Oxidative Damage Caused by Common Foodborne Pathogenic Bacteria in Egg Yolk

Background: Bacteria in foodstuff are the most important agent of foodborne disease. Aside from their infectious effects, obligate aerobes have a respiratory metabolism with oxygen as the terminal electron acceptor. Therefore, they can produce reactive oxygen species and free radicals in contaminated food. Malondialdehyde (MDA) is a product of lipid peroxidation used as an indicator of oxidative stress. Objectives: This study aimed to evaluate the oxidative damage produced by two common food pathogenic bacteria in foodstuff. Materials and Methods: The egg yolks were incubated with different dilutions (10 5 ,10 6 , and 10 7 ) of Staphylococcus aureus and Salmonella enteritidis at 37°C for 20 hours. The level of MDA in egg yolk was measured by fast and simple enzymatic or colorimetric methods, such as the thiobarbituric acid reactive species method. Results: The high group (10 7 ) had a higher MDA level of 1.97 ± 0.11 (µg MDA/g) in S. aureus and 1.65 ± 0.27 (mg MDA/L) in S. enteritidis than the control (0.90 ± 0.13 mg MDA/L). Conclusions: We concluded that common food pathogenic bacteria can induce oxidative damage in foodstuff aside from other common problems. Heating or sterilization methods cannot protect foodstuff from the damage caused by the presence of pathogenic bacteria.