methyl red test

The methyl red test is based on the fact that all the genus Enterobacteriaceae can ferment glucose, which produces pyruvic acid during the process of decomposing glucose. Further decomposition, due to different ways of glucose metabolism, can produce a large amount of acidity such as lactic acid, succinic acid, acetic acid and formic acid. The product can be tested by the principle that the pH of the medium is lowered to below pH 4.5, and the methyl red indicator is turned red. Basic Information Specialist classification: Digestive examination classification: pathogenic microbiological examination Applicable gender: whether men and women apply fasting: not fasting Analysis results: Below normal: Normal value: no Above normal: negative: Enterobacter, Hafnia. Positive: In the family Enterobacteriaceae, Salmonella, Shigella, Citrobacter, Proteus and the like. Tips: Before the check: taboo: pay attention to the normal diet, and keep it healthy. Normal value The color change range of methyl red is PH4.4~6.2, which means: 1. When the pH value is between 4.4 and 6.2, it is orange. 2. When the pH value is <= 4.4, it is red. Because it is close to the acid color, it is also called acid color. 3. When the pH value is >=6.2, it is yellow, because it is close to the color of the strong alkaline side, so it is also called alkali color. Clinical significance It is mainly used to identify Escherichia coli and Enterobacter aerogenes. The former is positive and the latter is negative. In the Enterobacteriaceae, Salmonella, Shigella, Citrobacter, Proteus, etc. are positive, while Enterobacter and Hafnia are negative. Abnormal results methyl red color reaction was positive. The person in need of inspection is suspected of being infected with a certain pathogenic microorganism. Positive results may be diseases: Shigella disease considerations Inappropriate crowd: No. Contraindications before check-up: Pay attention to the normal diet and keep it healthy. Requirements for inspection: Actively cooperate with the doctor. Inspection process Test method: pick a new test pure culture a little, inoculate in a common medium, culture at 36 ± 1 ° C or 30 ° C (30 ° C is better) 3 ~ 5 days, from the next day, Take 1ml of culture medium daily, add 1~2 drops of methyl red indicator, the positive is bright red, the weak positive is light red, and the negative is yellow. The result is judged until it is found to be positive or is still negative by the fifth day. Methyl red is an acidic indicator with a pH range of 4.4 to 6.0 and a pK value of 5.0. Therefore, below pH 5.0, red color is enhanced with acidity. Above pH 5.0, yellow color is enhanced with alkalinity. When pH is 5.0 or close to the top, the color change may not be obvious. In this case, the culture time should be prolonged and the test repeated. . Not suitable for the crowd no. Adverse reactions and risks no.