Stable azole drug resistance associated with a substrain of Candida albicans from an HIV‐infected patient

Abstract

Oral candidiasis is one of the earliest and most frequent complications of a failing immune system in HIV-infected individuals. For several years, oral candidiasis has been treated effectively with azole drugs, the one most frequently used is fluconazole. Unfortunately, extensive use of the drug for treatment and prophylaxis has led to treatment failure in an increasing number of patients. In most of these cases, strains of C. albicans isolated from the infection are less susceptible to fluconazole. The development of azole resistance in strains of C. albicans has been studied biochemically and more recently with molecular techniques. One excellent example of the development of azole resistance in C. albicans has been documented in a series of 17 C. albicans isolates from a single patient over a 2-year period. During this time, the patient experienced 14 episodes of oral candidiasis and was treated with increasing doses of fluconazole. Molecular and biochemical analyses confirms that the isolates are the same strain of C. albicans and that the resistance in these isolates is stable over 600 generations, suggesting that the changes in this strain are genetic in nature. In addition, the development of resistance is correlated with the identification of a substrain or variant of the original strain, as identified by restriction fragment length polymorphism (RFLP) analysis with the moderately repetitive probe, Ca3. The analysis of this series of isolates demonstrates that azole drug resistance is associated with several small genetic changes, each of which contributes to the overall resistance of the strain. Clearly, continual use of azole drugs by a patient can select for genetic changes that render oral candidiasis refractory to treatment.

Regulatory Circuitry Governing Fungal Development, Drug Resistance, and Disease

“…This widespread deployment of azoles coupled with the fungistatic nature of these drugs has led to the emergence of azole resistance in clinical isolates (13,111,120,507,624). Canonical mechanisms of azole resistance identified in clinical isolates and experimental populations include alterations of the drug target Erg11 and the overexpression of multidrug transporters.…”

Microevolutionary changes in Candida albicans identified by the complex Ca3 fingerprinting probe involve insertions and deletions of the full-length repetitive sequence RPS at specific genomic sites

“…The complex Candida albicans-specific DNA fingerprinting probe Ca3 (Soll et al, 1987 ;Sadhu et al, 1991 ;Anderson et al, 1993) has been used in a broad range of epidemiological studies (Soll et al, 1987(Soll et al, , 1989Schmid et al, 1990Schmid et al, , 1993Schmid et al, , 1995Odds et al, 1990 ;Soll, 1993 ;Hellstein et al, 1993 ;Schroeppel et al, The GenBank accession numbers for the sequences reported in this paper are AF121119, AF121120, AF121121, AF121122, AF121123, AF121124 and AF121125. 1994 ; Lockhart et al, 1995Lockhart et al, , 1996Kleinegger et al, 1996 ;Pfaller et al, 1998 ;Marco et al, 1999 ;White et al, 1997, Lockhart et al, 1999. Its effectiveness has been verified in a comparison with multilocus enzyme electrophoresis and random amplified polymorphic DNA analysis (Pujol et al, 1997).…”

Identification of promoter elements responsible for the regulation of MDR1 from Candida albicans, a major facilitator transporter involved in azole resistance

“…However, its inactivation does not increase susceptibility to benomyl, suggesting that other mechanisms are involved in this resistance (Goldway et al, 1995). MDR1 is usually not expressed at detectable levels in fluconazole-susceptible C. albicans isolates but its constitutive upregulation in some fluconazole-resistant isolates reveals a correlation between azole resistance and overexpression of MDR1 (Franz et al, 1998;Sanglard et al, 1995;White, 1997;White et al, 1997).…”