Clinical, Microbiological, and Molecular Characterization of Candia (Starmera) stellimalicola, a Rare Fungal Pathogen Causing Human Infections.

Abstract

Candia (Starmera) stellimalicola is a yeast species spread worldwide and recovered from varieties of ecological reservoirs, but human infections are rarely reported. In this study, we reported an intra-abdominal infection case caused by C. stellimalicola and described its microbiological and molecular characteristics. C. stellimalicola strains were isolated from ascites fluid of an 82-year-old male patient having diffuse peritonitis with fever and elevated WBC counts. Routine biochemical and MALDI-TOF MS methods failed to identify the pathogenic strains. Phylogenetic analysis of 18S, 26S and internal transcribed space (ITS) rDNA regions, as well as whole-genome sequence identified the strains as C. stellimalicola. Compared with other Starmera species, C. stellimalicola had unique physiological characteristics including thermal tolerance (able to grow at 42°C), which may prompt its environmental adaptability and potential for opportunistic human infection. Fluconazole minimum inhibitory concentration (MIC) values of the strains identified in this case was 2mg/L, and the patient had a favorable outcome after receiving fluconazole treatment. In comparison, the majority of C. stellimalicola strains previously documented had high MIC values (≥ 16mg/L) to fluconazole. In conclusion, with the raise in human infections caused by rare fungal pathogens, molecular diagnostic remains the most efficient way for accurate species identification; and antifungal susceptibility testing is essential to guide proper patient management.