Abstract
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.