The combined rapid detection and species-level identification of yeasts in simulated blood culture using a colorimetric sensor array

Nabin K Shrestha; Sung H Lim; Deborah A Wilson; Ana Victoria SalasVargas; Yair S Churi; Paul A Rhodes; Peter J Mazzone; Gary W Procop

doi:10.1371/journal.pone.0173130

The combined rapid detection and species-level identification of yeasts in simulated blood culture using a colorimetric sensor array

PLoS One. 2017 Mar 15;12(3):e0173130. doi: 10.1371/journal.pone.0173130. eCollection 2017.

Authors

Nabin K Shrestha^{1

2}, Sung H Lim³, Deborah A Wilson², Ana Victoria SalasVargas¹, Yair S Churi³, Paul A Rhodes³, Peter J Mazzone⁴, Gary W Procop²

Affiliations

¹ Department of Infectious Diseases, Medicine Institute, Cleveland Clinic, Cleveland, Ohio, United States of America.
² Department of Clinical Pathology, Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, Ohio, United States of America.
³ Specific Technologies, Mountain View, California, United States of America.
⁴ Department of Pulmonary and Critical Care Medicine, Respiratory Institute, Cleveland Clinic, Cleveland, Ohio, United States of America.

Abstract

Background: 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.

Methods: Culture 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.

Results: One 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.

Conclusion: The CSA combined rapid detection of pathogenic yeasts in blood culture with accurate species-level identification.

MeSH terms

Colorimetry / methods*
Kinetics
Volatile Organic Compounds / analysis*
Yeasts / isolation & purification*

Substances

Volatile Organic Compounds

Grants and funding

This study was partially supported by an internal grant from the Cleveland Clinic Research Programs Committees (NKS, AVSV; grant no. RPC: 2012-1057), and with material support from Specific Technologies, Mountain View, CA. Specific Technologies provided support in the form of salaries for authors SHL, YSC, PAR, and assisted with data analysis, the decision to publish, and in the preparation of the manuscript. The specific roles of these authors are articulated in the ‘author contributions’ section.