How Do You Prepare Blood Agar?

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.


aureus can infect other tissues when barriers have been breached (e.g., skin or mucosal lining)..

What is the use of MacConkey Agar?

Uses of MacConkey Agar It is used in the differentiation of lactose fermenting from lactose non-fermenting gram-negative bacteria. It is use in microbiological examination of food stuffs and for direct plating / inoculation of water samples for coliform counts. It is used for the examination of milk and dairy products.

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).

Is blood agar selective?

Blood Agar Is Not a Selective Medium Blood agar is an enriched medium that provides an extra rich nutrient environment for microbes. Therefore, BAP is not a selective growth medium, since it supports the growth of a wide range of organisms.

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.

Do all bacteria grow on blood agar?

Do all bacteria that grow on blood agar break down the blood? … No, the only thing that grows on blood agar is the bacteria because it breaks down RBCs. Blood agar is a differential medium because all the bacteria will grow on it due to the nutrients and iron.

Why blood agar is selective media?

A selective media is composed of specific ingredients to inhibit the growth of certain species of microbes in a mixed culture while allowing others to grow. … Blood agar is a differential medium that distinguishes bacterial species by their ability to break down red blood cells.

Why is MacConkey agar selective?

MacConkey Agar is Selective for Non-fastidious Gram-negative organisms. Therefore, MacConkey needed a way to limit this background of environmental flora and allow only his organisms of interest to grow. A medium that can perform this function is now known as a selective medium.

What type of medium is chocolate agar?

Chocolate agar (CHOC) or chocolate blood agar (CBA), is a nonselective, enriched growth medium used for isolation of pathogenic bacteria. It is a variant of the blood agar plate, containing red blood cells that have been lysed by slowly heating to 80°C.

Why is blood agar used for streptococcus?

Blood agar is commonly used to isolate not only streptococci, but also staphylococci and many other pathogens. Besides providing enrichments for the growth of fastidious pathogens, Blood agar can be used to detect hemolytic properties.

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.

Why do we use blood of sheep instead of human blood during preparation of blood agar?

Sheep blood has been preffered source in the Blood agar due to the fact that sheep RBCs are most sensitive to the the hemolytic toxins released by bacterial cells thus causing hemolytic zones around the colonies over the period of time.

What Bacteria grows on blood agar?

Blood Agar is used to grow a wide range of pathogens particularly those that are more difficult to grow such as Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species. It is also required to detect and differentiate haemolytic bacteria, especially Streptococcus species.

How do you collect blood from a sheep?

The jugular vein as a source of blood is the method of choice, whether for a single collection or for collection on a flock basis. The vein, lying subcutaneously in the neck with little or no fat cover,can readily be seen in the shorn sheep if it is properly restrained.

What is the use of nutrient agar?

Nutrient agar is a general purpose medium supporting growth of a wide range of non-fastidious organisms. It typically contains (mass/volume): 0.5% Peptone – this provides organic nitrogen. 0.3% beef extract/yeast extract – the water-soluble content of these contribute vitamins, carbohydrates, nitrogen, and salts.

What are the nutrients in blood agar?

Blood agar is almost identical to nutrient agar except that it contains five to ten percent sheep, rabbit, or horse blood….Blood agar consists of:Beef extract, for nitrogen.Blood, for nitrogen, amino acids, and carbon.Sodium chloride, for maintaining osmotic balance.Agar, for the solidifying agent.

What is the use of blood agar?

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

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.

What is the selective agent in blood agar?

colistenCNA-blood agar contains the selective agents colisten and nalidixic acid. Colisten negatively affects the cell membrane of many Gram(-) species, and nalidixic acid inhibits replication of DNA in susceptible species. The result is that CNA-blood selects for Gram(+) coccus-shaped species, and against everything else.

What Bacteria grows on MacConkey Agar?

Altogether, MacConkey agar only grows gram-negative bacteria, and those bacteria will appear differently based on their lactose fermenting ability as well as the rate of fermentation and the presence of a capsule or not.