From the Guidelines

Candida guilliermondii is a species of Candida, a type of fungus that can cause infections in humans.

It is one of the many species of Candida that can cause candidiasis, a fungal infection [ 1 ]
C. guilliermondii is less common than other species like C. albicans, but it can still cause significant infections, particularly in immunocompromised individuals
This species has been shown to be susceptible to certain antifungal medications, including voriconazole [ 1 ]

The treatment of C. guilliermondii infections often involves the use of antifungal medications, with the specific choice of medication depending on the severity of the infection and the patient's overall health
Voriconazole is one option for treating C. guilliermondii infections, particularly in cases where the fungus is resistant to other medications [ 1 ]
In general, the treatment of candidiasis, including infections caused by C. guilliermondii, requires a comprehensive approach that takes into account the patient's individual needs and the specific characteristics of the infecting fungus [ 1 ]

From the Research

Candida guilliermondii is an uncommon isolate throughout most of the world, known to behave as an environmental fungus, a human saprophyte, and an agent of serious infections 2.
It is a component of human microbiota, but has been infrequently associated with human infections, possibly due to its low pathogenicity 3.
C. guilliermondii is an ascomycetous species belonging to the Saccharomycotina CTG clade, with biotechnological interest, biological control potential, and clinical importance 4.

Illnesses caused by C. guilliermondii mostly involve compromised cancer hosts and can lead to unfavorable outcomes 2.
It has been reported to cause invasive candidiasis, with decreased susceptibility to antifungal agents 5.
C. guilliermondii has been isolated from clinical samples, including blood, ascitis fluid, and oesophagus biopsy, often in patients with immunosuppressed conditions or previous use of antibiotics 3.

C. guilliermondii may acquire or inherently express reduced in vitro sensitivity to all antifungal classes, although widespread resistance has not yet been described 2.
The yeast appears to be constitutively less susceptible to polyenes and echinocandins than other yeast-like fungi 2.
Decreased susceptibility to fluconazole has been noted, with 75% of isolates susceptible, and voriconazole has been shown to be more active in vitro against C. guilliermondii than fluconazole 5.

C. guilliermondii is rarely isolated from humans, but has been reported to be more common in Latin America, representing 3.7% of isolates collected from 2001 to 2003 5.
The ARTEMIS DISK Antifungal Surveillance Program has reported geographic and temporal trends in the isolation and antifungal susceptibilities of C. guilliermondii clinical isolates 5.