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Streptococcus pneumoniae: small colonies with raised edges displaying alpha-hemolysis on blood agar [8]: 223 Proteus sp. : swarming behaviour on blood agar [ 1 ] : 167 Serratia marcescens : red pigmentation: although considered characteristic of the species, only about 10% of specimens produce this pigment [ 8 ] : 236
Blood agar plates (BAPs) contain mammalian blood (usually sheep or horse), typically at a 5–10% concentration. BAPs are enriched, and differential media is used to isolate fastidious organisms and detect hemolytic activity. β-Hemolytic activity will show lysis and complete digestion of red blood cell contents surrounding a colony.
Thayer–Martin agar (or Thayer–Martin medium, or VPN agar) is a Mueller–Hinton agar with 5% chocolate sheep blood and antibiotics. It is used for culturing and primarily isolating pathogenic Neisseria bacteria , including Neisseria gonorrhoeae and Neisseria meningitidis , as the medium inhibits the growth of most other microorganisms.
Haemophilus influenzae satellite colonies (pin points) near Staphylococcus aureus (yellow) on blood agar plate. Bacterial culture of H. influenzae is performed on agar plates. The strongest growth is seen on chocolate agar at 37 °C in a CO 2-enriched incubator. [33] The ideal CO 2 concentration for the culture is ~5%. [34]
Hemolysis is the breakdown of red blood cells. The ability of bacterial colonies to induce hemolysis when grown on blood agar is used to classify certain microorganisms. This is particularly useful in classifying streptococcal species. A substance that causes hemolysis is called a hemolysin.
The colonies are quite small and usually only reach a size of 1-2mm. [17] When grown on blood agar, Histophilus will have a clear areas around the colonies. [8] The dew-drop shaped colonies grown on chocolate agar are tinged yellow which is a distinguishing factor of these colonies. [11]
The colony-forming unit (CFU) is an appropriate description of the colony's origin. In plate counts, colonies are counted, but the count is usually recorded in CFU. Due to the fact that colonies growing on plates may begin as either a single cell or a cluster of cells, CFU allows for a correct description of the cell density.
It forms white, raised, cohesive colonies about 1–2 mm in diameter after overnight incubation, and is not hemolytic on blood agar. [5] It is a catalase-positive, [10] coagulase-negative, facultative anaerobe that can grow by aerobic respiration or by fermentation. Some strains may not ferment. [3] [11]