Lecture 13: Staphylococcus species

Question 1

Staphylococcus epidermis

Answer 1

• can cause disease if gets in skin
• occasional opportunist
• ## Normal microbiota

Question 2

Staphylococcus aureus

Answer 2

• pathogen/opportunist
• an opportunist b/c some ppl are carrier
• cause folliculitis, toxin shock syndrome
• expresses virulence factors
• coagulate positive

Question 3

Coagulase enzyme

Answer 3

Converts blood plasma protein by fibrinogen (soluble protein) to fibrin

Question 4

Folliculitis (S. Aureus)

Answer 4

Present S. Aureus can go into hair pore which accumulates white blood cells (immune response and inflammation), looks like acne, overproduction of dead cells or sebaceous substance

Question 5

Furuncle/ boil (S. Aureus)

Answer 5

Inflamed tissue and is worse than folliculitis (it is worsened)

Question 6

Hair follicle infections

Answer 6

Folliculitis-> furuncle -> carbuncle -> bactermia -> sepsis (spread to bones or tissues)

Question 7

Why does S aureus cause this but not S epidermis?

Answer 7

S. aureus contains genes that include virulence factors

Question 8

Adherence virulence factors

Answer 8

• clumping factor: attaches the bacterium to fibrin, fibrinogen, and plastic devices
• coagulase: May slow progress of leukocytes into infected area by producing clots in the surrounding capillaries
• capsule: inhibits phagocytosis

Question 9

Clot formation

Answer 9

Platelets produce clotting factors called prothrombin then makes thrombin (enzyme activated by coagulase) which converts fibrinogen to fibrin

Question 10

Where is clumping factor (binds fibrin) most likely located in S aureus?

Answer 10

On the outer surface of cell wall. Since S aureus can convert fibrinogen to fibrin, it can utilize the clumping factor and bind to it.

Question 11

Colonization and spread of infection

Answer 11

• Enterotoxins: Super antigens cause food poisoning if ingested, cause toxic shock if systemic
• exfoliatin: protease (breaks down proteins) scalded skin syndrome, separated epidermal layers, breaks connections between skin cells

Question 12

Staphylococcal enterotoxin (food poisoning)

Answer 12

• Bacteria grows on food, eat food
• stimulates a severe inflammatory response in intestinal epithelium
  1 - caused release of inflammation signal using molecules
  2 - inflamed tissue is more prone to ion leakage
  3 - diarrhea (water enters lumen)

Question 13

Exfoliatin

Answer 13

• Degrades desmosome proteins

- Desmosomes connect the cytoskeleton of cells

Question 14

Exfoliatin-like virulence factors

Answer 14

Hyaluronidase: breaks extracellular matrix
Proteases: break cell connections and extracellular matrix like collagen
leukocidin, lipase,

Question 15

Disease-causing virulence factors

Answer 15

Toxic shock syndrome toxic

Question 16

Toxic shock syndrome

Answer 16

Causes massive cytokines and inflammation -> lose fluid -> blood pressure drops -> no oxygen to organs -> organ failure

Question 17

Immune response

Answer 17

1) macrophage ingests pathogen and displays antigens are called antigen presenting cell (APC)
2) t helper cell interacts with the APC
3) APC release interleukin 1 which stimulate t helper cell to secrete interleukin 2
4) interleukin 2 causes proliferation of cytotoxic T cell and B cell
5) cytotoxic bind to the antigen presenting cells that they recognize and the host cell dies
6) B cells differentiate into plasma cells which become antibodies (marks)

Question 18

Toxic shock syndrome toxin

Answer 18

Super antigen that cause systemic immune inflammatory response

• the production of toxin is inhibited by magnesium ion
• tampons were promoting super antigen production