microorganisms in GI tract part 1 W4 Flashcards
commensal microbiota?
normal inhabitant of the human body, living in communities called microbiota
how is commensal microbiota acquired?
birth - passage through birth canal, skin contact, breast feeding
what does microbiota provide for humans?
extract nutrition and energy from food
postnatal differentiation of mucosal structures (brush border)
physical barrier
antigen stimulation
regulation of metabolism
colonisation resistance against pathogens
what does the host provide for the microbiota?
nutrients and growth factors (diet, gut cell secretion)
protected habitat
means for dispersal
opportunistic pathogen meaning?
all pathogens are ‘commensals’ when contained in GI tract
when they cause a disease, they become pathogens. disease is not required for the pathogens survival
examples of opportunistic pathogens in the gut?
Escherichia coli
Bacteroides fragilis
Enterococcus faecium/faecalis
what is a pathogen? features?
also called obligate pathogen
pathogens need to cause disease to transmit between hosts (evolutionary survival)
can produce asymptomatic infection (but not commensal)
infections are not necessarily more severe than with opportunistic pathogens
examples of obligate pathogens?
Escherichia coli
Shigella dysenteriae
Salmonella Typhi
Campylobacter jejuni
what are zoonotic pathogens
commensal or pathogen in animals
transmitted to humans via insect vectors or direct contact
disease causation in humans is accidental and not necessary for evolutionary survival
zoonotic pathogens examples
Yersinia pestis (caused the plague via rats)
Borrelia burgdorferi (causes Lyme disease via ticks)
what are environmental pathogens
present in environment
transmitted to humans via contact or ingestion
disease causation in humans is accidental and not necessary for evolutionary survival
examples of environmental pathogens
Clostridioides difficile
Vibro Cholerae
protective factors in the GI tract against microbes?
tight epithelial barrier
intestinal microbiota
mucus (secreted from goblet cells)
GALT - gut associated lymphatic tissue (local immune cells)
pH
low oxygen
flow rate (peristalsis)
bile salts and digestive enzymes
opportunistic pathogenic mechanisms against the host?
ileus - disrupt flow rate, peristalsis is abolished allowing bacteria to reach the epithelium
appendicitis - blockade at start of appendix, stagnation, microbes grow and become more potent, cause inflammation
antibiotics kills intestinal microbiota, reduces physical barrier
immunosuppression
antacid drugs - environment no longer acidic
infection eg sepsis - leakage in GI epithelium
obligate pathogen mechanisms against the host?
toxin production - attack epithelium
increase flow rate - diarrhoea
direct invasion properties - adherence mechanisms, motility (flagellum, pili)
resistance to bile salts and digestive enzymes
capsule - avoid immune system
acquire virulence factor to become opportunistic pathogen
