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Haemolytic activity of Candida albicans and C. dubliniensis isolated from the oral cavity of immunocompromised patients

Objectives: The production of haemolysins is virulence factor of several pathogenic bacterial species, but haemolytic activity of clinical important polymorphic yeasts, Candida albicans and C. dubliniensis is poorly investigated. Here we present study on 66 strains of C. albicans isolated from the oral cavity of immunocompromised patients (HIV+ and leukaemia), and C. dubliniensis strains from oral cavity of HIV+ patients, and all strains were compared with C. albicans from the oral cavity of healthy donors (commensal microflora). Method: The haemolytic activity was investigated according to the method described by Luo et al., J. Clin. Microbiol. 39 (2001) 2971-2974, where the hemolytic zones (expressed as hemolytic index) around yeast inoculum (10-8 blastospores/mL) were measured on Sabouraud 3% (m/V) glucose agar with addition of 7% sheep blood after 48 h at 37 °C under 5% CO2. Hemolytic index was calculated as ratio between diameters of haemolytic zones and diameters of colony, which was larger than 1 (1 indicates no haemolytic activity). Results: All C. albicans and C. dubliniensis strains isolated from immunocompromised patients showed statistically higher hemolytic index (p < 0.05) than commensal isolates of C. albicans. There were no differences between strains isolated from immunocompromised patients. Conclusion: The expression of haemolytic activity of C. albicans and C. dubliniensis could be possible virulence factor, and haemolysis could promote invasiveness of opportunistic commensal flora, especially in the group of immunocompromised patients.

candida; haemolysis; HIV; oral cavity

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