Molecular identification and extracellular enzyme production of Rhodotorula spp.

Rhodotorula spp. have been associated with human infections, particularly in individuals with weakened immune systems. This study aimed to identify 31 isolates of Rhodotorula spp. recovered from coin-operated washing machines. The tubs, lint filters, detergent drawers, and fabric softener drawers were swabbed and streaked on Sabouraud dextrose agar (SDA) supplemented with 0.05 g L-1 chloramphenicol. Identification of Rhodotorula spp. was performed by using polymerase chain reaction (PCR) with fungus-specific primers targeting the internal transcribed spacer (ITS; ITS1-5.8-ITS2) regions. Moreover, the study investigated the production of extracellular enzymes, including phospholipase, esterase, and proteinase. The results showed that all 31 Rhodotorula spp. isolates grew well on SDA, forming round, smooth, moist mucoid, coral-red to salmon-colored colonies at 25 °C within 24 h. PCR analysis yielded approximately 620 bp products, and sequencing analysis identified 25 Rhodotorula mucilaginosa (80.65%) and 6 Rhodotorula dairenensis (19.35%) isolates. In this study, all R. mucilaginosa and R. dairenensis showed strong (pz = 0.7‒0.76) to very strong phospholipase activity (pz < 0.69). There were 16 R. mucilaginosa and 3 R. dairenensis that demonstrated esterase activity levels ranging from weak (pz = 0.91) to very strong (pz < 0.69). Only 14 R. mucilaginosa isolates displayed proteinase activity levels ranging from weak (pz = 0.92) to very strong (pz < 0.69). Therefore, the results implied that the potential pathogenic fungi distributed in the environment, particularly washing machines, may cause individuals to be at risk of being infected with these opportunistic yeasts, especially immunocompromised patients.