5- gastrointestinal bacteria Flashcards
what is normal flora?
- more bugs than human cells
- they colonise us (they’re there but not causing problems) →not all bugs abnormal
what does body do to keep bugs in right places?
natural defences like acidity in stomach, mucous & coughing etc
what areas of body don’t have any colonisers?
blood is sterile & cerebral fluid is sterile = should have no bugs
what is colonisation?
the establishment of a microorganism on or within a host; it may be short lived
what is a pathogen?
any microorganism that has potential to cause disease
what is virulence?
likelihood of causing disease
what is involved in diagnosing infection?
- history (notice patterns, generating differential diagnosis)
- examination (review differential diagnosis)
- investigations (radiological, biochemistry, immunology etc)
review differential diagnoses even further →microbiology (stool, urine, wound, tissue cultures)
microscopy - stool, urine, CSF, sputum, pus
serology
is immunosuppression same for each disease?
depleted phagocytes - bacteria problem
depleted T lymphocytes = bacteria but also sometimes funghi & protozoa) problem
→not all infections the same
what are important bacterial of GI causing diarrhoea?
- Salmonella
- Shigella
- Campylobacter
- enterotoxigenic Escherichia coli (ETEC), enterohemorrhagic Escherichia coli (with Shiga toxin)
- Clostridioides difficile
when do you give antibiotics for these?
very very rarely - most self limiting so only give when very severe or prolonged
what are main risk factors for general bacterial diarrhoea?
- raw milk (unpasteurised food)
- raw/undercooked food
- contaminated/untreated water contact
- childcare/healthcare/long term care/prison
- animal/animal excreta contact
what is campylobacter? (transmission, symptoms, some facts etc)
transmission = undercooked poultry - faecal oral transmission (can be person to person)
symptoms = diarrhoea, cramps, dysentery
- loves 37-41 degrees so lives happily in birds so when eat birds you contaminate yourself
- self limiting so no antibiotics until severe
- gram negative spiral shaped
what are risk factors for campylobacter?
- travel
- acid inhibitor = acid in body good for killing bugs
- undercooked poultry
what are complications of campylobacter?
- Guillan-Barre
- reactive arthritis
- irritable bowel
what is salmonella? (types, transmission, symptoms, facts etc)
main type = salmonella enterica (typhoidal is different type more in foreign countries)
transmission = foodborne - travel, eggs, dairy, reptiles, pet food
symptoms = blood diarrhoea (watery diarrhoea first)
- gram negative rod = can culture & PCR
what are risk for salmonella?
- contaminated food or water
- exposure to infected animals
- not washing hands
- eating raw or undercooked
who is at risk for salmonella?
- low stomach acid
- change in GI flora
- renal failure
- younger than 1 or older than 50
- immunosuppressed
- haemoglobinopathies
what are complications of salmonella for immunosuppressed people?
endocarditis, aortitis, bone and joint, visceral infections, meningitis
what bugs give dysentery?
shigella, e.coli, salmonella, campylobacter
what is e.coli? (transmission, symptoms and facts etc)
e.coli lives happily in gut but can also some types cause problems
- enterohaemorrhagic e.coli (EHEC) which produces shiga toxin and is food borne especially mince
- e.coli 0157 →risk factor of petting zoo/contact with animals or undercooked beef/pork etc
what is listeria? (transmission, symptoms and facts etc)
favourite fridge temp = 0-5 degrees
(why pregnant people avoid soft cheeses and cold counter food, unpasteurised milk)
symptoms = diarrhoea, also causes meningitis & bacteraemia
- gram positive rod
what are reasons for careful choice for antibiotics?
- Clostridioides difficile
- Haemolytic uraemic syndrome (destruction of red blood cells, kidney failure, and low platelet count triggered by e.coli)
what are important infections in abdomen i should know?
- Peritonitis (primary = bugs in ascites and secondary = peritoneum burst and full of poo with bugs)
- (Hepatitis), liver abscess
- Cholecystitis , cholangitis
- (Gastroenteritis) abscesses
- Perineal abscesses
what are antibiotics that work for gram negatives?
- aminoglycosides
- co-trimoxazole
what are abscess infections and how do you treat?
abscesses = no blood supply so antibiotics don’t penetrate well so pus must be removed (mostly surgery)
- small ones can be treated with antibiotics but large needs to be drained
is your worried about coliforms, anaerobes and enterococcus from colon burst in periotneum - what antibiotics should be given?
gentamicin (coliforms), metronidazole (anaerobes), amoxicillin (enterococcus)
what are enterobacteriaceae?
coliforms
- 53 genera (26 cause human infection)
- Gram negative
- Non spore forming
- Grow on a variety of solid media
- increasing resistance
what are gram negatives virulence factors?
- motility = flagella allows movement (shigella & klebsiella not mobile)
- colonisation factors = fimbriae (shorter than flagella but bind tight to tissue)
- endotoxin = cell wall component
- enterotoxin = e.g. shiga toxin
what bug hint is undercooked poultry?
campylobacter
what bug hint is reptiles?
salmonella
what bug hint is fridge temp?
listeria
what bug hint is travellers diarrhoea?
e.coli
what bug hint is sexually transmitted?
shigella
what bug hint is winter time, crowded setting?
norovirus
what bug hint is rapid onset vomiting, toxin?
staph aureus
what bug hint is reheated rice?
bacillus cereus
