Quick Answer: Is Chocolate Agar A Differential?

Why is MacConkey Agar yellow?

Lactose fermenters produce colonies that appear as yellow, whereas colonies of non-lactose fermenters appear blue on CLED agar.

E.

coli forms colonies, which appear as yellowish, because the agar will turn yellowish..

Why sheep blood is used in blood agar?

Blood agar contains general nutrients and 5% sheep blood. It is useful for cultivating fastidious organisms and for determining the hemolytic capabilities of an organism. Some bacteria produce exoenzymes that lyse red blood cells and degrade hemoglobin; these are called hemolysins.

Is E coli Gram positive or negative?

E coli is a gram-negative bacillus that grows well on commonly used media. It is lactose-fermenting and beta-hemolytic on blood agar. Most E coli strains are nonpigmented. The image below shows Escherichia coli on Gram staining.

What does Staphylococcus aureus look like on blood agar?

Individual colonies on agar are round, convex, and 1-4 mm in diameter with a sharp border. On blood agar plates, colonies of Staphylococcus aureus are frequently surrounded by zones of clear beta-hemolysis. … S. aureus can infect other tissues when barriers have been breached (e.g., skin or mucosal lining).

Is CNA agar selective or differential?

CNA is a selective, differential agar medium used for isolation of gram positive bacteria in a variety of specimen types.

What does a blood agar test for?

Blood Agar Plates (BAP) BAP tests the ability of an organism to produce hemolysins, enzymes that damage/lyse red blood cells (erythrocytes). The degree of hemolysis by these hemolysins is helpful in differentiating members of the genera Staphylococcus, Streptococcus and Enterococcus.

Is blood agar selective or differential or both?

Blood agar is a differential medium that distinguishes bacterial species by their ability to break down the red blood cells included in the media. Blood agar is often used to distinguish between the different species of pathogenic Streptococcus bacteria.

Is Mac selective or differential?

MacConkey agar (MAC) is a bacterial culture medium named after bacteriologist Alfred T. MacConkey (1861-1931). MacConkey agar is a selective and differentiating agar that only grows gram-negative bacterial species; it can further differentiate the gram-negative organisms based on their lactose metabolism.

Why is human blood not used in blood agar?

Agar prepared with human blood is not recommended, partly because of the safety risk to laboratory personnel, but mainly because it is said to result in poor bacterial isolation rates, although there are few published data to support this (2).

What does Defibrinated blood mean?

Whole blood from which fibrin has been removed. It does not clot. See also: blood. Medical Dictionary, © 2009 Farlex and Partners.

Why is blood agar used to grow throat cultures?

Blood agar allows differentiation of streptococci based upon the characteristic hemolysis that they produce. Beta hemolytic strep releases products into the medium called beta hemolysins, which lyse the red blood cells and cause a clear zone to form around the colonies.

What causes media differential?

Differential media are bacteriological growth media that contain specific ingredients to allow one to distinguish selected species or categories of bacteria by visual observation. Differential Media are used to distinguish between closely related organisms or groups of organisms.

Why do we use chocolate agar?

Chocolate agar (CHOC) or chocolate blood agar (CBA), is a nonselective, enriched growth medium used for isolation of pathogenic bacteria. … Chocolate agar is used for growing fastidious respiratory bacteria, such as Haemophilus influenzae and Neisseria meningitidis. In addition, some of these bacteria, most notably H.

What bacteria can grow on MacConkey Agar?

MacConkey agar is an indicator, a selective and differential culture medium for bacteria designed to selectively isolate Gram-negative and enteric (normally found in the intestinal tract) bacilli and differentiate them based on lactose fermentation.

What is the difference between selective and differential media?

Selective media generally selects for the growth of a desired organism, stopping the growth of or altogether killing non-desired organisms. Differential media takes advantage of biochemical properties of target organisms, often leading to a visible change when growth of target organisms are present.

Why is MacConkey agar selective as well as differential?

MacConkey Agar (MAC) is a selective and differential medium designed to isolate and differentiate enterics based on their ability to ferment lactose. Bile salts and crystal violet inhibit the growth of Gram positive organisms. Lactose provides a source of fermentable carbohydrate, allowing for differentiation.

Is TSA selective or differential?

TSA (Trypticase Soy Agar) and NA (Nutrient Agar) are General Purpose Media that are not selective or differential, their purpose is simply to grow many types of bacteria cheaply. Here we will use a general purpose media to compare the growth on the selective and differential media.

What type of media is blood agar?

Blood agar is an enriched, bacterial growth medium. Fastidious organisms, such as streptococci, do not grow well on ordinary growth media. Blood agar is a type of growth medium (trypticase soy agar enriched with 5% sheep blood) that encourages the growth of bacteria, such as streptococci, that otherwise wouldn’t grow.

What is a differential agar?

Differential media are bacteriological growth media that contain specific ingredients to allow one to distinguish selected species or categories of bacteria by visual observation. … Blood agar is one type of differential medium, allowing bacteria to be distinguished by the type of hemolysis produced.

What is the major difference between blood agar and chocolate agar?

Chocolate agar is used for the isolation of fastidious organisms, such as Haemophilus influenzae, when incubated at 35-37°C in a 5% CO2 atmosphere. The composition of chocolate agar and the Blood Agar is the same and the only difference is while preparing chocolate agar, the red blood cells are lysed.

Can media be both selective differential?

Selective and differential media can be combined and play an important role in the identification of bacteria by biochemical methods. Another commonly used medium that is both selective and differential is eosin-methylene blue (EMB) agar. … Therefore, EMB is selective for gram-negatives.