immunology pt. 1 Flashcards
(1st 50 slides)
what does microbiota do?
- regulates metabolism
- regulates + strengthens immune responses
- protects from foreign microbes
in neurological development
opportunistic pathogen (OP)
- are harmless but can cause a disease in the absence of normal host resistance
- NF to OP
1. overpop by microbes (compromised immune response)
2. disruption of balance of normal microbes by broad-spectrum antibiotics
3. traumatic intro to axenic areas of body
transient flora
may colonize but cannot stay for long
1. competition from resident flora
2. elimination by body’s immune system
3. physical/chem. changes that stops growth
skin microbiota
dry, acid environ. that does not support growth
- moist areas = colonized
- most inhabitants = G+, salt tolerable bacteria
oral cavity microbiota
complex, heterogenous microbial habitat
-»_space; [nutrients]
- toxic w/ anoxic microenviron.
bacteria colonize tooth surfaces + form biofilm
- acid made by anaerobic fermentation by streptococcus sp. makes dental caries
- beneficial strep. can neutralize acidic products + make H2O2 + antimicrobial compounds to limit pathogen growth
GI tract microbiota
pop = from diet and physical conditions (pH + O2)
- acidity of stomach + duodenum (pH=2) stops many from colonizing
> microbes can transit stomach embedded in food
> Toxins can persist
role of microbiota
- homeostasis
- vitamins
- microbial metabolism (energy)
- influences fecal transit time
- protects from pathogen - disrupted
- «_space;level obesity
> diabetes
> obesity
- susceptibility to disease
- signal to store lipids
role of microbiota (neurological developmet)
stimulates cells to make serotonin
- many antidepressants»_space; serotonin
benefical rxns of NF
- digestion of food
- absorption + production of nutrients
- make vitamins
dysbiosis
microbial imbalance/maladaptation
- causes: antibiotics and poor diet
probiotics
live microbes that are beneficial to the host
- not thought to colonize GI tract permanently
- «_space;GI discomfort, keep potential pathogen #’s «, improve bowel, maintain microbiota when there’s antibiotics
prebiotics
induce growth of microbes
- selectively fermentable ingredients that can change the microbe’s activity
UGT microbiota
bladder (sterile)
- altered conditions can change pathogens in urethra to multiply + be pathogenic
- e.coli + p.mirabilis freq causes UTI
acidic vaginal
- lactobacilius acidophilus, a resident organism in vagina, ferments glycogen making lactic acid
> maintains UGT pH
> controls NF pop + infection by pathogen
- antibiotics + hormones alter NF
>»_space; pH leads to outgrowth Candida (NF-OP) = yeast infections
frank pathogen
parasites that harms the host
- enters, colonizes, invades + causes damage
- some pathogens need to make toxin that enters
> Bacteria, not in humans
bacterial infectious process (growth) in 5 steps
- exposure/porals of entry (PoE) - transmission of agent + localization to body> access to tissue where they can multiply/toxin can act
: exposure must be appropriate and appropriate infectious dose must be present - adherence
- establishment + surviving host defenses
- invasiveness
- portal of exit
PoE/exposure
transmission
- direct contact
> infectious mononucleosis, gonorrhea, spray
- indirect contact
> from reservoir to host by suspended air particles, inanimate objects, or animate intermediates
> airborne
- vehicles that may indirectly transmit the infectious agent
> may passively carry the pathogen
>may help an agent grow, multiply, or make toxin
- vectors may carry infectious agents the mechanical means
> mosquitos, fleas and ticks
pathogen source
- exogenous
- true pathogens that come from ext. environ. and not of NF
> streptococcus - endogenous
- OP = NF that cause disease under certain conditios
> staphylococcus
infectious dose (ID50)
total # of pathogen req to establish infection 50% of exposed hosts
lethal dose (LD50)
total # of pathogen req to kill 50% of exposed host
adherence
- maintains pathogens in/on the body
- pathogens must adhere and invade
- some may be injected into the sterile site
- intoxications do not involve pathogens adherence, but microbial toxins that adhere to infections frequently begin on mucous membranes
bacteria + viruses adherence
start infection adhere to epithelial cells the macromolecular interactions between pathogen surface
1. species specificity: pathogen infect certain species
2. genetic specificity: certain strains w/n species are genetically resistant to pathogen
3. tissue tropism: pathogen has a preference for certain tissues w/n the host
adherence mech
- extracellular macromolecules
> slime layer, capsule - outer membrane proteins (adhesins) bind to host cell receptors
- fimbriae + pili
establishment + surviving host defenses
- nutrients = important for pathogen growth
- disruption of immune sys (fast-acting) parts
- disruption of phagocytic WBCs func
> capsules: stops phagocytosis, etc.
> leukocidins: toxins that kill WBC
> coagulase: makes fibrin clots to «_space;WBC’s ability from entering infected tissue that contributes to abscess formation
>intracellular growth: growth in human cell protects microbe from phagocytosis cells - outgrowth of infectious agent on tissues (local infection): pop»_space; in body
- bacteriocins:
A. toxins secreted by pathogen to kill NF
B. «_space;comp for resources
C. transferred on col plasmid
D. allow pathogen to out-compete NF on non-sterile tissues
- exoenzymes: degrade tissues for nutrients
- quorum sensing - breach in natural defenses
- inoculation into sterile site
invasiveness
invade additional tissues w/ production of virulence factors (enzyme/toxin: extracellular substances)
- cons:
1. direct damage to the host
> destruction of non/sterile tissues = OP + true pathogens
2. can spread throughout host via circulatory/lymphatic sys
