Biofilm Formation by Salmonella Typhimurium Under Different Environmental Conditions and the Antibiofilm Potential of Essential Oils: Implications for Food Safety Within the One Health Framework

Abstract

Foodborne pathogens, particularly Salmonella Typhimurium, pose a major public health concern due to their ability to persist in food-processing environments through biofilm formation. This study evaluated the biofilm-forming ability of Salmonella Typhimurium isolates recovered from meat-processing facilities on polystyrene surfaces under different growth medium conditions and incubation temperatures, as well as biofilm formation on stainless steel. Biofilm formation was assessed in tryptic soy broth, meat broth, and Luria–Bertani broth at 37 ± 1 °C, 15 ± 1 °C, and 5 ± 1 °C after 48 h. Moderate and strong biofilm-producing isolates were treated with oregano, cinnamon, clove, and thyme essential oils to evaluate their effects on pre-formed biofilms on polystyrene microtiter plates. Biofilm formation depended on both nutrient availability and temperature. All essential oils significantly reduced crystal violet-stained biofilm biomass relative to the untreated controls, with reductions ranging from 30.93% (thyme) to 89.66% (oregano). Scanning electron microscopy of biofilms formed on stainless steel revealed morphological alterations in bacterial cells following treatment with oregano and thyme essential oils, consistent with structural damage. However, neither essential oil, applied at the minimum inhibitory concentration or minimum bactericidal concentration, significantly affected (p > 0.05) Salmonella Typhimurium populations in artificially inoculated minced pork during refrigerated storage (4 ± 1 °C). These findings highlight the antibiofilm potential of essential oils under the tested in vitro conditions, while indicating that their antimicrobial efficacy in minced pork may be influenced by the applied concentrations, the physicochemical properties of the essential oils, and interactions with meat components.