Main content area

Use of attenuated total reflectance infrared microspectroscopy to discriminate Bacillus spores

Lamo-Castellvi, S. de, Rodriguez-Saona, L.E.
Journal of food safety 2011 v.31 no.3 pp. 401-407
coat proteins, technology, Geobacillus stearothermophilus, models, Bacillus amyloliquefaciens, Bacillus thuringiensis, Bacillus subtilis, agar, bacterial spores, pellets, reflectance, filters
In the present study, the potential of Fourier-transform infrared microspectroscopy to differentiate and discriminate Bacillus spp. spores that sporulated in two nonselective media were evaluated. Spore crops of Bacillus subtilis (ATCC 11779), Bacillus thuringiensis (ATCC 13368, ATCC 35866 and ATCC 55177), Bacillus amyloliquefacies (ATCC 496763) and Bacillus stearothermophilus (ATCC 7953) were obtained with Nutrient and Trypticase Soy Agar supplemented with 10 ppm of MnSO₄.H₂O. Spores were sonicated, washed with deionized water, and pellets (10⁸ cfu/mL) were deposited onto the grids of hydrophobic membrane filters and dried to produce a uniform and thin film. Spectra were collected in the attenuated total reflectance mode in the mid-infrared region (4,000-700 cm⁻¹). Our classification models, soft independent modeling of class analogy obtained from derivatized infrared spectra (1,800-900 cm⁻¹), showed that the discrimination among spore crops was mainly attributed to infrared frequencies of spore coat proteins. Despite regulatory efforts and emergence of new processing technologies, food-related illnesses remain a major concern for consumers and producers. Detection of bacterial spores using conventional methods is time consuming and challenging. Therefore, there is a need to develop rapid, simple and cost-effective methods to detect Bacillus spores. Fourier-transform infrared microspectroscopy is a viable technology to meet these demands.