Lyons C N, White T C
Department of Pathobiology, School of Public Health and Community Medicine, University of Washington and the Seattle Biomedical Research Institute, 98109-1651, USA.
Antimicrob Agents Chemother. 2000 Sep;44(9):2296-303. doi: 10.1128/AAC.44.9.2296-2303.2000.
Oral infections with the pathogenic yeast Candida albicans are one of the most frequent and earliest opportunistic infections in human immunodeficiency virus-infected patients. The widespread use of azole antifungal drugs has led to the development of drug-resistant isolates. Several molecular mechanisms that contribute to drug resistance have been identified, including increased mRNA levels for two types of efflux pump genes: the ATP binding cassette transporter CDRs (CDR1 and CDR2) and the major facilitator MDR1. Using Northern blot analyses, the expression patterns of these genes have been determined during logarithmic and stationary phases of cell growth and during growth in different carbon sources in a set of matched susceptible and fluconazole-resistant isolates that have been characterized previously. MDR1, CDR1, and CDR2 are expressed early during logarithmic growth, CDR4 is expressed late during logarithmic growth, and CDR1 is preferentially expressed in stationary-phase cells. There is a small decrease in expression of these genes when the cells are grown in carbon sources other than glucose. While increased mRNA levels of efflux pump genes are commonly associated with azole resistance, the causes of increased mRNA levels have not yet been resolved. Southern blot analysis demonstrates that the increased mRNA levels in these isolates are not the result of gene amplification. Nuclear run-on assays show that MDR1 and CDR mRNAs are transcriptionally overexpressed in the resistant isolate, suggesting that the antifungal drug resistance in this series is associated with the promoter and trans-acting factors of the CDR1, CDR2, and MDR1 genes.
致病性酵母白色念珠菌引起的口腔感染是人类免疫缺陷病毒感染患者中最常见且最早出现的机会性感染之一。唑类抗真菌药物的广泛使用导致了耐药菌株的出现。已确定了几种导致耐药的分子机制，包括两种类型的外排泵基因的mRNA水平升高：ATP结合盒转运蛋白CDRs（CDR1和CDR2）和主要易化子MDR1。使用Northern印迹分析，在一组先前已鉴定的匹配的敏感和氟康唑耐药菌株的细胞生长对数期和稳定期以及在不同碳源中生长期间，确定了这些基因的表达模式。MDR1、CDR1和CDR2在对数生长早期表达，CDR4在对数生长后期表达，而CDR1在稳定期细胞中优先表达。当细胞在除葡萄糖以外的碳源中生长时，这些基因的表达略有下降。虽然外排泵基因的mRNA水平升高通常与唑类耐药相关，但mRNA水平升高的原因尚未解决。Southern印迹分析表明，这些菌株中mRNA水平的升高不是基因扩增的结果。核转录分析表明，MDR1和CDR mRNA在耐药菌株中转录过度表达，表明该系列中的抗真菌药物耐药性与CDR1、CDR2和MDR1基因的启动子和反式作用因子有关。
