Candida auris reshuffles chromosomes to resist drugs

Resistance to a drug does not always begin with a single letter changed in DNA. In the yeast Candida auris, larger rearrangements of the genome may also matter: the duplication of a chromosome segment, or the appearance of an extra copy of a large stretch of one. Researchers combined genome sequencing, copy-number analysis, karyotyping and evolution experiments to see how such changes relate to reduced susceptibility to antifungal drugs.

In the case of azoles the team drew attention to small duplications covering ERG11, the gene encoding the target of that class of drug. A greater number of copies may increase the amount of protein the drug has to block. Where a duplication occurred together with mutations altering ERG11, the resistance effect could be stronger. This matters, because a standard analysis focused only on point mutations may miss the full mechanism.

A different pattern applied to the echinocandins, including caspofungin. Large duplications of chromosome one produced structures resembling additional chromosomes and were associated with reduced susceptibility. This does not replace the known changes in the FKS1 gene, but adds a further layer of explanation. The genome of C. auris is not a fixed instruction: under the pressure of treatment its architecture can change, and advantageous variants may persist in a population of cells.

The study does not provide a simple test that from tomorrow will predict the course of every infection. The relationship between copy number and a laboratory MIC value need not automatically determine the outcome of therapy in a patient. The site of infection, the patient's condition, the dose, other drugs and control of an outbreak within a facility all matter. Larger clinical datasets are needed, along with methods that reliably detect structural changes in routine diagnostics.

The practical conclusion concerns genomic surveillance. If a laboratory looks only for a few known mutations, it may miss an alternative route of adaptation. A fuller analysis of copy number and karyotype helps to explain where an unexpected susceptibility result comes from. For a patient, rapid diagnosis and treatment led by a medical team remain paramount; for a health system, limiting transmission and using drugs sensibly. The study shows why the adversary cannot be described by one mutation.

Structural changes also make technical demands. Short sequencing reads can be excellent for finding single mutations, but they reconstruct repeats and extra chromosomes less well. Combining several methods costs more, so researchers have to establish which signals from a routine test should trigger deeper analysis. Such an algorithm can concentrate resources on the most atypical isolates and detect new routes of resistance more quickly in clinical practice.

Evidence status — 29 August 2026

The peer-reviewed article was published on 10 July 2026. The team studied 79 Indian clinical isolates of the South Asian clade of Candida auris, collected from 2014 to 2021, combining sequencing, copy-number analysis, karyotyping and susceptibility tests. It confirmed recurrent duplications encompassing ERG11 and extra chromosomal structures associated with the response to caspofungin. This is mechanistic laboratory evidence, not a forecast of an individual patient’s outcome or a complete picture of every C. auris clade. Its practical value is diagnostic: surveillance restricted to point mutations can miss an important part of antifungal resistance.