Detection and phylogenetic characterization of a case of Histoplasma capsulatum infection in mainland China

Abstract

Histoplasmosis usually occurs in specific endemic areas. Sporadic cases have also been reported in mainland China. Here, we described an indigenous case of disseminated histoplasmosis. Phylogenetic analysis revealed that the Histoplasma capsulatum isolated in our case belongs to the Australian clade. Combined with previous studies, it revealed high genetic diversity among Chinese H. capsulatum isolates.

Figure 1.

(A) Bone marrow aspirate stained with Wright's stain shows numerous encapsulated oval or spherical intracellular and extracellular organisms (×1,000). (B) PAS staining of the cervical lymph node revealed ovoid-shaped microorganisms with dotlike inclusions (×1,000). (C) Phenol cotton blue stain of the isolated mold showing thick-walled and tuberculate macroconidia (×1,000). (D) Identification of H. capsulatum is confirmed by PCR assay based on the specific nucleotide sequence. Lanes 1 and 2, PCR products amplified with M-antigen probes Msp1F-Msp1R (111 bp) and Msp2F-Msp2R (279 bp); lanes 3 and 4, PCR products amplified with sequence-characterized amplified region markers 1281–1283₂₂₀ (220 bp) and 1281–1283₂₃₀ (230 bp); lane 5, ITS amplified with primers V9G and LS266. M = molecular size marker.

Figure 2.

Neighbor-joining tree from analysis of the combined data of the four loci. Branch lengths are proportional to Kimura's two-parameter distance. Numbers on the branches indicate bootstrap support of greater than 70%. The scale bar indicates the nucleotide substitutions per site. A = Netherlands clade; B = Australia clade; LAm A = Latin America group A clade; LAm B = Latin America group B clade; NAm 1 = North America 1 clade. *Isolates of H. capsulatum from China.