The relationship between antifungal usage and antifungal susceptibility in clinical isolates of Candida: A multicenter Korean study

There have been very few multicenter studies of the relationship between the use of antifungals and resistance to them. We investigated the antifungal susceptibility of 1,301 clinical isolates of Candida collected from nine Korean hospitals during a 3-month period in 2006 to explore the existence of this type of relationship. Antifungal usage in the preceding year, defined as the daily dose per 1,000 patient days (DDD/1,000 PD), was calculated for each hospital. Resistance to fluconazole, itraconazole, and amphotericin B was detected in 2, 9, and 0.2% of the isolates, respectively. The MIC₅₀/MIC₉₀ values were 0.03/0.125 mg/L for voriconazole, 0.06/0.25 mg/l for caspofungin, and 0.03/0.125 mg/l for micafungin. The total usage of systemic antifungals varied considerably among the nine hospitals, ranging from 6.1 to 96.2 DDD/1,000 PD. No relationship was found between the use of fluconazole (MIC ≥ 64 mg/l) or itraconazole (MIC ≥ 1 mg/ l) and resistance in the Candida species (P > 0.05). However, significant correlations were found between the percentage of Candida isolates that were non-susceptible to fluconazole (MIC ≥ 16 mg/l) and fluconazole usage (r = 0.733, P = 0.025) or total antifungal usage (r = 0.767, P = 0.016).