Immunopathogenesis of Emerging and Strains.

The emergence of a multidrug-resistant species, and , has been reported worldwide. In Thailand, information on them is limited. We collected clinical isolates from Thai patients with invasive candidiasis. Both species were compared with a laboratory strain. In vitro antifungal susceptibility and thermotolerance, and pathogenesis in the zebrafish model of infection were investigated. Both species demonstrated high minimal inhibitory concentrations to fluconazole and amphotericin B. Only tolerated high temperatures, like . In a zebrafish swim-bladder-inoculation model, the -infected group had the highest mortality rate and infectivity, suggesting the highest virulence. The case fatality rates of , and were 100%, 83.33%, and 51.52%, respectively. Further immunological studies revealed that both emerging species stimulated genes involved in the proinflammatory cytokine group. Interestingly, the genes relating to leukocyte recruitment were downregulated only for infections. Almost all immune response genes to had a peak response at an early infection time, which contrasted with . In conclusion, both emerging species were virulent in a zebrafish model of infection and could activate the inflammatory pathway. This study serves as a stepping stone for further pathogenesis studies of these important emerging species.