Physicochemical, Mechanical, and Molecular Properties of Nonlysogenic and P22-Lysogenic Salmonella Typhimurium Treated with Citrus Oil

Abstract

The aim of this study was to evaluate the phenotypic and genotypic properties of nonlysogenic Salmonella Typhimurium (STP22−) and lysogenic Salmonella Typhimurium (STP22+) in the presence of sublethal concentrations (SLC2D) of citrus essential oils (CEOs), which were used to evaluate antimicrobial susceptibility, cell surface hydrophobicity, autoaggregation ability, bacterial motility, lysogenic conversion, gene expression patterns, and antibiofilm formation. The SLC2D values of non–heat-treated (N-CEO) and heat-treated (H-CEO) CEO in an autoclave at 121°C for 20 min were 2.0 to 2.1 mg/ml against STP22− and 1.7 to 1.9 mg/ml against STP22+. The rates of injured STP22− and STP22+ cells treated with SLC2D of N-CEO and H-CEO ranged from 67 to 83%. The hydrophobicity and autoaggregation were decreased to 2.5 and 19.5% for STP22− and 4.7 and 21.7% for STP22+, respectively, in the presence of N-CEO. A noticeable reduction in the swarming motility was observed in STP22− with N-CEO (14.5%) and H-CEO (13.3%). The numbers of CEO-induced P22 were 5.40 log PFU/ml for N-CEO and 5.65 log PFU/ml for H-CEO. The relative expression of hilA, hilC, hilD, invA, invC, invE, invF, sirA, and sirB was down-regulated in STP22− and STP22+ with N-CEO and H-CEO. The numbers of adherent STP22− and STP22+ were effectively reduced by more than 1 log in the presence of CEO. These results suggest that CEO has potential to be used to control bacterial attachment, colonization, and invasion.