Gram-Positive Cocci

Question 1

What are the most important GP-Cocci?

Answer 1

Staphylococcus and Streptococcus.

Question 2

How can you differentiate between the 2 GP-Cocci?

Answer 2

Catalase test.
Catalase positive = Staphylococcus
Catalase negative = Streptococcus

Question 3

Grow in Bunches, GP-Cocci, Catalase Positive, Facultative Anaerobes. What am I?

Answer 3

Staphylococcus

Question 4

How can you differentiate between Pathogenic and Non-Pathogenic Staphylococcus?

Answer 4

Coagulase Test.
Coag +ve = High virulence
Coag -ve = Low Virulence

Question 5

Give 3 Coagulase +ve Staphylococcus species

Answer 5

S. aureus, S. intermedius, S. hyicus

Question 6

S. Aureus: What disease is it implicated in? (5)

Answer 6

Bovine, Mastitis, Canine Pyoderma, Wound Infections, Absesses, Otitis Externa.

Question 7

Staphylococcus: What are the important pathogenicity factors? (5)

Answer 7

Alpha toxin, Beta toxin, TSST-1, Protein A, Capsule.

Question 8

Staph Pathogenicity Factors: Alpha Toxin. What does it do? What species?

Answer 8

Haemolytic (B-haemolysis) causing narrow zone of haemolysis, Necrotising and damages cells. Most S. aureus and S. intermedius.

Question 9

Staph Pathogenicity Factors: Beta Toxin. What does it do?

Answer 9

Damages membranes, and makes RBC fragile. Wide zone of RBC change (not haemolysis)

Question 10

Staph Pathogenicity Factors: TSST-1. What does it do?

Answer 10

Toxic Shock Syndrome Toxin. Acts as super antigen and non specifically activates T cells, cytokine release.

Question 11

Staph Pathogenicity Factors: Protein A. What does it do?

Answer 11

Surface protein that binds IgG. (Prevents opsonisation and recognition of bacterial cells)

Question 12

Staph Pathogenicity Factors: Capsule. What does it do?

Answer 12

Inhibits surface Phagocytosis. Produced in vivo.

Question 13

What does Staphylococcus aureus look like in culture?

Answer 13

Opaque colonies, with yellow/golden pigment.

Question 14

Catalase negative, GP cocci, grow in chains. What am I?

Answer 14

Streptococcus

Question 15

What 4 broad groups can Streptococcus be put into?

Answer 15

Pyogenic (pus forming), Viridans (greening), Enterococci (faecal) and Lactic.

Question 16

How does the Lancefield grouping classify Streptococcus?

Answer 16

Relate to host and disease specificity.

Question 17

Streptococcus Lancefield Group A: What species? What does it cause?

Answer 17

S. pyogenes - causes tonsilitis in humans.

Question 18

Streptococcus Lancefield Group B: What species? What does it cause?

Answer 18

S. agalactiae. Major problem in contagious, chronic bovine mastitis.

Question 19

Streptococcus Lancefield Group C: What species? What does it cause?

Answer 19

S. zooepidemicus, S. equisimilis, S. dysgalactiae, S. equi (causes Strangles in horse - B haemolytic)

Question 20

Streptococcus Lancefield Group D: What species? What does it cause?

Answer 20

Only Streptococci to grow on MacConkey agar. May cause UTI and wound infections. Important: S. suis (pig pathogen)

Question 21

Streptococcus Lancefield Group D: S. Suis. What does it cause?

Answer 21

Lots of serotypes. In stressed animals, it can pass from sow to Piglet, and cause neonatal death.