Related Experiment Video
Updated: Aug 8, 2025
Whole Genome Sequencing of Candida glabrata for Detection of Markers of Antifungal Drug Resistance
Published on: December 28, 2017
Antifungal Tolerance and Resistance Emerge at Distinct Drug Concentrations and Rely upon Different Aneuploid
Feng Yang1,2, Eduardo F C Scopel2, Hao Li1,3
1Department of Pharmacy, Shanghai Tenth People's Hospital, School of Medicine, Tongji University, Shanghai, China.
Abstract:
Antifungal drug tolerance is a response distinct from resistance, in which cells grow slowly above the MIC. Here, we found that the majority (69.2%) of 133 Candida albicans clinical isolates, including standard lab strain SC5314, exhibited temperature-enhanced tolerance at 37°C and 39°C, and were not tolerant at 30°C. Other isolates were either always tolerant (23.3%) or never tolerant (7.5%) at these three temperatures, suggesting that tolerance requires different physiological processes in different isolates. At supra-MIC fluconazole concentrations (8 to 128 μg/mL), tolerant colonies emerged rapidly at a frequency of ~10-3. In liquid passages over a broader range of fluconazole concentrations (0.25 to 128 μg/mL), tolerance emerged rapidly (within one passage) at supra-MICs. In contrast, resistance appeared at sub-MICs after 5 or more passages. Of 155 adaptors that evolved higher tolerance, all carried one of several recurrent aneuploid chromosomes, often including chromosome R, alone or in combination with other chromosomes. Furthermore, loss of these recurrent aneuploidies was associated with a loss of acquired tolerance, indicating that specific aneuploidies confer fluconazole tolerance. Thus, genetic background and physiology and the degree of drug stress (above or below the MIC) influence the evolutionary trajectories and dynamics with which antifungal drug resistance or tolerance emerges. IMPORTANCE Antifungal drug tolerance differs from drug resistance: tolerant cells grow slowly in drug, while resistant cells usually grow well, due to mutations in a few known genes. More than half of Candida albicans clinical isolates have higher tolerance at body temperature than they do at the lower temperatures used for most lab experiments. This implies that different isolates achieve drug tolerance via several cellular processes. When we evolved different strains at a range of high drug concentrations above inhibitory levels, tolerance emerged rapidly and at high frequency (one in 1,000 cells) while resistance appeared only later at very low drug concentrations. An extra copy of all or part of chromosome R was associated with tolerance, while point mutations or different aneuploidies were seen with resistance. Thus, genetic background and physiology, temperature, and drug concentration all influence how drug tolerance or resistance evolves.
Insights
Antifungal drug tolerance in Candida albicans is temperature-enhanced in most clinical isolates. Tolerance evolves rapidly at high drug concentrations, while resistance emerges slowly at low concentrations, often linked to aneuploidy.
Area of Science:
- Microbiology and Infectious Diseases
- Antifungal Drug Discovery and Development
- Medical Mycology
Background:
- Antifungal drug tolerance is a distinct cellular response from resistance, characterized by slow growth in the presence of drugs above the minimum inhibitory concentration (MIC).
- Candida albicans is a significant human fungal pathogen, and understanding its drug tolerance mechanisms is crucial for effective treatment.
- Standard laboratory conditions may not accurately reflect the physiological state of fungal pathogens in vivo, particularly regarding temperature.
Purpose of the Study:
- To investigate the prevalence and characteristics of temperature-enhanced antifungal drug tolerance in clinical isolates of Candida albicans.
- To elucidate the evolutionary dynamics and genetic underpinnings of antifungal drug tolerance versus resistance.
- To determine the influence of drug concentration and genetic background on the emergence of tolerance and resistance.
Main Methods:
- Screening of 133 Candida albicans clinical isolates for fluconazole tolerance at different temperatures (30°C, 37°C, 39°C).
- Experimental evolution of tolerance and resistance by passaging strains in liquid media across a range of fluconazole concentrations.
- Genomic analysis (aneuploidy profiling) of evolved strains to identify genetic factors associated with tolerance and resistance.
Main Results:
- A majority (69.2%) of Candida albicans clinical isolates exhibited temperature-enhanced fluconazole tolerance at body temperatures (37°C and 39°C) compared to 30°C.
- Antifungal drug tolerance emerged rapidly (within one passage) at high, supra-MIC fluconazole concentrations, whereas resistance appeared after multiple passages at sub-MICs.
- Recurrent aneuploidies, particularly involving chromosome R, were frequently observed in tolerant strains and were associated with acquired tolerance.
Conclusions:
- Temperature significantly influences Candida albicans antifungal drug tolerance, with body temperature enhancing this phenotype in most clinical isolates.
- The distinct emergence dynamics and genetic basis (aneuploidy for tolerance vs. mutations/other aneuploidies for resistance) highlight fundamental differences between tolerance and resistance.
- Understanding these evolutionary pathways is critical for developing strategies to combat antifungal drug tolerance and resistance in clinical settings.
Related Concept Videos
02:56Treatment Resistant Cancers
01:29Nondisjunction
02:50Combination Therapies and Personalized Medicine
The combination of the drug acetazolamide and sulforaphane is a good example of combination therapy to treat cancer. The cells in the interior of a large tumor often die due to the hypoxic and...
01:30Development of Antibiotic Resistance