【 Principle 】

Tryptone, beef extract, and yeast extract are used as basic nutrients in the culture medium to provide nitrogen, carbon, vitamins, and other nutrients required for bacterial growth; High concentrations of sodium chloride mainly inhibit the growth of enterococci; Phosphates as buffering agents; When lithium chloride and Listeria monocytogenes grow on this medium, they hydrolyze seven leaf glycosides to produce 6,7-dihydroxycoumarin, which reacts with iron ions in ammonium iron citrate in the medium to produce a black substance, thereby turning the medium black.

Main components

Composed of tryptone, beef extract powder, yeast extract powder, sodium chloride, potassium dihydrogen phosphate, seven leaf glycoside, animal tissue enzyme digest, lithium chloride, disodium hydrogen phosphate, and distilled water.

Storage conditions and expiration date

Storage conditions: This product should be stored in a dark environment at 2-8 ℃.

Validity period: The unopened original packaging has a validity period of 6 months.

This product is a disposable product.

Food safety testing: According to GB 4789.30, selective enrichment of Listeria monocytogenes is performed on dairy products, meat products and other foods for qualitative testing and counting.

Food environment monitoring: detecting Listeria contamination on contact surfaces such as operation surfaces and cold chain equipment for traceability and risk control.

Feed and animal sample testing: screen for Listeria monocytogenes in animal feed and livestock products, and assess the risk of contamination in the breeding process.

Laboratory quality control: Verify the selective bacterial growth performance of the culture medium, ensuring the growth of target bacteria and inhibiting non target bacteria.

Listeria monocytogenes

Biological characteristics: Gram positive Bacillus subtilis, without spores or capsules, facultative anaerobic; Resistant to cold (can grow at 2-42 ℃, and can reproduce in refrigerated food), high salt, lithium chloride, and two antibacterial antibiotics; Producing β - glucosidase, which can hydrolyze seven leaf glycosides;

Foodborne pathogens contaminate fresh meat, dairy products, and ready to eat foods; Infection can cause sepsis, meningitis, miscarriage in pregnant women, and severe infections in newborns.

Cultivation characteristics: The cultivation conditions are 30 ℃, 24-48h; the liquid is uniformly turbid, and fine bacterial sediment can be seen at the bottom of the tube, with no gas bubbles produced throughout the process;

The hydrolysis products of seven leaf glycosides combine with iron ions, and the broth changes from light purple to brownish black/whole tube blackening; The fluorescence of the culture medium disappears under UV 366nm.