Intra-strain variability of Cryptococcus neoformans can be detected on Phloxin B medium

Judit Kucsera, Kyoko Yarita, Kanji Takeo, Soichi Yoshida, Attila Gácser, Zsuzsanna Hamari, Zoltán Avasi, Ferenc Kevei

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Abstract

A method was devised for easy detection of intra-strain variability of the human pathogenic yeast Cryptococcus neoformans. Cultivation of strains on a medium containing Phloxin B resulted in different coloured colonies. Generally, colonies were either pink or red; however there were also several colony-colour segregant in which both colours could be observed. A number of these segregants were isolated and analysed. Virulence factors such as the cell and capsule sizes were measured; further temperature sensitivity, growth rates, mating-types and melanin production were also studied. Segregants were examined by random amplified polymorphic DNA (RAPD) fingerprinting and electrophoretic karyotyping by pulsed-field gel electrophoresis (CHEF). They showed both phenotypic and genotypic differences. The main differences appeared in phenotypic characters and RAPD patterns; while the chromosomal patterns remained unchanged. Reversion frequency analysis revealed that the reason for this segregation could be due to phenotypic switching. The physiological reason for the colour changes was also investigated and was attributed to the differential ability of the cells to accumulate Phloxin B either into their capsules or into their cells. The method described here is potentially applicable for the detection of strain heterogeneity in both basic and clinical microbiology laboratories.

Original languageEnglish
Pages (from-to)111-119
Number of pages9
JournalJournal of basic microbiology
Volume42
Issue number2
DOIs
Publication statusPublished - Jul 3 2002

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ASJC Scopus subject areas

  • Applied Microbiology and Biotechnology

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