Highlights

• C. tropicalis was gamma irradiated to mimic head and neck cancer treatment
• Irradiated strain was more virulent and more adherent than non-irradiated strains
• Strain was isolated from a single patient so it's not clear how widespread this effect would be across the entire patient group

Summary 

The news is full of awe-inspiring medical treatments. More and more cancers are now manageable and treatable. Prosthetic limbs are cheaper and more lifelike than ever before and each new generation is set to shatter longevity records. 

As microbiologists, we tend to feel a bit nervous about this. There is no doubt that the medical breakthroughs are revolutionary, but how are they put to use? 

If the answer contains the words hospitalisation, catheterisation or surgery we know we have a serious problem. As great as the medical breakthroughs are, they are a hairs breadth away from being completely compromised by an infection. 

For new medical advances to deliver all that they promise, we have to find a way to manage the infectious that could arise when the treatment is ongoing.

New research from the State University of Maringá in Brazil has now added Gamma radiation to the list of treatments that could be compromised by an infection. They collected a clinical isolate of Candida tropicalis from a head and neck cancer patient and subjected it to the same type of gamma radiation that is used in the treatment of the cancer. 

They found that irradiated C. tropicalis was more adherent to abiotic surfaces, generated more biofilm and was more virulent in a mouse model.

While the study is preliminary and only once clinical isolate was irradiated. This study highlights the work that needs to be done to understand infection in the context of different types of treatment. 

Abstract

Background Studies 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. Methods C. 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. Results After 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. Conclusions Our 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.

Reference

Eliane Martins da Silva, Elaine Sciuniti Benites Mansano, Ellen Sayuri Miazima, Francielle Abigail Vilugron Rodrigues, Luzmarina Hernandes and Terezinha Inez Estivalet Svidzinski 

BMC Infectious Diseases (2017) 17:783 

 https://doi.org/10.1186/s12879-017-2879-6