Secreted aspartyl peptidases by the emerging, opportunistic and multidrug-resistant fungal pathogens comprising the Candida haemulonii complex

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.

SARS-CoV-2 Post-Infection and Sepsis by Saccharomyces cerevisiae: A Fatal Case Report-Focus on Fungal Susceptibility and Potential Virulence Attributes

The pandemic caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been responsible for approximately 6.8 million deaths worldwide, threatening more than 753 million individuals. People with severe coronavirus disease-2019 (COVID-19) infection often exhibit an immunosuppression condition, resulting in greater chances of developing co-infections with bacteria and fungi, including opportunistic yeasts belonging to the Saccharomyces and Candida genera. In the present work, we have reported the case of a 75-year-old woman admitted at a Brazilian university hospital with an arterial ulcer in the left foot, which was being prepared for surgical amputation. The patient presented other underlying diseases and presented positive tests for COVID-19 prior to hospitalization. She received antimicrobial treatment, but her general condition worsened quickly, leading to death by septic shock after 4 days of hospitalization. Blood samples collected on the day she died were positive for yeast-like organisms, which were later identified as Saccharomyces cerevisiae by both biochemical and molecular methods. The fungal strain exhibited low minimal inhibitory concentration values for the antifungal agents tested (amphotericin B, 5-flucytosine, caspofungin, fluconazole and voriconazole), and it was able to produce important virulence factors, such as extracellular bioactive molecules (e.g., aspartic peptidase, phospholipase, esterase, phytase, catalase, hemolysin and siderophore) and biofilm. Despite the activity against planktonic cells, the antifungals were not able to impact the mature biofilm parameters (biomass and viability). Additionally, the S. cerevisiae strain caused the death of Tenebrio molitor larvae, depending on the fungal inoculum, and larvae immunosuppression with corticosteroids increased the larvae mortality rate. In conclusion, the present study highlighted the emergence of S. cerevisiae as an opportunistic fungal pathogen in immunosuppressed patients presenting several severe comorbidities, including COVID-19 infection.

The Threat Called Candida haemulonii Species Complex in Rio de Janeiro State, Brazil: Focus on Antifungal Resistance and Virulence Attributes

Although considered rare, the emergent Candida haemulonii species complex, formed by C. haemulonii sensu stricto (Ch), C. duobushaemulonii (Cd) and C. haemulonii var. vulnera (Chv), is highlighted due to its profile of increased resistance to the available antifungal drugs. In the present work, 25 clinical isolates, recovered from human infections during 2011–2020 and biochemically identified by automated system as C. haemulonii, were initially assessed by molecular methods (amplification and sequencing of ITS1-5.8S-ITS2 gene) for precise species identification. Subsequently, the antifungal susceptibility of planktonic cells, biofilm formation and susceptibility of biofilms to antifungal drugs and the secretion of key molecules, such as hydrolytic enzymes, hemolysins and siderophores, were evaluated by classical methodologies. Our results revealed that 7 (28%) isolates were molecularly identified as Ch, 7 (28%) as Chv and 11 (44%) as Cd. Sixteen (64%) fungal isolates were recovered from blood. Regarding the antifungal susceptibility test, the planktonic cells were resistant to (i) fluconazole (100% of Ch and Chv, and 72.7% of Cd isolates), itraconazole and voriconazole (85.7% of Ch and Chv, and 72.7% of Cd isolates); (ii) no breakpoints were defined for posaconazole, but high MICs were observed for 85.7% of Ch and Chv, and 72.7% of Cd isolates; (iii) all isolates were resistant to amphotericin B; and (iv) all isolates were susceptible to echinocandins (except for one isolate of Cd) and to flucytosine (except for two isolates of Cd). Biofilm is a well-known virulence and resistant structure in Candida species, including the C. haemulonii complex. Herein, we showed that all isolates were able to form viable biofilms over a polystyrene surface. Moreover, the mature biofilms formed by the C. haemulonii species complex presented a higher antifungal-resistant profile than their planktonic counterparts. Secreted molecules associated with virulence were also detected in our fungal collection: 100% of the isolates yielded aspartic proteases, hemolysins and siderophores as well as phospholipase (92%), esterase (80%), phytase (80%), and caseinase (76%) activities. Our results reinforce the multidrug resistance profile of the C. haemulonii species complex, including Brazilian clinical isolates, as well as their ability to produce important virulence attributes such as biofilms and different classes of hydrolytic enzymes, hemolysins and siderophores, which typically present a strain-dependent profile.