What do we know about Candida guilliermondii? A voyage throughout past and current literature about this emerging yeast

Candida guilliermondii fungemia: a 12-year retrospective review of antimicrobial susceptibility patterns at a reference laboratory and tertiary care center

The prevalence of invasive candidiasis caused by non-albicans Candida species is increasing. Candida guilliermondii is an infrequent cause of candidemia but has been associated with decreased susceptibility to triazoles. Clinical data related to the infection with C. guilliermondii are sparse. Our study evaluated the antifungal susceptibility testing (AST) for C. guilliermondii isolates submitted to a reference laboratory over a 12-year period (2012-2023). AST patterns were examined using Clinical and Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) epidemiological cutoff values (ECVs) and breakpoints. Where isolates were identified from patients treated at our institution, retrospective chart review was performed to describe patient risk factors, treatment approaches, and outcomes associated with C. guilliermondii fungemia. One hundred twelve blood culture isolates of C. guilliermondii were identified, and clinical data were available for 21 fungemic patients. A significant number of isolates (9.8-20.5%) were observed to be non-wild type for various triazoles. All isolates were susceptible to micafungin. A majority (76.2%) of cases of C. guilliermondii fungemia treated at our tertiary care center were hospital-acquired, and two-thirds of patients were immunocompromised at the time of diagnosis. Ten of the 21 patients died within 60 days of fungemia, although mortality was directly or partially attributed to C. guilliermondii fungemia in only four cases (19.0%). Echinocandins may be used for empiric therapy for C. guilliermondii until the results of AST are available. Further research is required to determine appropriate clinical breakpoints for triazoles.

IMPORTANCE

Our study addresses a significant knowledge gap in the clinical management of this non-Candida albicans species. Our retrospective review includes comprehensive AST data for 112 Candida guilliermondii isolates, which is the largest number of isolates reported from the United States to date. Susceptibility data are supplemented by clinical outcomes, where isolates were identified for patients treated at Mayo Clinic. Key findings from our study include the observation that a notable proportion of C. guilliermondii isolates exhibit non-wild-type profiles for various triazoles. Importantly, all isolates remained susceptible to echinocandins, suggesting their efficacy as first-line therapy in the absence of timely susceptibility results. Furthermore, our study highlights the high mortality associated with C. guilliermondii fungemia in immunocompromised patients, emphasizing the urgent need for optimized treatment strategies.

Antifungal Susceptibility Data and Epidemiological Distribution of Candida spp.: An In Vitro Five-Year Evaluation at University Hospital Policlinico of Catania and a Comprehensive Literature Review

BACKGROUND

Invasive fungal infections represent a concerning healthcare issue, with Candida spp. reported as the main aetiological agent. Candida spp. bloodstream infections show high mortality rates, indicating increasing antifungal-resistance episodes as a contributing feature. Despite the global prevalence of C. albicans, non-albicans species emerged as significant in the last decades.

METHODS

The present manuscript reports a five-year evaluation on Candida spp. bloodstream isolates and their antifungal susceptibility profiles, aiming to enrich the literature and epidemiological data.

RESULTS

According to the gathered data, antifungal-resistance cases remained uncommon. However, the study revealed rare resistance phenotypes such as a single case of pan-echinocandin resistance C. albicans.

CONCLUSIONS

Finally, a comprehensive review of Candida spp. antifungal resistance integrates the data, emphasizing the extreme species-specific variability and the consequent importance of always providing species identification.

Sensitivity Analysis of C. auris, S. cerevisiae, and C. cladosporioides by Irradiation with Far-UVC, UVC, and UVB

Background

The World Health Organization has published a list of pathogenic fungi with prior-itizing groups and calls for research and development of antifungal measures, with Candida auris belonging to the group with high priority.

Methods

The photosensitivity towards short wavelength ultraviolet irradiation (Far-UVC, UVC, and UVB) was investigated and compared to other yeasts (Saccharomyces cerevisiae) and a mold (Cladosporium cladosporioides). The observed 1-log reduction doses were compared to literature values of other representatives of the genus Candida, but also with S. cerevisiae, Aspergillus niger, and A. fumigatus.

Results

For the determined 1-log reduction doses, an increase with higher wavelengths was observed. A 1-log reduction dose of 4.3 mJ/cm2 was determined for C. auris when irradiated at 222 nm, a dose of 6.1 mJ/cm2 at 254 nm and a 1-log reduction dose of 51.3 mJ/cm2 was required when irradiated with UVB.

Conclusions

It was observed that S. cerevisiae is a possible surrogate for C. auris for irradiation with Far-UVC and UVB due to close 1-log reduction doses. No surrogate suitability was verified for C. cladosporioides in relation to A. niger and A. fumigatus for irradiation with a wavelength of 254 nm and for A. niger at 222 nm.

Exploring extremophilic fungi in soil mycobiome for sustainable agriculture amid global change

As the Earth warms, alternatives to traditional farming are crucial. Exploring fungi, especially poly extremophilic and extremotolerant species, to be used as plant probiotics, represents a promising option. Extremophilic fungi offer avenues for developing and producing innovative biofertilizers, effective biocontrol agents against plant pathogens, and resilient enzymes active under extreme conditions, all of which are crucial to enhance agricultural efficiency and sustainability through improved soil fertility and decreased reliance on agrochemicals. Yet, extremophilic fungi's potential remains underexplored and, therefore, comprehensive research is needed to understand their roles as tools to foster sustainable agriculture practices amid climate change. Efforts should concentrate on unraveling the complex dynamics of plant-fungi interactions and harnessing extremophilic fungi's ecological functions to influence plant growth and development. Aspects such as plant's epigenome remodeling, fungal extracellular vesicle production, secondary metabolism regulation, and impact on native soil microbiota are among many deserving to be explored in depth. Caution is advised, however, as extremophilic and extremotolerant fungi can act as both mitigators of crop diseases and as opportunistic pathogens, underscoring the necessity for balanced research to optimize benefits while mitigating risks in agricultural settings.

Pan-azole-resistant Meyerozyma guilliermondii clonal isolates harbouring a double F126L and L505F mutation in Erg11

BACKGROUND

Meyerozyma guilliermondii is a yeast species responsible for invasive fungal infections. It has high minimum inhibitory concentrations (MICs) to echinocandins, the first-line treatment of candidemia. In this context, azole antifungal agents are frequently used. However, in recent years, a number of azole-resistant strains have been described. Their mechanisms of resistance are currently poorly studied.

OBJECTIVE

The aim of this study was consequently to understand the mechanisms of azole resistance in several clinical isolates of M. guilliermondii.

METHODS

Ten isolates of M. guilliermondii and the ATCC 6260 reference strain were studied. MICs of azoles were determined first. Whole genome sequencing of the isolates was then carried out and the mutations identified in ERG11 were expressed in a CTG clade yeast model (C. lusitaniae). RNA expression of ERG11, MDR1 and CDR1 was evaluated by quantitative PCR. A phylogenic analysis was developed and performed on M. guilliermondii isolates. Lastly, in vitro experiments on fitness cost and virulence were carried out.

RESULTS

Of the ten isolates tested, three showed pan-azole resistance. A combination of F126L and L505F mutations in Erg11 was highlighted in these three isolates. Interestingly, a combination of these two mutations was necessary to confer azole resistance. An overexpression of the Cdr1 efflux pump was also evidenced in one strain. Moreover, the three pan-azole-resistant isolates were shown to be genetically related and not associated with a fitness cost or a lower virulence, suggesting a possible clonal transmission.

CONCLUSION

In conclusion, this study identified an original combination of ERG11 mutations responsible for pan-azole-resistance in M. guilliermondii. Moreover, we proposed a new MLST analysis for M. guilliermondii that identified possible clonal transmission of pan-azole-resistant strains. Future studies are needed to investigate the distribution of this clone in hospital environment and should lead to the reconsideration of the treatment for this species.

First case report of Candida guilliermondii native left-sided valve endocarditis

Endocarditis, a life-threatening inflammation of the endocardium, is incited by bacteria, fungi, or other pathogenic microorganisms. Fungal endocarditis closely mirrors bacterial endocarditis in clinical signs and symptoms, leading to potential misdiagnoses. Here, we unveil the inaugural confirmed instance of native left-sided valve endocarditis attributed to Candida guilliermondii. Diagnosis was substantiated through valvular biopsies, blood and vegetative cultures. Treatment encompassed surgical excision of vegetations along with a six-week regimen of fluconazole administration (12 mg/kg/day), followed by 4 years of meticulous monitoring, resulting in sustained patient recovery.

Onychomycosis in immunocompromised population: Phenotypic and molecular identification

Onychomycosis is common among immunosuppressed individuals. Renal transplant recipients (RTR) and lupus nephritis (LN) patients are submitted to corticosteroid and other immunosuppressive therapy; and diabetes mellitus (DM) patients are intrinsically immunocompromised.

OBJECTIVES

The aim of this study was to characterise and identify fungal infections on the nails (feet and hands) in immunocompromised patients.

METHODS

The clinical material, nail scales (foot and/or hand), was collected from 47 RTR, 66 LN, 67 DM, and 78 immunocompetent individuals (control group). Phenotypic and molecular analyses were performed.

RESULTS

A total of 258 patients were examined. There was a female predominance, except in the RTR. The average age was 52 years old. Lateral distal subungual onychomycosis (OSDL) (75.2%), mainly affecting the hallux nail, was frequent. The predominance of dermatophyte on toenails and Candida species on fingernails was statistically significant. A higher frequency of fingernail involvement in LN and DM, and for LN, the difference was significant (p = .0456). Infections by Candida spp. were more frequent in DM. Using molecular methods, 87.2% of diagnoses were confirmed, identifying fungal agents at the species level. Dermatophytes, Trichophyton rubrum and Trichophyton interdigitale and the species of Candida, C. parapsilosis and C. albicans, were the most frequent fungal agents.

CONCLUSIONS

Molecular techniques (sequencing of ITS regions of rDNA) offer greater accuracy, although there is no difference, regarding the detection. Clinical presentation and fungal species may differ somewhat from the general population. Immunosuppression did not increase fungal detection positivity.

Non-albicans Candida Species: Immune Response, Evasion Mechanisms, and New Plant-Derived Alternative Therapies

Fungal infections caused by Candida species have become a constant threat to public health, especially for immunocompromised patients, who are considered susceptible to this type of opportunistic infections. Candida albicans is known as the most common etiological agent of candidiasis; however, other species, such as Candida tropicalis, Candida parapsilosis, Nakaseomyces glabrata (previously known as Candida glabrata), Candida auris, Candida guilliermondii, and Pichia kudriavzevii (previously named as Candida krusei), have also gained great importance in recent years. The increasing frequency of the isolation of this non-albicans Candida species is associated with different factors, such as constant exposure to antifungal drugs, the use of catheters in hospitalized patients, cancer, age, and geographic distribution. The main concerns for the control of these pathogens include their ability to evade the mechanisms of action of different drugs, thus developing resistance to antifungal drugs, and it has also been shown that some of these species also manage to evade the host's immunity. These biological traits make candidiasis treatment a challenging task. In this review manuscript, a detailed update of the recent literature on the six most relevant non-albicans Candida species is provided, focusing on the immune response, evasion mechanisms, and new plant-derived compounds with antifungal properties.

Meyerozyma guilliermondii species complex: review of current epidemiology, antifungal resistance, and mechanisms

Meyerozyma guilliermondii has been accepted as a complex composed of Meyerozyma guilliermondii, Meyerozyma carpophila, and Meyerozyma caribbica. M. guilliermondii is a saprophyte detected on human mucosa and skin. It can lead to serious infections in patients with risk factors like chemotherapy, immunodeficiency, gastrointestinal or cardiovascular surgery, and oncology disorders. Most deaths related to M. guilliermondii infections occur in individuals with malignancy. In recent decades, incidence of M. guilliermondii infections is increased. Sensitivity of this microorganism to conventional antifungals (e.g., amphotericin B, fluconazole, micafungin and anidulafungin) was reduced. Prophylactic and empirical uses of these drugs are linked to elevated minimal inhibitory concentrations (MICs) of M. guilliermondii. Drug resistance has concerned many researchers across the world. They are attempting to discover appropriate solution to combat this challenge. This study reviews the most important mechanisms of resistance to antifungals developed by in M. guilliermondii species complex.

The Flo Adhesin Family

The first step in the infection of fungal pathogens in humans is the adhesion of the pathogen to host tissue cells or abiotic surfaces such as catheters and implants. One of the main players involved in this are the expressed cell wall adhesins. Here, we review the Flo adhesin family and their involvement in the adhesion of these yeasts during human infections. Firstly, we redefined the Flo adhesin family based on the domain architectures that are present in the Flo adhesins and their functions, and set up a new classification of Flo adhesins. Next, the structure, function, and adhesion mechanisms of the Flo adhesins whose structure has been solved are discussed in detail. Finally, we identified from Pfam database datamining yeasts that could express Flo adhesins and are encountered in human infections and their adhesin architectures. These yeasts are discussed in relation to their adhesion characteristics and involvement in infections.

Emerging issue of fluconazole-resistant candidemia in a tertiary care hospital of southern italy: time for antifungal stewardship program

An increased number of patients is at risk of Candida spp. bloodstream infection (CBSI) in modern medicine. Moreover, the rising of antifungal resistance (AR) was recently reported. All consecutive CBSI occurred in our Hospital (consisting of 1,370 beds) between 2015 and 2018, were reviewed. For each case, Candida species, AR pattern, ward involved and demographic data of patients were recorded. Overall, 304 episodes of CBSI occurred, with a median (q1:first-,q3:third quartile) of 77 (71-82) CBSI/year. Over the years, a significant increase of CBSI due to C. albicans compared to non-albicans strains was recorded in medical wards (from 65% to 71%, p=0.030), while this ratio remained stable in others. An increase of resistant strains to multiple antifungals such as C. guillermondii was noticed in recent years (from 0% to 9.8%, p=0.008). Additionally, from 2015 to 2018 an increase in fluconazole-resistance was recorded in our Hospital (from 7.4% to 17.4%, p=0.025) and a slight increase in voriconazole-resistance (from 0% to 7% in 2018, p=0.161) was observed, while resistance to echinocandin and amphotericin B remained firmly below 2%. This study suggests a rapid spread of antifungal resistance in our Hospital; therefore, an appropriate antifungal stewardship programs is urgently warranted.

A case-series of bloodstream infections caused by the Meyerozyma guilliermondii species complex at a reference center of oncology in Brazil

Bloodstream infections (BSI) caused by Candida species are the fourth cause of healthcare associated infections worldwide. Non-albicans Candida species emerged in the last decades as agents of serious diseases. In this study, clinical and microbiological aspects of six patients with BSI due to the Meyerozyma (Candida) guilliermondii species complex from an oncology reference center in Brazil, were evaluated. To describe demographic and clinical characteristics, medical records of the patients were reviewed. Molecular identification of the isolates was performed by ITS1-5.8S-ITS2 region sequencing. Antifungal susceptibility was evaluated by the EUCAST method and the minimal inhibitory concentrations (MIC) assessed according to the epidemiological cutoff values. Virulence associated phenotypes of the isolates were also studied. Ten isolates from the six patients were evaluated. Five of them were identified as Meyerozyma guilliermondii and the others as Meyerozyma caribbica. One patient was infected with two M. caribbica isolates with different genetic backgrounds. High MICs were observed for fluconazole and echinocandins. Non-wild type isolates to voriconazole appeared in one patient previously treated with this azole. Additionally, two patients survived, despite infected with non-wild type strains for fluconazole and treated with this drug. All isolates produced hemolysin, which was not associated with a poor prognosis, and none produced phospholipases. Aspartic proteases, phytase, and esterase were detected in a few isolates. This study shows the reduced antifungal susceptibility and a variable production of virulence-related enzymes by Meyerozyma spp. In addition, it highlights the poor prognosis of neutropenic patients with BSI caused by this emerging species complex.

LAY ABSTRACT

Our manuscript describes demographic, clinical and microbiological characteristics of patients with bloodstream infection by the Meyerozyma guilliermondii species complex at a reference center in oncology in Brazil.

Changes in growth kinetic parameters, morphology and mitotic activity of yeasts Candida guilliermondii exposed to the low-intensity waves of 51.8-GHz frequency

Under the influence of electromagnetic waves of millimeter range with the frequency of 51.8 GHz, changes in the morphology, growth parameters and mitotic activity of yeasts C. guilliermondii NP-4 are revealed. Filamentous and giant cells appeared in a population of exposed yeasts. The sigmoid shape of the growth curve remained but the lag phase duration was increased by 2 h in comparison with non-exposed yeasts; accordingly, the log and stationary phases followed 2 h later. The specific growth rate in the log growth phase and colony-forming ability of exposed yeasts was decreased. It is suggested that yeasts have some response mechanisms to 51.8-GHz frequency electromagnetic waves. The results can be used to understand the response mechanisms of microorganisms to non-ionizing radiation, as well as to develop approaches to protect living organisms from it. The effect of electromagnetic waves of 51.8-GHz frequency to suppress yeasts can be applied in biotechnology and medicine.

Expect the unexpected: fungemia caused by uncommon Candida species in a Turkish University Hospital

Fungemia caused by uncommon Candida species (UCS) (other than C.albicans, C.glabrata, C.parapsilosis, C.tropicalis, C.krusei) is a rare but emerging threat with their potential to exhibit reduced susceptibility or resistance to antifungal agents. We identified 25 patients with UCS fungemia (9 C.kefyr, 8 C.lusitaniae, 4 C.dubliniensis, 2 C.guilliermondii, 1 C.pelliculosa, 1 C.rugosa) through January 2011 and August 2018. Echinocandins were the most common administered agents, followed by fluconazole. Overall mortality was 44%. Echinocandins and voriconazole showed sufficient activity against all tested isolates. High fluconazole MICs among C.guilliermondii, C.pelliculosa, and C.rugosa were determined. MIC value of C.pelliculosa was above the epidemiological cut-off proposed for fluconazole.

Pentose metabolism and conversion to biofuels and high-value chemicals in yeasts

Pentose sugars are widespread in nature and two of them, D-xylose and L-arabinose belong to the most abundant sugars being the second and third by abundance sugars in dry plant biomass (lignocellulose) and in general on planet. Therefore, it is not surprising that metabolism and bioconversion of these pentoses attract much attention. Several different pathways of D-xylose and L-arabinose catabolism in bacteria and yeasts are known. There are even more common and really ubiquitous though not so abundant pentoses, D-ribose and 2-deoxy-D-ribose, the constituents of all living cells. Thus, ribose metabolism is example of endogenous metabolism whereas metabolism of other pentoses, including xylose and L-arabinose, represents examples of the metabolism of foreign exogenous compounds which normally are not constituents of yeast cells. As a rule, pentose degradation by the wild-type strains of microorganisms does not lead to accumulation of high amounts of valuable substances; however, productive strains have been obtained by random selection and metabolic engineering. There are numerous reviews on xylose and (less) L-arabinose metabolism and conversion to high value substances; however, they mostly are devoted to bacteria or the yeast Saccharomyces cerevisiae. This review is devoted to reviewing pentose metabolism and bioconversion mostly in non-conventional yeasts, which naturally metabolize xylose. Pentose metabolism in the recombinant strains of S. cerevisiae is also considered for comparison. The available data on ribose, xylose, L-arabinose transport, metabolism, regulation of these processes, interaction with glucose catabolism and construction of the productive strains of high-value chemicals or pentose (ribose) itself are described. In addition, genome studies of the natural xylose metabolizing yeasts and available tools for their molecular research are reviewed. Metabolism of other pentoses (2-deoxyribose, D-arabinose, lyxose) is briefly reviewed.

Biotechnological applications of the non-conventional yeast Meyerozyma guilliermondii

Unconventional yeasts have attracted increased attentions owning to their unique biochemical properties and potential application in the biotechnological process. With the rapid development of microbial isolation tools and synthetic biology, more promising industrial yeasts have been isolated and characterized. Meyerozyma guilliermondii (anamorph Candida guilliermondii) is an ascomycetous yeast with several unique characteristics and physiology, such as the wide substrates spectrum and capability of various chemicals synthesis. The potential physiological and metabolic capabilities of M. guilliermondii, which can utilize various carbon sources including typical hydrophilic and hydrophobic materials were first reviewed in this review. Moreover, the wide applications of M. guilliermondii, such as for industrial enzymes production, metabolites synthesis and biocontrol were also reviewed. With the development of system and synthetic biology, M. guilliermondii will provide new opportunities for potential applications in biotechnology sectors in the future.

Fungi in sands of Mediterranean Sea beaches of Israel-Potential relevance to human health and well-being

BACKGROUND

Sand of sea harbour bacteria that may cause enteric and other infections in humans, and are controlled by regulatory measures. Data on fungi in sea sand are scarce. Thus, an international group of mycologists was formed to explore fungal flora in sand of various waterbodies.

OBJECTIVES

The aim was to explore fungal sand contamination in beaches of the Israeli Mediterranean Sea Coast, regarding possible impact on human health in three aspects: (a) faecal contamination, as judged by presence of the human enteric fungi; (b) contamination by fungi, causing dermal infections; (c) and the presence of moulds, causing respiratory allergies and pose a risk for infection in immunocompromised individuals.

METHODS

The study included sand screen of six urban beaches from north to south of the Israeli Mediterranean Coast. Sand samples were extracted by water, and the water wash was cultured and quantitated. The fungi were identified phenotypically, by MALDI-TOF MS system and ITS sequencing.

RESULTS

The screen revealed that about 80% of the isolates were moulds and about 20% yeasts. The mould species included opportunistic pathogens and potential allergens: Aspergillus fumigatus, Fusarium and Mucorales species. Yeast isolates included Candida, Cryptococcus and Rhodotorula species.

CONCLUSIONS

(a) Fungi are contaminating Israeli Mediterranean sand beaches; (b) the contaminating fungi include various yeast and mould species; (c) some of the yeasts and mould species found in sand are known opportunistic pathogens, or respiratory allergens; (d) the data could serve as basis for initiating regulatory measures to control fungal contamination of sand for the benefit of public health.

Phylogeny, evolution, and potential ecological relationship of cytochrome CYP52 enzymes in Saccharomycetales yeasts

Cytochrome P450s from the CYP52 family participate in the assimilation of alkanes and fatty acids in fungi. In this work, the evolutionary history of a set of orthologous and paralogous CYP52 proteins from Saccharomycetales yeasts was inferred. Further, the phenotypic assimilation profiles were related with the distribution of cytochrome CYP52 members among species. The maximum likelihood phylogeny of CYP52 inferred proteins reveled a frequent ancient and modern duplication and loss events that generated orthologous and paralogous groups. Phylogeny and assimilation profiles of alkanes and fatty acids showed a family expansion in yeast isolated from hydrophobic-rich environments. Docking analysis of deduced ancient CYP52 proteins suggests that the most ancient function was the oxidation of C4-C11 alkanes, while the oxidation of >10 carbon alkanes and fatty acids is a derived character. The ancient CYP52 paralogs displayed partial specialization and promiscuous interaction with hydrophobic substrates. Additionally, functional optimization was not evident. Changes in the interaction of ancient CYP52 with different alkanes and fatty acids could be associated with modifications in spatial orientations of the amino acid residues that comprise the active site. The extended family of CYP52 proteins is likely evolving toward functional specialization, and certain redundancy for substrates is being maintained.

Phenolic composition and biological activities of geographically different type of propolis and black cottonwood resins against oral streptococci, vaginal microbiota and phytopathogenic Fusarium species

AIMS

A multidisciplinary approach was used to compare phenolic composition, radical scavenging and antimicrobial activity of propolis samples from different geographical localities, and plant resin against various microorganisms.

METHODS AND RESULTS

Using UHPLC-qqqMS quantitative analysis, 28 phenolic compounds were determined. Caffeic and p-coumaric acids were identified as main phenolic acids in poplar propolis samples, except samples from Russia (P6) and China (P7). Radical scavenging activity (applying DPPH spectrophotometric assay) showed the highest activity of Serbian (40·51%) and Chinese (53·21%) propolis samples. Broth microdilution method was used for the oral cavity, fungal phytopathogenic and human vaginal isolates which have been identified at a molecular level. The most sensitive bacterial isolates were Lactobacillus acidophilus (MIC of 0·03-0·13 mg ml^-1 ) and the oral streptococci isolates (MIC values of 0·19-0·13 mg ml^-1 ). The most sensitive fungal phytopathogenic isolate was Fusarium oxysporum (MIC 0·003 mg ml^-1 ). All samples, except propolis from Serbia (P4) and Turkey (P5), showed a strong antifungal activity against Fusarium sporotrichioides, Fusarium subglutinans and Fusarium proliferatum.

CONCLUSION

The results of various tests indicate good radical scavenging and antimicrobial activity against important human and plant pathogens.

SIGNIFICANCE AND IMPACT OF THE STUDY

A detailed propolis analysis is important when proposing a preparation of new biological antimicrobial products which have a positive impact on human health and reduce antibacterial resistance.

Differential recognition of Candida tropicalis, Candida guilliermondii, Candida krusei, and Candida auris by human innate immune cells

Background

The deep-seated infections caused by the Candida genus are associated with a high mortality rate, and Candida albicans is the most frequent species associated with these diseases. The fungal wall is composed of macromolecules not synthesized by the host, and therefore is a source of ligands recognized by innate immune cells.

Methods

We performed a comparative study analyzing the cell wall composition and organization of Candida tropicalis, Candida guilliermondii, Candida krusei, and Candida auris, along with their ability to stimulate cytokine production and phagocytosis by human innate immune cells.

Results

We found that the wall of these species had the basic components already described in C. albicans, with most of the chitin and b1,3-glucan located underneath the mannan layer. However, the walls of C. krusei and C. auris were rich in chitin and the former had a lower content of mannans. C. guilliermondii contained changes in the mannan and the b1,3-glucan levels. These species were differentially phagocytosed by human macrophages and stimulated cytokine production in a dectin-1-dependent pathway. C. krusei showed the most significant changes in the tested parameters, whereas C. auris behaved like C. albicans.

Conclusion

Our results suggest that the cell wall and innate immune recognition of C. tropicalis, C. guilliermondii, C. krusei, and Candida auris is different from that reported for C. albicans.

Reidentification and antifungal susceptibility profile of Candida guilliermondii and Candida famata clinical isolates from a culture collection in Argentina

The aim of this work was to reidentify strains previously identified as Candida guilliermondii and Candida famata by conventional phenotypic methods conserved in a culture collection from Argentina using ribosomal DNA sequencing, ACT1 gene sequencing, and matrix-assisted laser desorption ionization - time of flight mass spectrometry (MALDI-TOF MS). In addition, we performed antifungal susceptibility tests of eight antifungal drugs commonly used in clinical treatment. We identified 68 isolates belonging to the Candida guilliermondii species complex (59 C. guilliermondii, 8 C. fermentati, and 1 Candida carpophila), 16 isolates belonging to the Candida famata species complex (8 C. famata, 6 Debaryomyces nepalensis, 1 Debaryomyces fabryi, and 1 Debaryomyces tyrocola). Although sequencing of ITS region was able to identify C. guilliermondii and D. nepalensis isolates, sequencing of ACT1 gene seems to be the most appropriate technique for differentiation between C. fermentati and C. carpophila and between members of the C. famata species complex others than D. nepalensis. MALDI-TOF MS has a good potential for the identification of these yeasts, particularly in clinical laboratories since is a rapid and easy to perform technique. Here, we report the first isolation of D. tyrocola from a human patient and the first isolation of D. nepalensis from lungs and blood of human patients. Finally, correct identification and determination of antifungal susceptibility of those closely related species could be a useful tool for clinicians to choose the most effective antifungal treatment.

Stress-Tolerant Yeasts: Opportunistic Pathogenicity Versus Biocontrol Potential

Stress-tolerant fungi that can thrive under various environmental extremes are highly desirable for their application to biological control, as an alternative to chemicals for pest management. However, in fungi, the mechanisms of stress tolerance might also have roles in mammal opportunism. We tested five species with high biocontrol potential in agriculture (Aureobasidium pullulans, Debayomyces hansenii, Meyerozyma guilliermondii, Metschnikowia fructicola, Rhodotorula mucilaginosa) and two species recognized as emerging opportunistic human pathogens (Exophiala dermatitidis, Aureobasidium melanogenum) for growth under oligotrophic conditions and at 37 °C, and for tolerance to oxidative stress, formation of biofilms, production of hydrolytic enzymes and siderophores, and use of hydrocarbons as sole carbon source. The results show large overlap between traits desirable for biocontrol and traits linked to opportunism (growth under oligotrophic conditions, production of siderophores, high oxidative stress tolerance, and specific enzyme activities). Based on existing knowledge and these data, we suggest that oligotrophism and thermotolerance together with siderophore production at 37 °C, urease activity, melanization, and biofilm production are the main traits that increase the potential for fungi to cause opportunistic infections in mammals. These traits should be carefully considered when assessing safety of potential biocontrol agents.

Candida sp. Infections in Patients with Diabetes Mellitus

Candidiasis has increased substantially worldwide over recent decades and is a significant cause of morbidity and mortality, especially among critically ill patients. Diabetes mellitus (DM) is a metabolic disorder that predisposes individuals to fungal infections, including those related to Candida sp., due to a immunosuppressive effect on the patient. This review aims to discuss the latest studies regarding the occurrence of candidiasis on DM patients and the pathophysiology and etiology associated with these co-morbidities. A comprehensive review of the literature was undertaken. PubMed, Scopus, Elsevier’s ScienceDirect, and Springer’s SpringerLink databases were searched using well-defined search terms. Predefined inclusion and exclusion criteria were applied to classify relevant manuscripts. Results of the review show that DM patients have an increased susceptibility to Candida sp. infections which aggravates in the cases of uncontrolled hyperglycemia. The conclusion is that, for these patients, the hospitalization periods have increased and are commonly associated with the prolonged use of indwelling medical devices, which also increase the costs associated with disease management.

Strong Synergism of Palmatine and Fluconazole/Itraconazole Against Planktonic and Biofilm Cells of Candida Species and Efflux-Associated Antifungal Mechanism

Fungal infections caused by Candida albicans and non-albicans Candida [NAC] species are becoming a growing threat in immunodeficient population, people with long-term antibiotic treatment and patients enduring kinds of catheter intervention. The resistance to one or more than one conventional antifungal agents contributes greatly to the widespread propagation of Candida infections. The severity of fungal infection requires the discovery of novel antimycotics and the extensive application of combination strategy. In this study, a group of Candida standard and clinical strains including C. albicans as well as several NAC species were employed to evaluate the antifungal potentials of palmatine (PAL) alone and in combination with fluconazole (FLC)/itraconazole (ITR) by microdilution method, checkerboard assay, gram staining, spot assay, and rhodamine 6G efflux test. Subsequently, the expressions of transporter-related genes, namely CDR1, CDR2, MDR1, and FLU1 for C. albicans, CDR1 and MDR1 for Candida tropicalis and Candida parapsilosis, ABC1 and ABC2 for Candida krusei, CDR1, CDR2, and SNQ2 for Candida glabrata were analyzed by qRT-PCR. The susceptibility test showed that PAL presented strong synergism with FLC and ITR with fractional inhibitory concentration index (FICI) in a range of 0.0049-0.75 for PAL+FLC and 0.0059-0.3125 for PAL+ITR in planktonic cells, 0.125-0.375 for PAL+FLC and 0.0938-0.3125 for PAL+ITR in biofilms. The susceptibility results were also confirmed by gram staining and spot assay. After combinations, a vast quantity of rhodamine 6G could not be pumped out as considerably intracellular red fluorescence was accumulated. Meanwhile, the expressions of efflux-associated genes were evaluated and presented varying degrees of inhibition. These results indicated that PAL was a decent antifungal synergist to promote the antifungal efficacy of azoles (such as FLC and ITR), and the underlying antifungal mechanism might be linked with the inhibition of efflux pumps and the elevation of intracellular drug content.

In Vitro Activity of Isavuconazole against Opportunistic Fungal Pathogens from Two Mycology Reference Laboratories

Monitoring antifungal susceptibility patterns for new and established antifungal agents seems prudent given the increasing prevalence of uncommon species associated with higher antifungal resistance. We evaluated the activity of isavuconazole against 4,856 invasive yeasts and molds collected worldwide. The 4,856 clinical fungal isolates, including 2,351 Candida species isolates, 97 non-Candida yeasts, 1,972 Aspergillus species isolates, and 361 non-Aspergillus molds, including 292 Mucorales isolates collected in 2015 to 2016, were tested using CLSI methods. The MIC values for isavuconazole versus Aspergillus ranged from 0.06 to ≥16 μg/ml. The modal MIC for isavuconazole was 0.5 μg/ml (range, 0.25 [A. nidulans and A. terreus species complex] to 4 μg/ml [A. calidoustus and A. tubingensis]). Eight A. fumigatus isolates had elevated isavuconazole MIC values at ≥8 μg/ml (non-wild type). Isavuconazole showed comparable activity to itraconazole against the Mucorales The lowest modal isavuconazole MIC values were seen for Rhizopus spp., R. arrhizus var. arrhizus, and R. microsporus (all 1 μg/ml). Candida species isolates were inhibited by ≤0.25 μg/ml of isavuconazole (range, 96.1% [C. lusitaniae] to 100.0% [C. albicans, C. dubliniensis, C. kefyr, and C. orthopsilosis]). MIC values were ≤1 μg/ml for 95.5% of C. glabrata isolates and 100.0% of C. krusei isolates. Isavuconazole was active against the non-Candida yeasts, including Cryptococcus neoformans (100.0% at ≤0.5 μg/ml). Isavuconazole exhibited excellent activity against most species of Candida and Aspergillus Isavuconazole was comparable to posaconazole and voriconazole against the less common yeasts and molds. Isavuconazole was generally less active than posaconazole and more active than voriconazole against the 292 Mucorales isolates. We confirm the potentially useful activity of isavuconazole against species of Rhizopus as determined by CLSI methods.

Emerging multidrug-resistant Candida species

PURPOSE OF REVIEW

To describe the epidemiology, strategies for early detection, and clinical management of infections caused by the most commonly found multidrug-resistant (MDR) Candida spp.

RECENT FINDINGS

Increasing numbers of reports describing invasive infections by MDR Candida auris and Candida glabrata has been reported in medical centers worldwide.

SUMMARY

We checked all papers published along the last 10 years describing epidemiological, diagnostic, and clinical aspects of infections by MDR Candida spp., with emphasis on C. auris and C. glabrata spp. C. auris has been reported in 15 countries and multidrug resistance rates is usually above 30%. Horizontal transmission is a great concern regarding C. auris. C. glabrata ranks the second most reported Candida spp. in deep-seated infections from United States and some European Centers, although multidrug resistance rates above 10% are restricted to some US centers. Candida haemulonii complex isolates with poor susceptibility to azoles and amphotericin B have been isolated in superficial and deep-seated infections, whereas Candida guilliiermondii complex isolates with poor susceptibility to azoles and echinocandins have been recovered from catheter-related bloodstream infections. Other potential MDR Candida species are Candida krusei, Candida lusitaniae, Candida kefyr, Yarrowia (Candida) lypolitica, and Candida rugosa.

Risk assessment for the spread of Candida sp. in dental chair unit waterlines using molecular techniques

AIMS

The aim of this study was to evaluate the presence of yeasts in dental chair unit waterlines (DCUWLs) and to test their ability to form biofilms.

MATERIALS AND METHODS

Eighteen dental waterlines were analysed by culture in liquid Sabouraud in order to allow the quantification and the purification of isolated yeasts from their internal surfaces. All isolates were identified by standard laboratory procedures, including CHROMagar Candida medium for orientation, commercial yeast identification system Api Candida, MALDI-TOF MS and DNA sequencing. To evaluate their kinetics of antifungal susceptibility during different phases of biofilm formation, these yeasts were subjected to three antifungal agents.

RESULTS

From the 18 DCUWLs studied, 10 were altered (55.56%). Eleven strains of Candida sp. [Candida albicans (2), Candida guilliermondii (5) and Candida glabrata (4)] and two species of non-Candida; Rhodotorula spp. (1) and Trichosporon spp. (2) were identified. The majority of yeasts in planktonic form were susceptible to amphotericin B, caspofungin and voriconazole, except C. albicans was resistant to voriconazole. In the biofilm form, caspofungin was the most effective antifungal agent for all isolated strains. For the other antifungal agents, sessile cells were resistant.

CONCLUSION

Several types of yeasts were identified; the most frequently isolated genus was Candida. The majority of these yeasts had the ability to form biofilms and resisted antifungal agents used in this study.

Hypersensitivity Pneumonitis Caused by a Home Ultrasonic Humidifier Contaminated with Candida guilliermondii

We herein report the first documented case of acute hypersensitivity pneumonitis in which Candida guilliermondii was the possible causative organism. A young Japanese woman presented to our hospital with relapsing respiratory symptoms accompanied by high fever. A detailed interview revealed that the onset of the symptoms occurred shortly after using a humidifier in her home. Her symptoms showed spontaneous improvement soon after admission, and an examination of her bronchoalveolar lavage fluid revealed the specific infiltration of inflammatory cells, which predominantly consisted of lymphocytes. Precipitin testing showed a positive reaction to C. guilliermondii, which was isolated from the home humidifier. Repeated history taking is essential for diagnosing occult respiratory disorders.

Clinical manifestations of candidemia caused by uncommon Candida species and antifungal susceptibility of the isolates in a regional hospital in Taiwan, 2007-2014

OBJECTIVE

This retrospective study investigated clinical manifestations of candidemia caused by uncommon Candida species and antifungal susceptibility of the isolates in a regional hospital in Taiwan.

METHODS

The uncommon Candida species was initially defined as Candida species other than C. albicans, C. tropicalis, C. glabrata complex, C. parapsilosis complex and C. krusei. All uncommon Candida isolates were identified and confirmed by molecular methods. In vitro susceptibility testing of the uncommon Candida species to nine antifungal agents was conducted using the broth microdilution method with the Sensititre YeastOne (SYO) system (Trek Diagnostic Systems, Ltd., East Grimstead, UK).

RESULTS

Twenty-one patients, comprising 11 males and 10 females with a median age of 69 years, were recruited. Cancer (n = 11) was the most common underlying disease, 19 (90.5%) cases had prior antibiotic exposure, and only two patients had prior antifungal use. The overall in-hospital mortality rate was 38.1% (n = 8). C. guilliermondii (n = 11) was the most common pathogen, followed by C. curvata (n = 3). C. guilliermondii isolates exhibited relatively high rates of azole minimum inhibitory concentrations (MICs) above epidemiological cut-off values (ECVs), whereas C. pelliculosa and C. lusitaniae isolates all remained susceptible to azoles. All three C. curvata isolates had high caspofungin (>8 mg/L) and fluconazole MICs (8 mg/L) and could be defined as multidrug-resistant.

CONCLUSIONS

Uncommon Candida species frequently exhibit high rates of non-susceptibility to antifungals. Identification of all Candida isolates at the species level from blood samples is of value for treatment.

The identification of Meyerozyma guilliermondii from blood cultures and surveillance samples in a university hospital in Northeast Turkey: A ten-year survey

Meyerozyma (Pichia) guilliermondii exists in human skin and mucosal surface microflora. It can cause severe fungal infections like candidemia, which is an opportunistic pathogen. One hundred and forty-one M. guilliermondii isolates, consisting of 122 blood culture isolates, belonging to 126 patients; 13 total parenteral nutrition solution isolates; and two rectal swab isolates were identified according to carbohydrate assimilation reactions in a university hospital in Turkey between January 2006 and December 2015. Following Candida albicans (34.0%) and C. parapsilosis (21.2%), the third yeast species most commonly isolated from blood cultures in the Farabi Hospital was M. guilliermondii (20.6%). The patients were hospitalised in 27 different departments. A total of 50% of the patients were in pediatric departments, 49.2% were in intensive care units, and 17.2% were in haematology-oncology departments. Molecular identification of the isolates was performed using DNA sequence analysis of ribosomal ITS gene regions and IGS amplification-AluI fingerprinting (IGSAF). With molecular identification, 140 isolates were identified as M. guilliermondii and one isolate was identified as Candida membranifaciens. It was observed that the ITS1 region specifically helps in identifying these species. It was demonstrated that biochemical and molecular methods were 99.3% consistent in identifying M. guilliermondii. The Wild-Type (WT) Minimum Inhibitory Concentrations (MICs) distribution of fluconazole, voriconazole, itraconazole, and flucytosine were determined using the Sensititre YeastOne YO2V system after 24h of incubation. One M. guilliermondii strain was determined to be non-WT for fluconazole, voriconazole, itraconazole and flucytosine. In total, three M. guilliermondii strains, for fluconazole, were determined to be non-WT in this study.

Candida guilliermondii Complex Is Characterized by High Antifungal Resistance but Low Mortality in 22 Cases of Candidemia

The objectives of our study were to describe the characteristics of patients with Candida guilliermondii candidemia and to perform an in-depth microbiological characterization of isolates and compare them with those of patients with C. albicans candidemia. We described the risk factors and outcomes of 22 patients with candidemia caused by the C. guilliermondii complex. Incident isolates were identified using molecular techniques, and susceptibility to fluconazole, anidulafungin, and micafungin was studied. Biofilm formation was measured using the crystal violet assay (biomass production) and the XTT reduction assay (metabolic activity), and virulence was studied using the Galleria mellonella model. Biofilm formation was compared with that observed for C. albicans The main conditions predisposing to infection were malignancy (68%), immunosuppressive therapy (59%), and neutropenia (18%). Clinical presentation of candidemia was less severe in patients infected by the C. guilliermondii complex than in patients infected by C. albicans, and 30-day mortality was lower in C. guilliermondii patients (13.6% versus 33.9%, respectively; P = 0.049). Isolates were identified as C. guilliermondiisensu stricto (n = 17) and Candida fermentati (n = 5). The isolates produced biofilms with low metabolic activity and moderate biomass. The G. mellonella model showed that C. guilliermondii was less virulent than C. albicans (mean of 6 days versus 1 day of survival, respectively; P < 0.001). Patients with candidemia caused by the C. guilliermondii complex had severe and debilitating underlying conditions. Overall, the isolates showed diminished susceptibility to fluconazole and echinocandins, although poor biofilm formation and the low virulence were associated with a favorable outcome.

Molecular epidemiology and azole resistance mechanism study of Candida guilliermondii from a Chinese surveillance system

We studied the molecular epidemiology and mechanism of azole resistance of 164 C. guilliermondii isolates from a nationwide multi-center surveillance program. The isolates were identified by ITS gene sequencing, and the in vitro susceptibility to fluconazole and voriconazole was determined by broth microdilution method. The 14-α-demethylase gene ERG11 was amplified and sequenced, and microsatellite analysis was performed to study the genetic relatedness of the isolates. Amongst the 164 C. guilliermondii isolates, 15 (9.1%) and 17 (10.4%) isolates were assigned to be non-wild type (non-WT) to fluconazole and voriconazole, respectively. Sixteen sequence types (STs) were detected by comparing the amino acid sequence polymorphisms of the ERG11 gene. Fifteen isolates of STs 9, 10, 12, 13, 14, 15 and 16, were all assigned to be non-WT to fluconazole and voriconazole. By microsatellite analysis, 40 different genotypes were identified. Thirty-seven isolates from one hospital (Z1) shared the same ERG11 sequence type (ST 2), microsatellite genotype (PU40) and drug resistance pattern. In conclusion, this is the first molecular epidemiology study of C. guilliermondii in China. The rate of non-WT isolates to azoles was high and the accurate contribution of ERG11 gene mutations to azole resistance need be confirmed by further studies.

Disruption of Protein Mannosylation Affects Candida guilliermondii Cell Wall, Immune Sensing, and Virulence

The fungal cell wall contains glycoproteins that interact with the host immune system. In the prominent pathogenic yeast Candida albicans, Pmr1 acts as a Golgi-resident ion pump that provides cofactors to mannosyltransferases, regulating the synthesis of mannans attached to glycoproteins. To gain insight into a putative conservation of such a crucial process within opportunistic yeasts, we were particularly interested in studying the role of the PMR1 homolog in a low-virulent species that rarely causes candidiasis, Candida guilliermondii. We disrupted C. guilliermondii PMR1 and found that loss of Pmr1 affected cell growth and morphology, biofilm formation, susceptibility to cell wall perturbing agents, mannan levels, and the wall composition and organization. Despite the significant increment in the amount of β1,3-glucan exposed at the wall surface, this positively influenced only the ability of the mutant to stimulate IL-10 production by human monocytes, suggesting that recognition of both mannan and β1,3-glucan, is required to stimulate strong levels of pro-inflammatory cytokines. Accordingly, our results indicate C. guilliermondii sensing by monocytes was critically dependent on the recognition of N-linked mannans and β1,3-glucan, as reported in other Candida species. In addition, chemical remotion of cell wall O-linked mannans was found to positively influence the recognition of C. guilliermondii by human monocytes, suggesting that O-linked mannans mask other cell wall components from immune cells. This observation contrasts with that reported in C. albicans. Finally, mice infected with C. guilliermondii pmr1Δ null mutant cells had significantly lower fungal burdens compared to animals challenged with the parental strain. Accordingly, the null mutant showed inability to kill larvae in the Galleria mellonella infection model. This study thus demonstrates that mannans are relevant for the C. guilliermondii-host interaction, with an atypical role for O-linked mannans.

Management of Candida guilliermondii joint infection in a dog

Background

Candida spp. are dimorphic fungi in the family Cryptococcaceae. Infections with Candida spp. are usually rare conditions in dogs, but immunocompromised patients have a higher risk for developing invasive candidal infections.

Case presentation

A 5-year-old male Boxer, positive to Leishmania infantum, was referred to the Veterinary Teaching Hospital of the Department of Veterinary Medicine, University of Perugia, Italy for examination of a non-weight bearing left hind limb lameness of a duration of at least 3 months. During this period, treatment involved systemic anti-inflammatory medications and intra-articular corticosteroid administration. On presentation, clinical examination and radiographic findings were suggestive of cranial cruciate ligament deficiency. To support this diagnosis a stifle arthroscopy was performed: it confirmed a partial rupture of cranial cruciate ligament. Samples culture of synovial fluid and membrane was routinely collected as well, and revealed Candida guilliermondii joint infection. Treatment for the C. guilliermondii joint infection involved systemic anti-fungal therapy, joint lavage and intra-articular administration of antifungal drugs. Lameness improved markedly during this treatment, but lameness did not resolve completely, probably due to cranial cruciate ligament deficiency. Tibial tuberosity advancement (TTA) was chosen in order to treat stifle instability and was performed 4 weeks following cessation of treatment of the C. guilliermondii joint infection. Six month after TTA the dog showed a completely recovery with no lameness.

Conclusions

To the authors’ knowledge, this is the first case of Candida spp. joint infection reported in dogs. The cause of the progression of the joint C. guilliermondii infection remains unclear but it may be associated with leishmaniasis or intra-articular corticosteroid injections. Treatment with systemic and intra-articular anti-fungal therapies was successful. In the evaluation of hind limb lameness in a chronically immunocompromised dog, it would be advisable to consider also an intra-articular Candida spp. infection.

In situ photoimmunotherapy for cutaneous granuloma caused by itraconazole-resistant Candida guilliermondii

Cutaneous granulomas caused by Candida guilliermondii are difficult to cure. In situ photoimmunotherapy (ISPI) is a novel method composed of local photothermal therapy and immunoadjuvant. In this study, ISPI was used the first time clinically for cutaneous granuloma caused by itraconazole-resistant C.guilliermondii. A 10-week cycle of ISPI was composed of (1) 5% imiquimod applied topically every other day and (2) irradiation of lesions with an 808-nm diode laser at Days 14, 28, 42, and 56. Here we report our first case. A patient was treated with ISPI for four cycles. After the treatment, the lesions were eliminated without recurrence during a 12-month follow-up. Our results demonstrate that ISPI can be used as an effective treatment modality for cutaneous fungal granuloma.

Identification and Antifungal Susceptibility Profile of Candida guilliermondii and Candida fermentati from a Multicenter Study in China

With molecular sequencing as a gold standard, the Vitek MS, Bruker Biotyper MS, and Vitek-2 Compact systems correctly identified 92.7%, 97.0%, and 15.2% of 164 Candida guillermondii isolates, respectively, and none of 8 C. fermentati isolates. All of the isolates showed high susceptibility to echinocandins, but some C. guilliermondii isolates showed low azole susceptibility.

Uncommon Candida Species Fungemia among Cancer Patients, Houston, Texas, USA

Many uncommon Candida species that cause bloodstream infections (BSIs) are not well-characterized. We investigated the epidemiology, antifungal use, susceptibility patterns, and factors associated with all-cause death among cancer patients in whom uncommon Candida spp. BSIs were diagnosed at a cancer treatment center during January 1998–September 2013. Of 1,395 Candida bloodstream isolates, 79 from 68 patients were uncommon Candida spp. The incidence density of uncommon Candida spp. BSIs and their proportion to all candidemia episodes substantively increased during the study period, and the rise was associated with increasing use of echinocandin antifungal drugs. Thirty-seven patients had breakthrough infections during therapy or prophylaxis with various systemic antifungal drugs for >7 consecutive days; 21 were receiving an echinocandin. C. kefyr (82%), and C. lusitaniae (21%) isolates frequently showed caspofungin MICs above the epidemiologic cutoff values. These findings support the need for institutional surveillance for uncommon Candida spp. among cancer patients.

Azole resistance in Candida spp. isolated from Catú Lake, Ceará, Brazil: an efflux-pump-mediated mechanism

Since, there is no study reporting the mechanism of azole resistance among yeasts isolated from aquatic environments; the present study aims to investigate the occurrence of antifungal resistance among yeasts isolated from an aquatic environment, and assess the efflux-pump activity of the azole-resistant strains to better understand the mechanism of resistance for this group of drugs. For this purpose, monthly water and sediment samples were collected from Catú Lake, Ceará, Brazil, from March 2011 to February 2012. The obtained yeasts were identified based on morphological and biochemical characteristics. Of the 46 isolates, 37 were Candida spp., 4 were Trichosporon asahii, 3 were Cryptococcus laurentii, 1 Rhodotorula mucilaginosa, and 1 was Kodamaea ohmeri. These isolates were subjected to broth microdilution assay with amphotericin B, itraconazole, and fluconazole, according to the methodology standardized by the Clinical and Laboratory Standards Institute (CLSI). The minimum inhibitory concentrations (MICs) of amphotericin B, itraconazole, and fluconazole were 0.03125–2 μg/mL, 0.0625 to ≥16 μg/mL, and 0.5 to ≥64 μg/mL, respectively, and 13 resistant azole-resistant Candida isolates were detected. A reduction in the azole MICs leading to the phenotypical reversal of the azole resistance was observed upon addition of efflux-pump inhibitors. These findings suggest that the azole resistance among environmental Candida spp. is most likely associated with the overexpression of efflux-pumps.

Isavuconazole, micafungin, and 8 comparator antifungal agents' susceptibility profiles for common and uncommon opportunistic fungi collected in 2013: temporal analysis of antifungal drug resistance using CLSI species-specific clinical breakpoints and proposed epidemiological cutoff values

The in vitro activities of isavuconazole, micafungin, and 8 comparator antifungal agents were determined for 1613 clinical isolates of fungi (1320 isolates of Candida spp., 155 of Aspergillus spp., 103 of non-Candida yeasts, and 35 non-Aspergillus molds) collected during a global survey conducted in 2013. The vast majority of the isolates of the 21 different species of Candida, with the exception of Candida glabrata (MIC90, 2 μg/mL), Candida krusei (MIC90, 1 μg/mL), and Candida guilliermondii (MIC90, 8 μg/mL), were inhibited by ≤0.25 μg/mL of isavuconazole. C. glabrata and C. krusei were largely inhibited by ≤1 μg/mL of isavuconazole. Resistance to fluconazole was seen in 0.5% of Candida albicans isolates, 11.1% of C. glabrata isolates, 2.5% of Candida parapsilosis isolates, 4.5% of Candida tropicalis isolates, and 20.0% of C. guilliermondii isolates. Resistance to the echinocandins was restricted to C. glabrata (1.3-2.1%) and C. tropicalis (0.9-1.8%). All agents except for the echinocandins were active against 69 Cryptococcus neoformans isolates, and the triazoles, including isavuconazole, were active against the other yeasts. Both the mold active triazoles as well as the echinocandins were active against 155 Aspergillus spp. isolates belonging to 10 species/species complex. In general, there was low resistance levels to the available systemically active antifungal agents in a large, contemporary (2013), global collection of molecularly characterized yeasts and molds. Resistance to azoles and echinocandins was most prominent among isolates of C. glabrata, C. tropicalis, and C. guilliermondii.

Candida fermentati as a cause of persistent fungemia in a preterm neonate successfully treated by combination therapy with amphotericin B and caspofungin

A case of persistent candidemia in a preterm neonate caused by Candida fermentati, identified by sequencing of the internally transcribed spacer region of ribosomal DNA (rDNA), is described. The neonate was treated for 30 days by combination therapy with amphotericin B (AmBisome) and caspofungin with a successful outcome, and no drug-related side effects were observed.

Experimental therapy with azoles against Candida guilliermondii

We evaluated the in vitro killing activity of voriconazole (VRC) and posaconazole (PSC) against two clinical isolates of Candida guilliermondii. The two drugs showed fungistatic activity against both isolates and were effective in reducing kidney fungal burden in a neutropenic murine model of disseminated candidiasis in infected mice. PSC was significantly more effective than VRC against one of the strains. The serum levels of PSC and VRC were above the corresponding MICs for these isolates.

The Candida pathogenic species complex

Candida species are the most common causes of fungal infection. Approximately 90% of infections are caused by five species: Candida albicans, Candida glabrata, Candida tropicalis, Candida parapsilosis, and Candida krusei. Three (C. albicans, C. tropicalis, and C. parapsilosis) belong to the CTG clade, in which the CTG codon is translated as serine and not leucine. C. albicans remains the most commonly isolated but is decreasing relative to the other species. The increasing incidence of C. glabrata is related to its reduced susceptibility to azole drugs. Genome analysis suggests that virulence in the CTG clade is associated with expansion of gene families, particularly of cell wall genes. Similar independent processes took place in the C. glabrata species group. Gene loss and expansion in an ancestor of C. glabrata may have resulted in preadaptations that enabled pathogenicity.

Ca(2+)-CaM regulating viability of Candida guilliermondii under oxidative stress by acting on detergent resistant membrane proteins

Reactive oxygen species (ROS) play a vital role in reducing viability of yeast cells. The Ca(2+)-CaM signaling pathways are involved in regulating the intracellular ROS level in yeast cells under stress. Detergent resistant membranes (DRMs), the sterol-rich microdomains, participate in a wide range of cellular processes including growth, trafficking and death in yeast cells. In the present study, we found that Trifluoperazine (TFP), an antagonist of CaM, could increase the viability of Candida guilliermondii cells under H2O2 stress. Based on comparative analysis of DRM sub proteomics, a total number of 29 differentially expressed protein spots were identified, among which 8 protein spots belong to the electron transport chain and 7 protein spots belong to transporters. It is suggested that TFP treatment could modulate the intracellular ROS generation in yeast cells. We additionally ascertained that TFP treatment could effectively alleviate the ROS accumulation and protein damage in C. guilliermondii cells under H2O2 stress, via investigating the intracellular ROS levels and protein oxidative damage in yeast cells. These findings firstly revealed that the Ca(2+)-CaM signaling pathway is related to the viability of yeast cells under H2O2 stress, and provide novel evidences for exploring Ca(2+)-CaM's role in regulating this viability via acting on DRM proteins.

BIOLOGICAL SIGNIFICANCE

Detergent-resistant membranes (DRMs), which are more resistant to extraction with cold non-ionic detergents, have been considered the functional microdomains in the plasma membrane. In yeast, DRMs are involved in a wide range of additional cellular processes including cell growth and death. The Ca(2+)-CaM signaling pathways could regulate the stress tolerance of yeast cells by modulating the intracellular ROS generation. In this study, we found that trifluoperazine (TFP), a calmodulin antagonist, could increase the viability of C. guilliermondii under H2O2 stress. Based on comparative analysis of DRM sub proteomics, electron transport chain proteins and transporters were identified to be associated with the Ca(2+)-CaM transduction. We proved that TFP treatment decreases the intracellular ROS accumulation and alleviates oxidative damage to cellular proteins. These results ascertain that Ca(2+)-CaM is involved in regulating the viability of C. guilliermondii under oxidative stress via acting on the DRM proteins.

Epidemiology and outcomes of invasive candidiasis due to non-albicans species of Candida in 2,496 patients: data from the Prospective Antifungal Therapy (PATH) registry 2004-2008

This analysis describes the epidemiology and outcomes of invasive candidiasis caused by non-albicans species of Candida in patients enrolled in the Prospective Antifungal Therapy Alliance (PATH Alliance) registry from 2004 to 2008. A total of 2,496 patients with non-albicans species of Candida isolates were identified. The identified species were C. glabrata (46.4%), C. parapsilosis (24.7%), C. tropicalis (13.9%), C. krusei (5.5%), C. lusitaniae (1.6%), C. dubliniensis (1.5%) and C. guilliermondii (0.4%); 111 infections involved two or more species of Candida (4.4%). Non-albicans species accounted for more than 50% of all cases of invasive candidiasis in 15 of the 24 sites (62.5%) that contributed more than one case to the survey. Among solid organ transplant recipients, patients with non-transplant surgery, and patients with solid tumors, the most prevalent non-albicans species was C. glabrata at 63.7%, 48.0%, and 53.8%, respectively. In 1,883 patients receiving antifungal therapy on day 3, fluconazole (30.5%) and echinocandins (47.5%) were the most frequently administered monotherapies. Among the 15 reported species, 90-day survival was highest for patients infected with either C. parapsilosis (70.7%) or C. lusitaniae (74.5%) and lowest for patients infected with an unknown species (46.7%) or two or more species (53.2%). In conclusion, this study expands the current knowledge of the epidemiology and outcomes of invasive candidiasis caused by non-albicans species of Candida in North America. The variability in species distribution in these centers underscores the importance of local epidemiology in guiding the selection of antifungal therapy.