Correlation Between Drug Resistance and Virulence of Candida Isolates from Patients with Candidiasis

This article aims to provide a theoretical basis for new or adjuvant strategies to facilitate the early diagnosis and treatment of candidiasis and to determine if drug-resistant Candida would affect virulence.

Our strains were collected from patients diagnosed with candidiasis in our hospital. The strains were identified by MALDI-TOF system and ITS sequencing. Antifungal sensitivity testing in vitro was performed to evaluate susceptibility of these isolates to current widely used antifungal drugs. The Galleria mellonella larvae model infected by Candida spp. was used to compare the virulence of drug-resistant and susceptible Candida spp.

A total of 206 Candida strains were collected from clinical specimens. Candida albicans was the most common species among them, and was predominantly isolated from male patients aged over 40 years in ICU environments suffering from pulmonary and/or cerebral conditions. The accuracy rate of MALDI TOF-MS identification was 92.72% when compared with ITS sequencing as the standard method. Most Candida species, except for C. tropicalis which showed high resistance to micafungin, showed high susceptibilities to voriconazole, itraconazole, amphotericin B and micafungin but were highly resistant to terbinafine. For each specific Candida species, the G. mellonella larvae model revealed that the virulence of drug-resistant Candida isolates did not markedly differ from that of the drug-susceptible isolates, however, the virulence was dose-dependent on inoculated fungal cells in this model.

The possibility of Candida infection should not be neglected in patients at critical care hospital settings and C. albicans is the most common causative agent. MALDI-TOF MS has the advantages of rapidity and high accuracy, and should be a preferred method for identification of Candida spp. in a clinical laboratory. Voriconazole, itraconazole, amphotericin B and micafungin can still be recommended as the first line antifungals to treat candidiasis.