Abstract
BackgroundA colorimetric sensor array (CSA) has been demonstrated to rapidly detect and identify bacteria growing in blood cultures by obtaining a species-specific “fingerprint” of the volatile organic compounds (VOCs) produced during growth. This capability has been demonstrated in prokaryotes, but has not been reported for eukaryotic cells growing in culture. The purpose of this study was to explore if a disposable CSA could differentially identify 7 species of pathogenic yeasts growing in blood culture.MethodsCulture trials of whole blood inoculated with a panel of clinically important pathogenic yeasts at four different microorganism loads were performed. Cultures were done in both standard BacT/Alert and CSA-embedded bottles, after adding 10 mL of spiked blood to each bottle. Color changes in the CSA were captured as images by an optical scanner at defined time intervals. The captured images were analyzed to identify the yeast species. Time to detection by the CSA was compared to that in the BacT/Alert system.ResultsOne hundred sixty-two yeast culture trials were performed, including strains of several species of Candida (Ca. albicans, Ca. glabrata, Ca. parapsilosis, and Ca. tropicalis), Clavispora (synonym Candida) lusitaniae, Pichia kudriavzevii (synonym Candida krusei) and Cryptococcus neoformans, at loads of 8.2 × 105, 8.3 × 103, 8.5 × 101, and 1.7 CFU/mL. In addition, 8 negative trials (no yeast) were conducted. All negative trials were correctly identified as negative, and all positive trials were detected. Colorimetric responses were species-specific and did not vary by inoculum load over the 500000-fold range of loads tested, allowing for accurate species-level identification. The mean sensitivity for species-level identification by CSA was 74% at detection, and increased with time, reaching almost 95% at 4 hours after detection. At an inoculum load of 1.7 CFU/mL, mean time to detection with the CSA was 6.8 hours (17%) less than with the BacT/Alert platform.ConclusionThe CSA combined rapid detection of pathogenic yeasts in blood culture with accurate species-level identification.
Highlights
The presence of microorganisms in the bloodstream is a significant clinical finding, and always has an impact on clinical decision making
Culture trials of whole blood inoculated with a panel of clinically important pathogenic yeasts at four different microorganism loads were performed
The current standard methodology for blood cultures involves incubation in automated blood culture systems that monitor for growth of microorganisms based on a colorimetric or fluorometric detection of CO2, followed by Gram staining and appropriate subculturing on solid media, followed by identification and susceptibility testing based on mass spectrometry and biochemical testing performed in other instruments
Summary
The presence of microorganisms in the bloodstream is a significant clinical finding, and always has an impact on clinical decision making. Broad-range PCR for the identification of microbial pathogens directly from blood has been evaluated as an alternative rapid identification method, but this has had variable results [8,9,10] Several of these technological advancements have been shown to reduce the time to bacterial identification once blood culture bottles turn positive. A colorimetric sensor array (CSA) has been demonstrated to rapidly detect and identify bacteria growing in blood cultures by obtaining a species-specific “fingerprint” of the volatile organic compounds (VOCs) produced during growth. This capability has been demonstrated in prokaryotes, but has not been reported for eukaryotic cells growing in culture. The purpose of this study was to explore if a disposable CSA could differentially identify 7 species of pathogenic yeasts growing in blood culture
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