MORPHOLOGY OF STREPTOCOCCUS PYOGENES
Shape – Streptococcus pyogenes is a Round shape (coccus) bacterium
Size – The size of Streptococcus pyogenes is about 0.5 µm – 1 µm (diameter)
Arrangement Of Cells – S. pyogenes is arranged in Chains
Motility – S. pyogenes is a Non-motile bacterium.
Flagella – Streptococcus pyogenes is a Non-flagellated bacterium
Spores – S. pyogenes is a Non-sporing Bacterium
Capsule – present in Some Species of Streptococcus
Gram Staining Reaction – Gram +ve bacterium
CULTURE REQUIREMENTS OF STREPTOCOCCUS PYOGENES
⇒ Special requirements – Streptococcus pyogenes requires enriched media for the growth and readily grows in a media containing Blood, Serum or Sugars, commonly Blood Agar medium is used for the cultivation of Streptococcus pyogenes.
⇒ Optimum temperature – S. pyogenes grows best at 37°C
⇒ Optimum pH – 7.4-7.6
⇒ Oxygen requirements – Streptococcus pyogenes is an Aerobic and Facultative anaerobic bacterium i.e. can tolerate high levels of oxygen as well as readily grows in an environment with the low level of oxygen too. Presence of 5-10% CO2 promotes the growth and hemolysis in the medium.
⇒ There are various culture media used for the cultivation of Streptococcus pyogenes in the laboratory and most commonly the Blood Agar and PNF medium is used, the media are as follows –
- Nutrient Agar medium
- Sheep Blood Agar medium
- Crystal Violet Blood Agar medium (selective medium)
- PNF medium is also a selective culture medium for the isolation of Streptococcus pyogenes
- The liquid medium (Nutrient Broth medium, TSB medium, Peptone water etc.)
⇒ The PNF medium which is the Selective medium for Streptococcus pyogenes can be prepared by incorporating Polymixin B Sulfate, Neomycin sulfate and Fusidic Acid in the Horse Blood Agar medium for the growth of Streptococcus pyogenes.
CULTURAL CHARACTERISTICS OF STREPTOCOCCUS PYOGENES
|Cultural Characteristics||NAM (Nutrient Agar Medium||Blood Agar Medium (BAM)||Crystal Violet Blood Agar (CVBA) medium||PNF medium|
|Hemolysis||-----||β - Hemolysis||β - Hemolysis||β - Hemolysis|
|Shape||Circular (Pin point)||Circular (Pin point)||Circular (Pin point)||Circular (Pin point)|
|Size||0.5-1 mm||0.5-1 mm||0.5-1 mm||0.5-1 mm|
|Elevation||Low Convex - convex||Low Convex||Low Convex||Low Convex|
|Surface||Matt (in Virulent strains) ; Glossy (In Non-Virulent Strains) ; mucoid (in case of Capsule production)||Matt (in Virulent strains) ; Glossy (In Non-Virulent Strains) ; mucoid (in case of Capsule production)||Matt (in Virulent strains) ; Glossy (In Non-Virulent Strains) ; mucoid (in case of Capsule production)|
|Color||Light yellow||Light golden yellow, surrounded by clear zone (beta hemolysis).||Yellow||Golden yellow, surrounded by clear zone (beta hemolysis).|
|Structure||Semi-Transparent - Opaque||Semi-Transparent||Semi-Transparent - Opaque||Semi-Transparent - Opaque|
In liquid culture media like peptone water and Nutrient broth or Glucose broth, the growth of the bacterium occurs as a granular turbidity with a powdery deposits which is due to the heavy bacterial chains that settle down and appears as a powdery deposit which is further analyzed for the morphology (under the microscope), gram reaction, biochemical tests, and Streptococcus pyogenes specific tests.