Objective: Currently, Candida parapsilosis is an emerging cause of non-C. albicans- related invasive candidiasis worldwide. Three phenotypically close species, C. parapsilosis, C. orthopsilosis and C. metapsilosis are defined as “Candida parapsilosis group”. Candida parapsilosis is frequently found in human commensal flora, natural environments, and inexplicably, in extreme indoor environments. This study aimed to examine the tolerance characteristics of C. parapsilosis to similar conditions of domestic dishwashing and washing machines.

Method: We investigated the thermo-, halo-, pH and cycloheximide tolerance of 21 reference strains of C. parapsilosis (n = 8), C. orthopsilosis (n = 7), and C. metapsilosis (n = 6).

Results: All isolates grew at 40°C but showed no growth at temperatures at or above 42°C (45°C and 50°C). All C. parapsilosis, C.metapsilosis, and C. orthopsilosis strains tolerated 5-10% NaCl, pH 2.5-10, and 0.01% cycloheximide. However, the isolates did not grow at pH 12.5 or in the presence of 0.1% cycloheximide. Notably, all the examined isolates of the C. parapsilosis species group can show tolerance at least one of the following conditions as; 10% NaCl, pH 2.5-10, and 0.01% cycloheximide. The survival rates of Candida parapsilosis, C. metapsilosis and C. orthopsilosis isolates at 45°C were 50%,16.6%, and 14.2%, respectively. In addition, although 75% of C. parapsilosis isolates were tolerant to 17% NaCl, C. metapsilosis and C. orthopsilosis isolates were not tolerant to this condition.

Conclusion: Thermophilic and halophilic properties of Candida parapsilosis are thought to play an important role in the tolerance mechanism against extreme conditions in household appliances.