Staphylococcus

Question 1

Name 3 different organisms of Staph

Answer 1

• Staph. Aureus
• Staph Saprophyticus
• Staph epidermidis

Question 2

Where do Staphylococcus reside in warm blooded animals?

Answer 2

• Mucosal surfaces

- skin

Question 3

List where Staph. Epidermidis inhabits, what type of pathogen it is, and what often causes infection

Answer 3

• Skin
• Opportunistic pathogen
• Causes infections associated with artificial prosthetics

Question 4

List where Staph. Saprophyticus is usually pathogenic, which gender it is more common in and the sites of colonisation

Answer 4

• More common in females
• Urinary Tract pathogen
• Causes UTI
• Sites of colonisation = rectum, urethra, cervix

Question 5

What type of Staph is “golden staph”

Answer 5

Staph. Aureus

Question 6

Explain the different types of infections that can occur from Staph. Aureus

Answer 6

Bone infection, skin infection, boils, deep skin infection, toxin mediated disease, abscess

Question 7

What is bacteraemia and what can it lead to? (staph)

Answer 7

Presence of bacteria in the blood stream, leads to endocarditis or pneumonia (rare)

Question 8

Briefly describe the different virulence factors of Staph. Aureus

Answer 8

• Different sections: Adhesion, invasion, evasion, toxic mediated, resistance

Question 9

What are the different adhesion factors and their associated gene (staph)

Answer 9

• Fibronectin Binding Protein A (fnpA)
• Fibronectin Binding Protein B (fnpB)
• Collagen Binding Protein (can)
• Fibrinogen Binding Protein (fbpA)

Question 10

List the different invasion factors and their associated gene (staph)

Answer 10

• Alpha (hla), beta (hlb), gamma (hlgA,B,C), delta (hld) haemolysin
• Hyaluronidase (hysA)
• Staphylokinase (sak)

Question 11

Describe what alpha toxin (haemolysin) is, its potency and structure/how it works (staph)

Answer 11

• Responsible for haemolysis, highest potency in damaging membrane
• Monomer binds to membrane and forms heptamer with a central pore causing leaking of cellular content

Question 12

Explain the mechanism of action of B haemolysin, how is it encoded? (staph)

Answer 12

• Damages membranes rich in sphingomyelin (not common in humans)
• Encoded by a lysogenic bacteriophage

Question 13

Explain the structure of delta haemolysin and its role (staph)

Answer 13

Very small peptide toxin (26 amino acids), regulatory role

Question 14

Explain what Gamma haemolysin is and the difference between its 2 components (staph)

Answer 14

• Fast (HlgA, HlgB) and slow components (HlgC), slow is non toxic
• Responsible mainly for severe necrotizing skin infections

Question 15

What is Hyaluronidase and what does it do? (staph)

Answer 15

• Enzyme for hyaluronic acid
  
  • This breaks down connective tissues and allows for
    dissemination

Question 16

What is Staphylokinase and what does it do? How is it encoded?

Answer 16

• Plasminogen activator
• Same as streptokinase
• Encoded by lysogenic bacteriophages

Question 17

List the different evasion factors and the gene that encodes them (staph)

Answer 17

• Coagulase (coa)
• Clumping factor (clfA)
• Protein A (spa)
• Leukocidin (lukR)
• Super Oxide Dismutase (sod)
• Catalase (katA)

Question 18

What is Coagulase, what forms is it in and what is its mechanism of action? (staph)

Answer 18

• 2 forms, Free and cell associated
• Works by coagulating fibrogen to form fibrin which can be used to wall off infection and at as a barrier to PMNs
• Forms Abscess

Question 19

What is Protein A and how does it lead to evasion (staph)

Answer 19

Surface of staph aureus coated with protein A, has high affinity for Fc region of IgG

Question 20

What proteins lead to toxin mediated diseases and what genes encode for them (staph)

Answer 20

• TSST-1 (tstH)

- Enterotoxins A, B, C1-3, D, E, H (entA-H)

Question 21

What are symptoms of toxic shock syndrome (staph)

Answer 21

Organ failure, nails falling off, skin peeling, headache, fever, hypotension

Question 22

What is TSST-1 and what is its mechanism of action? Which condition is it synthesised in, Aerobic or Anaerobic? (staph)

Answer 22

Protein responsible for Toxic shock syndrome, works by entering blood stream through tampon, Aerobic

Question 23

What is a pathogenicity island (staph)

Answer 23

A region of coding which determines virulence factors

Question 24

What is the difference between an antigen and a super antigen? (staph)

Answer 24

Super antigen also releases excess IL2 production, stimulated TNFa and induces shock as it can activate up to 20% of T cells whereas a normal antigen can only activate roughly 0.001%

Question 25

What is the difference between Staph. Aureus and Strep. Pyogenes when causing Toxic Shock Syndrome

Answer 25

TSST-1 is from Staph aureus and enters blood stream through tampon, Strep pyogenes enters bloodstream as a whole bacteria and produces Spe

Question 26

Explain the mechanism of action of Staph Food Poisoning

Answer 26

Enterotoxins injested, acts on receptors in gut initiating Emetic reflex after 4-6 hrs

Question 27

What are examples of acquired virulence factors? How are they acquired? (staph)

Answer 27

- Penicillin, Methicillin, vancomycin Resistance | - Acquired through use of antibiotics