A case of lymphocutaneous sporotrichosis caused by Sporothrix schenckii sensu stricto finally diagnosed by molecular identification based on "ITS" and "CAL" coding regions in combination with phenotypic analysis

Abstract

A 54-year-old female farmer presented with a pea-sized red nodule on the left upper limb near the wrist for 15 days, which occurred after trauma, gradually became swollen and ruptured, and developed into multiple nodules arranged in a chain in 30 days. Skin examination revealed multiple hard purple-red nodules arranged in a line on her left upper limb, some of which were ruptured with a small amount of purulent exudate. Histopathological examination further revealed that the focus of infection manifested as pyogenic granuloma-like inflammation mainly infiltrated with mixed inflammatory cells. Periodic acid Schiff (PAS) staining showed no fungal structures, including fungal spores, hyphae and asteroid body. The biopsy tissue culture yielded the fungus. According to the morphological analysis of the cultures and results of molecular identification based on internal transcribed spacer (ITS) and calmodulin (CAL) coding regions, this case was finally diagnosed as lymphocutaneous sporotrichosis caused by Sporothrix schenckii sensu stricto. The patient was treated with oral potassium iodide 10% solution in a dose of 10 ml thrice a day. After 2-month treatment, the patient felt that the lesions were obviously improved, but afterwards she was lost to follow-up. This research report suggests that phenotypic analysis combined with ITS/CAL-based molecular identification can accurately identify Sporothrix schenckii complex at the species level. Key words: Sporotrichosis; Sporothrix; Phenotype; Sequence alignment; Sporothrix schenckii sensu stricto