Question

Based on colony morphology alone, could you reliably tell the difference between Staph and Strep? If no, which different tests can be performed to tell them apart?

Answer 1

Colony morphology is a method that scientists used to describe the characteristics of an individual colony of bacteria growing on agar in a petri dish.It can be used to identify them.

Straphylococcus and Streptococcus are both Gram positive organisms and cocci in shape.They are Non-motile,Non-sporing and facultative anaerobes.But they possess some of the differences.They are:

Characteristics	Staphylococcus	Streptococcus
Arrangement	Grape-like clusters	A chain of round cells
Division	Staphylococci divide in various directions(multiple axes)	Division occurs in one linear direction(single axes)
Catalase test	Positive(Catalase is an enzyme to convert hydrogen peroxide to water and oxygen gas)	Negative
Enriched media	Staph does not need enriched media(not fastidious)	Sterp needs enriched media(fastidious)
habitat	Staphylococci are found on the skin	Streptococci are found in the respiratory tract
Hemolysis	No hemolysis or beta hemolysis	Either alpha,or beta or gamma hemolysis
Species number	About 40 staphylococcal species have been identified so far	About 50 Streptococcal species have been identified so far
Pathogenesis	Most of the stephylococcal species are non-pathogens	Streptococcus cause many diseases
Common diseases	Food poisoning,bacterial conjuctivities,skin diseases,community acquired meningitis,Surgical site infection,Wound infection,Impetigo,cellulitis and toxic shock syndrome.	Strep throat,Scarlet fever,Impetigo,Toxic shock syndrome,Cellulitis and necrotising fasciitis(flesh eating disease),sinusitis,blood infections,pneumonia and meningitis in newborns
Pathogenic species	Staphylococcus aureus Staphylococcus epidermidis Staphylococcus haemolyticus Staphylococcus hominis Staphylococcus saprophyticus etc	Streptococcus pyogenes Streptococcus agalactiae Streptococcus bovis Streptococcus pneumoniae etc
Species differentiation	Coagulase test Novobiocin sensitivity test Biochemical test	Type of hemolysis Cell wall carbohydrate group(A,B,C etc) Bile solubility test CAMPT test Optochin sensitivity test