--- â‘´ Enrichment
Currently, the commonly used mononuclear L. monocytogenes detection enrichment broth mainly includes half the amount of Fraser broth, Fraser broth (FB), UVM (Modified University of Vermont broth, also called UVM1), LEB (Listeria enrichment broth) and BLEB (buffered Listeria enrichment broth)
Half-volume Fraser broth and Fraser broth? Selective and distinctive. ? Add ammonium ferric citrate and aescin to play a different role. Listeria can hydrolyze aescin and react with the iron ions in the medium to make the medium black. It can be intuitively judged from the color of the culture solution whether there is growth of Listeria monocytogenes.
Lithium chloride, acridine yellow and nalidixic acid act as selectivity factors.
Half the amount of Fraser broth uses the same additives as Fraser broth
Half amount Fraser broth: nalidixic acid 10mg / L, acridine yellow 12.5mg / L; Fraser broth: nalidixic acid 20mg / L, acridine yellow 25mg / L UVM
UVM has only selectivity and no difference
Add nalidixic acid and acridinium hydrochloride as selectivity factors. Although it contains aescin, no ferric ammonium citrate is added, and no black color reaction can occur. LEB and BLEB
Only selectivity makes no difference
LEB is based on the addition of selective factors such as acriflavine hydrochloride, nalidixic acid and cycloheximide on the basis of TSB-YE; the added sodium pyruvate helps recovery of damaged cells; it does not contain aescin and Ferric ammonium citrate, no color reaction.
BLEB is a buffer system added on the basis of LEB: potassium dihydrogen phosphate and disodium hydrogen phosphate detection procedures --- ⑵ separation
Separation media are: OXA, PALCOM, LPM, MOX, etc., but the first choice is still OXA. The separation principle is mainly based on Listeria monocytogenes with β-D-glucosidase activity, which can hydrolyze escin in the culture medium to produce escin, which reacts with iron ions to produce a color reaction and make the colonies brown. With a brown halo, and both pathogenic and non-pathogenic Listeriosis can occur this reaction? There are also some selective color development media, such as BCM, ALOA, CHROMagar listeria, Rapid'L. Mono The principle is mainly to detect the hemolysin encoded by the virulence gene, and this hemolysin only exists in Listeria monocytogenes and Listeria monocytogenes, so these two bacteria can be well Separated from other species of Listeria. Testing procedures-⑶ identification
Blue colony test (Henry illumination) Typical movement: phase contrast microscope, slight rotation or flip head dynamic test: 7 days, umbrella growth catalase test: positive Gram stain: positive Brevibacterium hemolysis test: puncture inoculation blood plate nitric acid Salt reduction test: 5 days, negative
Sugar fermentation test: glucose, maltose and escin, positive for Listeria genus, except for Listeria mannitol negative, Listeria mannitol negative, xylose and rhamnose have the most detection significance. Currently, the national standard method (GB / T4789.30) is commonly used for the detection of Listeria monocytogenes.
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