# Challenges in Identifying Uncommon Clinical Isolates of Candida Species Using Conventional Phenotypic Methods: A Clinical Concern

## TL;DR

This study shows that traditional methods for identifying Candida species, especially rare ones like C. auris, are unreliable, leading to potential misdiagnosis and treatment issues.

## Contribution

The study evaluates the limitations of conventional and chromogenic methods in identifying uncommon Candida species in a rural hospital setting.

## Key findings

- Conventional phenotypic and chromogenic methods failed to accurately identify Candida auris.
- Non-albicans Candida species showed higher resistance to antifungals like fluconazole and voriconazole.
- Long-term antibiotic use was the most common risk factor for Candida infections in the study population.

## Abstract

Background

Candida species, particularly non-albicans Candida species, have emerged as a major cause of human infection, often exhibiting multidrug resistance due to either acquired or intrinsic resistance to antifungals. Therefore, accurate speciation of Candida isolates is crucial. However, despite reported misidentification issues with conventional methods, many mycology laboratories, including those in resource-poor healthcare facilities, still rely on them. This study compared various Candida speciation methods, including conventional phenotypic methods, chromogenic media, and the VITEK 2 compact system (bioMérieux, Marcy l'Etoile, France), and assessed the antifungal susceptibility patterns of clinical isolates at a rural tertiary care hospital.

Methodology

This prospective cross-sectional study was conducted from May 2024 to April 2025. Candida species were isolated from various clinical specimens (blood, urine, sputum, and pus) and subsequently speciated using conventional phenotypic methods (germ tube test, growth at 45°C, carbohydrate fermentation, and assimilation tests), HiCrome Candida differential agar, and the VITEK 2 compact system. Antifungal susceptibility testing was performed using the disc diffusion method on Mueller-Hinton agar supplemented with methylene blue.

Results

A total of 78 Candida isolates were obtained during the study period, with the majority isolated from urine (n = 44; 56.4%). Risk factor analysis of patients with Candida infections revealed that long-term antibiotic use (22.5%) was the most frequently associated factor. Among the isolates, seven were identified as Candida albicans, while the remaining isolates were non-albicans Candida species, including Candida tropicalis (n = 53), Candida parapsilosis (n = 15), Candida auris (n = 2), and Candida glabrata (n = 1). The VITEK 2 YST ID results were considered the reference method, and conventional phenotypic and chromogenic medium methods showed a varying degree of accuracy. Neither conventional phenotypic nor chromogenic medium accurately identified C. auris. High resistance rates were observed for fluconazole (57.7%), itraconazole (n = 66.7%), and voriconazole (60.3%), with non-albicans Candida species exhibiting higher resistance than C. albicans.

Conclusion

This study highlights the increasing trend of non-albicans Candida species as the predominant cause of Candida infections in rural Haryana, India, emphasizing the need for accurate Candida species identification due to their high multidrug resistance. Notably, conventional phenotypic methods and chromogenic media failed to accurately identify C. auris, highlighting the limitations of these approaches.