YANG Xinyi, CHEN Xinfei, LI Jin, ZHANG Han, WANG Qing, DENG Changzi, SUN Ziyong, CHEN Zhongju, HAO Qiaoxin, LIU Zhenjia, CHENG Bin, WANG Ziran, DAI Rongchen, HUANG Yuyan, ZHU Huiqing, LIU Feiyi, ZHAO Yiying, XU Yingchun, XIAO Meng
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Objective To assess the diagnostic performance of a novel domestic chromogenic medium for Candida auris. Methods This study utilized 184 Candida strains, including 5 reference strains, 65 strains of C. auris, 16 strains from 5 species of the C. haemulonii complex, and 98 clinical isolates of 14 other Candida species. Species identification was performed using a domestic C. auris chromogenic medium (ATAU), with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and ribosomal DNA internal transcribed spacer sequencing serving as gold standards. In addition, the consistency in diagnostic efficacy was compared between ATAU and imported traditional Candida chromogenic agar media (CRCA) for common Candida species. The difference in species identification capability was also assessed between ATAU and novel imported C. auris chromogenic agar media (CRAU) for the C. auris-C. haemulonii complex. Results Under the culture conditions of 35°C for 48 hours, compared with the results of the gold standard identification, the sensitivity of ATAU for the identification of C. auris was 100%, the specificity was 97.4%, and the overall coincidence rate was 98.3%. One strain of C. vulturna, which belongs to the C. auris - C. haemulonii complex, was misidentified as C. auris. In addition, the strains of C. pseudohaemulonii grow slowly at the culture temperature of 35°C even if their chromogenic features were similar to those of C. auris. Therefore, they can be distinguished. However, at 30°C, it was difficult to distinguish C. duobushaemulonii and C. haemulonii from C. auris. In addition, one strain each of C. metapsilosis (1/10) and one strain C. parapsilosis (1/10) were misidentified as C. auris. The sensitivity and specificity of both ATAU and CRCA for the identification of C. albicans and C. krusei were 100%, and the agreement rate between the two methods was 100%. The sensitivity of both methods was 90.0% for identification of C. tropicalis, and the specificity was 100% and 99.4%, respectively. Both methods missed the same strain of C. tropicalis, but one strain of C. catenulata (1/7) was misidentified as C. tropicalis on CRCA. The sensitivities of both methods were 100% for identification of C. glabrata. The identification specificity was 100% for CRCA, but 99.4% for ATAU, because a strain of C. orthopsilosis (1/10) was misidentified. Both ATAU and CRAU accurately detected C. auris, performed similarly in identifying the C. haemulonii complex and the strains that are easily misidentified on ATAU. It showed lower specificity in identifying C. glabrata. Conclusions ATAU has good diagnostic performance for C. auris and common Candida species (C. albicans, C. tropicalis, C. glabrata, C. krusei). The coincidence rate with the gold standard method is greater than 97%. Especially, the sensitivity for C. auris reaches 100%. Therefore, this chromogenic medium is suitable for the screening of nosocomial infections caused by C. auris and preliminary identification of common Candida species. However, identification based on mass spectrometry can be used to confirm the results of ATAU.
