Abstract
BackgroundStudies have shown that radiation from radiotherapy increases the yeast colonization of patients. However it is not clear, if such radiation alters the yeast itself. The aim of the present study was therefore to report the direct impact of gamma radiation on Candida tropicalis.MethodsC. tropicalis was obtained from a patient with a carcinoma, a suspension of this yeast containing 2.0 × 103 colony forming units per milliliter was prepared. It was submitted to gamma radiation dosage similar to that used in the treatment of head and neck cancer. After a cumulative dose of 7200 cGy some virulence attributes of C. tropicalis, including macro and micromorphological characteristics, adhesion and biofilm abilities, murine experimental infection and phagocytosis resistance were evaluated on irradiated and non-irradiated yeasts.ResultsAfter irradiation the colony morphology of the yeast was altered from a ring format to a smooth appearance in most colonies. Scanning electron microscopy revealed notable differences in the structures of both these colonies and the yeast cells, with the loss of pseudohyphae following irradiation and an increase in extracellular matrix production. The adherence and biofilm production of the yeast was greater following irradiation, both in terms of the number of yeasts and total biomass production on several abiotic surfaces and TR146 cells. The phagocytic index of the irradiated yeasts was not statistically different; however, the presence of cellular debris was detected in the kidneys of infected animals. Mice infected with irradiated yeasts developed an infection at the site of the yeast inoculation, although systemic infection was unchanged.ConclusionsOur findings show for the first time that C. tropicalis, one of the most important yeasts from colonization, which cause fatal candidemia in cancer patients, is affected by gamma irradiation, with changes to its virulence profile.
Highlights
Studies have shown that radiation from radiotherapy increases the yeast colonization of patients
The aim of the present study was to evaluate the possible impact of a complete gamma radiation, scheme similar to those used in the treatment of head and neck cancer, applied directly on yeast, evaluating some virulence parameters of a C. tropicalis isolate, which was obtained from a patient with laryngeal carcinoma
Comparative assays between the irradiated and nonirradiated yeasts showed that gamma irradiation altered some parameters of C. tropicalis, such as its morphological characteristics, local infection capacity, adhesion on abiotic and biotic surfaces, biofilm formation and phagocytic index
Summary
Studies have shown that radiation from radiotherapy increases the yeast colonization of patients. C. tropicalis is considered an important agent of candidemia, especially in neoplasia patients [9, 10] This is partly due to the virulence characteristics of this species, such as its high adhesion capacity and ability to form biofilm on surfaces [11]. C. tropicalis from clinical isolates naturally exhibits highly diversified macromorphological variations known as phenotypic switching [12, 13], an ability associated with cell damage in epithelial tissue This virulence attribute has been observed in animal model [14], it is not known if the same occurs in humans. It is not known if yeast exposed to radiation suffer changes in their putative virulence factors
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