Bacteriology: Bugs lab algorithms

Question 1

Alpha-hemolytic streps-Partial hemolysis- green colonies

Answer 1

Strep. pneumoniae (Optochin sensitive, Bile soluble, Quellung +ve, Capsule +); Viridans streps e.g. Strep. mutans (Optochin resistant, bile insoluble, no capsule)

Question 2

Beta-hemolytic streptococci- Complete hemolysis; clear colonies

Answer 2

S. pyogens (Bacitracin sensitive; GAS); S. agalactiae (Bacitracin resistant, CAMP factor +, GBS)

Question 3

Gamma-hemolytic - No hemolysis

Answer 3

Enterococci e.g. E. faecalis, E. faecium (grow in 6.5% NaCl); Nonenterococci e.g. S. bovis (do not grow in 6.5% NaCl; GDS)

Question 4

Staphylococci (All Catalase +ve)

Answer 4

S. aureus (coagulase +ve, ferments mannitol); Coagulase -ve, do not ferment mannitol: S. epidermidis (Novobiocin sensitive) and S. saprophyticus (Novobiocin resistant)

Question 5

Beta-hemolytic bacteria

Answer 5

S. aureus, Strep. pyogens, Strep. agalactiae, Listeria monocytogens