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Candida albicans bloodstream infections are comprised of diverse populations of strains, including antifungal tolerant strains that emerge during treatment failure

Summary

Researchers found that Candida albicans bloodstream infections contain multiple different strains, not just one strain as previously thought. Some strains are more tolerant to antifungal medications like micafungin, and when treatment is started, the drug-tolerant strains can be eliminated while drug-sensitive strains increase in number. This discovery suggests that treatment failures may occur because pre-existing drug-resistant strains are selected for during treatment.

Background

The traditional model suggests bloodstream infections are caused by a single strain, but Candida albicans exhibits significant genomic and phenotypic plasticity. It remains unknown whether within-patient strain diversity is common during candidiasis bloodstream infections.

Objective

To determine whether C. albicans bloodstream infections contain diverse populations of strains and to characterize genetic and phenotypic differences between strains within individual patients.

Results

Blood cultures from each patient contained mixed populations of strains differing by SNPs, indels, gene copy numbers, chromosome aneuploidies, and loss of heterozygosity. Chromosome 7 trisomy strains outcompeted euploid strains in the absence of antifungal treatment but were suppressed by micafungin despite identical MICs. After 2 days of micafungin treatment, euploid strains increased from 24% to ≥95% of the population.

Conclusion

Positive blood cultures contain diverse C. albicans populations rather than single identical strains. Antifungal treatment failures may result from selection of pre-existing resistant or tolerant strains, challenging standard clinical microbiology practices that focus on single isolates.
  • Published in:Open Forum Infectious Diseases,
  • Study Type:Experimental Study,
  • Source: 10.1093/ofid/ofae631.033, PMC11777160
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