Epidemiology And In Vitro Susceptibility Of Yeasts Causing Invasive Fungal Infections In China

[Objective] To investigate the epidemiology and antifungal susceptibility of yeast isolates causing invasive fungal infections collected from the third surveillance year of China Hospital Invasive Fungal Surveillance Net (CHIF-NET) study, and trends in epidemiology and antifungal susceptibility during the first three years’CHIF-NET surveillance.[Methods] There were22hospitals participated in the third year’s CHIF-NET surveillance (CHIF-NET12). All1619isolates collected were identified to species level by unique molecular identification methods, and antifungal susceptibility testing to fluconazole and voriconazole was performed by Clinical and Laboratory Standards Institute (CLSI) disk diffusion method. In addition, all data from11hospitals consecutively involved in the first three years’CHIF-NET studies were retrospectively analyzed, and minimum inhibitory concentrations (MICs) of all non-Candida albicans yeast strains from these hospitals against nine antifungal agents were determined by YeastOne chromogenic broth microdilution method.[Results] Of all isolates collected during CHIF-NET12, Candida species was predominant (91.8%), followed by Cryptococcus species (6.5%), Trichosporon species (0.6%) and other yeast species (1.2%). Candida species was commonly removed from most specimen types including in blood samples (94.4%), whereas Cryptococcus species was predominant in cerebrospinal fluid. Comparing to molecular identification results, only87.3%of initial identifications were correct. The corrected identification rates were higher amongst common Candida species (>80%) but significantly lower amongst uncommon Candida species and yeasts. Candida albicans was the commonest Candida species but its proportion was<50%. Other common Candida species identified included Candida tropicalis (18.0%), Candida parapsilosis complex (16.2%) and Candida glabrata complex (12.0%).97.1%of the Cryptococcus isolates belonged to Cryptococcus neoformans complex. There were significant geographic variation in distribution of different yeast species causing invasive fungal infections. By using CLSI disk diffusion testing, the majority of C. albicans, C. tropicalis, C. par apsilosis complex and C. glabrata isolates were susceptible to fluconazole and voriconazole (>91.0%).11.8%of the C. glabrata complex isolates were resistant to fluconazole, most of which were non-wild type to voriconazole. While most Candida krusei isolates remained susceptible to voriconazole (91.7%). Some of the less common yeast species showed reduced susceptibility to azoles tested. During CHIF-NET10-12, a total of2367isolates were collected from11hospitals consecutively participated. Forty-three yeast species were identified by molecular approaches. During three years, there was no significant change in proportion on genus level. However, the proportion of C. albicans isolates increased continuously (35.4%to42.5%, p=0.001) while the proportion of non-albicans Candida species decreased (55.0%to46.5%, p=0.001). This was in controversial to the global trends and mostly owned to the notable drop in prevalence of C. parapsilosis complex isolates. C. parapsilosis complex isolates showed good susceptibilities to all antifungal agents tested but exhibited higher MICs to echinocandins. The high prevalence of azole cross-resistant C. tropicalis isolates and reduced activity of echinocandins to C. glabrata isolates should were noted. In addition, echinocandins were less active against Cryptococcus and Trichosporon species. The emerging of some less common yeast species, especially those drug-resistant ones in some of the hospitals should be aware.[Conclusions] The three years’CHIF-NET study has accumulated valuable micro-organism and clinical information sources. The application of standard molecular identification and antifungal susceptibility testing methods was essential. This studied provided useful data to the field of invasive fungal infections previous we lack of knowledge. However, continuous surveillance is still demanded to monitory the trends of epidemiology and susceptibility of yeasts causing invasive fungal infections in China.