Chocolate Agar

Chocolate Agar

Blood agar that has been heated to open the pyrrole ring, forming hemin, a required growth factor for bacteria lacking hemolysins. Chocolate agars are usually incubated in a microaerophilic—3–10% CO2—environment, providing ideal growth conditions for H influenzae, Neisseria spp, and fastidious anaerobes

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agar

a dried hydrophilic, colloidal substance extracted from various species of red algae. When suspended in a liquid medium and heated to 212°F (100°C), the agar dissolves. When it is allowed to cool to 110°F (43°C) the medium becomes a solid gel. It is used in culture media for bacteria and other microorganisms, in making emulsions, and as a supporting medium for immunodiffusion and immunoelectrophoresis. Because of its bulk it is also used in medicines to promote peristalsis and relieve constipation.

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birdseed agar

one containing Guizotia abyssinicia (Niger) seed and creatinine, used for growing Cryptococcus neoformans. Called also Niger agar.

bismuth sulfite agar

a special preparation used for isolation of salmonellae from food.

blood agar

a culture medium used for the growth of bacteria. Consists of agar and intact erythrocytes.

brain heart infusion agar

used for cultivating the yeast phase of dimorphic fungi.

brilliant green agar

used to cultivate salmonellae.

chocolate agar

an enriched agar for the growth of Hemophilus, some Actinobacillus, and Taylorella spp. A molten agar and blood mixture is held at 122°F (50°C) prior to pouring plates. The additional nutrients supplied are hemin and NAD.

agar diffusion test

see antimicrobial sensitivity test.

eosin-methylene blue (EMB) agar

used for the identification of Eschericha coli.

agar gel immunodiffusion test

see immunodiffusion tests.

MacConkey agar

contains bile salts, lactose and neutral red indicator for isolation of enterobacteria.

mannitol salt agar

selective for staphylococci.

milk agar

contains skim milk and used to demonstrate casein digestion.

Niger seed agar

see birdseed agar (above).

nutrient agar

the basic growth medium for bacteria, composed of beef extract and peptone.

potato dextrose agar

used in cultivating fungi; promotes sporulation and pigmentation.

Sabouraud's dextrose agar

one used for isolation of fungi. See also dermatophyte test medium.

agar sausage

see medium sausage.

xylose lysine (XLD) agar

used to differentiate Enterbacteriaceae.