Faculty of Veterinary Medicine, Urmia University Food Safety and Packaging 3092-7668 1 3 2025 11 01 Changes in antibiotic susceptibility of Salmonella Typhimurium and Listeria monocytogenes under conditions of biofilm formation and freezing stress in meat juice model 181 186 121802 10.30466/fsp.2025.56711.1021 EN Ata Kaboudari Department of Microbiology and Food Safety, Faculty of Veterinary Medicine, Lorestan University, Korramabad, Iran 0000-0001-5090-9552 Journal Article 2025 10 31 The aim of this study was to investigate the changes in antibiotic susceptibility /resistance of bacteria isolated from biofilms in the presence of freezing stress in different meat juices (beef, mutton and goat). Gram-positive and Gram-negative bacteria of food origin (<em>Listeria monocytogenes</em> and <em>Salmonella enterica </em>ser<em>. </em>Typhimurium) were selected. Meat juice model was selected as a nutritious and complex environment containing a wide range of different compounds. Biofilms were studied in 96-well microplates and disk diffusion method was used to measure the antibiotic susceptibility. The results showed that the bacteria isolated from biofilms in meat juice models and freezing conditions exhibited significant changes in their antibiotic susceptibility. Long-term freezing (3 weeks and 1 month) significantly increased the antibiotic resistance. Both bacteria became resistant to chloramphenicol. The results indicated that foods should not be subjected to long-term freezing conditions so that existing pathogens do not acquire the ability to resist antibiotics. https://fsp.urmia.ac.ir/article_121802_e460378d332d97b78d2f8af35ee5f6ba.pdf