Pathogenesis

Question 1

Colonization vs. infection

Answer 1

Colonization - without harming the body

Infection - microbes damage tissues (directly via proliferation or actions of virulence factors or by stimulating the immune response)

Question 2

Possible outcomes of infection

Answer 2

Question 3

Horizontal transmission

Pathogen transmission

Answer 3

1. Inhalation
2. Ingestion
3. Wound
4. Sex
5. Blood-to-blood
6. hand/hand, hand/eye, hand/mouth, or mouth/mouth

Question 4

Vertical transmission

Pathogen transmission

Answer 4

Pathogens passed from mother to fetus or infant - can occur in utero (antenatal/prenatal) or in the days/weeks immediately before, during, or after birth (perinatal), or after birth (postnatal)

Question 5

Arhtropod vectors

Answer 5

mosquitoes, ticks, fleas, and mites

Question 6

Quorum sensing

Answer 6

Mechanisms microbes use to assess the density of the local cell population allowing them to coordinate virulence factor production

Important to biofilm formation becuase it regulates polysaccharide matrix production

QSM compounds: usually acylated homoserine lactones, peptides, or alcohols

Question 7

A/B subunit toxins

Answer 7

B - binds to host cell surface

A - enters host cell and performs the action of the toxin

B binds
A has activity

Question 8

Intracellular Pathogen Cytopathic effects (CPE)

Answer 8

1. Cell lysis
2. Vacuolation
3. Inclusion body formation
4. Cell fusion
5. Parasitophorous vacuole (PV)
6. Transformation

Question 9

Botulinim toxin action

Answer 9

A/B subunit toxin

Question 10

Cholera toxin action

Answer 10

A/B subunit toxin

B - binds to ganglioside GM1 on intestinal epithelial cells

A - enters cell and activates adenylate cyclase - increases cellular cAMP - results in the secretion of electrolytes and water into the intestinal lumen

Question 11

Cytolethal distending toxins

Answer 11

A/B subunit toxin

Cause host cell DNA damage - cause senescence in immune cells, but also increases the possibility of cancer-causing mutations

Question 12

Pore forming toxins

Answer 12

Hemolysins are one type of bacterial pore forming toxins - leak or lyse RBCs

Question 13

Superantigens

Answer 13

Cause non-specific activation of T cells and professional antigen presenting cells which results in systemic release of inflammatory cytokines

i.e. S. aureus secretes a superantigen - causes toxic shock syndrome

Question 14

What immune cells target intracellular pathogens

Answer 14

Cytotoxic T cells, neutrophils and NK cells

Question 15

Pro-inflammatory mediators

Answer 15

Type I interferons (IFN-alpha/beta) and inflammatory cytokines (IL-6, IL-1beta, and TNF-alpha)

Question 16

Systemic Inflammatory response syndrome (SIRS)

Answer 16

Systemic circulation of DAMPs/PAMPs results in cytokine storm and other mediators - in which disseminated intravascular coagulation and severe hypotension can lead to shock, ischemic tissue damage, multiorgan failure, and death

Question 17

How do pathogen virulence factors transform host cells?

Answer 17

1. Inactivate the host cellular growth suppressors p53 and Rb
2. Increase activity of host cell growth activators (hormones and cytokines)
3. Inhibit apoptosis - pathogens inhibit p53 and/or other apoptosis pathway factors - or by inducing mutations in host genes encoding these regulatory proteins
4. Producing genotoxins that damage host cell DNA, cause incomplete host cell chromosome segregation, or induce host epigenetic changes
5. Increasing host cell oxidative stress

Question 18

Candida albicans

Normal flora distribution

Answer 18

Mouth, colon, vagina

Question 19

Methods of dissemination

Answer 19

1. Direct spread between cells or tissues using virulence factors
2. Transversion across epithelial barriers at sites of mucosal associated lymphoid tissues (MALT)
3. Hematogenous spread in the bloodstream and/or lymphatics is most common mechanism for systemic dissemination
4. Neuronal - some virsues

Question 20

What age pop. is there the strongest immune response?

Answer 20

Young adults

i.e. chicken pox can be life-threating in a young adult

Question 21

Direct spread of Listeria monocytogenes

Answer 21

Expresses a virulence protein at one end of the bacterial cell to stimulate polymerization of host cell actin. These “actin comet tails” push the bacteria through the cytoplasm into neighboring cells or the surrounding tissue

Question 22

Multi-nucleated giant cells

Answer 22

This type of cytopathic effect is typically observbed in host cells infected with enveloped viruses - VAPs/viral fusion proteins are inserted into the host cell plasma membrane

Question 23

Syncitium

Common cytopathic effect

Answer 23

Fused cells (multinucleated giant cells)

Question 24

Syncitium

Common cytopathic effect

Answer 24

Fused cells (multinucleated giant cells)

Question 25

Mechanisms by which pathogens can promote cancer

Answer 25

Question 26

Immune Mediated Tissue Damage in Response to Pathogen

Answer 26

1. CD8+ CTL and NK cell killing of infected cells
2. Molecular mimicry and autoimmunity
3. Immune complex deposition
4. Inflammatory mediators

Question 27

Host cell mimicry in S. pyogenes infection

Answer 27

IgG/IgM mad against M proteins (streptococcal cell wall proteins) are able to cross react with cardiac tissue - cause rheumatic fever

Activates complement proteins C3a and C5a