The European Confederation of Medical Mycology (ECMM) survey of candidaemia in Italy : in vitro susceptibility of 375 Candida albicans isolates and production

Objectives.To investigate the in vitro antifungal susceptibility pattern of 375 Candida albicans bloodstream isolates recovered during the European Confederation of Medical Mycology survey of candidaemia performed in Lombardia, Italy and to test the ability to form biofilm. Methods. In vitro susceptibility to flucytosine, fluconazole, itraconazole, posaconazole, voriconazole and caspofungin was performed by broth microdilution following the NCCLS guidelines. Findings were correlated to the patient’s underlying conditions and previous antifungal treatment. Biofilm production was measured using the XTT-reduction assay in 59 isolates selected as representative of different pattern of susceptibility to flucytosine and azoles. Results. MICs (mg/L) at which 90% of the strains were inhibited were, respectively, ≤0.25 for flucytosine, 0.25 for caspofungin, 4 for fluconazole, and 0.06 for itraconazole, voriconazole, and posaconazole. Flucytosine-resistance was detected in 5 isolates and was associated with serotype B in 2/29 and serotype A in 3/346. Resistance to fluconazole was detected in 10 isolates, nine of these exhibited reduced susceptibility to the other azoles. Among the 10 patients with fluconazole-resistant C. albicans bloodstream infection, only one, an AIDS patient, had been previously treated with fluconazole. Elderly and surgery were associated with resistance. Biofilm production was observed in 23 isolates (39%) and was significantly associated with serotype B. No relationship was detected with the pattern of antifungal susceptibility. Conclusions. Resistance is uncommon in Candida albicans isolates recovered from blood cultures, while biofilm production is a relatively frequent event. Periodic surveillance are warranted to monitor the incidence of in vitro antifungal resistance as well as of biofilm production.