Comparative evaluation of impedance, chromogenic and reference methods for identification of Staphylococcus aureus contamination in foods

Staphylococcus aureus (S. aureus) is one of the three major causes of food poisoning in the world, causing the disease in hundreds of thousands of people every year. Today, due to the production and processing the varieties of different foodstuffs, it is necessary to employ faster and more sensitive methods for controlling food quality, to gain the requirements of the regulatory centers. New qualitative control methods can be used for impedance and also for using chromogenic culture media. Their advantage over the reference method is the lack of high-volume laboratory operations and their relatively high rate of achievement. Therefore, evaluation of applying impedance, chromogenic and reference environments in the food quality control was considered. In the present work, 100 samples were evaluated for S. aureus infection by reference, impedance and chromogenic methods. Based on the results, 32, 21 and 57 samples were contaminated by S. aureus, respectively. The statistical analysis by SPSS16 software, using Cochran test showed that there is a significant difference between the three methods in detecting S. aureus (P<0.001). Statistical analysis showed that there is not a significant difference between reference and impedance methods, Although there is significant difference between the chromogenic technique and reference method (P>0.05), which means the reference and impedance methods have the same function and impedance can be used as an alternative technique for the reference method. Also the chromogenic technique could not be used instead of the impedance method.