Gram-Positive Cocci Flashcards
What are the most important GP-Cocci?
Staphylococcus and Streptococcus.
How can you differentiate between the 2 GP-Cocci?
Catalase test.
Catalase positive = Staphylococcus
Catalase negative = Streptococcus
Grow in Bunches, GP-Cocci, Catalase Positive, Facultative Anaerobes. What am I?
Staphylococcus
How can you differentiate between Pathogenic and Non-Pathogenic Staphylococcus?
Coagulase Test.
Coag +ve = High virulence
Coag -ve = Low Virulence
Give 3 Coagulase +ve Staphylococcus species
S. aureus, S. intermedius, S. hyicus
S. Aureus: What disease is it implicated in? (5)
Bovine, Mastitis, Canine Pyoderma, Wound Infections, Absesses, Otitis Externa.
Staphylococcus: What are the important pathogenicity factors? (5)
Alpha toxin, Beta toxin, TSST-1, Protein A, Capsule.
Staph Pathogenicity Factors: Alpha Toxin. What does it do? What species?
Haemolytic (B-haemolysis) causing narrow zone of haemolysis, Necrotising and damages cells. Most S. aureus and S. intermedius.
Staph Pathogenicity Factors: Beta Toxin. What does it do?
Damages membranes, and makes RBC fragile. Wide zone of RBC change (not haemolysis)
Staph Pathogenicity Factors: TSST-1. What does it do?
Toxic Shock Syndrome Toxin. Acts as super antigen and non specifically activates T cells, cytokine release.
Staph Pathogenicity Factors: Protein A. What does it do?
Surface protein that binds IgG. (Prevents opsonisation and recognition of bacterial cells)
Staph Pathogenicity Factors: Capsule. What does it do?
Inhibits surface Phagocytosis. Produced in vivo.
What does Staphylococcus aureus look like in culture?
Opaque colonies, with yellow/golden pigment.
Catalase negative, GP cocci, grow in chains. What am I?
Streptococcus
What 4 broad groups can Streptococcus be put into?
Pyogenic (pus forming), Viridans (greening), Enterococci (faecal) and Lactic.
How does the Lancefield grouping classify Streptococcus?
Relate to host and disease specificity.
Streptococcus Lancefield Group A: What species? What does it cause?
S. pyogenes - causes tonsilitis in humans.
Streptococcus Lancefield Group B: What species? What does it cause?
S. agalactiae. Major problem in contagious, chronic bovine mastitis.
Streptococcus Lancefield Group C: What species? What does it cause?
S. zooepidemicus, S. equisimilis, S. dysgalactiae, S. equi (causes Strangles in horse - B haemolytic)
Streptococcus Lancefield Group D: What species? What does it cause?
Only Streptococci to grow on MacConkey agar. May cause UTI and wound infections. Important: S. suis (pig pathogen)
Streptococcus Lancefield Group D: S. Suis. What does it cause?
Lots of serotypes. In stressed animals, it can pass from sow to Piglet, and cause neonatal death.
