Opportunistic infxns

Question 1

How does this factor arise?
This factor predisposes indivs to which opportunistic infxns?
- Granulocytopenia (Low PMNs)

Answer 1

Chemotherapy or radiation therapy

GN and staphylococcus

Question 2

How does this factor arise?
This factor predisposes indivs to which opportunistic infxns?
- Cellular immune dysfxn

Answer 2

AIDS, age, smoking, T cell defects

Intracellular pathogens (salmonella)
Mycobacterium tuberculosis
Listeria monocytogenes

Question 3

How does this factor arise?
This factor predisposes indivs to which opportunistic infxns?
Humoral immune dysfunction

Answer 3

Agammaglobulinemia
Splenectomy

Encapsulated pathogens
S. pneumoniae, meningococci

Question 4

How does this factor arise?
This factor predisposes indivs to which opportunistic infxns?
Foreign body

Answer 4

IV or urinary catheter, bone implant

GN, Staphylococci

Question 5

How does this factor arise?
This factor predisposes indivs to which opportunistic infxns?
Surgery

Answer 5

Staphylococci
Ecoli
Pseudomonas

Question 6

Importance of iron in bacteria growth

Answer 6

almost all bacteria require iron for growth
- cept lactobacilli & treponema pallidum

Our bodies have most Fe2+ bound to transferrin or lactoferrin to keep iron levels down low
Our body also shunts income iron into storage (liver)

Question 7

Host responses and defenses to prevent bacteria from taking up iron

Answer 7

1. Iron binding proteins
   - Transferrin, lactoferrin
   - keep body’s levels low
2. Shunt incoming iron into storage (liver)
3. Decrease Iron adsorption (intestine)
4. Decrease expression of microbial iron binding compounds (siderophores)
   - down reg. bacteria’s ability to make siderophores which compete and bind our Fe.

Question 8

FX of endotoxin on Hageman factor (XII)

Answer 8

activates Hageman factor (XII) -->
PLasminogen activator (fibrinolysis)
\+ 
Bradykinin 
(hypotension)

Can also activate complement activation and TNF
(good and bad FX depending on lvls)

Question 9

Why is pseudomonas so highly resistant to treatment?

Answer 9

High innate resistance mech (many efflux pumps)

Propensity to form biofilms

Question 10

Pathognomonic of P. aeruginosa septicemia

Answer 10

Ecthyma gangrenosum

• gun metal gray infarcted lesion surrounding erythema
• evolves into a necrotic black/gray eschar and surrounding erythema
• one of phospholipases is highly cytotoxic to ENDOthelial cells and not epithelial cells –> vascular thrombosis

Question 11

Most people with CF will die from what?

Answer 11

Lung infxn with Pseudomonas aeruginosa

• settled in lung for life
• forms a type of biofilm

Question 12

CF pts cant make Cl- but they can make ___

Answer 12

Ca2+ gels the compounds that pseudomonas makes.
- macrophages cant get thru biofilm, get madder and madder –> inflammation and destroys the lungs.

*must shake/pound chest of pts with CF to clear their lungs

Question 13

Small doses of endotoxin can stimulate the immune system, but at higher doses, it sets off a cascade that cannot be controlled, leading to severe shock.
What is the primary effector cell in the cascade?

Answer 13

The macrophage
- gets overstimulated by endotoxin –> releases TNF –>
tells macrophages to release more cytokines –>
targets endothelial cells

Question 14

Nutritional immunity

Answer 14

ability of host to withhold trace nutrients from organisms

Question 15

Pseudomonas is NOT the leading cause of nosocomial or opportinistic infxn, so why do we care?

Answer 15

It is number 1 in terms of mortality

Question 16

Antibiotic resistance of pseudomonas is due to what?

Answer 16

Chromosomally mediated resistance associated with multiple efflux pumps

• not via plasmids

Question 17

Virulence factor of pseudomonas

what bacteria toxin is it similar to?

Answer 17

1. Exotoxin A
   - ADP ribosyl transferase: inhibits activity of EF-2 in mammalian cells
   - stops protein synthesis liek diphteria toxin
   - regulated by iron similarly

Question 18

Why is pseudomonas exotoxin A not have the same distal effects as diphtheria toxin when they both act the same?

Answer 18

1. Cell receptors are different
   - target cells and tissues are different
2. Diphtheriae only produces superficial infection
   (epidermal growth factor precursor)

*pseudomonas can invade tissue and blood stream

Question 19

WHy cant vaccination against diphtheria work against pseudomonas?

Answer 19

no immunological cross reactivity btwn their toxins and virtually no primary aa seq. similarity

Question 20

What allows pseudomonas to survive solely on the surfactant of the lung?

Answer 20

multiple phospholipases

Question 21

What compounds are critical for pseudomonas to form biofilms?

Answer 21

Homoserine lactones

in a process called quorum sensing

Question 22

Wound infxns in diabetics commonly contain what organisms?

Answer 22

pseudomonas and S. aureus

- very slow to heal and very diff to tx

Question 23

Alginate

Answer 23

mucoid substances prod by pseudomonas in CF pts
- a gluuronic mannuronic acid polymer

• CF pts tend to select for pseudomonas strains that make alginate
• due to high Ca2+ and osmolarity of CF lung