Reduced azole susceptibility of oral isolates of Candida albicans from HIV-positive patients and a derivative exhibiting colony morphology variation

Abstract

Approximately 50 % (15/28) of a selection of oral isolates of Candida albicuns from separate individuals infected with the human immunodeficiency virus (HIV) exhibited low susceptibility to ketoconazole as determined by hyphal elongation assessment. Nine of these isolates exhibited colony morphology variation or switching at 37 "C, of which six expressed low ketoconazole susceptibility. To determine whether colony morphology variation could give rise to derivatives with reduced azole susceptibility, several high-frequency switching variants of three HIVpatient isolates were recovered and assessed. All but one of the variants expressed similar azole susceptibility profiles to their respective parental strains. However, the C. albicans derivative 132ACR expressed significantly reduced susceptibility to ketoconazole in comparison to its parental strain 132A. In whole cells, on the basis of total growth the switched derivative 132ACR was markedly less susceptible than its parental isolate 132A to ketoconazole at 10 p~. A much smaller difference was observed with fluconazole at 10 PM, with the switched derivative 132ACR exhibiting a threefold lower susceptibility compared with the parental isolate 132A. The incorporation of [14C]acetate in control and azole-treated cells of both organisms was higher for the parental strain. When cell lysates of strain 132A and its derivative 132ACR were incubated with 114C]mevalonic acid and ketoconazole, the IC,, for 14C-label incorporation into 63-4 demethyl sterols was fivefold higher for lysates of the . switched derivative 132ACR compared with those of the parental strain 132A. With fluconazole the IC5,, value for the derivative 132ACR was 25-fold higher than for strain 132A. The 14-sterol demethylase of the switched derivative 132ACR was possibly less sensitive to azole inhibition than that of the enzyme of strain 132A. These studies indicated that colony morphology variation in vifro can generate derivatives with stable, reduced azole susceptibility without prior exposure to azoles.

Correlation of in vitro fluconazole resistance of Candida isolates in relation to therapy and symptoms of individuals seropositive for human immunodeficiency virus type 1

“…First, does azole and/or polyene therapy select for changes in the mucosal mycoflora (1,9,16,23,26), such as for the inherently resistant organisms C. krusei and T. glabrata (1,3,8,11,20,22,(29)(30)(31)? Second, does azole therapy induce the development of azole and/or polyene resistance in the mycoflora present during its use (2,4,10,14,23,24,27), or is azole therapy even necessary for resistant C. albicans to be present (5,10)? Finally, what is the effect of drug dosage and length of exposure to azoles on the development of clinical resistance?…”

Differential Filamentation of Candida albicans and Candida dubliniensis Is Governed by Nutrient Regulation of UME6 Expression

“…All Candida strains were routinely cultured on yeast extract-peptone-dextrose (YPD) agar at 37°C. For liquid culture, cells were grown with shaking (at 200 rpm) in YPD broth at 30°C or 37°C, as indicated in the figure legends (9). Genotypes of strains used in this study are listed in Table S1 in the supplemental material.…”

Molecular Mechanisms of Itraconazole Resistance in Candida dubliniensis

“…Total genomic DNA of C. dubliniensis clinical isolates and derivatives was prepared from cells grown for 18 h in YEPD broth cultures, as described by Gallagher et al (8).…”