MICROBIOLOGY OF THE GUT Flashcards
outline the cycle of malnutrition and GI infections?
GI infections exacerbate malnutrition and malnutrition lowers resistance to GI infection
what is gastroenteritis?
infectious diarrhoea and vomiting due to inflammation of the GI tract, particularly the stomach and small intestine.
what are symptoms of gastroenteritis?
diarrhoea, vomiting and abdominal pain. Fever, lack of energy and dehydration can also occur.
how long do gastroenteritis symptoms typically last?
<2 weeks
what are some examples of causative organisms of gastroenteritis?
rotavirus, norovirus, adenovirus, E.coli, campylobacter jejune, salmonella, shigella, entamoeba histolytica
outline the pathophysiology of gastroenteritis?
Pathogen invades the epithelium in the gastrointestinal wall and causes these cells to die. Now the epithelial cells cant digest and absorb food and water and so it cant enter your system = vomiiting, diarrhoea and dehydration.
why can you not cohort patients with gastroenteritis?
as you dont know the causative organism so patients might get other patient’s infections
what should you ask a patient to try to find the cause of gastroeneteritis?
travel history contact history social events food pets
what type of diet can help reduce symptoms of gastroenteritis?
low dairy, low fat and high fibre diet
what diagnostic tests can be done for gastroeneteritis?
stool sample and blood tests
whats the treatment for gastroeneteritis?
oral rehydration therapy
antibiotics sometimes
how can you avoid gastroeneteritis?
good hygiene
cook food really well
drink clean water
why are antibiotics not always given in gastroenteritis?
the illness is usually self limiting, can damage the flora of GI tract and can make E.coli 0157 worse
what are some host defences against GI infection?
behavioural e.g. put off by sewage smells
gastric ph low
bile acids and salts can emulsify cell membranes of bacteria
peristalsis
mucus - physical and lysozymes
immunity - secretory IgA
regional flora of GI tract
outline the pattern of regional GI flora?
small nubers at the stomach and small intestine with nubers increasing as you head towards the colon
anaerobes also increase as you move towards the colon
whats the function of the appendix?
a MALT and stores normal flora from the bowel so can replenish it
what are the benefits of our microbiome?
bacteria make folate and biotin, release nutrients like Fe2+/Ca2+/amino acids, remove toxins such as heterocyclic amines, outcompete pathogenic bacteria and release energy by converting carbs to sugars
what type of bacteria are clostridium difficile?
obligate anaerobes that are gram positive and look like purple rods in the lab
outline how we catch C.Diff?
the bacteria thrives in deep soil in nature but when they feel the stress of fresh oxygenated air they produce spores which sprout into clostridia
how is c.diff spread?
feacal oral
when can c.diff cause problems?
when the diversity of the normal flora changes and c.diff can thrive and causw overgrowth e.g. chemotherapy, prolonged elemental diet and antibiotic use.
what are risk factors for C.diff
o
old age
recent stay at hospital or nursing home
weakened immune system
previous exposure to c.diff
what antibiotics are main risk factors for c.diff?
clindamycin, cephalosporins, ciprofloxacin and co-amoxiclav
what exotoxins does c.diff produce?
toxin a and b
what is c.diff toxin A?
enterotoxin that causes fluid accumulation in the bowel
what is c.diff toxin B?
enters cells ans causes apoptosis which can lead to pseudomembranous colitis.
what are symptoms of C.diff infection?
diarrhoea without blood
abdo pain
pyrexia
what can c.diff infectons lead to?
toxic megacolon, malnutrition, perforated bowel
how is diagnosis for c.diff done?
stool testing for c.diff toxins
colonscopy
sigmoidoscopy
how do we manage c.diff?
stop taking antibiotics if possible probiotics isolate patient apecific anti-C.diff antimicrobials e.g. metronidazole/vancomycin/fidaxomicin oral rehydration therapy faecal transplants
what is bacterial overgrowth?
an abnormal increase in the overall bacterial population in the small intestine — particularly types of bacteria not commonly found in that part of the digestive tract (large intestine flora move backwards)
what are complications of bacterial overgrowth?
malnutrition anaemia osteoporosis vitamin deficiencies kidney stones
Outline the principle diagnostic test for bacterial overgrowth?
• hydrogen breath test -
These tests work by measuring levels of hydrogen and possibly methane in your breath. Your body will produce unusual levels of hydrogen if:
- You can’t properly break down lactose and fructose,in your small intestine.
- Small intestine bacteria overgrowth (SIBO).
how do you treat bacterial overgrowth?
treat the underlying condition
give rifaxamin
why do we give rifaxamin in bacterial overgrowth?
it kills gram negative bacteria but is only active in the small intestine where we should only have gram positive bacteria
which bacteria is autism associated with?
C. boltiae
which bacteria is asthma/atopy associated with?
clostridia and reduced bifidobacteria
which bacteria is obesity associated with?
actinobacteria and decreased bacteroides
what are pre-biotics? whats an example?
a source of food for your gut’s healthy bacteria. They’re carbs your body can’t digest e.g. raw dry chicory root
what are probiotics? what are eamples?
live microorganisms promoted with claims that they provide health benefits when consumed, generally by improving or restoring the gut flora.
e.g. kefire, kimchi, miso, soft aged cheeses
