7-62 MxED AcID FERMENTATION OF E, COU E col is a representative Methy Red positive organism and is recommended as a positive controlfor the test. Its mixed acid fermentation produces the end products listed in order of abundance. Most of the formate is converted to H, and CO.gases. Note: The amount of succinate falls between acetate and formate, but is derived from PEP, not pyruvate. Salmonella and Shigella are alsoMethyl Red positive.