Quick Answer: What Does Chocolate Agar Contain?

What grows MacConkey Agar?

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..

What color is E coli on MacConkey Agar?

dark pinkPresumptive identification of E. coli was made based on its characteristic morphology colony on the selective medium MacConkey agar. Rapid lactose fermenting colonies of E. coli appear dry, donut shaped and dark pink in color and are surrounded with dark pink area of precipitated bile salts.

What is the difference between EMB agar and MacConkey Agar?

An example of a selective medium is MacConkey agar. It contains bile salts and crystal violet, which interfere with the growth of many gram-positive bacteria and favor the growth of gram-negative bacteria. … EMB contains the dyes eosin and methylene blue that inhibit the growth of gram-positve bacteria.

What is the difference between blood agar and Cled Agar?

For routine urine culture, inoculation of specimens in a combination Blood agar (BA) and MacConkey agar is commonly used approach whereas CLED agar can be used as a sole medium, reducing the cost without compromising the quality.

What kind of agar is used to grow bacteria?

Examples of standard general purpose media that will support the growth of a wide variety of bacteria include nutrient agar, tryptic soy agar, and brain heart infusion agar. A medium may be enriched, by the addition of blood or serum.

What is added to chocolate agar TSA?

Chocolate agar with the addition of bacitracin becomes selective for the genus Haemophilus. Another variant of chocolate agar called Thayer-Martin agar contains an assortment of antibiotics which select for Neisseria species.

Does E coli grow on chocolate agar?

Chocolate agar, however, does not reveal hemolysis data, so species differentiation among the members of Haemophilus must be performed in another manner. … This is an agar upon which only Gram-negative bacteria can grow. What is more is that E. coli will grow into red colonies, as there is a pH indicator present.

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 bacteria does not grow on 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.

How do you make blood agar?

Preparation of Blood AgarSuspend 28 g of nutrient agar powder in 1 litre of distilled water.Heat this mixture while stirring to fully dissolve all components.Autoclave the dissolved mixture at 121 degrees Celsius for 15 minutes.Once the nutrient agar has been autoclaved, allow it to cool but not solidify.More items…•

What is the principle of blood agar?

Blood Agar is a general-purpose enriched medium used to grow fastidious organisms and to differentiate bacteria based on their hemolytic properties. It is a highly nutritious medium generally used as a basal medium for preparing blood agar by supplementation with blood.

Why is agar used to grow bacteria?

Agar, which is a polysaccharide derived from red seaweed (Rhodophyceae) is preferred because it is an inert, non-nutritive substance. The agar provides a solid growth surface for the bacteria, upon which bacteria reproduce until the distinctive lumps of cells that we call colonies form.

Does Streptococcus grow on chocolate agar?

Chapter 8: Identification and Characterization of Streptococcus pneumoniae. … pneumoniae is a fastidious bacterium, growing best at 35-37°C with ~5% CO2 (or in a candle-jar). It is usually cultured on media that contain blood, but can also grow on a chocolate agar plate (CAP).

Is blood agar selective?

Blood Agar Is Not a Selective Medium If a bacterial growth medium is selective, that means that it grows only certain types of microbes while inhibiting the growth of other types of microbes. Blood agar is an enriched medium that provides an extra rich nutrient environment for microbes.

Why is chocolate agar Brown?

Red blood cell lysis gives the medium a chocolate-brown coloration when prepared from which the agar gets its name. The most common bacterial pathogens that require this enriched medium for growth include Neisseria gonorrhoeae and Haemophilus species.

Does bacteria grow on chocolate?

Moraxella organisms are small, gram-negative bacteria that grow well on blood or chocolate agar. They are catalase and oxidase positive. These small diplococci are morphologically difficult to distinguish from Neisseria. Some Moraxella species are gram-negative bacilli.

How do you interpret MacConkey Agar?

Result Interpretation on MacConkey Agar Lactose fermenting strains grow as red or pink and may be surrounded by a zone of acid precipitated bile. The red colour is due to production of acid from lactose, absorption of neutral red and a subsequent colour change of the dye when the pH of medium falls below 6.8.

What is blood agar used for?

Blood agar is a general purpose enriched medium often used to grow fastidious organisms and to differentiate bacteria based on their hemolytic properties.

Does chlamydia grow on chocolate agar?

Chlamydia species are obligate intracellular bacteria that require growth inside mammalian cells for propagation and survival. As a result, Chlamydia cannot be grown on conventional bacteriological medium. This property makes Chlamydia difficult organisms to grow and maintain in the laboratory.

What is the purpose of fermentation in chocolate?

In chocolate, fermentation is the process that creates aromas, bold flavor and rich color. There are two stages: alcohol and acetic fermentation. First, natural yeast converts the sugars in the cocoa pulp into alcohol. Then bacteria oxidize the alcohol into acetic acid.

How do you make a chocolate agar?

Preparation of Chocolate Agar:Heat-lyse a volume of horse or sheep blood that is 5% of the total volume of media being prepared very slowly to 56°C in a water bath.Dispense 20 ml into 15×100 mm Petri dishes. … Place the plates in sterile plastic bags and store at 4ºC until use.More items…•