Identification and characterization of 4 Prototheca wickerhamii strains / 临床检验杂志

ABSTRACT

Objective@#To identify and characterize the 4 strains of Prototheca isolated from the clinical samples of skin or ascites samples in China. @*Methods@#The taxonomic position of 4 yeast-like organisms was revealed by polyphasic taxonomic approach, i.e., cultural and morphologic characteristics, commercial biochemical systems of Vitek 2 (YST kit) and Vitek matrix-assisted laser desorption/ionization time of flight (MALDI-TOF) mass spectrometry (MS) systems in combination with phylogenetic analysis based on the gene sequences of 16S and 28S rRNA. @*Results@#The 4 strains of Prototheca were characterized as cream-white, smooth, moist yeast-like colonies on Sabouraud gentamicin chloramph agar after incubation for 3 days. However, round, oval-shaped or elliptical sporangiums with mulberry-like or strawberry-like endospores were observed by optical microscope, which showed distinct differences from the general yeast species. The 4 isolates were identified as Prototheca wickerhamii with Vitek YST kits by Vitek 2 systems and Vitek MALDI-TOF MS systems. The genome for the 4 isolates was characterized with the existence of the prokaryotic 16S rRNA gene and eukaryotic 28S rRNA gene. The 16S rRNA gene sequence of the 4 strains showed more than 99.7% similarity to that of P. wickerhamii. Sequence analysis of 28S rRNA gene showed that the organisms included multiple copies of different sequences, which showed sequence similarities of 91.9% to 100% even in the same strain. The phylogenetic dendrogram based on 16S rRNA and 28S rRNA gene sequences showed that the 4 strains of Prototheca formed a cluster along with P. wickerhamii. @*Conclusion@#The 4 yeast-like organisms could be identified as P. wickerhamii, and 16S rRNA gene should be the suitable molecular target for the identification.