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Dear sir,
Selective and differential media are used to isolate or identify particular organisms. Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms. While differential media are used to differentiate closely related organisms or groups of organisms.
The streptococci are classified by their hemolytic activity. Three types of hemolytic reactions can be observed on blood agar plates ().
Blood agar is a bacterial growth medium which is nutrient agar supplemented with a5% concentration of sheep blood. It is considered to be differential but not selective because it is
- An enriched medium that provides a rich nutrient environment for many types of bacteria, while a selective medium supports the growth of certain types of bacteria but inhibits other types.
- Used to distinguish pathogenic bacteria based on the effect of bacterial enzymes known as hemolysins which lyse red blood cells.
Blood agar can be both selective and differential, as well as Mannitol Salt Agar, MacConkey Agar, and Eosin Methylene Blue media.
Blood agar media is used for the isolation and differentiation of Gram positive cocci, specifically Streptococcus species. So, it is selective for streptococcus. Blood agar is mainly used clinically to detect the presence of Streptococcus pyogenes, the human pathogen which causes "strep throat".
thanks alot,
Lubna Al-Sharif
غراء الدم هو وسط منمي عام للجراثيم وليس إصطفائي لأنه يسمح لنمو أنواع كثيرة من الجراثيم الإيجابية والسلبية الغرام Differential not selective
Blood agar as differential media
It can be considered as both selective and differential.
differential
Blood agar is growth medium for bacterial which considered to be differential but not selective & it is an enriched medium that provides a rich nutrient for many types of bacteria.
Selective media allow certain types of organisms to grow, and inhibit the growth of other organisms. While differential media are used to differentiate closely related organisms or groups .
