Background: A disposable colorimetric sensor array has been shown to identify pathogenic bacteria in blood cultures with great accuracy. The purpose of this study was to explore if the assay had potential for identifying pathogenic yeasts in blood cultures.
Methods: Inocula of five different ATCC strains of Candida species (C.albicans, C. glabrata, C. krusei, C.tropicalis, and C. parapsilosis) were prepared at a concentration of 2 McFarland. Serial 1:100, 1:100 and 1:50 dilutions were performed and 0.5 mL of the original and each dilution were inoculated into two BacT/ALERT FA FAN® blood culture bottles with 10 mL of packed human red blood cells added. One bottle was monitored using a colorimetric sensor array (CSA) and the other in a BacT/ALERT blood culture system (BacT). For the CSA, a kinetic profile which differentiated each Candida species was obtained. The time to detection of the microorganism by the CSA method was then compared with the time to obtain a positive signal in the BacT/ALERT system.
Results: The different Candida species had distinct colorimetric patterns. Time to pathogen identification with the CSA method compared favorably with the time to positive signal in the BacT/ALERT blood culture monitoring system. Time to detection increased with decreasing microorganism concentration. For all species combined, median time to pathogen identification by the CSA method was 27.0 hours for the lowest concentration tested to 9.3 hours for the highest, compared to 36.3 and 7.6 hours, respectively, for pathogen detection by the BacT/ALERT system.
Conclusion: The colorimetric sensor array tested has potential for identifying pathogenic Candida species in blood cultures in a clinically timely manner, with species identification sooner than even a positive signal in the BacT/ALERT blood culture system at lower microorganism concentrations.
A. V. Salas Vargas,
Y. S. Churi, Specific Technologies: Employee and Shareholder, Salary
S. H. Lim, Specific Technologies: Employee and Shareholder, Salary
G. Procop, None
P. Mazzone, Metabolomx: Research Contractor, Research support
N. Shrestha, None