Introduction to infection and diarrhoea Flashcards
2 diagnostic features for gastroenteritis
more than 3 loose stools a day
accompanying features
2 main causes of dysentery
shigella or entamoeba histolytica
Clinical features of dysentery
large bowel inflammation and bloody stools
Does gastroenteritis need a microbiological diagnosis?
No
What chart can you use to rate the consistencies of stools and what are the numbers in this?
Bristol stool chart
1-7
4 main epidemiologies of gastroenteritis
contaminated foodstuff
poor storage of produce
travel related infections
person to person spread
Why is salmonella rare in UK?
vaccinate hens
Commonest bacterial pathogen in gastroenteritis
campylobacter
Commonest pathogen of gastroenteritis?
viral
Most common pathogen for food poisoning
campylobacter
Pathogen causing most hospital admissions in food poisoning
salmonella
Commonest source of food poisoning
poultry meat - undercooked
spike in summer with BBQ
4 main defences against enteric infections
hygiene
stomach acid
normal flora
immunity
Type of salmonella in HIV
invasive non typhoidal
3 categories of diarrhoeal illness
non inflammatory/secretory
inflammatory
mixed picture
Example of secretory diarrhoea
cholera
Example of inflammatory diarrhoea
shigella dysentery
Example of mixed picture diarrhoea
C. diff
Effects of secretory toxin
increase cAMP and chloride, sodium, potassium and water loss
Travellers diarrhoea cause
enterotoxigenic E.coli
Clinical features of secretory diarrhoea
frequent watery stool
little abdominal pain
treating secretory diarrhoea
rehydration
Pathogenesis of inflammatory diarrhoea
inflammatory toxin damage
mucosal destruction
Clinical features of inflammatory diarrhoea
pain and fever
2 main pathogens of inflammatory diarrhoea
bacterial
amoebic dysentery - parasite
Treating inflammatory diarrhoea
antimicrobials may be appropriate
mainstay treatment still rehydration
Duration of diarrhoea - when is it unlikely to be infective gastroenteritis ?
longer than 2 weeks
3 ways to assess hydration
postural bp
skin turgor
pulse
3 main risks in history for food poisoning
dietary
travel
contact
SIRS features of inflammation
fever, raised WCC, increase RR, increase HR
Assessing a child for dehydration
sunken eyes and cheeks dry tongue and mouth sunken fontanelles decreased skin turgor few or no tears
What type of diarrhoea is fluid and electrolyte loss severe?
secretory
In secretory diarrhoea why is the patient hypokalaemic and hyponatraemic?
replace salt with hypotonic solution
lose potassium in stool
5 main investigations in infective gastroenteritis
3 stool cultures blood culture renal function blood count - haemolysis and neutrophilia abdominal X-ray if distended
3 differential diagnoses for diarrhoea
IBD
carcinoma
spurious - secondary to constipation
2 clues the diarrhoea and fever is occurring with sepsis outwith the gut?
lack of abdominal pain/tenderness
no blood or mucus In stools
Treating gastroenteritis main treatment and how this can be done
rehydration - oral or IV?
ORHT? - salt and sugar solution
iv saline
incubation of campylobacter
up to 7 days
When are stools negative in campylobacter?
6 weeks
2 post infective sequalae of campylobacter gastroenteritis
Guillian barre syndrome
reactive arthritis
How to do a routine bacterial culture
variety of media and incubation conditions
takes 3 days
Is campylobacter associated with sporadic or outbreaks?
sporadic
Time of symptom onset of salmonella gastroenteritis
48 hours or more
What percent of people still have positive stools for salmonella after 20 weeks?
20%
association with chronic salmonella gastroenteritis?
gallstones
What is a common post infectious condition after slamonella gastroenteritis?
IBS
What is the basis of how salmonella is cultured?
lactose non fermenter
Tests following the lactose non fermenter tests of salmonella
antigen and biochemical tests
What species are most salmonella genetically serotypes of?
salmonella enterica
How are salmonella strains named?
after place of isolation
2 commonest salmonella isolates in UK
enteritidis
typhimurium
What do salmonella typhi and paratyphi cause and not cause?
cause paratyphoid and typhoid fever
do not cause gastroenteritis
How is Ecoli O157 spread?
contaminated meat
low inoculum person to person spread
What toxin does Ecoli produce?
(verocyto)toxin
Clinical symptom of Ecoli O157
frequent bloody stool
Does Ecoli O157 or the toxin get into the blood?
toxin
What can Ecoli O157 toxin cause?
Haemolytic uraemic syndrome
3 ways HUS is characterised
renal failure
haemolytic anaemia
thrombocytopenia
Thrombocytopenia
low platelet count
Treatment of Ecoli O157
supportive - not antibiotics
Where has there been outbreaks of shigella sonnei?
nurseries
What Ecoli strain is the only one easily distinguishable?
Ecoli O157
3 pathogens of food poisoning outbreaks
staph aureus
bacillus cereus
clostridium perfingens
5 occasions when antibiotics are used in gastroenteritis
immunocompromised severe sepsis or invasive infection valvular heart disease chronic illness diabetes
The 4 C antibiotics in c diff
ciprofloxacin
co-amoxiclav
cephalosporin
clindamycin
Range of severity of c diff
mild diarrhoea –> pseudomembranous colitis
What 2 toxins does c diff make and which drives inflammation?
enterotoxin - A
cytotoxin - B - inflammation
5 treatments of c diff
metronidazole oral Vancomycin fidaxomicin stool transplants surgery? - also stop precipitating antibiotics
4 ways to prevent c diff infection
reduce use of broad spectrum antibiotics
avoid 4C antibiotics
antimicrobial management team and local policy
hand washing
2 parasites
protozoa
helminths
How are parasite infections diagnosed?
microscopy - parasites, cysts, ova
Vegetative form and cyst form of giardia lamlia found how?
duodenal biopsy
string test
Stool microscopy for cysts
Treatment of giardia lamlia
metronidazole
Where are most UK parasites found?
contaminated water
What does entamoeba histolytica cause?
amoebic dysentery
What is found in a symptomatic and asymptomatic patient with amoebic dysentery
symptomatic - vegetative form - hot stool
asymptomatic - cysts
Long term complication of amoebic dysentery
amoebic liver abscess - Anchovy pus
Treatment of amoebic dysentery
metronidazole
Viral diarrhoea in children under 5 pathogen
rotavirus
How is viral diarrhoea diagnosed?
antigen detection
What vaccine for viral diarrhoea is available?
rotavirus
Norovirus is a common cause of what? where is it found?
oubreaks of winter vomiting disease
cruise ships, hospital, community
Diagnoses of norovirus
PCR
Is norovirus infectious?
yes very only need 18 particles
often close wards
strict infection control
