gut microbiology Flashcards
how many species in normal flora
> 800
difference between resident and transient flora
resident - for life
transient - temporarily carried, reduced, or changed
types of symbiosis
commensalism, mutualism
what does commensal mean
when TOGETHER the flora don’t cause any harm to the host
why is the stomach sterile
too inhospitable for normal flora
what microbe can cause gastric ulcers
helicobacter pylori
what kind of bacteria exist in the large intestine
obligate and facultative anaerobes - bifidobacteria, enterobacteria etc.
examples of diseases associated with microbiome alterations
crohn’s
IBS, ulcerative collitis
intestinal properties affected by the microbiome
modulation of digestion and absorption - inc energy harvesting
host metabolism/energy homeostasis - endocrine function, inflammatory signals
structural host defences
seamless epithelium, tight junctions - sloughing/turnover
mechanical host defences
peristalsis
chewing
fluid movement
biochemical host defences
gastric acid
bile
mucous
immonological host defences
secretory IgA, intra-epithelial lymphocytes
benefits of gut flora
colonisation resistance
metabolites of benefit to host
normal immunity development
aids digestion
what do probiotic organisms do
produce lactic and organic acids
what do prebiotics do
alter gut ecosystem, promote growth of probiotes
uses of probiotics in medicine
control infant diarrhoea
relieve constipation
improve lactose digestion
why is microbial antagonism good
maintains flora - competition, complex reactions - limits growth of competitors and pathogens
what happens if flora is lost
bacterial or pathogen overgrowth
what can cause loss of flora
drugs eg ciprofloxicin
def of gastroenteritis
acute syndrome characterised by GI symptoms in any combination
def of diarrhoea
frequent passage of loose, fluid, unformed stools
clinical consequences of diarrhoea
can lead to severe dehydration excessive fluid and electrolyte loss hypovolaemia hypokalaemia long term morbidity and reduced growth
def of dysentery
inflammatory disorder of the GI tract - usualy LI
def of enterocolutis
inflammation involving mucosa of small and large intestine
how are diarrhoeal diseases transmitted
shed in faeces - faecal - oral route
what is the GI response to superficial microbial invasion
local inflammation
what can cause perforation/ulceration of the mucosal epithelium
peritonitis/intra abdominal abscess
mechanisms of diarrhoea
bacterial toxins - enterotoxins exotoxins cytotoxins adherence damage to epithelium penetration and invasion
why is the infectious dose important
affects incubation time, severity of disease
what is food poisoning
symptoms caused by preformed toxins in the food, often heat-stable
what is food associated infection
infection with live organism that grows in the gut and causes symptoms
