Use of casein, tyrosine, and hypoxanthine in the identification of nonfermentative gram-negative bacilli.

Four hundred and five (405) strains of nonfermentative gram-negative bacilli (NFB) were identified using conventional tests. The NFB studied include 323 originating from clinical specimens, 37 from environmental samples, and 45 authentic strains from other workers and from our culture collections. All these strains were studied for their ability to degradate casein, tyrosine, and hypoxanthine. It was found that these tests are useful in identifying NFB within 24 to 48 h when used with other tests.