Superficial candidosis by Candida duobushaemulonii: An emerging microorganism

Revealing the impact of Rapamycin on the virulence factors of the Candida haemulonii complex

The incidence of invasive fungal infections caused by Candida species is increasing, particularly in immunocompromised individuals. This increasing incidence poses a dual challenge, comprising escalating antifungal resistance and the necessity for accurate fungal identification. The Candida haemulonii complex further complicates these challenges due to limited identification tools. Like some other Candida species, infections involving this complex show resistance to multiple antifungals, requiring innovative therapeutic approaches. Rapamycin, known for its antifungal properties and immunosuppressive characteristics, was investigated against the C. haemulonii complex species. Results revealed a rapamycin minimal inhibitory concentration (MIC) range of 0.07 to >20 µM, with fungicidal effects in most strains. In vitro analyses using the rapamycin maximum plasma concentration (0.016 µM) showed reduced surface properties and decreased production of extracellular enzymes. Rapamycin also hindered biofilm formation by some strains. Even when treated at the human therapeutic dose, which is lower than the MIC, phenotypic variations in C. haemulonii were detected, hinting at the possible attenuation of some virulence factors when exposed to rapamycin.

Candida haemulonii Species Complex: A Mini-review

Candida haemulonii species complex (CHSC) are emerging multidrug-resistant yeast pathogens able to cause life-threatening human infections in at-risk populations for invasive candidiasis worldwide. A recent laboratory survey conducted in 12 medical centers found that prevalence rates of Candida haemulonii complex isolates rose from 0.9 to 1.7% along the period between 2008 and 2019. We present a mini-review addressing recent aspects of the epidemiology, diagnosis and therapy of infections due to CHSC.

Candida haemulonii Complex and Candida auris: Biology, Virulence Factors, Immune Response, and Multidrug Resistance

There is worldwide concern about the constant increase in infections caused by Candida species that are multiresistant to antifungal drugs. The most common candidiasis is caused by Candida albicans, however, the species of the Candida haemulonii complex and Candida auris are emerging opportunistic pathogens, which isolation from clinical samples has significantly increased in the past years. The special interest in the study of these species lies in their ability to evade the action of antifungal drugs, such as amphotericin B, azoles, and echinocandins. In addition, the phenotypic changes of these species have given them the ability to easily adapt to environmental changes, including the host milieu and immunity. In this paper, a detailed review of the current literature on the C. haemulonii complex and C. auris is shown, analyzing aspects such as biology, immune response, putative virulence factors, infection, treatment, and the current strategies for diagnosis.

Antifungal susceptibility profiles and drug resistance mechanisms of clinical Candida duobushaemulonii isolates from China

Candida duobushaemulonii, type II Candida haemulonii complex, is closely related to Candida auris and capable of causing invasive and non-invasive infections in humans. Eleven strains of C. duobushaemulonii were collected from China Hospital Invasive Fungal Surveillance Net (CHIF-NET) and identified using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF), VITEK 2 Yeast Identification Card (YST), and internal transcribed spacer (ITS) sequencing. Whole genome sequencing of C. duobushaemulonii was done to determine their genotypes. Furthermore, C. duobushaemulonii strains were tested by Sensititre YeastOne™ and Clinical and Laboratory Institute (CLSI) broth microdilution panel for antifungal susceptibility. Three C. duobushaemulonii could not be identified by VITEK 2. All 11 isolates had high minimum inhibitory concentrations (MICs) to amphotericin B more than 2 μg/ml. One isolate showed a high MIC value of ≥64 μg/ml to 5-flucytosine. All isolates were wild type (WT) for triazoles and echinocandins. FUR1 variation may result in C. duobushaemulonii with high MIC to 5-flucytosine. Candida duobushaemulonii mainly infects patients with weakened immunity, and the amphotericin B resistance of these isolates might represent a challenge to clinical treatment.

Candida auris and other phylogenetically related species - a mini-review of the literature

The lesser-known non-albicans Candida species are often overlooked and difficult to diagnose in most microbiology laboratories. Candida auris, a relatively newly discovered species, is responsible for outbreaks in various geographical regions. Because of its increased resistance to antifungal drugs, C. auris is responsible for hard-to-treat infections and its pathogenicity is still incompletely elucidated. Non-albicans species phylogenetically related to C. auris, like the C. haemulonii complex might also play a role in human pathology. The current summary of the literature presents the emergence, virulence, laboratory identification, and molecular mechanisms responsible for antifungal resistance of emergent rare non-albicans Candida species.

Physiological characterization and molecular identification of some rare yeast species causing onychomycosis

INTRODUCTION

Onychomycosis are infections with a variety of etiological agents. Although dermatophytes are responsible for most infections, yeasts are gaining importance as agents of these pathologies. The use of antifungals has increased the incidence of what had been considered rare or novel pathogens. We reidentify three rare yeasts from a culture collection of onychomycosis agents by matrix-assisted laser desorption/ionization time of flight/mass spectrometry (MALDI-TOF/MS) and sequencing the internal transcribed spacer (ITS) regions or the intergenic spacer (IGS) 1 region of ribosomal DNA (rDNA), and present their enzymatic and antifungal susceptibility profiles.

MATERIAL AND METHODS

We performed a phenotypical characterization and molecular identification of five yeast isolates. We tested the urease, gelatinase, DNase, phospholipase, protease, and esterase activities, as well as the hemolytic activity. We evaluated the antifungal susceptibility to amphotericin B, fluconazole, anidulafungin and caspofungin.

RESULTS

Phenotypic methods could not identify the isolates. MALDI-TOF/MS was able to properly identify Candida duobushameulonii. The five isolates were successfully identified by sequence analysis as Candida duobushaemulonii, Meyerozyma caribbica and Cutaneotrichosporon dermatis. Candida duobushameulonii showed hemolytic, phospholipase, and protease activities. Meyerozyma caribbica was positive for gelatinase and protease activities. All antifungals exhibited minimum inhibitory concentrations (MICs) ≤2μg/mL against both species. The three isolates of Cutaneotrichosporon dermatis showed urease, DNase, and esterase activities, and resistance to echinocandins (MICs ≥8μg/mL), while amphotericin B and fluconazole exhibited low MICs against these isolates (0.50-2μg/mL).

DISCUSSION

Sequencing of the ITS or IGS1 regions of rDNA remains the best method for identifying cryptic species over other commercially available systems. More reports are needed to define the enzymatic and antifungal profiles for these species. This is the first report of Meyerozyma caribbica and Cutaneotrichosporon dermatis as etiological agents of onychomycosis.

Liver abscess caused by Candida haemulonii var. vulnera. First case report in Peru

BACKGROUND

Liver abscesses caused by Candida species are mainly found in immunocompromised hosts, associated with conditions (such as neutropenia and mucositis) that facilitate the spreading of microorganisms from the gastrointestinal tract.

CASE REPORT

We present the case of a non-immunocompromised 72-year-old woman with a liver abscess caused by Candida haemulonii var. vulnera, in whom potential associated conditions could be polycystic kidney disease and renal replacement therapy. The patient experienced clinical resolution after percutaneous drainage and treatment with caspofungin.

CONCLUSIONS

To our knowledge, this is the first case reported in Peru of a liver abscess due to Candida haemulonii var. vulnera, a clinical presentation that has not been described previously. This finding should prompt us to establish active surveillance of causal agents of systemic candidiasis.

Candida duobushaemulonii: An Old But Unreported Pathogen

Candidiasis caused by species of the Candida haemulonii complex (Candida haemulonii and Candida duobushaemulonii) and closely related species, Candida auris and Candida pseudohaemulonii are increasing. These species often show reduced susceptibility to antifungal drugs, such as azoles and amphotericin B or, less frequently, echinocandins. However, conventional phenotypic identification methods are unable to accurately differentiate these species and, therefore, their prevalence may have been underestimated. In this study, 150 isolates that were probably misidentified were reanalyzed using two novel PCR approaches. We found that one isolate previously identified in 1996 as Candida intermedia was C. duobushaemulonii, being one of the oldest isolates of this species described to date. We also found that this isolate had reduced susceptibility to fluconazole, itraconazole, and amphotericin B.

Insights into the Multi-Azole Resistance Profile in Candida haemulonii Species Complex

The Candida haemulonii complex (C. duobushaemulonii, C. haemulonii, and C. haemulonii var. vulnera) is composed of emerging, opportunistic human fungal pathogens able to cause invasive infections with high rates of clinical treatment failure. This fungal complex typically demonstrates resistance to first-line antifungals, including fluconazole. In the present work, we have investigated the azole resistance mechanisms expressed in Brazilian clinical isolates forming the C. haemulonii complex. Initially, 12 isolates were subjected to an antifungal susceptibility test, and azole cross-resistance was detected in almost all isolates (91.7%). In order to understand the azole resistance mechanistic basis, the efflux pump activity was assessed by rhodamine-6G. The C. haemulonii complex exhibited a significantly higher rhodamine-6G efflux than the other non-albicans Candida species tested (C. tropicalis, C. krusei, and C. lusitaneae). Notably, the efflux pump inhibitors (Phe-Arg and FK506) reversed the fluconazole and voricolazole resistance phenotypes in the C. haemulonii species complex. Expression analysis indicated that the efflux pump (ChCDR1, ChCDR2, and ChMDR1) and ERG11 genes were not modulated by either fluconazole or voriconazole treatments. Further, ERG11 gene sequencing revealed several mutations, some of which culminated in amino acid polymorphisms, as previously reported in azole-resistant Candida spp. Collectively, these data point out the relevance of drug efflux pumps in mediating azole resistance in the C. haemulonii complex, and mutations in ERG11p may contribute to this resistance profile.

Susceptibility of the Candida haemulonii Complex to Echinocandins: Focus on Both Planktonic and Biofilm Life Styles and a Literature Review

Candida haemulonii complex (C. haemulonii, C. duobushaemulonii and C. haemulonii var. vulnera) is well-known for its resistance profile to different available antifungal drugs. Although echinocandins are the most effective class of antifungal compounds against the C. haemulonii species complex, clinical isolates resistant to caspofungin, micafungin and anidulafungin have already been reported. In this work, we present a literature review regarding the effects of echinocandins on this emergent fungal complex. Published data has revealed that micafungin and anidulafungin were more effective than caspofungin against the species forming the C. haemulonii complex. Subsequently, we investigated the susceptibilities of both planktonic and biofilm forms of 12 Brazilian clinical isolates of the C. haemulonii complex towards caspofungin and micafungin (anidulafungin was unavailable). The planktonic cells of all the fungal isolates were susceptible to both of the test echinocandins. Interestingly, echinocandins caused a significant reduction in the biofilm metabolic activity (viability) of almost all fungal isolates (11/12, 91.7%). Generally, the biofilm biomasses were also affected (reduction range 20–60%) upon exposure to caspofungin and micafungin. This is the first report of the anti-biofilm action of echinocandins against the multidrug-resistant opportunistic pathogens comprising the C. haemulonii complex, and unveils the therapeutic potential of these compounds.

Identification of Candida Species from Clinical Samples in a Honduran Tertiary Hospital

Candida species are one of the most important causes of human infections, especially in hospitals and among immunocompromised patients. The correct and rapid etiological identification of yeast infections is important to provide adequate therapy, reduce mortality, and control outbreaks. In this study, Candida species were identified in patients with suspected fungal infection, and phenotypic and genotypic identification methods were compared. A total of 167 axenic fungal cultures and 46 clinical samples were analyzed by HardyCHROM^®, MicroScan^®(Omron Microscan Systems Inc, Renton, WA, USA), and PCR-RFLP (Restriction Fragment Length Polymorphisms). The species of the C. albicans complex were the most frequent, followed by C. tropicalis and C. glabrata. Less common but clinically relevant species of Candida were also isolated. The comparison between the three methods was concordant, especially for the most common Candida species. Fungal DNA amplification was successful in all clinical samples.