Decrease in Candida albicans strains with reduced susceptibility to fluconazole following changes in prescribing policies

This study was undertaken to identify prescribing policies likely to favour or limit fluconazole resistance within a clinical department. Fluconazole exposure within the infectious diseases and clinical haematology units was investigated, and data were compared with in vitro susceptibility of Candid a albicans isolates obtained in these units. Fluconazole utilization was de termined by the number of fluconazole treatment-days per 100 hospitalizatio n days (penetration index). In the infectious diseases unit, separate evalu ations for low-dose fluconazole (50 mg) prescribed as intermittent or prolo nged treatment, and for higher-dosing schedules (fluconazole 200 mg) were m ade. Susceptibility of C. albicans isolates was surveyed in a broth microdi lution assay by measuring the inhibitory concentration 50% (IC50) The penet ration index (PI) for fluconazole 50 mg declined from 1992 to 1977 in infec tious diseases (P = 0.0048). In the meantime, total usage of fluconazole in creased, due to increased prescribing of fluconazole 200 mg (P = 0.0724). T he IC50 of C. albicans isolates tested in infectious diseases decreased bet ween 1994 and 1996 from 7.33 mug/ml to 1.64 mug/ml (P = 0.0075). In clinica l haematology, declines in C. albicans IC50 and fluconazole PI were not sig nificant (P = 0.35 and P = 0.07, respectively). These data suggest that pro longed or repeated exposure to low-dose fluconazole, rather than total cumu lative use, was associated with fluconazole resistance in the infectious di seases unit. Moreover, restoration of a normal ecology was observed when lo w-dose prolonged or intermittent prescriptions were reduced. (C) 2001 The H ospital infection Society.