McClung Toabe HiVeg™ Agar Base

Principle And Interpretation

McClung Toabe HiVeg Agar Base is prepared by incorporating vegetable peptones in place of animal peptones, making it free from BSE/TSE risks. It can be used for the same purpose of McClung Tabe Agar Base (1) for isolating Clostridium perfringens from foods. Clostridium perfringens food poisoning is one of the most common types of human foodborne illness. The foods usually involved are cooked meat or poultry products containing large number of viable cells. A heat-labile enterotoxin produced only by sporulating cells induces the major symptoms of diarrhea in perfringens poisoning. Although the enterotoxin is not preformed in the food, the foods in which conditions are favourable for sporulation may contain enterotoxin (2). Therefore, enumeration of these microorganisms in food plays a significant role in investigation of food borne illness (3). McClung and Toabe formulated this medium for isolation and differentiation of Clostridium species from foods on the basis of their lecithinase and lipase activity that can be visualized by addition of 50% egg yolk. This medium contains HiVeg peptone No.3 as a source of carbon, nitrogen, vitamins and minerals. Dextrose is the carbohydrate source. Sodium chloride maintains osmotic balance of the medium. Magnesium sulphate provides divalent cations and sulfate. Disodium hydrogen phosphate and monopotassium phosphate maintain pH balance and provide a source of phosphates. Lecithinase producing clostridia, such as Clostridium perfringens, hydrolyze the lecithin and produce opaque halos of precipitation surrounding the slightly raised colonies. Add 25 grams of food sample to be tested in two tubes containing 25 ml Fluid Thioglycollate HiVeg Medium (MV009) with inverted Durham's tubes. Incubation is carried out at 46°C for 4 -6 hours. Observe the growth and gas production and streak it on McClung Toabe HiVeg Agar plates and incubate.