Modified Duncan Strong (DS) medium is used for isolation and differentiation of Clostridium perfringens from other clostridia from foods on the basis of raffinose fermentation.

• Formulated as per Duncan and Strong
• Isolation and differentiation of C. perfringens from other Clostridia from foods on the basis of raffinose fermentation
• Rapid detection of the Clostridium perfringens enterotoxin

Clostridium perfringens , a gram-positive, rod shaped, anaerobic, spore-forming bacteria, is the major cause of food poisoning in humans

Modified Duncan Strong (DS) Medium is formulated as per Duncan and Strong, and is recommended by APHA for the isolation and differentiation of C. perfringens from other Clostridia from foods on the basis of raffinose fermentation. It is also recommended for the rapid detection of the Clostridium perfringens enterotoxin.

Proteose peptone and yeast extract provide nitrogenous compounds and other nutrients for bacterial growth. Sodium thioglycollate helps to create anaerobic conditions suitable for clostridial growth. Disodium phosphate acts as a buffering agent. Raffinose in the medium is fermented by C. perfringens to produce acid within 72 hours, but not by culturally similar species like Clostridium baratii , Clostridium celatum , Clostridium sardiniense etc. To test for acid, transfer 1 mL of culture to a test tube or spot plates and add 2 drops of 0.04% bromothymol blue. A yellow colour indicates acid production. Inoculate about 2 gm of the food sample into 15- 20 mL of Chopped Liver Broth. After an incubation at 35-37° C for 20 to 24 hours, tubes showing turbidity are streaked on Perfringens Agar Base containing Egg Yolk Emulsion to obtain presumptive C. perfringens . These presumptive colonies can be confirmed by inoculating into Motility Nitrate Medium, Buffered, Lactose Gelatin Medium and Modified Duncan Strong (DS) Medium.

A heat labile enterotoxin produced only by sporulating cells induces the major symptoms of diarrhea in perfringens poisoning. C. perfringens is commonly found in raw meats, poultry, dehydrated soups and sauces, raw vegetables and certain other foods or food ingredients.