Bacterial Pathogen

Question 1

Coagulase?

Answer 1

Essential virulence factor associated with formation fibrin capsule

• -> interfering phagocytosis
• -> fibrin clot –> abscess

Question 2

Alpha-toxin?

Answer 2

major cytotoxic agent

member of pore forming beta-barrel toxin family

Question 3

Superantigen toxins?

Answer 3

Class of antigen cause non-specific activation of T-cells, resulting

• polyclonal Tcell activation
• massive cytokine release

Question 4

Mechanism of scalded skin syndrome?

Answer 4

The toxin (serine protease) cleaves the proteins (desmoglein I) attaching dermis and epidermis –> scalding off epidermis

Question 5

Mechanism(s) of (localized focal abscess) cutaneous infections?

Answer 5

1. Adherence : fibronectin binding protein
2. Alpha-toxin : damage tissue & interfere with phagocytosis
3. Coagulase, fibriogen-binding protein, Protein A interfere phagocytosis

Question 6

Scalded skin syndrome in adult vs. newborn

Answer 6

Adult: localized infection
Newborn: systemic infection –> does NOT have previous antibodies against the bacteria

Question 7

Symptoms of Toxic Shock Syndrome?

Answer 7

High fever
Shock
Vomiting
Muscle pain
Renal/hepatic injury or failure

Question 8

Staphylococcal Food Poisoning?

Answer 8

Ingestion contaminated food with superantigen toxin

–> vomiting & diarrhea (1-5 hours)

Question 9

Characteristic of enterotoxin

Answer 9

heat stable –> not destroyed by cooking

Question 10

SSNA?

Answer 10

Staph species, not aureus

Question 11

CNS?

Answer 11

Coagulase negative staphylococcus

Question 12

Endocarditis?

Answer 12

Bacteria grows on damaged heart valve

Question 13

Purpose of M-protein?

Answer 13

1. Inhibit phagocytosis by binding factor H
   - -> reduces C3b opsonization
   - -> produce C5a peptidase
2. enhance adherence to epithelial cells

Question 14

Cellulitis?

Answer 14

Spreading infection of the cutaneous & subcutaneous tissues

Question 15

Glomerulonephritis

Answer 15

immune complex disease (following skin/pharyngeal infection)
Strep antigen-antibody complexes deposited in kidney
–> accumulate at the basement membrane
–> complement-mediated damage

Question 16

Rheumatic fever

Answer 16

autoimmune inflammatory disease

• fever, inflammation of heart, joints
• NO bacteria on the heart tissue
• antibody-mediated damage

Question 17

How to make pneumococcal vaccines effective in kids (get polysaccharide antigen to work)?

Answer 17

Conjugated vaccines: chemically couple polysaccharide antigen to protein immunogen –> the whole complex is immunogenic

Question 18

Which bacteria frequently cause nosocomial infection (hospital acquired)?

Answer 18

Enterococcus faecalis & E. faecium

Question 19

Why positive culture of clostridium difficile in stool not enough to diagnose pt with diarrhea and fever?

Answer 19

Unless toxin A & toxin B detected in the stool, presence of C. diff in stool does NOT mean it is the one causing the disease

Question 20

Why patient on antibiotics treatment at risk for C. diff infection?

Answer 20

Depletion of intestinal flora by antibiotic, resulting overgrowth of C. diff

Question 21

When should one use inactive toxoid vs. anti-toxin for tetanus?

Answer 21

1. Inactive-toxoid is used to induce production of protective anti-toxin antibody
2. Immunization with antitoxin (tetanus IgG) to treat non-immune individuals with clinical signs of tetanus.

Question 22

Mechanism of E. coli GI disease

Answer 22

• Pili adherence to intestinal mucosa

* Toxin disrupts electrolyte balance in gut

Question 23

Mechanism of E. coli UTI

Answer 23

• Adherence to bladder eipthelium
• Specific interactions with bladder epithelial cells
• beta-hemolytic

Question 24

How to recover from the damage of tetanus?

Answer 24

The ONLY way is to grow that particular neuron

Question 25

Difference between endotoxin, exotoxin and enterotoxin

Answer 25

Endotoxin = LPS from (-) gram cell wall
Exotoxin = protein secreted that is insoluble
Enterotoxin = exotoxin that acts on GI system

Question 26

Mechanism of E. coli Abdominal infections

Answer 26

• Mixed infection
• Abscess (from anaerobic bacteria)
• Release/escape contents of colon to peritoneal cavity & adjacent tissues