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Evidence of microevolution in a clinical case of recurrent Cryptococcus neoformans meningoencephalitis
E Blasi1, A Brozzetti, D Francisci
1Dipartimento di Scienze Igienistiche, Microbiologiche e Biostatistiche, Università di Modena e Reggio Emilia, Italy. blasi.elisabetta@unimo.it
Abstract:
The aim of this study was to examine three serial isolates of Cryptococcus neoformans from a patient with AIDS for genotypical and phenotypical characteristics. The isolates were obtained during a first episode of cryptococcosis (simultaneous sampling of blood and cerebrospinal fluid) and after a relapse 3 years later (sampling of cerebrospinal fluid). Pulsed-field gel electrophoresis and random amplification of polymorphic DNA revealed that the blood isolate 1525 (first episode) was different from the two cerebrospinal fluid isolates (1526, first episode; 1782, relapse), yet the cerebrospinal fluid isolates were indistinguishable from each other regardless of the analysis performed. Phenotypical studies showed that isolate 1782 had significantly improved resistance to phagocytosis and killing by monocytes and polymorphonuclear cells and an altered efficacy in evoking cytokine response (augmentation of tumour necrosis factor-alpha, interleukin [IL]-1beta, IL-10, and interferon-gamma, decrease of IL-12). Interestingly, capsule size and antifungal drug resistance remained unchanged, while production of phospholipase and protease was consistently enhanced in the 1782 isolate with respect to the 1525 and 1526 isolates. In conclusion, in serial Cryptococcus neoformans isolates from a patient with AIDS, phenotypical changes but not molecular changes were documented, thus supporting the role of microevolution as a pathogenetic mechanism(s) for persistence/reactivation of fungal organisms.
Insights
Serial Cryptococcus neoformans isolates from an AIDS patient showed phenotypical changes, not molecular ones. These adaptive changes in virulence factors likely explain fungal persistence and reactivation in immunocompromised individuals.
Area of Science:
- Medical Mycology
- Infectious Diseases
- Immunology
Background:
- Cryptococcus neoformans is an opportunistic fungal pathogen.
- Individuals with Acquired Immunodeficiency Syndrome (AIDS) are highly susceptible to cryptococcosis.
- Understanding fungal adaptation mechanisms is crucial for managing persistent infections.
Purpose of the Study:
- To investigate genotypical and phenotypical changes in serial Cryptococcus neoformans isolates from an AIDS patient.
- To determine if microevolution contributes to fungal persistence or reactivation.
Main Methods:
- Genotyping using pulsed-field gel electrophoresis (PFGE) and random amplification of polymorphic DNA (RAPD).
- Phenotypical characterization including resistance to phagocytosis and immune cell killing.
- Assessment of cytokine response, capsule size, antifungal drug resistance, and enzyme production (phospholipase, protease).
Main Results:
- Genotyping revealed distinct molecular profiles between the initial blood isolate and subsequent cerebrospinal fluid isolates.
- Cerebrospinal fluid isolates from the same patient, sampled years apart, were indistinguishable genotypically.
- The relapsed isolate (1782) demonstrated enhanced resistance to phagocytosis and killing, altered cytokine profiles, and increased phospholipase/protease production.
- Capsule size and antifungal drug resistance remained stable across isolates.
Conclusions:
- Phenotypical adaptations, rather than molecular changes, were observed in serial Cryptococcus neoformans isolates.
- Microevolution of virulence factors may play a significant role in the persistence and reactivation of fungal infections in AIDS patients.
- These findings highlight the dynamic nature of fungal pathogens during chronic infections.