Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/19/2012
Publication Date: 3/15/2012
Publication URL: http://handle.nal.usda.gov/10113/56293
Citation: Davis, R., Paoli, G., Mauer, L.J. 2012. Evaluation of fourier transform infrared (FT-IR) spectroscopy and chemometrics as a rapid approach for subtyping E. coli O157:H7 isolates. Food Microbiology. 31:181-190. Interpretive Summary: Regulatory agencies require rapid and reliable methods to classify bacteria in order to track outbreaks of foodborne illness and the emergence of new virulent subtypes of foodborne pathogens such as Escherichia coli O157:H7. Here we report for the first time the use of an infrared light-based method (Fourier transform infrared spectroscopy; FT-IR) for the classification of strains of E. coli O157:H7. This study demonstrated that FT-IR is suitable for relatively rapid (= 16 h) and economical classification of E. coli O157:H7 with comparable accuracy to other common classification methods showing 94% agreement with genetic-based methods. In addition, the method was applied to classify strains of Escherichia coli O157:H7 based on their capacity to produce toxin, an important factor contributing to the progression of human disease. The developed method could be applied by government agencies to rapidly and reliably identify and track foodborne outbreaks.
Technical Abstract: The importance of tracking outbreaks of foodborne illness and the emergence of new virulent subtypes of foodborne pathogens have created the need for rapid and reliable subtyping methods for Escherichia coli O157:H7. Fourier transform infrared (FT-IR) spectroscopy coupled with multivariate statistical analyses was used for subtyping 30 strains of E. coli O157:H7 that had previously been typed by multilocus variable number tandem repeat analysis (MLVA) and pulsed field gel electrophoresis (PFGE). Hierarchical cluster analysis (HCA) and canonical variate analysis (CVA) of the FT-IR spectra resulted in the clustering of the same or similar MLVA types and separation of different MLVA types of E. coli O157:H7. The developed FT-IR method showed better discriminatory power than PFGE in subtyping E. coli O157:H7. Results also indicated the spectral relatedness between different outbreak strains. However, the grouping of some strains was not in complete agreement with the clustering based on PFGE and MLVA. Additionally, HCA of the spectra differentiated the strains into 30 subclusters, indicating the high specificity and suitability of the method for strain level identification. Strains were also classified (97 % correct) based on the type of Shiga toxin present using CVA of the spectra. This study demonstrated that FT-IR spectroscopy is suitable for rapid (= 16 h) and economical subtyping of E. coli O157:H7 with comparable accuracy to MLVA typing. This is the first report of using an FT-IR-based method for subtyping E. coli O157:H7.