How is blood agar related to chocolate agar?
Chocolate agar is prepared by heating blood agar, which in turn ruptures the red blood cell (RBC) and releases nutrients that aid in the growth of fastidious bacteria, most notably Haemophilus and Neisseria species. The name is derived from the fact that the lysis of RBC gives the medium a chocolate-brown color.
What is the difference between blood agar and chocolate agar?
Chocolate agar is essentially the same as blood agar except that during preparation the red blood cells are lysed when added to molten agar base.
Does chocolate agar show hemolysis?
The name chocolate agar is referring to the color of the medium and not to its content. Hemolysis cannot be observed on hematin agar.
What routine media should be used for the isolation of Haemophilus influenzae?
The standard medium used for growth of H. influenzae is a chocolate agar plate (CAP), which can be prepared with heat-lysed horse blood, a good source of both hemin and NAD, although sheep blood can also be used.
Why sheep blood is used in 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 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. In the U.S., blood agar is usually prepared from tryptic soy agar or Columbia agar base with 5% sheep blood.
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 treatment for Haemophilus influenzae?
Antibiotics and supportive care are the mainstays of treatment for Haemophilus influenza infections. Initially, invasive and serious H influenzae type b (Hib) infections are best treated with an intravenous third-generation cephalosporin until antibiotic sensitivities become available.
Does Haemophilus influenzae grow on chocolate agar?
Haemophilus influenzae requires both factors X and V; accordingly, it grows on chocolate agar but not on blood agar (Fig. 30-2), although it may appear on a blood agar plate as tiny satellite colonies around the colonies of other bacteria that have lysed red blood cells.
What bacteria grows best on blood agar?
The primary purpose of Blood agar is for the cultivation and isolation of fastidious organisms like Neisseria and Streptococcus.
What bacteria can grow 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.
What is the use of blood agar and chocolate agar?
– Blood agar and Chocolate agar are enriched media. – They are used for the growth of Gram positive cocci and Gram negative fastidious organisms ( see below) like Neisseria and Haemophilus species. – They can be used to indicate hemolysis.
How to prepare sterile blood agar?
Transfer the blood agar base to the water bath at a temperature of 50°C. Once the base has cooled down, start adding sterile blood agar (5% of defibrinated blood) and mix well to prevent the formation of air bubbles. Dispense about 15 ml to a sterile petri plate. Store the plate at 2 to 8 degree Celsius in a sealed plastic bag.
What is the composition of chocolate agar for Haemophilus?
Potassium phosphate helps to maintain a uniform pH during growth. Hemoglobin solution provides X factor (hemin) required by Haemophilus species, and isovitox enrichment provides V-factor (nicotinamide dinucleotide), and other complex compounds that enhance the growth of Neisseria species. The composition of chocolate agar is the same as blood agar.
Why is blood agar used as a differential media?
Blood agar is a differential medium because it helps detect and differentiate haemolytic bacteria such as Streptococcus species. It detects hemolysis by cytolytic toxins that are secreted by some strain of bacteria. (1, 2, and 3) Blood agar as a selective medium Blood agar can be used as a selective medium for some types of pathogens.