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Complementation analysis of resistance to 5-fluorocytosine in Candida albicans
Abstract:
A complementation test was devised to study allelism among the genetic determinants of resistance to 5-fluorocytosine in Candida albicans. Complementation was demonstrated in control hybrids produced by crossing a resistant strain that was deficient in cytosine deaminase activity with four other resistant strains deficient in UMP pyrophosphorylase activity. This complementation test was used to test allelism of the resistance determinants present in five clinical isolates. All were found to bear recessive alleles of the locus (FCY1) that determined 5-fluorocytosine resistance associated with low levels of UMP pyrophosphorylase activity.
Insights
Genetic resistance to 5-fluorocytosine in Candida albicans was studied using a complementation test. Researchers found that five clinical isolates all carried recessive alleles of the FCY1 gene, linked to low UMP pyrophosphorylase activity.
Area of Science:
- Medical Mycology
- Molecular Genetics
- Antifungal Resistance
Background:
- Candida albicans is an opportunistic fungal pathogen.
- Antifungal drug resistance is a significant clinical challenge.
- 5-fluorocytosine is an important antifungal agent, but resistance can develop.
Purpose of the Study:
- To investigate the genetic basis of 5-fluorocytosine resistance in Candida albicans.
- To determine allelism of resistance determinants using a complementation test.
- To identify the specific genes involved in conferring resistance.
Main Methods:
- Devised a complementation test to study allelism of resistance genes.
- Produced control hybrids by crossing resistant strains with specific enzyme deficiencies (cytosine deaminase and UMP pyrophosphorylase).
- Applied the complementation test to five clinical isolates of Candida albicans.
Main Results:
- Demonstrated complementation in control hybrids, validating the test.
- Tested allelism of resistance determinants in five clinical isolates.
- All five isolates were found to possess recessive alleles of the FCY1 locus.
Conclusions:
- The FCY1 gene locus is responsible for 5-fluorocytosine resistance in the studied isolates.
- Resistance is associated with low levels of UMP pyrophosphorylase activity.
- The complementation test is effective for studying allelism of drug resistance genes in Candida albicans.