What bacteria grow on blood agar

Alpha hemolysis on cooked blood agar plate
Beta hemolysis on blood agar plate

Blood agar In microbiology, it serves as a breeding ground for microorganisms that require components of the blood of mammals for growth.

The culture medium consists of 5 to 10% defibrinated blood (usually sheep or horse blood; in special cases also rabbit or pig blood; rarely human blood) and enables the detection of certain classes of pathogens and the assessment of the haemolytic properties of the cultured bacteria (e.g. Streptococci).

  • α hemolysis (Greening): The bacteria do not produce any haemolysins, they cause a greenish zone on blood agar, which is not due to real haemolysis but to discoloration and a loss of potassium in the red blood cells.[1] The reduction in hemoglobin to biliverdin causes the green color. There are still intact erythrocytes.
  • β hemolysis: The bacteria produce streptolysin O or S and are surrounded by a clear zone of hemolysis. The hemoglobin is completely broken down, this is a real hemolysis.[1] All erythrocytes in this area are completely hemolyzed.
  • γ hemolysis: These bacteria do not show any hemolysis behavior.

The Cooked blood agar (also: Chocolate agar) is a variant of blood agar in which the agar is briefly heated to 80 ° C[2] erythrocyte lysis is achieved. The lysis releases hemin ("factor X") and NAD ("factor V") into the agar, where they can be metabolized by bacteria that are not themselves hemolyzing (e.g. Haemophilus influenzae). Boiled blood plates are sometimes activated with increased CO2-Tension incubates, especially capnophile germs, i.e. CO2-Preferring bacteria, as well as all Neisseria, multiply much better this way.

See also

Individual evidence

  1. 1,01,1Michael T. Madigan, John M. Martinko, Jack Parker: Brock microbiology. German translation edited by Werner Goebel, 1st edition. Spektrum Akademischer Verlag GmbH, Heidelberg 2000, ISBN 978-3-8274-0566-1, p. 562
  2. ↑ Technical information Blood agar (base) of Merck KGaA, accessed on February 11, 2013