Use of Thermal and Emerging Non-Thermal Treatments Reveal Biomolecular and Morphological Changes in Pathogenic E. coli

(1) Background: We sought to explore the changes in the biomolecular profile and morphology of Pathogenic heat-resistant <i>E. coli</i> isolated from animal-based food. (2) Methods: Six strains underwent heat (60 °C for 6 min), ultrasound (US; 299 W), UVC (4950 mJ/cm²), and combined treatments (UVC+US and heat+UVC). Afterwards, biomolecular characterization across four spectral regions was evaluated by Fourier transform infrared (FT-IR) spectroscopy and analyzed by principal component analysis (PCA) for treated and non-treated strains (control group). These regions are fatty acids (3010-2800 cm^-1), proteins and peptides (1700-1200 cm^-1), carbohydrates (1200-900 cm^-1), and amide A (3280-3120 cm^-1). Additionally, treated and untreated strains were assessed for surface damage using scanning electron microscopy (SEM). (3) Results: Among all the regions studied, the amide A and fatty acids regions exhibited the most significant variations in absorbance for treated strains compared to the control. Treatments such as US, heat, and UVC+US tended to increase Principal Components (PCs) and, consequently, absorbance. On the other hand, UVC and heat+UVC showed the opposite trend in these regions. SEM images showed filamentous cells for strains treated with UVC and UVC+US, indicating that cells continued to replicate under these conditions. These results highlight how thermal and non-thermal treatments influence specific biomolecular and morphological regions of <i>E. coli.</i> The methodologies used provide reliable data for understanding stress responses, which can guide the development of more effective technologies for eliminating multi-resistant pathogens.