5. Staphylococci
-Staphylococcus aureus
• (culture)Growth on Blood agar:
• –yellow colonies (golden staph)
• –Narrow zone of beta hemolysis
• –Consistency of colonies is like butter,
can be picked up easily by bacterial loop.
6. Streptococci
-Streptococcus pyogenes
• (culture) Growth on Blood agar:
• –Pin point size colonies
• –Wide zone of beta hemolysis
• –Consistency of colonies is tough,
can not be picked up easily by
bacterial loop.
7. Catalase Test
Catalase production.
•is responsible for the splitting of hydrogen peroxide (H2O2)
into oxygen and water.
•The oxygen is detected as a steady evolution of gas bubbles
from the culture.
12. • Coagulase test:
+ve : Staphylococcus aureus
-ve :
•Staphylococcus epidermidis
•Staphylococcus saprophyticus
•The enzyme coagulase
acts with a plasma factor
to convert fibrinogen to a
fibrin clot.
(clouding and solidification of plasma)
Staphylococcus aureus is known to produce
coagulase, which can clot plasma into gel in tube.
This test is useful in differentiating S.aureus from
other coagulase-negative staphylococci.
17. *Lancefield grouping is a method of grouping beta hemolytic bacteria based on the carbohydrate composition of bacterial antigens found on their cell walls.
18.
19. s. pyogenes: I live in
the nose and mouth.
pharyngitis - 'strep
throat‘, abscesses,
otitis media and
sinusitis, cellulitis,
rashes, gangrene,
rheumatic fever and
toxic shock.
S. agalactiae: I'm a Gram
Positive coccus and a Beta
hemolytic strept.
In pregnant women, I cause
premature labor & urinary
tract infections - in the baby.
I cause pneumonia,
meningitis, shock and
bacteraemia.
The enzyme catalase catalyzes the release of water and oxygen from hydrogen peroxide , The rapid production of bubbles (effervescence) when bacterial growth is mixed with a peroxide solution is interpreted as a positive test (i.e., the presence of catalase).
Catalase production.
•is responsible for the splitting of hydrogen peroxide (H2O2) into oxygen and water.
•A test culture is exposed to 3% H2O2.
•H2O2 is broken down to H2O and O2.
•The oxygen is detected as a steady evolution of gas bubbles from the culture.
Principle: The free coagulase secreted by S.aureus reacts with coagulase reacting factor (CRF) in plasma to form a complex, which is thrombin. This converts fibrinogen to fibrin resulting in clotting of plasma.
Rebecca Lancefield grouping is a method of grouping beta hemolytic bacteria based on the carbohydrate composition of bacterial antigens found on their cell walls.
Middle line : staph aureus
Staph aureus ferments mannitol turns pink to yellow( due to acid production)
Staph epidermidis non mannitol fermenter> no color change( pink).
