Persistence of Clonal Azole-Resistant Isolates of Candida albicans from a Patient with Chronic Mucocutaneous Candidiasis in Colombia

Exploring the Potential Mechanism of Action of Piperine against Candida albicans and Targeting Its Virulence Factors

Plant-derived compounds have proven to be a source of inspiration for new drugs. In this study, piperine isolated from the fruits of Piper nigrum showed anti-Candida activity. Furthermore, the mechanisms of action of piperine and its impact on virulence factors in Candida albicans, which have not been comprehensively understood, were also assessed. Initially, piperine suppressed the hyphal transition in both liquid and solid media, hindered biofilm formation, and resulted in observable cell distortions in scanning electron microscope (SEM) samples, for both fluconazole-sensitive and fluconazole-resistant C. albicans strains. Additionally, the morphogenetic switches triggered by piperine were found to rely on the activity of mutant C. albicans strains. Secondly, piperine treatment increased cell membrane permeability and disrupted mitochondrial membrane potential, as evidenced by propidium iodine and Rhodamine 123 staining, respectively. Moreover, it induced the accumulation of intracellular reactive oxygen species in C. albicans. Synergy was obtained between the piperine and the fluconazole against the fluconazole-sensitive strain. Interestingly, there were no hemolytic effects of piperine, and it resulted in reduced cytotoxicity on fibroblast cells at low concentrations. The results suggest that piperine could have a dual mode of action inhibiting virulence factors and modulating cellular processes, leading to cell death in C. albicans.

In Vivo Microevolutionary Analysis of a Fatal Case of Rhinofacial and Disseminated Mycosis Due to Azole-Drug-Resistant Candida Species

Ten Candida species strains were isolated from the first known fatal case of rhinofacial and rhino-orbital-cerebral candidiasis. Among them, five strains of Candida parapsilosis complex were isolated during the early stage of hospitalization, while five strains of Candida tropicalis were isolated in the later stages of the disease. Using whole-genome sequencing, we distinguished the five strains of C. parapsilosis complex as four Candida metapsilosis strains and one Candida parapsilosis strain. Antifungal susceptibility testing showed that the five strains of C. parapsilosis complex were susceptible to all antifungal drugs, while five C. tropicalis strains had high minimum inhibitory concentrations to azoles, whereas antifungal-drug resistance gene analysis revealed the causes of azole resistance in such strains. For the first time, we analyzed the microevolutionary characteristics of pathogenic fungi in human hosts and inferred the infection time and parallel evolution of C. tropicalis strains. Molecular clock analysis revealed that azole-resistant C. tropicalis infection occurred during the first round of therapy, followed by divergence via parallel evolution in vivo. The presence/absence variations indicated a potential decrease in the virulence of genomes in strains isolated following antifungal drug treatment, despite the absence of observed clinical improvement in the conditions of the patient. These results suggest that genomic analysis could serve as an auxiliary tool in guiding clinical diagnosis and treatment.

Emergence and circulation of azole-resistant C. albicans, C. auris and C. parapsilosis bloodstream isolates carrying Y132F, K143R or T220L Erg11p substitutions in Colombia

Methods

Over a four-year period, 123 Candida bloodstream isolates were collected at a quaternary care hospital. The isolates were identified by MALDI-TOF MS and their fluconazole (FLC) susceptibility patterns were assessed according to CLSI guidelines. Subsequently, sequencing of ERG11, TAC1 or MRR1, and efflux pump activity were performed for resistant isolates.

Results

Out of 123 clinical strains,C. albicans accounted for 37.4%, followed by C. tropicalis 26.8%, C. parapsilosis 19.5%, C. auris 8.1%, C. glabrata 4.1%, C. krusei 2.4% and C. lusitaniae 1.6%. Resistance to FLC reached 18%; in addition, a high proportion of isolates were cross-resistant to voriconazole. Erg11 amino acid substitutions associated with FLC-resistance (Y132F, K143R, or T220L) were found in 11/19 (58%) of FLCresistant isolates. Furthermore, novel mutations were found in all genes evaluated. Regarding efflux pumps, 8/19 (42%) of FLC-resistant Candida spp strains showed significant efflux activity. Finally, 6/19 (31%) of FLC-resistant isolates neither harbored resistance-associated mutations nor showed efflux pump activity. Among FLC-resistant species, C. auris 7/10 (70%) and C. parapsilosis 6/24 (25%) displayed the highest percentages of resistance (C. albicans 6/46, 13%).

Discussion

Overall, 68% of FLC-resistant isolates exhibited a mechanism that could explain their phenotype (e.g. mutations, efflux pump activity, or both). We provide evidence that isolates from patients admitted to a Colombian hospital harbor amino acid substitutions related to resistance to one of the most commonly used molecules in the hospital setting, with Y132F being the most frequently detected.

Inhibitory Effects and Mechanism of Action of Elsinochrome A on Candida albicans and Its Biofilm

Biofilm-associated Candida albicans infections, the leading cause of invasive candidiasis, can cause high mortality rates in immunocompromised patients. Photodynamic antimicrobial chemotherapy (PACT) is a promising approach for controlling infections caused by biofilm-associated C. albicans. This study shows the effect of Elsinochrome A (EA) against different stages of C. albicans biofilms in vitro by XTT reduction assay and crystal violet staining. The mechanism of action of EA on C. albicans biofilm was analyzed with flow cytometry, confocal laser microscopy, and the Real-Time Quantitative Reverse Transcription PCR (qRT-PCR). EA-mediated PACT significantly reduced the viability of C. albicans, with an inhibition rate on biofilm of 89.38% under a concentration of 32 μg/mL EA. We found that EA could not only inhibit the adhesion of C. albicans in the early stage of biofilm formation, but that it also had good effects on pre-formed mature biofilms with a clearance rate of 35.16%. It was observed that EA-mediated PACT promotes the production of a large amount of reactive oxygen species (ROS) in C. albicans and down-regulates the intracellular expression of oxidative-stress-related genes, which further disrupted the permeability of cell membranes, leading to mitochondrial and nuclear damage. These results indicate that EA has good photodynamic antagonizing activity against the C. albicans biofilm, and potential clinical value.

Genetic diversity and molecular epidemiology of Candida albicans from vulvovaginal candidiasis patients

Candida albicans (C. albicans) is a common cause of vulvovaginal candidiasis (VVC). In this paper, the genetic diversity and molecular epidemiology of 173C. albicans strains were investigated by multilocus sequence typing (MLST). A total of 52 diploid sequence types (DSTs) were recognized, and 27 (51.9%) of which have not been reported in the MLST database. Genotyping was performed on the multiple isolates collected from patients with recurrent VVC (RVVC, referring to VVC which attacks more than 4 times in one year) in different acute infectious phases. The results showed that 59.1% (26/44) of the patients suffered a relapse, with DST 79 (65.4%) as the dominant genotype. The etiology of the remaining 40.9% (18/44) of patients was reinfection, and the main genotypes included DST 79 (33.3%), DST 124 (8.6%) and DST 1895 (8.6%). DST 79 (45%) and DST 1395 (7.5%) were the main isolates of VVC patients, while DST 79 (24.1%), DST 727 (6.9%), DST 732 (6.9%) and DST 1867 (6.9%) were the main types of healthy volunteers. The results of the genotypes between RVVC patients and other groups were statistically different. Furthermore, cluster analysis was carried out on 1468 isolates, among which 1337 were downloaded from the MLST database, 130 were divided into 8 Clades in the present study and the remaining one was taken as a singleton. 92.3% isolates from relapse patients, 58.3% isolates from re-infected patients, 77.5% isolates from VVC patients and 51.7% isolates from volunteers were distributed in Clade 1. The analysis of the genotypes of multiple isolates from RVVC patients further demonstrated that point mutation and loss of heterozygosity contributed to the microevolution of C. albicans.