Minimal inhibitory concentration (MIC) of caspofungin and itraconazole inhibiting growth of Candida strains calculated from the linear regression equation

ABSTRACTPurposeThe aim of the study was to compare the susceptibility of Candida species to caspofungin and itraconazole.Material and methods118 strains of Candida species were used in the study: 8 pattern strains and 110 strains isolated from different ontocenoses. The susceptibility of fungi strains to drugs was determined by diffusion in agar gel. The minimal inhibitory concentration (MIC) was calculated from the linear regression equation with the use of the method by Kadłubowski.ResultsThe MIC value for caspofungin for the pattern strains ranged from 0.321 mg/L to 0.552 mg/L and for itraconazole from 0.019 mg/L to 0.11 mg/L. All the analyzed strains isolated from patients exhibited susceptibility to caspofungin; 5 strains of Candida albicans (8.06%) proved to be resistant to itraconazole. The MIC values for caspofungin ranged from 0.114 mg/L to 1.26 mg/L and for itraconazole from 0.012 mg/L to 16.1 mg/L.Conclusions1. All the studied pattern strains are susceptible to the examined drugs; all those isolated from patients show susceptibility to caspofungin; some Candida albicans strains (8.06%) are resistant to itraconazole. 2. The mean MIC values calculated from the activity curves are 0.426 mg/L for caspofungin and 1.0245 mg/L for itraconazole. 3. The mean MIC values calculated for caspofungin are lower than for itraconazole in the case of Candida albicans, C. glabrata and C. tropicalis. Having compared the influence of the drugs on C. famata, C. lusitaniae, C. parapsilosis and C. ciferri we proved there are statistically significant differences (0.0046>p<0.044).