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

Abstract

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.

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

“…De Almeida et al found that four C. duobushaemulonii isolated in Brazil has high MICs to azole and amphotericin B (de Almeida et al, 2016). Ramos et al has been reported echinocandinsresistance strains isolated in Brazil (Ramos et al, 2022). Regretfully, previous studies lacked 5-flucytosine antifungal drug sensitivity and only 18.2% (2/11) C. duobushaemulonii tested were 5-flucytosine-resistance (Cendejas-Bueno et al, 2012;de Almeida et al, 2016;Ramos et al, 2022).…”

“…Ramos et al has been reported echinocandinsresistance strains isolated in Brazil (Ramos et al, 2022). Regretfully, previous studies lacked 5-flucytosine antifungal drug sensitivity and only 18.2% (2/11) C. duobushaemulonii tested were 5-flucytosine-resistance (Cendejas-Bueno et al, 2012;de Almeida et al, 2016;Ramos et al, 2022). In the literature review, we can see that despite the low isolation rate of C. duobushaemulonii, strains resistant to azoles, echinocandins, amphotericin B, or 5-flucytosine have been emerging.…”

First two fungemia cases caused by Candida haemulonii var. vulnera in China with emerged antifungal resistance

“…Infections caused by C. haemulonii var. vulnera were later reported in Brazil, India, Argentina, and Peru ( de Almeida et al, 2016 ; Kumar et al, 2016 ; Isla et al, 2017 ; Pérez-Lazo et al, 2021 ; Ramos et al, 2022 ). In addition, by retesting a set of previously collected strains, Rodrigues et al found a C. haemulonii var.…”

“…Candida haemulonii var. vulnera belongs to the C. haemulonii species complex, along with C. haemulonii sensu stricto and C. duobushaemulonii ( Gade et al, 2020 ; Rodrigues et al, 2021 ; Ramos et al, 2022 ). Generally, C. haemulonii species complex isolates display high multidrug-resistant rates and transmission properties, which have attracted increased attention ( Gade et al, 2020 ).…”

“…Moreover, antifungal resistance to azoles, echinocandins, and amphotericin B has been reported in C. haemulonii var. vulnera isolates ( Cendejas-Bueno et al, 2012 ; Isla et al, 2017 ; Ramos et al, 2022 ).…”