Abstract

Background: The different species of Rhodotorula are living in the environment and considered as normal inhabitants in the human body. In addition, they are found as common contaminants of skin, urine, respiratory and gastrointestinal systems among normal individuals. Out of several species of Rhodotorula, Rhodotorula mucilaginosa, R. glutinis and R. minuta were considered as human pathogens. They are causing invasive Rhodotorulosis among immunocompromised patients. Several studies show that extracellular enzymes are among the most important pathogenic factors in yeasts. In the present study we aimed to the detection of extracellular enzymes and the formation of biofilm by different species of Rhodotorula.

Materials and Methods: In the present study 68 isolates of Rhodotorula including, R. glutinis (58 isolates) R. mucilaginosa (5 isolates), R. minuta (3 isolates) and Rhodotorula species (2 isolates) were examined for extracellular enzymes excretion. Standard methods were used for the evaluation of phospholipase, proteinase, esterase and hemolytic activity. In addition biofilm formation was also evaluated using polystyrene microplates.

Results: Our results show that 82.4% of tested Rhodotorula isolates had phospholipase activity with higher Pz values (<0.70) in 69.1% of isolates. Esterase activity was detected among 29.4% of R. glutinis, R. minuta and Rhodotorula species, whereas 5 isolates of R. mucilaginosa were negative for this enzyme. The best biofilm formation results were obtained from incubation at 25°C after 72h (23.5%).

Conclusions: According to this study there is a remarkable difference in the extracellular enzymatic activity among tested Rhodotorula species. In addition, 82.4% of isolates were positive for phospholipase activity, in comparison to 29.4% for esterase and 69.1% for hemolytic activity. Biofilm formation was very weak among tested isolates.

Keywords: Biofilm formation, extracellular enzymes, Rhodotorula.

Graphical Abstract