Is Streptococcus agalactiae beta hemolytic?
Streptococcus agalactiae or group B streptococcus (GBS)—a gram-positive, β-hemolytic organism in the Streptococcus genus that carries the Lancefield group B antigen.
Is Streptococcus agalactiae alpha or beta hemolytic?
Group B streptococci (Strep. agalactiae) are facultative gram-positive diplococci that are usually easily grown. They have a narrow zone of β-hemolysis on blood agar plates.
Is Group B Strep alpha or beta hemolytic?
Group B Streptococcus (GBS) are generally beta hemolytic on blood agar plates (right hand side).
What type of hemolysis is Streptococcus?
Streptococcus pneumoniae and a group of oral streptococci (Streptococcus viridans or viridans streptococci) display alpha hemolysis. This is sometimes called green hemolysis because of the color change in the agar.
What type of hemolysis is Streptococcus pneumoniae?
Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis. This phenotype is utilized by clinical microbiology laboratories to report culture findings of alpha-hemolytic streptococci, including S. pneumoniae, and other bacteria.
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 does Alpha hemolysis look like on blood agar?
Alpha hemolysis (α) is the reduction of the red blood cell hemoglobin to methemoglobin in the medium surrounding the colony. This causes a green or brown discoloration in the medium. The color can be equated with “bruising” the cells.
Does Streptococcus grow on blood agar?
The streptococci are usually isolated on Blood agar. Blood agar is one of the most commonly used media in a clinical lab. It consists of an enriched agar base (Tryptic Soy agar) to which 5% sheep red blood cells have been added.
What does beta hemolysis on blood agar mean?
Beta hemolysis represents a complete breakdown of the hemoglobin of the red blood cells in the vicinity of a bacterial colony. There is a clearing of the agar around a colony. Beta hemolysis is characteristic of Streptococcus pyogenes and some strains ofStaphylococcus aureus.
Does Streptococcus pneumoniae grow on blood agar?
It is usually cultured on media that contain blood, but can also grow on a chocolate agar plate (CAP). On a blood agar plate (BAP), colonies of S. pneumoniae appear as small, grey, moist (sometimes mucoidal), colonies and characteristically produce a zone of alpha-hemolysis (green) (Figure 1).
What is alpha hemolysis on blood agar?