicans was the most common isolate observed in 50% of the patients with co-infection, followed by C. tropicalis (20%) and C. glabrata (20%). Candida co-infection was found in 62.5% of female patients, while it was observed in only 29.4% of the male patients (P value 0.0133). Mean ± SD age of the patients with C. glabrata infection was 65.83 ± 3.19, while the mean ± SD age of the patients with other Candida infections was 43.25 ± 20.44 (P value 0.0138).

CONCLUSION

Many patients with pulmonary tuberculosis have co-infection with Candida spp. The prevalence of non-albicans Candida species is increasing and may be associated with inadequate response to anti-tubercular drugs. C. glabrata infection has a strong association with old age.

Efficacy of micafungin in invasive candidiasis caused by common Candida species with special emphasis on non-albicans Candida species

The incidence of invasive candidiasis caused by non-albicans Candida (NAC) spp. is increasing. The aim of this analysis was to evaluate the efficacy of micafungin, caspofungin and liposomal amphotericin B in patients with invasive candidiasis and candidaemia caused by different Candida spp. This post hoc analysis used data obtained from two randomised phase III trials was conducted to evaluate the efficacy and safety of micafungin vs. caspofungin and micafungin vs. liposomal amphotericin B. Treatment success, clinical response, mycological response and mortality were evaluated in patients infected with C. albicans and NAC spp. Treatment success rates in patients with either C. albicans or NAC infections were similar. Outcomes were similar for micafungin, caspofungin and liposomal amphotericin B. Candida albicans was the most prevalent pathogen recovered (41.0%), followed by C. tropicalis (17.9%), C. parapsilosis (14.4%), C. glabrata (10.4%), multiple Candida spp. (7.3%) and C. krusei (3.2%). Age, primary diagnosis (i.e. candidaemia or invasive candidiasis), previous corticosteroid therapy and Acute Physiology and Chronic Health Evaluation II score were identified as potential predictors of treatment success and mortality. Micafungin, caspofungin and liposomal amphotericin B exhibit favourable treatment response rates that are comparable for patients infected with different Candida spp.

Determination of antifungal susceptibility patterns among the clinical isolates of Candida species

CONTEXT

Candida species are opportunistic yeasts that cause infections ranging from simple dermatosis to potentially life-threatening fungemia. The emergence of resistance to antifungal drugs has been increased in the past two decades.

AIM

the present study we determined to find out the susceptibility profiles of clinical isolates of Candida species against four antifungal drugs, including amphotericin B, ketoconazole, fluconazole and itraconazole.

MATERIALS AND METHODS

Antifungal susceptibility testing of the yeasts was done in accordance with the proposed guidelines for antifungal disk diffusion susceptibility testing of yeasts based on the CLSI document M44-A.

RESULTS

A total of 206 yeast isolates were assessed. Among the evaluated Candida species, the highest rates of resistance to ketoconazole were seen in Candida glabrata (16.6%) and Candida albicans (3.2%). Susceptibility and intermediate response to fluconazole were seen in 96.6% and 3.4% of the Candida isolates, respectively. A total of 19 (9.2%) yeast isolates showed petite phenomenon including 11 C. glabrata, 3 C. albicans, 2 Candida dubliniensis and one isolate of each Candida krusei and Candida parapsilosis.

CONCLUSION

The high number of petite mutation in the isolated yeasts should be seriously considered since it may be one of the reasons of antifungal treatment failure.