Bacterial Pathogenesis

Question 1

how do pathogens evade our bodily restriction of them

Answer 1

they adhere/invade host tissues, secrete toxins/effectors, steal nutrients from host, subvert, evade and counteract immune defenses

Question 2

what do primary pathogens do / what do opportunisitc pathogens do

Answer 2

cause disease in healthy hosts - will get sick every time (example Shigella flexneri) / cause disease only in compromised hosts or following entry into unprotected sites (example lysteria)

Question 3

how did Koch identify his postulates

Answer 3

you can isolate a bacteria from a diseased organism, regrow that bacteria in medium, reintroduce the bacteria into an organism, and be able to isolate the same bacteria again

Question 4

what are molecular koch’s postulates

Answer 4

1. the phenotype under study should be found in pathogenic strains of a species 2. inactivation of virulence genes should be associated with a decrease in pathogenesis 3. replacement of inactivated gene should restore pathogenicity

Question 5

what are virulence factors

Answer 5

what pathogens use to meet requirements of infection cycle - include toxins, attachement proteins, capsules, and other devices

Question 6

where are most virulence genes in bacterial pathogens found / where do pathogenicity islands appear

Answer 6

some reside on plasmids or in phage genomes - often clustered into pathogenicity islands that encode virulence functions / appear to have been horizontally transmitted via conjugation or transduction (moved between bacterial species)

Question 7

what is a pathogenicity island / what are they usually linked and associated to

Answer 7

a region of the genome that has a distinct nucleotide ratio (GC/AT ratio) - indicates horizontal gene transfer / linked to a tRNA gene and associated with genes homologous to phage/plasmid genes

Question 8

what is a microbial factor that promotes attachment called

Answer 8

an adhesin - a specific virulence factor required for attachment or adhesion

Question 9

what do adhesins bind to

Answer 9

pili and nonpilus proteins

Question 10

how do bacteria avoid our chemical defenses in mucosal colonization

Answer 10

they modify their peptidoglycan structure to prevent breakdown from lysozyme - they change the charge of their membrane to repel the positively charged defensins (antimicrobial peptides) - they ahve specific receptors that harvest essential molecules (iron)

Question 11

how does Neisseria gonorrhoeae avoid adaptive immunity

Answer 11

they have proteases that cut the antibodies we have - it also mutates its type IV pillus often to avoid antibody attachment (immobilization)

Question 12

how do cells invade host tissues

Answer 12

enter through damaged skin, damaged epithelium or epithelial cell invasion

Question 13

how do Salmonella and Shigella force uptake into epithelial cells

Answer 13

they use a Type III secretion system by using needles to inject proteins in a cell

Question 14

what is M cell transcytosis

Answer 14

when a bacteria uses getting phagocitzed by a macrohage to get across the epithelial layer - some can replicate in the macrophage

Question 15

what does SEC stand for

Answer 15

Subvert , Evade , Counteract

Question 16

what does subvert entail

Answer 16

the deployment of effectors/toxins to block signaling pathways or to remove key immune cells that aid in bacterial clearance

Question 17

what are toxins and effectors / how are toxins deployed / how are effectors deployed

Answer 17

proteins produced and secreted by pathogens to disable immune defenses and attain nutrients / secreted into the extracellular space / injected into host cells using specialized secretion apparatuses

Question 18

how does S. aureus get toxin into a host cell

Answer 18

create a pore in the host cell with a receptor that is only found on immune cells - this puts the bacteria at an advantage

Question 19

how does Diptheria toxin get induced

Answer 19

during iron starvation so that the iron gets released from our dead cells to fuel the pathogen

Question 20

how does the EPEC - Enteropathogenic E. coli cause food borne diarrheal disease

Answer 20

it injects its toxin into the cell of the epithilium - this toxin rearanges its cytoskeleton and allows it to get nutrients from the dead cells

Question 21

what does Evade entail / what does this for a pathogenic cell

Answer 21

mask MAMPs to avoid immune detection / capsules block our immune cell proteins from binding to outer things on the cell

Question 22

what does counteract entail / how does staphylococcus aureus do this

Answer 22

shields used to render host defenses useless against the pathogen - counterattacks the anitbody response evolved / binds the antibodies backward by binding to its Fc region which makes the immune system not see the bacteria is infected

Question 23

what is Yersinia pestis / what features does it have

Answer 23

the bacteria that causes the plague / a gram negative rod, facultative anaerobe, primary pathogen, facultative intracellular pathogen, plasmid encoded virulence factors and has a T3SS

Question 24

how does yersinia pestis avoid our immune system

Answer 24

it completely changes its structure of lipid A core in the LPS that we usually use as a MAMP to induce inflammation through the PRR TLR4 - make it undetectable by TLR4

Question 25

what does the Type III needle protein bind to / what do the effectors do

Answer 25

the formyl peptide (fMet) on the phagocytes and injects them with effectors / they block cytokine production and disrupt actin polymerization required for phagocytosis

Question 26

when the TLRs and NLRs are turned off what happens to inflammation / why does yersinia cause swollen lymph nodes

Answer 26

there is none because the immune response would not be working / because the macrophages are killed in the lymphoid tissue and the yersinia is released all of the bacteria build up and cause swelling