The role of magnesium, copper, zinc and ferrum in recovery of cold-shocked bacteria

This work was conducted to study the role of Mg, Cu, Fe and Zn, on the recovery of cold-shocked bacteria in different combinations. Isolation of bacteria contaminating the frozen foods was performed and a design of a proper medium that recover almost all injured cells was achieved. The studied bacteria were Escherichia coli, Salmonella spp. Staphylococcus aureus and Klebsiellapneumoniae. The organisms were isolated from frozen foods (Sausages, Hamburgers, Meat ball and Ice creams) and identified to the species level. The isolated bacteria were sub cultured in nutrient broth medium and incubated at 37˚C for 24 hours and ten-fold dilutions were prepared for each species of bacteria using normal saline as a diluent. The bacteria were shocked at -20˚C for one hour. The frozen bacteria were left to thaw at room temperature for 30min and from the last two end dilutions, 0.1ml was transferred to the surface of recovery media and incubated at 37˚C for 24 hours. Using Miles and Misra (1938) method was applied for counting the bacteria.