3-Host Bacterial Relations Flashcards
symbiosis
intimate and prolonged associated b/t 2+ orgs of diff species
-commensalism, mutualism, parasitism
normal microbiota
flora
community of microbes that live in/on indiv
niche
shelter physcial space, food for others
that plays a role in microbial community
microbiome
aggregate collection of genes/genomes from microbiota
can tell you what a microbiota is doing
pre vs pro biotics
prebiotic = food ingredient that supports growth of 1+ members of microbiota
probiotics= live microbes ingested to benefit host, debatable
where is microbiota at
conflicting bc not able to culture well
-seq prone to contamination (16S)
loose rules of microbiota location
- any site exposed to environ, if not direct link to outside then not normal microbiota
-sterile anatomic sites
placenta, fetus, middle ear debatable
resident microbiota
long term
part of noraml microbiota
staphylococcus epidermidis @skin and nares
transient microbiota
microbes that attempt to colonize but fail
streptococcus pyogenes @oropharynx
factors that affect microbiome
- mode of delivery neonate
- host genetics
- host immune resp
- diet
- xenobiotics (antibiotics)
- infectinos
- diurnal rhythm
- environment exposures
- age
microbiota development
- fetus- sterile
- neonate- colonized by vaginal bacteria or rapidly colonzied after birth c section
- childhood- change early (breastmilk) then stable late childhood
- healthy adult- stable
- elderly- inc susceptibilty to infection from microbiota
aka changes as we age
intestinal microbita functions
- biosynthesis- vitamins, hormones, neurotrans
- metabolism- diet, bile salts, drugs
- influence-homeostasis, host cell prolif, bone density, neurologic signaling
how intestinal microbiota protects from infection
- occupy niches to prvent colonization/access to host tissue
- primes innate immunity by stim mucin, IgA
- promote epi cell resistance and low level inflamm
strict pathogens
orgs that are always associated with disease
myobacterium tuberculosis
neisseria gonorrhoeae
rabies virus
opportunistic pathogens
members of normal mb that take advantage of condtiions to cause disease
E. coli from intestines to urinary tract
most infectious diseases caused by
pathogenicity
ability of microorg to cause disease
virulence is measure of pathogenicty
virulence factors
enable
-colonization
-immune evasion
-entry/survival within host cells
-obtain nutrients to survive in host
entry into host mechanism
- transplacental
- secretions
- stool -oral
- skin
- blood
- zoonotic
- arthropod
barriers to entry
- mechanical
- enzymes
- chemicals
- immunity
- commensals
- physical
adherence
first step
binds to host cell surface via adhesin proteins with pili (often not always)
biofilms
bacteria encased in exopolymeric substance to adhere to surface and stay stationary
-found on moist/wet surface
biofilm characteristics
-slower metabolism than free floating planktonic
-inc resist to antibiotics
-inc genetic exchange
-resistant to disinfection
pathogenic action
after adhered and colonzied
1. toxin production
2. invade cells, or
3. disseminate
4. tissue destruction
5. endotoxins- lipid A of LPS
6. exotoxins- cytolytic enz, toxic rxns
AB toxins
A = active
B = binding
type of exotoxin- direct tissue damage, destructive
superantigens
bind both TCR and MHCII without an antigen so get cytokine storm
S. aureus TSST1, Staph. enterotoxin, S. pyogenes erythrogenic toxins
mechanisms for evading
- antigenic masking by capsule
- mimicry- make host see as self
- shift/variation- change proteins on cell surface so moving target for immune system
- resist complement
- inactivate antibody via proteases
how to escape phagocytic clearance
- inhib opsonization
- inhib chemotaxis
- kill phagocyte
- inhib
intravenous catheter contamination
opportunistic
- staphylococcus epidermidis (skin)
- sstaphylococcus aureus (skin)
wound surgical site infection
opportunistic
- staphylococcus aureus - skin
- klebsiella pneumoniae- intestine
- pseudomonas aeruginosa- skin
tooth decay/dental caries
streptococcus mutans - teeth
urinary tract infections
escherichia coli-intestine
E.coli
pseudomembrane colitis
- clostridiodes difficile- intestine, from antibiotic therapy spores that survive and overgrow
otitis media
middle ear infection
1. streptococcus pneumoniae
2. non typeable haemophilus influenzae
3. moraxella catarrhalis - nasopharynx
what’s NOT virulence factor
- peptidoglycan
- factors in metabolism required for survival outside host aka core metabolism proteins
- chromosome
- membranes
- ribosomes
