Daniels - Staph

Question 1

Staphylococcus genus properties

Answer 1

(Same as streptococcus except for catalase)
Gm +
Non-sport forming
Predominantly facultative anaerobes
CATALASE POSITIVE

Question 2

What differentiates S. aureus & 6 other species among the 42 total species

Answer 2

It is coagulase positive

coagulase negative staph. are mostly opportunistic

Question 3

S. aureus diseases

Answer 3

• Integumentary & wounds
• Bacteremia
• Aspiration pneumonia
• UTI
• Toxic shock syndrome
• Scalded skin syndrome
• Food poisoning

Question 4

Where is S. aureus present?

Answer 4

30-40% prevalence in nasal carriage
Muco-cutaneous junctions
Skin, mucosal surfaces
Hearty environmental survival (clothing, surfaces)
Usually behave commensally (opportunistic)

Question 5

How does S. aureus enter?

Answer 5

Damage to skin/follicles

Damage to mucosal surfaces

Question 6

S. aureus multiplication/spread

Answer 6

Variable with

• bacterial inoculum (how much there is)
• Host immunocompetence
• location of infection

Question 7

Populations at elevated risk for staph infection

Answer 7

Young/elderly
Diabetics
Immunosuppressed individuals
HIV+
Dialysis patients
IV Drug users

Question 8

MSCRAMM

What is it and examples

Answer 8

Microbial Surface Components Recognizing Adhesive Matrix Molecules
Ex:
-Fibronectin binding proteins
-Collagen binding protein
-Clumping factors bind fibrinogen

Question 9

How do staphylococcus bacteria damage tissue

Answer 9

Acute suppurative inflammation(accumulation of pus)

Pus = neutrophils (aka PMNs)

Question 10

Function of PMNs

Answer 10

Phagocytosis
Release ROS
Release signaling molecules to call more WBCs to the area

Question 11

Why can PMNs be bad?

Answer 11

The ROS payload attacking bacteria also damages host tissue (sustained inflammation)

Question 12

Virulence factors of S. aureus

Answer 12

Polysaccharide capsule- blocks phagocytosis
Protein A- blocks Ab function
Pore-forming toxins- pop PMNs and other cells leading to more damage and inflammation

Question 13

SSSS

What it is and effect

Answer 13

Staphylococcal Scalded Skin Syndrome

Proteases cleave desmosomes & cause layers of epidermis to separate

Question 14

What is TSST-1

What does it do

Answer 14

A superantigen
Forces MHC II on CD4+ t cell to bind to APC regardless of whether it recognizes antigen
Creates cytokine storm by CD4+ T cells

Question 15

What are the cytokines and effects of them brought out by TSST

Answer 15

IL1 -> Fever
TNFa & B -> Hypotension, capillary leakage
IFNgamma, IL2 -> Rash

Question 16

What is the most common enterotoxin secreted by S. aureus

Answer 16

Enterotoxin A

Question 17

Can cooking food kill S. aureus?

Answer 17

It will kill the bacteria, but not the toxin that they have formed

Question 18

What are the two Penicillin Binding Proteins?

What do they do?

Answer 18

Transpeptidases and transglycosylases

They make the crosslinks in peptidoglycan (target of penicillin)

Question 19

Which PBPs does MSSA have?

Answer 19

PBP = Penicillin binding protein
MSSA = Methicillin susceptible S. aureus

PBP 1,2,3(3’,4’)

Question 20

Which PBPs does MRSA have?

Answer 20

PBP = Penicillin binding protein
MRSA = Methicillin resistant S. aureus

PBP 1,2,2a,3(3’,4’)

Question 21

Why are most strains of S. aureus resistant to penicillins?

Answer 21

Because of their blaZ penicillinase enzyme

Question 22

MRSA frequently carries resistance genes to what other drug classes?

Answer 22

• Macrolides/Lincosamides
• Sulfonamides
• Fluoroquinolones
• Tetracyclines

Question 23

What is used to treat MRSA?

Answer 23

Vancomycin

Question 24

What are problems with using vancomycin to treat MRSA?

Answer 24

VRSA & VISA which have VanA resistance gene

Question 25

What are the colonization sites of MRSA?

Answer 25

Groin
Axilla
Nares