Phenotypic Characteristics of <i>Prototheca</i> Species Occurring in Humans and Animals

The genus Prototheca consists of achlorophyllic algae that are ubiquitous in the environment and also occur in animal intestines; occasionally, infections in humans and animals are observed. In this study, we conducted tests of assimilative abilities and thermotolerance in comparison with morphological characteristics of six opportunistic species (Prototheca blaschkeae, Prototheca bovis, Prototheca ciferrii, Prototheca cutis, Prototheca miyajii, and Prototheca wickerhamii) along with Prototheca paracutis. Five of the seven species could be differentiated by physiological characteristics, but P. wickerhamii and P. cutis had identical profiles. Of the cattle-associated species, only P. bovis was able to grow at 42°C. Both type strains of P. cutis and P. miyajii were most susceptible to ravuconazole compared with the other azoles.