Identification of Listeria species by Fourier-transform infrared spectroscopy

Abstract

Differentiation of the genus Listeria is significant for food industry, but only few reliable methods are available so far. In the present study, 56 strains isolated from 345 samples of cow raw milk were used. The isolated pure cultures were defined by PCR-based method using specific primers of 16S-23S IGS region of DNA. Bacterial strain samples were submitted to spectroscopic measurements by the trans-mission method at a wavelength of 3000–700 cm–1 using Fourier-transform infrared (FTIR) spectro-photometry. Hierarchical cluster analysis (HCA) was performed based on the identification of the 56 isolated strains. The utilisation of HCA in univariate-FTIR spectral analyses as the most progressive chemometric method was supported by the correct identification of 86.9% bacteria of the genus Lis-teria at the species level. These results explained the ability of univariate-FTIR spectrum analysis for determination of suspected Listeria species.

Keywords

• Fourier-transform infrared spectra
• hierarchical cluster analysis
• Listeria
• polymerase chain reaction
• raw milk