First case of fungemia caused by a rare and pan-echinocandin resistant yeast Sporopachydermia lactativora in China

Abstract

The cactophilic yeasts, Sporopachydermia species, are intrinsic resistance to echinocandins. We report the first case of fungemia caused by S. lactativora in China. Sporopachydermia lactativora could colonise and infect multiple animal tissues and could represent a new emerging fungal pathogen of humans and should not be ignored in clinical settings.

Keywords: Fungemia; Sporopachydermia lactativora; antifungal resistance; emerging fungal pathogen; pan-echinocandin resistance.

Figure 1.

Morphologies of Sporopachydermia lactativora strain RJ001. (a) Colony morphology of S. lactativora grown on blood agar. The blood agar plate was incubated at 35 °C for 2 d. (b) Microscopic evaluation of Gram-stained S. lactativora cells. Scale bar, 10 µm. (c) Colony and cellular morphologies of S. lactativora strain RJ001 on YPD, Lee’s glucose, Lee’s GlcNAc (Xie et al. 2013), SD, and PDA media. Yeast cells were plated on the media and cultured at 30 °C or 37 °C for 5 d. Scale bar for colonies, 5 mm; for cells, 10 µm.

Figure 2.

Fungal burden analyses of Sporopachydermia lactativora (Sl), Candida auris (Cau), Candida albicans (Cal), and Saccharomyces cerevisiae (Sc) in a mouse systemic infection model. Strains used: Sporopachydermia lactativora (RJ001), C. auris [BJCA001(Wang et al. 2018)], C. albicans (SC5314), and Saccharomyces cerevisiae (∑10560-2D). Four 6-week-old female BALB/c mice were used for systemic infection with each fungal strain. Cells of each strain were initially plated on YPD solid medium at 30 °C for 2 d, washed and then diluted with 1 × PBS. For each mouse, 5 × 10⁵ (panel A) or 2 × 10⁷ fungal cells (panel B) were injected via the tail vein. After 24 h of infection, the mice were euthanised, and five organs were collected, weighed, ground, and plated on YPD solid medium supplemented with chloramphenicol (final concentration, 34 µg/mL) for fungal burden assays. The statistical significance of the difference between Sporopachydermia lactativora and other species is indicated (*, p < 0.05; **, p < 0.01; ***, p < 0.001; two tailed student’s t-test). Black dots represent the CFU. Error bars represent standard deviations. Of note, when 2 × 10⁷ C. albicans cells were injected into the mice, all mice died within 24 h. Therefore, fungal burden data for C. albicans at this inoculation were not obtained.