Differentiating Similar Bacterial Species

Question 1

Lactobacillus spp.

Answer 1

Medium sized, long, thin rods that form chains, no spores

Question 2

Differentiating Bacillus cereus from Bacillus sp.

Answer 2

• B. cereus*: Hemolytic and Penicillin Resistant
• Bacillus* spp.: non-hemolytic and Penicillin Sensitive

Question 3

Differentiating Lactobacillus and Corynebacterium

Answer 3

• Lactobacillus:* Catalase (-)
• Corynebacterium:* Catalase (+)

Question 4

Differentiating Moraxella catarrhalis and Neisseria sp.

Answer 4

Catarrhalis Disk Test, (+) blue for M. catarrhalis, (-) Neisseria

Question 5

Differentiating S. aureus and S. epidermidis

Answer 5

After (+) Catalase test

Slide Coagulase: S. aureus (+), S. epidermidis (-)

Question 6

Differentiating Enterococcus and Group D Strep.

Answer 6

After (-) or weakly (+) Catalase

If γ or α Hemolytic:

Enterococcus is PYR and Bile Esculin (+)

Grp D Strep is PYR (-) and Bile Esculin (+)

Question 7

Differentiating Group A Strep from Group B, C, or G

Answer 7

After (-) or weakly (+) Catalase

Β Hemolytic:

Grp A PYR (+)

Grp B, C, or G PYR (-)

Question 8

Differentiating Neisseria Spp.

Answer 8

Fermentation sugar tubes, letter of species correlates with name of sugar fermented

Question 9

Differentiating S. pneumoniae and Viridans Strep.

Answer 9

Mucoid, concave, and alpha hemolytic colonies, GPC, Catalase (+), Optochin disk test on plate - >14mm and Bile soluble S. pneumoniae

Question 10

Differentiating S. aureus, S. epidermidis, and S. saprophyticus

Answer 10

Grow on CNA

Slide coagulase (+): S. aureus

Novobiocin: > 16mm S. epidermidis