Infectious diarrhoea Flashcards
What is gastro-enteritis?
accompanying features?
three or more loose stools/day
fever, vomiting, blood or mucus in stool, abdominal pain
What is dysentery?
large bowel inflammation, bloody stools
Epidemiology of gastro-enteritis
food poisoning organisms
poor storage procedure
travel related infections (salmonella)
person to person spread - norovirus
most common cause of intestinal disorders?
viruses - campylobacter
What pathogen causes the most hospital admissions for intestinal disturbances?
salmonella
Campylobacter is the most common ?
foodborne pathogen
Defences against enteric infection?
HYGEINE
stomach acidity - antacids and infection
normal gut flora - c.diff diarrhoea
immunity - HIV, salmonella
those on antacids?
no protection rom normal gastric acid, more at risk
Clinical features of diarrhoeal illness? (3) - give examples
Non-inflammatory/secretory - CHOLERA
Inflammatory.- SHIGELLA DYSENTRY
Mixed picture - TOXINS - c.diff
Features of Non-inflammatory diarrhoea?
frequent watery stools and little abdo pain, secretory toxin-mediated
- cholera - increases cAMP levels and Cl secretion
enterotoxigenic E. coli (travellers’ diarrhoea)
Non-inflammatory diarrhoea treatment ?
rehydration
Mechanism of diarrhoea in cholera?
Increased cAMP results
in loss of Cl from cells
along with Na and K
Osmotic effect leads to
massive loss of water from
the gut
Features of inflammatory diarrhoeal illness?
treatment?
frequent fluid stools, pain, fever
bacterial infection, amoebic dysentery
antimicrobials, rehydration
Assessing the patient
history - Symptoms and their duration
risk of food poisoning - travel history
asses hydration - postural BP, skin turgor, pulse
features of inflammation (SIRS) - FEVER , raised WBC
Assessing an infant?
sunken eyes and cheeks decreased skin turgor sunken fontelle few or no tears dry mouth or tongue
Fluid and electrolyte losses - when can this be severe?
what can you get? (2)
secretory diarrhoea
- Hyponatraemia due to sodium loss with fluid replacement by hypotonic solutions
- Hypokalaemia due to K loss in stool (40-80mmol/l of K in stools)
Assessing the patient - investigations
- stool culture +/- molecular or Ag testing
- blood culture
- renal function
- blood count - neutrophilia , haemolysis
- abdo x-ray
Differential diagnosis of gastroenteritis? (3)
Inflammatory bowel disease
Spurious diarrhoea -secondary to constipation
Carcinoma
Diarrhoea and fever can occur with ?
sepsis outside the gut
Treatment of gastro-enteritis?
rehydration - iv or oral (community)
- Oral rehydration with salt/sugar solution
- iv saline
Campylobacter gastroenteritis features ? (3-4)
- can have longer incubation > 7 days
- Stools negative within 6 weeks
- abdominal pain can be severe
- uncommon to be invasive
- Post-infection sequelae - Guillain-Barre syndrome, Reactive arthritis
Salmonella gastroenteritis features?
- symptom onset usually <48 hrs after exposure
- diarrhoea usually lasts <10 days
- <5% positive blood cultures
abscesses other places in body, Osteomyelitis
post infection - IB is common
Prolonged Salmonella gastroenteritis may be associated with?
gallstones
Routine Bacterial CultureCampylobacter - species that cause most infections?
isolated or outbreaks?
Two species cause most infections:
C. jejuni (90%)
C. coli (9%)
isolated
Routine Bacterial CultureSalmonella - the 2 species?
S.enterica and S.bongori
Most Common Salmonella Infections in UK?
Salmonella enteritidis and Salmonella typhimurium
often from abroad
What do – S. typhi and S. paratyphi cause?
enteric fever (typhoid and paratyphoid) and not gastro-enteritis
E.coli is an?
Infection. e.g. contaminated meat or person-to-person spread (low incoulum)
E.coli is characterised by
frequent bloody stools
fever
seizures
lethargy
What does E.coli O157 produce?
SHIGA TOXIN (same toxin also produced by Shigella spp) (previously called verocyto- toxin)
Difference between E.coli and the toxin?
E.coli stays in gut, toxin gets into the blood
When the E.coli toxin gets into the blood, what can happen?
hemolytic-uraemic (HUS) syndrome (haemolytic anaemia and renal failure)
What is hemolytic-uraemic (HUS) syndrome characterised by?
renal failure, haemolytic anaemia and thrombocytopenia.
E.coli patients need?
renal support
E.coli treatment - avoid ?
antibiotics
Toxin stimulates platelet activation which causes?
micro-angiopathy
What are the 4 species of Shigella
S. sonnei, S.flexneri, S.boydii, S. dysenteriae) – outbreaks of Shigella sonnei in children’s nurseries
several other forms of E. coli cause diarrhoea - name some
enteroinvasive
enteropathogenic
enterotoxic (traveller’s diarrhoea
Occasional causes of food poisoning outbreaks (3)
Staph aureus (toxin) Bacillus cereus (re-fried rice) Clostridium perfringens (undercooked meat/cooked food left out - toxin accumulates in spore formation)
When should I give antibiotics?
Campylobacterdrugs
salmonella drugs
main therapy - rehydration
- immunocompromised, positive blood cultures
severe sepsis or invasive infection
chronic illness e.g. malignancy
C = macrolines, clarithromycin S = ciprafloxin
When are antibiotics not indicated?
healthy patient with non-invasive infection
What does C.diff produce?
enterotoxin (A) and cytotoxin (B) (inflammatory)
Treatment of C.diff
metronidazole oral vancomycin - remains in gut Fidaxomicin (new and expensive) Stool transplants surgery may be required
In C.diff - a patient will often give a history of?
previous antibiotic treatment – the “4 C antibiotics”
C.diff ranges from
mild diarrhoea to severe colitis
CDI – prevention (5)
- Reduction in broad spectrum antibiotic prescribing
- Avoid 4 Cs – cephalosporins, co-amoxiclav, clindamycin, ciprofloxacin
- Antimicrobial Management Team (AMT) and local antibiotic policy
- Isolate symptomatic patients
- Wash hands between patients
CDI - Management
What are severity markers? (4)
Stop precipitating antibiotic (if possible)
- oral metronidazole if no severity markers
WCC>15
raised temp >38.5
acute rising creatinine
suspicion of toxic megacolon/colitis
Parasitology - request lab?
stools looked at under the microscope
parasites, cysts and ova please” or P, C and O
Uk parasites -protozoa 1
what is it called? what 2 forms?
symptoms?
transmitted by?
Treat with?
- Giardia duodenalis - cyst form - trophozoites
- diarrhoea, gas, malabsorption, failure to thrive, watery diarrhoea
- direct contact with cattle/cats/dogs/other people
food/water contaminated with faeces
with metronidazole
Trophozoites can be seen on
or string test
UK parasites - protozoa 2
symptoms?
exists in what 2 forms?
treatment?
Cryptosporidium parvum
cryptosoridosis - watery Diarrhoea, nausea and vomiting, abdo pain
oocysts , trophozoites
rehydration
Imported parasites - Entamoeba histolytica causes?
long term complication?
treatment?
would do antibody detection for?
amoebic dysentery (instestinal amoebiasis) cyst and trophozoite forms
amoebic liver abscess - when aspirated - brown colour, anchovy pus
metronidazole
to remove cysts- further treatment
- invasive disease
Viral Diarrhoea: Rotavirus, Norovirus, Adenovirus
Rotavirus - most common in children under 5 - vaccine at 8 and 12 weeks
What strains of adenovirus cause diarrhoea?
40 and 41
Viral Diarrhoea: Norovirus is also known as
type of virus?
Winter vomiting disease – diarrhoea and vomiting
- small round structured viruses (SRSV)
Diagnosis of Norovirus?
PCR
very infectious -18 virus particles (1g stool=5 billion infectious doses
