Bacteria under Microscope

Staphylococcus aureus

Staphylococcus aureus    
                         microscopy, gram-positive bacteria




Microscopic appearance:

Cocci in grape-like clusters


Clinical significance:

  • Frequently found as part of the normal skin flora on the skin and nasal passages
  • It is estimated that 20% of the human population are long-term carriers of S. aureus
  • Skin infections (pimples, impetigo, boils (furuncles), cellulitis folliculitis, carbuncles, scalded skin syndrome, abscesses)
  • Postsurgical wound infections
  • Pneumonia
  • Meningitis
  • Osteomyelitis
  • Endocarditis
  • Toxic shock syndrome (TSS)
  • Bacteremia
  • One of the five most common causes of nosocomial infections
  • Methicillin resistant Staphylococcus aureus (MRSA) infections
    Text: Wikipedia

Colony morphology:

Staphylococcus aureus identification
A Beta-hemolytic colonies of Staphylococcus aureus on sheep blood agar. Cultivation 24 hours, aerobic atmosphere, 37°C.  
B Yellow colored colonies of Staphylococcus aureus on Tryptic Soy Agar. Carotenoid pigment staphyloxanthin is responsible for the characteristic golden colour of S. aureus colonies. This pigment acts as a virulence factor. Cultivation 24 hours in an aerobic atmosphere, 37°C.  
C Colonies of Staphylococcus aureus seen with transmitted light. Cultivated on Columbia agar with 5% defibrinated sheep blood, 24 hours in an aerobic atmosphere, 37°C. Colonies are surroundend by a wide zone of beta-hemolysis.