Registration and Identification of Toxic S. aureus genes Isolated from Tilapia Fish Using Multiplex PCR Technique

Document Type : Research Paper


1 M. Sc. Student of the Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran.

2 Professor of the Department of Food Science and Technology, Science and Research Branch, Islamic Azad University, Tehran, Iran.

3 Assistant Professor of the Department of Biology, Science and Research Branch, Islamic Azad University, Tehran, Iran.


Introduction: Aquatic animal products are considered very important food items in the food basket regarding their high calorie, protein, and omega-3 unsaturated fat. Many aquatic animals, including fish, may always be infected with pathogenic microorganisms at various stages, from hunting to purchasing. Eventually, these factors would cause severe poisoning in humans. The present study investigates the registration and identification of Staphylococcus aureus’s toxic genes isolated from tilapia using the Multiplex PCR technique.
Materials and Methods: The sample size included 42 subjects (21 fresh fish samples and 21 frozen fish samples). First, after preparing the samples, Staphylococcus aureus was isolated and examined as surface culture in Baird-Parker medium. Next, a Coagulase test was performed, and the enterotoxin gene was identified by DNA extraction. Finally, gene sequencing was carried out automatically and systematically.
Results: The results suggested that 92.9% of the total samples (21 fresh tilapia and 18 frozen fish) had no Staphylococcus aureus, and 7.1% of the samples were infected with Staphylococcus aureus. The coagulase test results also suggested that all three frozen fish samples were coagulase positive. Examining enterotoxin-producing genes (SEA, SEB, SEC, SED, SEE, and SEG) among three frozen samples infected with Staphylococcus bacteria revealed SEA enterotoxin gene only in one frozen sample. Conclusion: The results showed that due to the low cost and much shorter time required to identify toxic Staphylococcus aureus genes using Multiplex PCR, this method is highly effective in studying the genotypes of Staphylococcus isolates. Therefore, by using this method, one can improve the food health level in the society.


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