Prevalence and Pattern of Antifungal Drug Minimum Inhibitory Concentration (MIC) of Invasive Candidiasis and its Associated Risk Factors

Abstract

Background. Invasive candidiasis is defined by the growth of Candida species in the bloodstream or other internal organs. It is a global concern due to increasing multidrug resistance and high mortality rates. This study aimed to update prevalence data on Candida infections in the Philippines, analyzing demographic factors (age, sex), specimen sources, and associated risk factors. We compared antifungal resistance patterns against CLSI epidemiological cutoff values (ECVs) and clinical breakpoints and examined MIC variations by underlying disease to inform potential standardized empiric therapies.

Methodology. We conducted a retrospective analytical cross-sectional study (SLMC‑IERC approval, minimal risk) reviewing one year of Candida speciation and susceptibility results from January to December 2024 at a private tertiary hospital. All aseptically collected samples that tested positive for Candida species were included. Respiratory and wound specimens required a Gram stain demonstrating yeasts or hyphae prior to culture, while urine cultures were included only if they yielded ≥100,000 CFU/mL. Identification and susceptibility testing were performed using the VITEK 2 system, with results interpreted using CLSI breakpoints and ECVs.

Results. Among 266 patients with Candida infections, invasive candidiasis predominated in those aged ≥ 60 years (66.4%). Candida albicans (21.7%) and C. tropicalis (13.5%) were more frequent in females, while C. parapsilosis (13.2%) and C. glabrata (5.3%) were more common in males. Blood and CSF samples strongly correlated with invasive disease and underlying risk factors. C. albicans was linked to infection-related conditions (13.9%), malignancy (9.0%), and cardiovascular disease (6.8%). C. parapsilosis (23.3%) and C. tropicalis (20.7%) were frequently associated with infection, malignancy, and metabolic disorders. C. glabrata (7.5%), noted for antifungal resistance, was isolated in patients with direct infections (3.4%) and malignancies (1.9%). Among azoles, fluconazole demonstrated greater susceptibility against Candida species, requiring lower concentrations for inhibition, despite a higher resistance rate (13.22%) compared to voriconazole (8.95%). Among echinocandins, micafungin showed better susceptibility than caspofungin. Amphotericin B demonstrated the highest overall susceptibility (93–100%), though MICs approached ECV limits. Most susceptible MIC values were: fluconazole 0.5 µg/mL for C. albicans and C. parapsilosis, 1.0 µg/mL for C. tropicalis; voriconazole and caspofungin 0.12 µg/mL; micafungin 0.06 µg/mL; amphotericin B 0.5 µg/mL; and flucytosine <1 µg/mL for all species.

Conclusion. These findings support a species-specific, risk-adapted approach to antifungal therapy, incorporating demographic and clinical variables. Continuous surveillance of invasive candidiasis prevalence and antifungal MIC trends, with periodic breakpoint updates, is crucial to preserve therapeutic efficacy. Effective management of multidrug-resistant Candida infections also requires close collaboration between clinicians and pharmacists, as well as the development of new dosing strategies based on pharmacokinetic/pharmacodynamic (PK/PD) principles.