Quick Answer: What Is The Selective Agent In Blood Agar?

What is the selective agent in MSA medium?

Mannitol Salt Agar (MSA) This is a medium that is both selective and differential.

The high salt concentration (7.5%) is the selective ingredient.

Staphylococcus species, which commonly inhabit human skin, can grow on this high salt concentration (left plate in picture below)..

What grows best on MacConkey Agar?

MacConkey’s is a selective medium that inhibits the growth of Gram-positive bacteria due to the presence of crystal violet and bile salts. Gram-negative bacteria grow well on MAC.

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 are the selective agents in MacConkey’s Agar?

MacConkey’s agar is selective. It contains the selective agents crystal violet and bile salts. These selective ingredients inhibit (select against) the growth of Gram(+) bacteria but allow (select for) the growth of Gram(-) bacteria. The MacConkey’s medium is also differential.

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.

Is blood agar selective or differential?

Blood Agar This medium can be made selective by the addition of antibiotics. This medium is differential because: Blood Agar tests for the production of hemolysin which breaks down red blood cells.

What 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.

Are blood agar plates 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 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.