Chapter 2 and 18 Flashcards
What age group is most susceptible to infectious disease
very young (under 3) and very old (over 60)
What factors put a person at risk for developing a infectious disease?
age, host genetic makeup (receptors), host hygiene and behaviors, nutrition and exercise, pre-existing conditions, occupation, immune status and immunopathogenesis.
In order to prevent colonization, what three mechanisms does the body use?
lungs: mucociliary escalator= moves pathogens out
bladder: detrusor contraction= propels urine with tremendous force
intestines: peristaltic action= constant flow
What is the first step of pathogenesis?
attachment or adhesion
what are two types of adhesins?
Pili adhesins and non-pili adhesins
characteristics of pili adhesins?
they have hairlike appendages - tips with receptors for host cells
What do adhesins help with?
colonization and biofilm formation
what is a Fimbriae?
a pilli
how do non-pilus attach to host?
cell wall proteins that bind to host proteins like integrin or fibronectin cause a more intimate relationship.
Pili are made up of (a) ___________ pilin protein (b) ____________
a) identical
b) subunits
the tip of the pilus contains adhesion protein that binds host cell ____________
a) receptors
Bordetella pertactin is a example of what host protein?
integrin
streptococcus protein F is a example of what host protein?
fibronectin
streptococcus protein M is a example of what host protein?
fibronectin and the completement regulatory factor H
Neisseria meningitidis uses what type of pili?
IV pilli -> Neisserial Opa nonpilis membrane proteins
What does a microbe detect to determine if it is in a host or not? (5 things)
1) temperature
2) Iron levels
3) Magnesium levels
4) pH levels
5) Hormones
If a microbe detects it is in a host cell what will it being to express?
Virulence genes
what type of pathogen is more likely to have interactions with the host immune system?
extracellular pathogens
What type of pathogens are less likely to be detected by the immune system?
intracellular pathogens because they are inside the host cell.
facultative intracellular pathogens
can live either inside host cells or free from them
What are four ways extracellular pathogens avoid the host immune system?
1) capsules
2) cell surface proteins
3) surface antigens
4) cell-cell communication (quorum sensing)
what do capsules do?
coat bacterial cell walls and can prevent phagocytes from binding.
how does the immune system eventually circumvent the avoidant strategy of capsules?
immune defense mechanisms can eventually circumvent this avoidance strategy by producing opsonizing antibodies (immunoglobulin G) against the capsule itself
How does cell surface proteins on S.aureus sequester antibodies to aid in immune avoidance?
Protein A can bind to the Fc region on antibodies which hides the pathogen from phagocytosis
What are the two ways Protein A binding to the Fc site of antibodies hides the pathogen from phagocytes?
1) causes the antigen-binding sites to point away from the microbe.
2) if the antigen-binding site binds to one bacterium, protein A from a second bacterium can bind to the Fc region and block phagocyte recognition
Salmonella can _________ to change flagellin A to flagellin B and confuse the immune system.
a) vary surface antigens.
Cell-cell communication (quorum sensing) helps pathogens evade the immune system by creating fake cytokines, what do the cytokines do to prevent attack of the pathogen?
These fake factors can manipulate the balance of helper T cells and send immunity down the wrong path for combating the microbe
autoinducer molecule will a) ________ as the number of bacteria grow
a) rise
when the pathogen detects increased levels of a autoinducer, what will it do next?
turns on virulence gene expression
what are three examples of facultative intracellular pathogens?
salmonella, shigella and listeria
pathogens that invade and reproduce inside a host cell only
Obligate intracellular pathogens
three examples of Obligate intracellular pathogens?
Rickettsia, coxiella, bartonella
what are the three fates of intracellular pathogens?
fate 1= THRIVE UNDER STRESS
fate 2= INHIBITING PHAGOSOME-LYSOSOME FUSION
fate 3= ESCAPE FROM THE PHAGOSOME
Fate 1:
In order to survive inside the host cell, bacteria’s such as Coxiella burnetii allow themselves to be engulfed by lysosomes (phagosome- lysosome fusion) in which they than differentiate into a form able to replicate in the phagolysosome which results in?
Inclusion bodies
Fate 2:
Pathogens like salmonella can remain inside a phagosome and ________________?
prevent fusion with the lysosome
Fate 3:
Pathogen such as shigella and listeria can a) _________________ and than move throughout the b) _________________ into adjacent cells by forming c) _________________
a) break out of the phagosome
b) cytoplasm
c) actin tails
Microbial exotoxins are categorized on the basis of their?
cellular targets and mechanisms of action
Part of the outer membrane of the Gram-negative cell wall that includes LPS?
Endotoxin
When is endotoxin released?
When Gram negative pathogens die.
what symptoms are triggered by the “cytokine storm” inflicted by endotoxins?
Fever, activation/depletion of clotting factors (petechiae), activation of complement, vasodilation, shock or death.
what classification of cells secrete exotoxins?
both gram negative and postive
what classification of cells secrete endotoxins
gram negative cells only
where does the pathogen C. diphtheriae remain in the body?
the pharynx
When is the C. diphtheria toxin released?
conditions with low levels of iron!
