Characterization of Lichtheimia hongkongensis, a novel fungal species that causes mucormycosis

Three thermotolerant “Lichtheimia-like” isolates from patients suffering from mucormycosis (nasopharyngeal swab of a liver transplant recipient, gastric biopsy of a renal transplant recipient, and skin biopsy of a man with burn, respectively) were characterized. Phenotypic characteristics, including colony morphology, microscopic morphology and thiamine dependency, were determined. Microscopic examination of agar block smear preparations showed that most side branches of the three “Lichtheimia-like” isolates and Lichtheimia ramosa were circinate, with abundant pleomorphic giant cells with fingerlike projections commonly observed. Sequence analysis of four loci (internal transcribed spacer region of the ribosomal DNA, partial elongation factor 1-α gene, partial β-actin gene, and the D1-D2 region of 28S rRNA) showed that the three “Lichtheimia-like” isolates and L. ramosa formed a distinct cluster, and are closely related to, but distinct from, other Lichtheimia sp. A new species, Lichtheimia hongkongensis (synonym of L. ramosa), was proposed to describe this fungus. It was also hypothesized that a proportion of “A. corymbifera (L. corymbifera)” reported in the literature could be L. hongkongensis. In this study, 13 fungal strains that were reported as “A. corymbifera (L. corymbifera)” in the literature in an 11-year period were collected. Microscopic examination of agar block smear preparations of these 13 strains revealed unique characteristics of L. hongkongensis, including circinate side branches and pleomorphic giant cell with finger-like projections. Phylogenetic analysis also showed that all 13 strains are closely related with L. hongkongensis. It was confirmed that a significant number of reported A. corymbifera (L. corymbifera) infections are L. hongkongensis infections which are of global distribution. In order to confirm the distinct phylogenetic position of L. hongkongensis, the mitochondrial genomes of three L. hongkongensis strains and a strain of L. corymbifera were sequenced. L. hongkongensis ...