Staphylococcus aureus: Morphology,Culture and Biochemical reaction
STAPHYLOCOCCUS AUREUS:
- Natural habitat:-Nostril (30%)and skin
- MC route of infection-Skin.
- MC source of infection: Patients own colonizing strain
Morphology:
- Gram-positive, cocci, 0.5-1.5µm in diameter; occur characteristically in group, also singly and in pairs
- Form irregular grapelike clusters (since divide in 3 planes)
- Shows Transient colonization
- Non-motile, non- sporing and few strains are capsulated
- For phage typing23 phages of staphylococcus aureus are used
- Catalase positive, beta-hemolytic staphylococcus
CULTURE:
- Aerobes and facultative anaerobes
- Opt. Temp. For growth= 37°C
- Opt. pH for growth= 7.5
On Nutrient agar
- golden yellow and opaque colonies with smooth glistening surfac
- 1-2 mm in diameter
- max. pigment production@22 °C
On Blood agar
- golden yellow colonies
- surrounded by a clear zone of hemolysis (beta-hemolysis)
- esp. when incubated in sheep or rabbit blood agar in atmosphere of 20% CO2
On MacConkey agar
- Smaller colonies than those on NA(0.1-0.5 mm)
- Pink coloured due to lactose fermentation
On Mannitol salt agar,
- S.aureus ferments mannitol and appear as yellow colonies
- MSA is a useful selective medium for recovering S.aureus from faecal specimens, when investigating food poisoning
BIOCHEMICAL REACTION:
- Catalase positive; oxidase negative
- 3-lactamase production in Staphylococci is under plasmid control
- Ferment glucose, lactose, maltose, sucrose and mannitol, with production of acid but no gas
- Indole test= negative
- MR test= positive
- VP test= positive
- Hydrolyse gelatin
- Reduces nitrate to nitrite
- Phospahatase= positive
- DNA-ase test= positive
Exam Question
STAPHYLOCOCCUS AUREUS:
- Natural habitat:-Nostril (30%)and skin
Morphology:
- Shows Transient colonization
- For phage typing23 phages of staphylococcus aureus are used
- Catalase positive, beta-hemolytic staphylococcus
BIOCHEMICAL REACTION:
- Catalase positive; oxidase negative
- 3-lactamase production in Staphylococci is under plasmid control
Don’t Forget to Solve all the previous Year Question asked on Staphylococcus aureus: Morphology,Culture and Biochemical reaction