Infectious Diarrhoea Flashcards
define diarrhoea
subjective
fluid and frequent stools
define gastroenteritis
objective
3 or more loose stools per days and companying features
define dysentery
obvious with large bowel inflammation and bloody stools
what may cause gastroenteritis?
contaminated food e.g. chicken and campylobacter
poor storage of produce
travel related e.g. salmonella
person to person spread - norovirus
what is the most common foodborne pathogen?
campylobacter
what is the pathogen linked to the most hospital admissions?
salmonella
commonest organisms causing gastroenteritis in scotland (3)
campylobacter
salmonella
e. coli O157
what defences do we have against enteric infections?
hygiene
stomach acid
normal flora
immunity
clinical features of non-inflammatory/secretory diarrhoea
secretory toxin mediated
frequent watery stools with little abdo pain
rehydration
example of non-inflammatory/secretory diarrhoea
cholera
enterotoxigenic e. coli ETEC
mechanism of diarrhoea in cholera
increased cAMP levels and Cl secretion
example of inflammatory diarrhoea
shigella
dysentery
clinical features of inflammatory diarrhoea
inflammatory toxin damage and mucosal destruction causing pain and fever
bacterial infection/amoebic dystenery
antimicrobials may be appropriate but rehydration alone often enough
what may cause mixed non-inflammatory and inflammatory diarrhoea
C. diff
assessing a patient with diarrhoea
symptoms and duration
risk of food poisoning
assess hydration
features of inflammation
it is unlikely to be infective gastroenteritis if it lasts longer than?
2/52
fluid and electrolyte losses in diarrhoea
These can be severe with secretory diarrhoea – 1-7l/day containing 80-100 mmol Na. Hyponatraemia
due to sodium loss with fluid replacement by hypotonic solutions. Hypokalaemia due to K loss in stool
(40-80mmol/l).
investigations in diarrhoea
stool culture blood culture renal function blood count - neutrophilia, haemolysis AXR if abdomen distended and tender
differential diagnosis for infective diarrhoea
IBD
spurious diarrhoea secondary to constipation
carcinoma
diarrhoea and fever can occur with sepsis outside the gut. what make this more likely?
lack of abdo pain and tenderness goes against gastroenteritis
no blood or mucus in stool
treatment of infective diarrhoea
rehydration
oral with salt/sugar
iv saline
incubation period of campylobacter
7 days
when will stool samples be negative for campylobacter?
6 weeks
severity of abdo pain in campylobacter
severe
post infection sequelae of campylobacter
Guillain-Barre syndrome
Reactive arthritis
what makes it difficult to find a pathogen in stool cultures?
normal flora
how long does it take to complete all tests in a stool culture?
3 days
common strains of campylobacter
c. jejuni
c. coli
how long after exposure do symptoms of salmonella develop?
<48 hrs
how long does diarrhoea in salmonella gastroenteritis last?
<10days
20% of patients with salmonella gastroenteritis will still have +ve stools after how long?
20/52
what is prolonged carriage of salmonella associated with?
gallstones
what condition is common after salmonella gastroenteritis?
post-infectious irritable bowel
culturing salmonella
- Screened out as lactose non-fermenters then antigen and biochemical tests
- Thousands of species with individual names
- Genetically most are serotypes of the same species – salmonella enterica
what salmonella species cause enteric fever and not gastroenteritis?
s. typhi and s. paratyphi
how is e. coli O157 spread?
contaminated meat
person to person
typical illness in e. coli O157
frequent bloody stools
what does e. coli O157 produce?
verocyto toxin
e. coli stays in the gut, where does the toxin go?
blood
the e. coli O157 toxin can cause?
haemolytic uraemic syndrome
what is HUS? and how to treat
characterised by renal failure, haemolytic anaemia and thrombocytopenia
o Treatment supportive no antibiotics
o Toxin binds to globotriaosylceramide
o Platelet activation stimulated
o Micro-angiopathy results
o Attach to endothelial glomerular tubule and mesangial cells
what other bacteria may cause diarrhoea?
shigella other forms of ecoli: enteropathogenic, enterotoxic, enteroinvasive staph aureus bacillus cereus clostridium perfringens
when are antibiotics indicated for gastroenteritis?
immunocopromised severe sepsis or invasive infection valvular heart disease chronic illness diabetes
clostridium difficile infection is commonly associated with what antibiotics?
clindamycin
cephalosporins
co-amoxiclav
ciprofloxacin
severity of diarrhoea in clostridium difficile
mild to severe colitis
what does clostridium difficile produce?
enterotoxin and cytotoxin
treatment of clostridium difficile
metronidazole oral vancomycin fidaxomicin stool transplant surgery
prevention of clostridium difficile
reduce broad spectrum
isolate symptomatic patients
wash hands
what parasites may cause diarrhoea?
protoza and helmonths
giardia lamblia
cryptosporidium parvum
entamoeba histolytica
parasite diarrhoea diagnosis
generally by microscopy
where is girardia lamblia found?
contaminated water
what does girardia lamblia cause?
diarrhoea, malabsorption, failure to thrive
where may a vegetive form of girardia lamblia be found?
duodenal bioposy
what is seen on stool microscopy of girardia lamblia?
cysts
treatment of girardia lamblia
metronidazole
where is cryptosporidium parvum found?
contaminated water - animal faeces
what is seen on stool microscopy of cryptosporidium parvum?
cysts
treatment of cryptosporidium parvum
none
entamoeba histolytica causes?
amoebic dysentery
long term complication of entamoeba histolytica
amoebic liver abscess - anchovy pus
treatment of entamoeba histolytica
metronidazole
causes of viral diarrhoea
adenovirus
norovirus
rotavirus
most common cause of viral diarrhoea in children under 5
rotavirus
how is viral diarrhoea diagnosed?
antigen detection
when is viral diarrhoea most common?
winter
where does norovirus commonly cause outbreaks?
hospital
community
cruise ships
diagnosis of norovirus
PRCR
