Detection of Candida albicans in the venous blood of the surgical febrile patients by real-time quantitative PCR

Abstract

Objective To establish the real-time quantitative PCR (RQ-PCR) assay for detecting Candida albicans (C.albicans) in whole blood and its clinical application in the febrile surgical patients who may develop gut barrier damage and gut microorganism translocation.Methods The NAG1 gene,which is a single copy in C.albicans genome,was selected as the target gene for designing the primers and probe.The plasmid was fabricated and produced as standard samples.C.albicans genomes were extracted with QIAamp(R) DNA Blood Mini Kit,and the total 20 μl TaqMan RQ-PCR amplification reaction system was established.The 74 venous blood samples from the surgical febrile patients were detected for C.albicans load.Results The specificities of the primers and probe were excellent,the correlation coefficients of the standard curves were between 0.9918 and 0.9985,and the efficiency of amplification was 0.88-1.027 for the samples above the lowest detection limit (100 copies/μl examine fluid,or nearly 1.1 × 103 cfu/ml whole blood).The average accuracy of the RQ-PCR equipment was (99.64±2.08) %,the sensitivity was 97.46%,the specificity was 100%,and the average coefficients of variation (CV) of the intra-and inter-assay were (14.76±2.64)% and (17.85±3.53)%,respectively.The average recovery rate of C.albicans DNA in whole blood samples was (88.60±5.73) %,and the average CV of recovery rate was (11.70 ±5.36) %.The number of copies of C.albicans genes per unit blood was not significantly different among the same original blood samples stored separately under-20℃ for 3 or 6 months when compared with its freshly collected blood (P = 0.267).In the 74 whole blood samples obtained from the febrile surgical patients,the positive rate of C.albicans genes was 2.7% and the highest load was 4.42×103 cfu/ml.Conclusions RQ-PCR is a rapid,sensitive,highly specific,and reproducible method in detecting C.albicans NAG1 gene.Clinically it can be used to quantitatively evaluate the numbers of C.albicans in the whole blood.A small percentage of the febrile surgical patients may develop blood infection of C.albicans. Key words: Real-time quantitative PCR; Candida albicans; Whole blood; Surgical infection; Fever