Increasing trend of fluconazole-non-susceptible Cryptococcus neoformans in patients with invasive cryptococcosis: a 12-year longitudinal study

Background: This study aimed to investigate the rate of fluconazole-non-susceptible Cryptococcus neoformans in Southern Taiwan for the period 2001-2012 and analyze the risk factors for acquiring it among patients with invasive cryptococcosis. Methods: All enrolled strains were isolated from blood or cerebrospinal fluid samples of the included patients. If a patient had multiple positive results for C. neoformans, only the first instance was enrolled. Susceptibility testing was performed using the Clinical and Laboratory Standards Institutes M27-A3 broth micro-dilution method. The MIC interpretative criteria for susceptibility to fluconazole were <= 8 mu g/ml. A total of 89 patients were included. Patients (n = 59) infected by fluconazole-susceptible strains were compared with those (n = 30) infected by non-susceptible strains. The patients' demographic and clinical characteristics were analyzed. Results: The rate of fluconazole-non-susceptible C. neoformans in the study period significantly increased over time (p < 0.001). The C. neoformans isolated in 2011-2012 (odds ratio: 10.68; 95 % confidence interval: 2.87-39.74; p < 0.001) was an independent predictive factor for the acquisition of fluconazole-non-susceptible C. neoformans. Conclusions: The rate of fluconazole-non-susceptible C. neoformans has significantly increased recently. Continuous and large-scale anti-fungal susceptibility tests for C. neoformans are warranted to confirm this trend.