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UV light for 366nm detection, used for microbial detection in water and food. For example, Escherichia coli in water cultured in MUG-containing medium will produce fluorescence reaction and can also be used for the detection of laboratory proteins and compounds.
Escherichia coli is a β - Glucosidase ( β- D-galactosidase ) that decomposes ONPG (Ortho-nitrophenyl- β- D-galactopyranoside ) to make the culture medium yellow and produce β - glucuronidase ( β -glucuronidase ) Decomposes MUG (4-methyl-umbelliferyl- β -D-glucuronide ) to make the culture liquid fluorescing bacteria at a wavelength of 366 nm.
0.2 ml of the above culture was taken, inoculated into a test tube containing 5 ml of MUG medium, cultured, observed under ultraviolet light at 366 nm at 5 hours and 24 hours, and the uninoculated MUG medium was used as a background control. If the culture in the tube was fluorescent It is positive for MUG, does not show fluorescence, and is negative for MUG. After observation, a few drops of sputum matrix test solution is added along the wall of the culture tube, the liquid surface is rose red, which is positive for sputum matrix, and is the true color of the reagent. The background control should be negative for MUG and negative for sputum matrix.
If the MUG is positive, the sputum matrix is ​​positive, and the test sample is judged to have Escherichia coli;
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If the plate grows aseptically, or the grown colonies do not match the morphological characteristics of the colonies listed in the table, the Escherichia coli is not detected in the test sample. If the colonies growing on the plate are consistent with the morphological characteristics of the colonies listed in the table or suspected , should be separated, purified, stained microscopic examination and appropriate biochemical tests to confirm whether it is Escherichia coli.
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Characteristics of coliforms: Magenta methylene blue: purple-black, light-purple, blue-violet or pink. The center of the colony is dark purple or has no obvious dark center, round, slightly convex, neat edges, smooth surface, moist, often Metallic luster
366nm Escherichia coli assay fluorescence observer use method
Escherichia coli definition
Detecting importance
Escherichia coli is included in the test items in GB/T 5750-2006. And in the interpretation of the "Sanitary Standard for Drinking Water" GB5749-2006: " Only Escherichia coli is fecal source specific, is the most accurate and specific indicator of fecal contamination . "
Second, use:
Escherichia coli assay fluorescence observation method: Place the desktop UV lamp in the dark, plug in the power supply, and irradiate the EC-MUG tube after 24 hours of incubation under the lamp. If there is blue fluorescence, it will be the large intestine. Escherichia positive tube;
Third, note:
For each observation, use an unopened EC-MUG tube and the EC-MUG tube to be tested while observing the UV lamp. If the EC-MUG tube is fluorescent, the UV is under the UV light and the unopened EC. -MUG tube comparison, there is a clear difference. Unplug the power after each test.
Fourth, the specific method: take the test solution 10ml (equivalent to the test sample 1g, 1ml), directly or after treatment, inoculate to the appropriate amount (not less than 100ml) of bile salt lactose medium, culture for 18-24 hours, necessary Can be extended to 48 hours.
If the MUG is negative, the sputum matrix is ​​negative, and the Escherichia coli is not detected. If the MUG is positive, the sputum matrix is ​​negative, or the MUG is negative, and the sputum matrix is ​​positive, the culture of the bile salt lactose medium should be inoculated. 3. Incubate on a medium of sorghum methylene blue agar medium or MacConkey agar medium for 18-24 hours.