Ch. 15: Microbal Mechanisms of Pathogenicity

Question 1

Portals of Entry: Mucous Membrane

Answer 1

1. Mucous Membranes:
   - respiratory tract: pneumonia, influenza, TB, and measles (Bordetella pertussis)
   - GI tract: food, water, viruses, Hep.A, Polio (Shigella dysentry, V. cholera, Salmonella sps)
   - genitourinary tract: N. gonorrhea, T.pallidum, Chlamydia trachomatis, Herpes, AIDS
   - conjunctiva: Morizella lacunate, Psuedomas argenuea

Question 2

Portals of Entry: Skin and Parenteral

Answer 2

2. Skin:
   - S. aerus, Propinobacterum acnes, fungi
3. Parenteral:
   - Ricksettisa rickettsii, C. tetani, C. perfringens, Enertococcus fecealis

Question 3

Attachment

Answer 3

• adhesions that bind specifically to complementary surface receptors on the cells of host
• are glycoproteins or lipoproteins
• receptors are sugars such as mannose or focus
  ex. S. mutans: attach to tooth by its glycocalyx
• glucosyltransferase converts glucose into GLUC= plaque
  ex. S. pyogenes: attach by M protein on cell wall
• acid/heat resistant protein

Question 4

Exoenzymes

Answer 4

1. Coagulases: coagulate fibrinogen in blood= blood clot
   ex. S. aureus, and some streptococcus
2. Kinases: digest fibrin clots to isolate infection
   ex. S. pyogenes, few staphylococcus
3. Hylauonidase: hydrolyses hyaluronic acid (holds together cells of the body)
   ex. C. perfringens and S.pyogenes
4. Collagenase: hydrolyzes collagen
   ex. C. perfringes

Question 5

Exotoxins

Answer 5

• produced inside bacteria as part of growth and metabolism
• are proteins
• gram positive; few are gram negative
• specific signs and symptoms
  ex. Tetnus- lockjaw, opsithotonos
• body produces antibodies called antitoxins that provide immunity
• toxoid vaccine: stimulate antitoxin production so that immunity is produced
  ex. Tetnus and Diphtheria vaccine DTP

Question 6

A-B toxins

Answer 6

• 2 polypeptides
• A part= active enzyme
• B part= binding component

Question 7

Membrane-disrupting toxins

Answer 7

• cause lysis of host cells in plasma membranes
• Leukocidins: destroy WBCs ex. S. pyogenes
• Hemolysins: destroy RBCs ex. S. pyogenes
• Erythrogenic toxin: streptococci ex. Scarlett Fever (disrupt blood vessels)

Question 8

SuperAntigens

Answer 8

• provoke intense immune response
• increase T cell production
• release cytokines
• circulate in body through blood to vital organs
• symptoms: fever, nausea, vomiting, diarrhea, and shock
  ex. S. aureus poisoning ot TSS

Question 9

Diptheria Toxin

Answer 9

• Corynebacterium diphtheria
• inhibit protein synthesis
• forms membrane
• suffocation
• A-B toxin

Question 10

Tetanus Neurotoxin

Answer 10

• destroy nerve function
• spasms (back- later)
• affect C.V./Resp. which leads to death

Question 11

Botullinum Neurotoxin

Answer 11

• prevents transmission of impulses from the nerve cell to the muscle
• inhibit release of ACh
• causes paralysis

Question 12

Chloera (Vibrio Entertoxin)

Answer 12

• destroy intestinal cells by becoming little pumps
• uses CAMP messenger systems
• profuse diarrhea

Question 13

Endotoxins

Answer 13

• part of cell wall
• Gram negative
• Lipid A
• are released when bacteria die and cell walls undergo lysis, freeing endotoxin
• antibiotics: lyse bacterial cells, releasing endotoxin and lead to immediate worsening but usually improves as endotoxin breakdown
• same symptoms: fever (Pyrogenic fever), GI tract (nausea, vomiting, diarrhea), shock, possible death

Question 14

Pyrogenic Response

Answer 14

• ingested by phagocytes
• LPS are released; macrophages produce cytokines called interleukin-1
• cytokines are carries via the blood to the hypothalamus, temperature control of brain
• cytokines induce hypothalamus to release lipids called prostaglandins, which reset thermostat in hypothalamus at higher temperature= fever
  1st Stage: chills, shivering, I-L1 increases
  2nd Stage: crisis, extreme sweat, I-L1 decreases

Question 15

Shock

Answer 15

• life threatening decrease in blood pressure
• phagocytosis of gram neg bacteria causes phagocytes to secrete tumor necrosis factor )TNF) or cachectin
• damages blood capillaries, permeability is increased, and lose large amount of fluid
  = decrease in BP