Set 1: General Characteristics & Lab Identification

Microscopic appearance of Staphylococci

Gram-positive cocci arranged in grape-like clusters.

Catalase test result for Staphylococci

Positive (produces bubbles). This distinguishes them from Streptococci (which are negative).

General growth characteristics

Facultative anaerobe, non-motile, resistant to drying and heat (60°C for 1 hour).

Salt tolerance

High salt tolerance (can grow in 7.5-10% NaCl), allowing them to survive on salty skin and grow on Mannitol Salt Agar.

Staphylococcus aureus colony appearance

Golden-yellow pigment colonies.

Staphylococcus epidermidis colony appearance

White colonies.

Coagulase Test purpose

Distinguishes S. aureus (Positive) from other Staphylococci (Negative like S. epidermidis).

Hemolysis on Blood Agar

S. aureus usually shows Beta-hemolysis (clear zone)

Mannitol Salt Agar (MSA) reaction

S. aureus ferments mannitol (turns agar yellow)

Novobiocin susceptibility

S. saprophyticus is Resistant