Listeria Chromogenic Agar (also known as OA Agar or CRM014 Chromogenic Agar) is a solid medium specifically designed for the selective isolation and rapid identification of Listeria monocytogenes. Through the action of β-glucosidase and esterase secreted by Listeria, substrates are hydrolyzed, releasing a blue-green chromogenic substance and forming a surrounding milky-white opaque halo (resulting from lipase hydrolysis of lecithin), yielding visually distinguishable colonies with high specificity.

Food rapid separation and screening: Fresh meat, dairy products, etc. are subjected to Fraser enrichment and streaked to quickly distinguish between pathogenic Listeria monocytogenes and harmless Listeria monocytogenes.

Foodborne infection detection: Inoculate patients' feces, vomit, and leftover food, quickly screen for suspicious bacterial colonies, and assist in clinical traceability diagnosis.

Risk assessment of food environment: Cold chain equipment, operating platforms, and containers are coated with samples to increase bacterial growth, locate the source of contamination, and block cross contamination.

Import and export refrigerated food quarantine: Customs conducts spot checks on fresh and low-temperature pre packaged food, with higher identification than PALCAM, shortening the testing cycle.

Purification of positive sample single colony: Fraser darkened and turbid tube was transferred to a plate to obtain characteristic colonies for biochemical and serum typing confirmation.

Validation of disinfection and antisepsis effect: after disinfection of food materials and appliances, the samples were cultured, and residual Listeria monocytogenes was detected to evaluate the disinfection and sterilization effect.

Listeria monocytogenes

Biological characteristics: Gram positive Bacillus subtilis, facultative anaerobic, cold loving, tolerant to high salt and antibacterial antibiotics in the culture medium;

Unique phosphatidylinositol phospholipase C (PI-PLC) can decompose specific chromogenic substrates; Foodborne pathogens can invade the internal organs and central nervous system, causing sepsis, meningitis, and miscarriage in pregnant women.

Colony characteristics: Typical blue-green/blue-green colonies, surrounded by an opaque milky white halo (PI-PLC substrate decomposition characteristic), with round and smooth colonies of uniform size.

Other Listeria species (Inoue, Will, Listeria)

Biological characteristics: Both are G ⁺ short rod-shaped bacteria, tolerant to antibacterial systems, capable of hydrolyzing seven leaf glycosides, but do not produce PI-PLC and have no strong pathogenicity; Growing blue-green colonies without peripheral milky white halos, which can be preliminarily distinguished from Listeria monocytogenes.