COMPARISON OF 3 METHODS FOR TESTING AZOLE SUSCEPTIBILITIES OF CANDIDA-ALBICANS STRAINS ISOLATED SEQUENTIALLY FROM ORAL CAVITIES OF AIDS PATIENTS

Three susceptibility testing procedures were compared to determine flu conazole, itraconazole, and ketoconazole MICs against 47 Candida albic ans strains isolated sequentially from the oral cavities of five AIDS patients undergoing azole therapy. They included the broth microdiluti on method (BM), performed according to the National Committee for Clin ical Laboratory Standards' tentative standard, the agar dilution metho d (AD), and the Etest; the latter two tests were performed both in Cas itone agar (AD-Cas and Etest-Cas) and in RPMI (AD-RPMI and Etest-RPMI) . Twenty-four- and 48-h MICs obtained by AD and Etest were compared wi th 48-h MICs obtained by BM. The MICs of all the azoles determined by BM were usually lower than those obtained by the other methods, mainly due to different reading criteria. In order to assess the most approp riate way of evaluating the agreement of MICs obtained by different me thods with those produced by the proposed reference method (BM), we us ed the mean differences calculated according to Bland and Altman's met hod. Comparison of fluconazole MICs obtained by BM and AD-Gas yielded a mean difference of 3, and the percentages of agreement within +/-2 d ilutions were 98 and 100% at 24 and 48 h, respectively. For ketoconazo le and itraconazole MICs, lower mean differences were noted, and agree ment ranged from 96 to 100%. Agreement between the AD-RPMI and BM resu lts was poor for all azoles, and an increase in MICs was always observ ed between the Ist-and 2nd-day readings. Similarly, Etest-Cas gave bet ter agreement with BM than did Etest-RPMI for all the azoles. BM, AD-G as, and Etest-Cas each demonstrated a progressive increase in fluconaz ole MICs against strains isolated sequentially from a given patient, i n accordance with the decreased clinical response to fluconazole.