A Tellurite-Iron-Rosolic Acid Medium Selective for B. dysenteriae (Flexner)

Abstract

The medium is made as follows: 0.5 g. of Na tauroglycocholate and 0.5 g. of lactose are dissolved in about 10 cc. of boiling water in 100 cc. wide-neck flat-bottom extrn. flask; then melted nutrient agar cooled to 60[degree]C. is added up to the 100 cc. mark, followed by 0.5 cc. of 1% K tellurite, 2 cc. of 4% iron citrate and 0.5 cc. of 1% alcoholic soln. of rosolic acid. Mannite fermenting types of Shigella dysenteriae grow profusely, whereas there is great inhibition of most strains of Escherichia coli and Aerobacter aerogenes. The growth of Salmonella food-poisoning organisms, typhoid and paratyphoid bacilli, Sonne''s bacillus, and cholera vibrios is suppressed.