Rapid detection of bacterial pathogens using flourescence spectroscopy and chemometrics

Authors: Sohn, Mi Ryeong; Himmelsbach, David; Barton Ii, Franklin; Cray, Paula

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/10/2008
Publication Date: 8/23/2008
Citation: Sohn, M., Himmelsbach, D.S., Barton Ii, F.E., Cray, P.J. 2008. Rapid detection of bacterial pathogens using flourescence spectroscopy and chemometrics. United States Japan Natural Resources Food & Agriculture Panel, 37th Annual Meeting, 25-29 August, 2008, Chicago, IL.

Interpretive Summary: global concern of food-borne illness, particularly from ingestion of food-borne bacteria, necessitates a rapid detection within food and environmental matrices. Several methods have been reported for detecting bacterial pathogens. However the biggest issue is the detection speed and sensitivity. Traditional culture methodology is time-consuming because bacterial pathogens often occur in low numbers, therefore, an enrichment procedure from hours to days may be required prior to the application of a rapid detection assay. From the background, there is a strong need for the development of more direct, rapid and sensitivity techniques for detecting bacterial pathogens, particularly in foods. The current study was conducted to investigate the potential of fluorescence spectroscopy combined with multivariate analysis as a rapid method for detecting bacterial pathogens without culture enrichment or antibody conjugation. Results showed the fluorescence spectroscopy has the potential to detect and to rapidly classify bacterial pathogens, when coupled with multivariate analysis. The research result will give an interest to audiences who work in the field of identification of bacteria or microorganisms and food safety.

Technical Abstract: This work presents the development of a method for rapid bacterial identification based on the fluorescence spectroscopy combined with multivariate analysis. Fluorescence spectra of pure three different genera of bacteria (Escherichia coli, Salmonella, and Campylobacter) were collected from 200 to 700 nm. To find the optimum excitation and emission wavelengths for each bacteria sample, synchronous scan technique was employed and resulted in two maximum Ex at 225 nm and 280 nm and one maximum Em at 335-345 nm for all three bacteria. Due to the similarity in spectral pattern among three bacteria, it was difficult to classify them based on the raw spectra, however, the application of principal component analysis (PCA) to the spectral data resulted in successful classification of the bacteria by their genus as well as concentration. Detecting salmonella on the surface of shell eggs was affected by the contaminants such as feces and cuticle, thus it was difficult to directly assay salmonella on the surface of shell eggs. However, distinguishing between unwashed eggs and washed eggs was successfully performed using PCA. The results demonstrated that fluorescence spectroscopy, when coupled with chemometrics, has the potential to detect and to differentiate bacterial pathogens. This method is rapid and easy to perform compared to standard methods, and requires minimum sample preparation.