CP23 - Gastroenteritis Flashcards
what are facultative organisms?
those that can grow in both aerobic and anaerobic conditions
what are the benefits of gut flora?
metabolism
colonisation resistance for other bacteria
antibody induction eg. during allergies
what factors affect the flora present in the gut?
diet
breast/bottle feeding
what is the common flora found in the gut?
- bactericides
- prevotella
- Clostridia
- Bifidobacteria
- enterobacteriacea
- enterococci
why are a lot of GI diseases associated with travel?
putting your normal gut flora in a different environment and having them encounter different substances can cause problems
what are the common mechanisms through which bacteria cause gastroenteritis?
- endotoxin production
2. Adherence
which bacteria cause gastroenteritis by endotoxin production?
vibrio cholera - sporadic cases seen in returning travellers
E. coli
C. diff
Staph aureus - food poisoning
Bacillus cereus - spores can survive cooking. food poisoning can occur when meat cooked in advance and kept warm
C. perfringens
which bacteria cause gastroenteritis by adherence?
shigella Sonnei and shigella flexneri - bacillary dysentry
E. coli
Campylobacter jejune -undercooked meat, both toxin and adherence
salmonellae - food poisoning, typhoid, paratyphoid
what is bacillary dysentry?
infection of the intestines resulting in severe diarrhoea with the presence of blood and mucous in the faeces
what is typhoid?
an infectious bacterial fever with an eruption of red spots on the chest and abdomen and severe intestinal irritation
what is paratyphoid?
a fever resembling typhoid but caused by different but related bacteria
what are the parasitic causes of gastroenteritis?
entamoeba
G. lambia
cryptosporidium
what are the viral causes of gastroenteritis?
norovirus
rotavirus
what is the epidemiology of gastroenteritis?
food borne diseases have reduced while non food borne diseases have increases in prevalence
how does gastroenteritis present?
acute onset
D&V - ask for frequency, mucous, blood
abdo pain
systemic effects - fever etc.
other complications - dehydration, renal failure, haemolytic uraemia syndrome, toxic megacolon, Guillain-Barre syndrome, salmonella
what facts are important to ask for if gastroenteritis is suspected?
travel history food history any unwell people they may be in contact with immunotherapy blood in stool
how long does a GI infection last for in an otherwise healthy patient?
24 hours
what investigations need to be done if a GI infection is suspected?
bloods - FBC, U&Es, CRP, cultures - only for disseminated infections
creatinine - a marker of infection
AXR if severe
assess stool for ova, parasites and cysts, microscopy
what is viral gastroenteritis also called?
winter vomiting disease - caused by norovirus. common
what are the symptoms of viral gastroenteritis?
diarrhoea, projectile vomiting
how long does viral gastroenteritis last?
24-48 hours
how is viral gastroenteritis usually managed?
no specific treatment infection allowed to follow its course lots of water to prevent dehydration good hygiene to prevent spread it is rarely dangerous
what is cryptosporidiosis?
cryptosporidium infection
predominantly waterborne, because oocysts are resistant to chlorine based disinfectants like those found in swimming pools
what are the effects of cryptosporidiosis on the body?
watery diarrhoea, mild to severe disease. most commonly in young children
no specific treatment
what is the main virulence factor of E. coli?
shiga toxin
what are the effects of shiga toxin?
premature destruction of RBCs, and these can then clog kidneys, causing haemolytic-uraemia syndrome
what is the main species that produces shiga toxin?
shigella
what is the mechanism of shiga toxin action?
- activates g protein leading to increased levels of cAMP
- activates ion channels
- cells over-excrete chloride ions
- water follows ions out of cells into the bowel
- this can be up to 6L a day, rapid dehydration results
what is the direct result of efflux of K or Cl ions from cells?
diarrhoea
what are the 2 types of salmonella?
typhoidal - can disseminate
non-typhoidal - cannot disseminate
how is gastroenteritis treated?
- supportive management
- avoid antibiotics, because they may increase the duration of salmonella carriage or may worsen HUS caused by E. coli
- point 2 to be ignored if patient is at an extreme age, if the infection is caused by campylobacter
or if the patient becomes septic
what is antibiotic diarrhoea?
diarrhoea cause due to disruption of gut flora by antibiotics
symptoms could range from mild diarrhoea to pseudomembranous colitis (toxic megacolon, perforation, shock)
c diff infection can cause pseudomembranous colitis plaques
what are the risk factors for c diff diarrhoea?
old age and primary illness
which antibiotics put you at a high risk for C diff?
generally, the broader the spectrum,the greater the risk
cephalosporins
clindamycin
which antibiotics put you at a medium risk of c diff?
ampicillin amoxicillin co-trimoxazole macrolides fluoroquinolones
which antibiotics put you at a low risk of c diff?
ahminoglycosides metronidazole anti-psudomonal penicillins tetracyclines rifampicin vancomycin
how are c diff infections treated?
antibiotics - oral metronidazole or vancomycin
faecal transplant - either faecal or oral route
what are the benefits of faecal transplants?
c diff cycle is broken by repairing the problems with the gut flora
increasing the diversity of the microflora in the patient’s gut
