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GASTROINTESTINAL INFECTIONS - Coggle Diagram
GASTROINTESTINAL INFECTIONS
Viral diarrhoea
most common cause of diarrheal disease
Most commonly Norovirus
transmitted by stool or vomit, or aerosol/person-person
self-limiting
recovery without intervention
more likely if there is contact history or no fever
Bacterial diarrhoea
Suspect when severe, in returned travellers, bloody diarrhoea, fevers
Toxin-mediated
: shorter incubation period, N/V, abdominal pain
C. difficile
antibiotic-associated
hypervirulent strain (ribotype 27/28)
toxin A: disrupts colonic mucosal cell adherence
diarrhoea, abdominal pain and sometimes pseudomembranous colitis
toxin B: associated with apoptosis
cephalosporins, quinolones, lincosamide, hospitalisation, chemotherapy, use of PPIs (due to reduction of gastric acid)
diagnosis by toxic detection in stool (can remain positive for weeks)
PCR most sensitive
if PCR positive, do EIA to detect toxins (stays positive even after treatment complete)
1st line: metronidazole
2nd line: vancomycin (only disease where oral is indicated since it is almost not absorbed by gut)
3rd line: fidaxomicin
faecal transplant
Shigella
most common cause of bloody diarrhoea (esp. in children)
toxin-mediated (enterotoxic, cytotoxic and neurotoxic)
incubation period usually with 3 days
bloody diarrhoea, high fever, abdominal pain, malaise
destructive to colonic epithelium (invasion and apoptosis)
complications
haemolytic-uraemic syndrome: haemolysis and renal failure (esp. in children)
intestinal obstruction
arthritis (those with HLA B27 gene)
seizures
diagnosis: stool culture or PCR detection
hydration, electrolyte replacement, antibiotics (ceftriaxone) for severe/immunocompromised
high rates of antibiotic resistance - susceptibility testing
Non-toxin mediated
: longer incubation period
enterohaemorrhagic E. coli
common in outbreaks (undercooked meat)
Shiga-like toxin
incubation period 3-9 days
bloody diarrhoea, abdominal pain, no/low grade fever
avoid antibiotics (may precipitate haemolytic-uraemic syndrome) and fluid resuscitation
enteropathogenic and enteroaggregative E. coli cause less severe but persistent diarrhoea
Campylobacter
most common cause of bacterial diarrhoea
oral transmission (contaminated water/meat)
severe abdominal pain, fever
complications: Guillain-Barre syndrome, reactive arthritis
self-limiting if mild disease
azithromycin or ciprofloxacin if severe
vibrio cholera
associated with poor sanitation and outbreaks (floods, war)
rice water diarrhoea
aggressive rehydration and azithromycin, vaccine also available
Salmonella
non-typhoid Salmonella
food-borne (poultry, eggs, milk)
rehydration (antibiotics usually not indicated)
enteric fever (typhoid)
caused by typhoidal Salmonella enterica subspecies enterica serovar Typhi/Paratyphi - Salmonella typhi and paratyphi
gram negative bacilli
mostly in SE Asia
transmission by food/water (rarely human-human)
incubation period 8-14 days (shed for 5-6 weeks)
invades GI epithelium
enlarged lymph nodes, mononuclear cell infiltration
can lead to intestinal or gallbladder perforation
hygiene, clean water, vaccine
fluoroquinoles, macrolides, ceftriaxone
susceptibility testing
fever, abdominal pain, myalgia, diarrhoea, coated tongue
blood culture (diagnosis), stool culture, serology, leukocytosis, deranged LFTs
Parasites
Giardia lamblia
most common parasite)
faecal-oral spread, contaminated water/uncooked food, human-human
symptom onset 1-3 weeks after ingestion
diarrhoea, steatorrhoea, flatulence, abdominal cramps, nausea
tinidazole (single dose) and metronidazole (3 days)
Entamoeba histolytica
intestinal and extraintestinal protozoa mostly found in tropical regions
faecal-oral, contaminated water
asymptomatic, diarrhoea, abdominal pain
amebic dysentery (bloody stools, fever) or liver abscess
travel, institutionalised, MSM
diagnosis by stool OCP, PCR or serology
tinidazole and metronidazole
Nematodes
classical roundworms
more common where sanitation/hygiene compromised
can affect growth/development in children
Strongyloides stercoralis
soil-transmitted helminth (ubiquitous in soil; tropical regions)
larvae penetrate skin
walking barefoot
asymptomatic, local rash
if immunocompromised or superimposed bacterial infection, disseminated infection can be fatal
serology and stool OCP
ivermectin (oral)
Ascaris lumbricoides
soil-transmitted helminth
most common global worm-related infection
albendazole
Hookworm
soil-transmitted helminth
walking barefoot
lives in small intestine
usually asymptomatic, but can cause major anaemia
Whipworm
(trichuris trichuria)
found in humid climates
humans usually ingest eggs in unwashed vegetables
usually asymptomatic but can cause severe infection
Pinworm
(Enterobius vermicularis)
much smaller worms
usually in children (daycare centres)
treatment for worms usually albendazole or mebendazole