Rapid Differentiation of Listeria monocytogenes Epidemic Clones III and IV and Their Intact Compared with Heat‐Killed Populations Using Fourier Transform Infrared Spectroscopy and Chemometrics

• Published in: Journal of food science Vol. 79; no. 6; pp. M1189 - M1196
• Main Authors: Nyarko, Esmond B, Puzey, Kenneth A, Donnelly, Catherine W
• Format: Journal Article
• Language: English
• Published: United States The Institute 01.06.2014; Blackwell Publishing Ltd; Wiley Subscription Services, Inc
• Subjects: Chemometrics; clones; data collection; differentiation; Discriminant Analysis; epidemic clones; Epidemics; Food Microbiology; Fourier transform infrared (FT-IR) spectroscopy; Fourier transform infrared spectroscopy; Fourier transforms; Hot Temperature; Humans; Infrared; Infrared spectroscopy; Listeria monocytogenes; Listeria monocytogenes - isolation & purification; Listeriosis - microbiology; Listeriosis - prevention & control; multivariate; Multivariate Analysis; Populations; Public health; reflectance; Reproducibility of Results; Species Specificity; Spectra; Spectroscopy; Spectroscopy, Fourier Transform Infrared - methods; Statistical analysis; Strain; wavelengths; epidemic clones; Listeria monocytogenes; multivariate; differentiation; Fourier transform infrared (FT-IR) spectroscopy
• ISSN: 0022-1147; 1750-3841; 1750-3841
• DOI: 10.1111/1750-3841.12475

The objectives of this study were to determine if Fourier transform infrared (FT‐IR) spectroscopy and multivariate statistical analysis (chemometrics) could be used to rapidly differentiate epidemic clones (ECs) of Listeria monocytogenes, as well as their intact compared with heat‐killed populations. FT‐IR spectra were collected from dried thin smears on infrared slides prepared from aliquots of 10 μL of each L. monocytogenes ECs (ECIII: J1‐101 and R2‐499; ECIV: J1‐129 and J1‐220), and also from intact and heat‐killed cell populations of each EC strain using 250 scans at a resolution of 4 cm⁻¹ in the mid‐infrared region in a reflectance mode. Chemometric analysis of spectra involved the application of the multivariate discriminant method for canonical variate analysis (CVA) and linear discriminant analysis (LDA). CVA of the spectra in the wavelength region 4000 to 600 cm⁻¹ separated the EC strains while LDA resulted in a 100% accurate classification of all spectra in the data set. Further, CVA separated intact and heat‐killed cells of each EC strain and there was 100% accuracy in the classification of all spectra when LDA was applied. FT‐IR spectral wavenumbers 1650 to 1390 cm⁻¹ were used to separate heat‐killed and intact populations of L. monocytogenes. The FT‐IR spectroscopy method allowed discrimination between strains that belong to the same EC. FT‐IR is a highly discriminatory and reproducible method that can be used for the rapid subtyping of L. monocytogenes, as well as for the detection of live compared with dead populations of the organism.