Food and waterborne illness

Pathophysiology

• Pre-formed toxin
  • S. aureus, B. cereus, C. bolutinum
  • Rapid onset of symptoms (1-6 hours)
• Toxin produced after ingestion
  • Vibrio, Shigella, Shiga-toxin E. coli
  • Diarrhoea and lower GI symptoms from 24 hours after exposure
  • Can cause death of epithelium (shiga-toxin and Shigella) or massive fluid shifts (Vibrio and enterotoxigenic E. coli)
• Direct invasion of epithelium
  • Enteric viruses, Salmonella, enteroinvasive E. coli and Campylobacter
  • Diarrhoea due to transient malabsorption and systemic features

Incubation periods

Clinical features

• Suspicion: Recent ingestions, restaurants, street foods, seafood, raw food
• Recent travel or camping, contact with food handlers
• Dominant vomiting: Norovirus, Rotavirus, Astrovirus, S. aureus, B. cereus
• Water, non-bloody diarrhoea: ETEC, Giardia, V. cholerae, enteric viruses, Cryptosporidium, Cyclospora
• Bloody diarrhoea: Shigella, Campylobacter, Salmonella, EIEC, Shiga-toxin E. coli (0157:H7 and non-O157:H7), V. parahaemolyticus, Yersinia, Entamoeba
• Persistent diarrhoea> 14 days: Giardia, Cyclospora, Entamoeba, Cryptosporidium
• Neurological signs: C. botulinum, Scromboid, Ciguatoxin, tetrodotoxin, toxic mushroom, GBS
• Systemic illness: Listeria monocytogenes, Brucella, Salmonella typhi, Salmonella paratyphi, Vibrio vulnificus, HepA/E

Diagnosis

• Routine stool testing is not indicated
• FBC, U&E recommended if toxic or prolonged symptoms

Diagnosis

• Stool tests indicated:
  • Water diarrhoea with signs of hypovolaemia
  • Bloody diarrhoea
  • Fever >38.5
  • >1 week
  • Severe abdominal pain or tenderness
  • Hospitalised
  • Recent antibiotic use: C. difficile Toxin + PCR
  • Recent travel: S. typhi, Paratyphi A, B, C specifically
  • >70yo or immunosuppressed
  • Pregnant women
  • Infants
  • IBD

Diagnosis

• Routine stool culture
  • Will identify non-typhoidal Salmonella, Campylobacter and Shigella
• Ova and parasites
  • Indicated for immunocompromised, >2 weeks, community waterborne outbreaks, MSM
  • May need 3 specimens spaced out by 24 hours each to identify parasite due to intermittent shedding
  • Does not test for Cryptosporidium or microsporidia as need to request separately
• Faecal leukocytes not sensitive or specific for invasive disease
• C. diff toxins EIA + PCR
• Multiplex PCR simultaneously screens for multiple viruses/bacteria/parasites but subsequent culture is required for suspectibility testing and public health utility

Empirical antibiotic therapy

• Indicated if severe disease: High fever, tachycardia, leucocytosis, abdominal tenderness, severe abdo pain, high-volume diarrhoea, blood in stool OR immunocompromised OR >1 week of symptoms
• Ciprofloxacin 500mg BD for 3 days
• If recently hospitalised for >48 hours: Need empirical C. difficile therapy
• Antibiotics and antimotility agents are contraindicated in patients with Shiga toxin-producing E. coli 0157:H7 due to increased risk of HUS (especially children and elderly)

EHEC and 0157:H7

• Severe bloody diarrhoea
• Lasts 5-10 days
• From undercooked beef, unpasteurised milk, juices, raw fruit and veges
• Stool culture or toxin assay
• Supportive
• Avoid antibiotics as risk of HUS (especially in children)

ETEC

• Watery diarrhoea, vomiting
• Lasts 3-7 days
• Water or food contaminated with human faeces
• Stool culture

Listeria

• Fever, myalgias, nausea, diarrhoea, premature delivery if pregnant
• Fresh soft cheeses, poorly pasteurised dairy, deli meats, hot dogs
• Blood or CSF culture
• Listeriolysin O antibody assay
• Treatment: Ampicillin or Bactrim

Campylobacter

• Usually self-limited but antibiotics indicated if severe, prolonged, immunocompromised, third trimester pregnancy, frail
• Often bloody diarrhoea
• Lasts 2-10 days
• Raw poultry, unpasteurised milk or contaminated water
• Diagnosed on routine stool culture
• Azithromycin 500mg orally for 3 days OR
• Ciprofloxacin 500mg BD for 3 days

Salmonella

• Antibiotic therapy of mild cases of non-typhoidal Salmonella prolongs excretion of pathogenic organisms and does not improve outcomes
• Identified on routine stool culture
• Antibiotics indicated if:
  • Neonates <3 mo
  • 3-12 mo and toxic
  • >65yo
  • Severe illness, prosthetic vascular grafts, haemoglobinopathies
  • Immunocompromise
• Azithromycin 1g PO then 500mg daily for 6 days OR Cipro 500mg BD for 5-7 days

Shigella

• Highly infectious so treatment recommended for public health reasons in:
  • Children <6yo
  • Institutionalised
  • MSM
  • Immunosuppressed
  • Food handlers and healthcare workers
  • Severe disease
• Identified on routine stool culture
• Ciprofloxacin 500mg BD for 5 days

Cholera

• Profuse watery diarrhoea, vomiting
• Lasts 3-7 days
• From contaminated water, fish, shellfish, street food
• Specifically ordered stool culture
• Azithromycin 1g PO stat or Cipro 1g PO stat

Non-cholera Vibrio

• V. parahaemolyticus usually from shellfish
• Water diarrhoea, cramping, vomiting
• Lasts 2-5 days
• Special stool culture
• Usually self-limiting but if severe: Doxycycline 100mg BD for 10 days

Yersinia

• Can cause acute enterocolitis, pharyngitis and mesenteric adenitis
• = Pseudoappendicitis
• Post-infectious arthalgia and erythema nodosum can occur
• Typically undercooked pork, tofu
• For severe, immunocompromised or extraintestinal disease:
  • Cipro 500mg BD for 5 days

Rotavirus

• Becoming less common since routine vaccination
• First episode (usually in infancy) is the most severe
• Incubation 1-3 days then vomiting and fever for 3 days and diarrhoea for 4-5 days
• Supportive rehydration is key

Norovirus

• Most common cause of gastroenteritis in adults and children
• 24-48 hour incubation
• Symptoms last 48-72 hours
• Vomiting then watery diarrhoea
• Sudden onset projectile is characteristic
• Norovirus outbreak likely if meeting all Kaplan criteria:
  • Average duration 12-60 hours
  • Average incubation 24-48 hours
  • >50% of patients report vomiting
  • No bacterial pathogen identified

Adenovirus

• Mostly serovars 40 and 41 in young children
• Fever, vomiting and diarrhoea

Astrovirus

• Childhood diarrhoeal illness
• Milder version of rotavirus
• Vomiting rare
• Faecal testing does not identify this

Bacillus cereus

• Preformed toxin
  • Sudden onset nausea, vomiting +- diarrhoea
  • Lasts 24 hours
• Diarrhoeal toxin
  • Watery diarrhoea, cramping, nausea
  • Lasts 1-2 days
  • Meats, gravies, vanilla sauce

Brucella

• Fever, chill, myalgias, arthralgias, weakness, bloody diarrhoea
• Can last weeks
• From raw milk, unpasteurised cheese or contaminated meat
• Diagnosed on serology or stool culture

Clostridium botulinum

• Preformed toxin
  • Vomiting, diarrhoea, blurred vision, dysphagia, descending paralysis
  • Hyporeflexia and fixed dilated pupils!!
  • Lasts days to months
  • Poorly canned foods, canned fish, herbed oils
  • Diagnosed on stool or serum toxin testing or stool culture
  • Supportive care and botulinum antitoxin
• Infants
  • Seen in infants <12mo with lethargy, weakness, poor suck
  • From honey and corn syrup
  • Botulism Ig

Staph aureus

• Preformed toxin
  • Sudden onset severe nausea, vomiting, diarrhoea, fever
  • Improperly refridgerated meats, potato or egg salad, left out pastries

Hepatitis A

• Diarrhoea, jaundice, dark urine, flulike illness, abdominal pain
• 2wk to 3 months duration
• From shellfish, raw produce, contaminated water or infected contacts

Cryptosporidium

• Watery diarrhoea, cramping, fever
• Weeks to months duration – often relapsing
• Usually self-limiting
• Nitazoxanide

Cyclospora

• Resembles cryptosporidium
• Treated with bactrim
• Continue secondary prophylaxis if HIV infected and CD4 <200

Dientamoeba fragilis and Blastocystic hominis

• Most patients do not benefit from treatment
• Consider metronidazole therapy in concert with gastroenterologist if no other cause for symptoms identified

Entamoeba histolytica

• Treatment of asymptomatic carriage recommended to prevent invasive disease and spread
  • Paromomycin
• Invasive amoebiasis
  • Tinidazole or metronidazole

Giardiasis

• Most common protozoal cause of chronic diarrhoea
• If symptomatic
  • Tinidazole or metronidazole

Isospora belli

• Self-limiting gastroenteritis
• Chronic diarrhoea if immunocompromised
• Treat with bactrim

Microsporidia

• Self-limiting diarrhoea
• Chronic diarrhoea in the immunocompromised

Antibiotic-associated diarrhoea

• Usually no pathogen identified
• C. difficile is found in the minority
• Discontinue antibiotics if able
• Large RCT of probiotics failed to show benefit
• C. difficile
  • Causes the most severe form of antibiotic-associated diarrhoea
  • Can occur anytime after a course of Ab’s
  • Use of PPI’s is also a risk factor
  • Cephalosporins, quinolones and lincosamides most commonly identified
  • Diagnosis
    • Colonoscopy or histopathology showing pseudomembraneous colitis OR
    • Identification of organism or toxin in patient with symptoms and no other cause

Antibiotic-associated diarrhoea

• Identifying C. difficile
  • C. diff glutamate dehydrogenase (GDH) sensitive but not specific
  • C. diff culture of limited value
• Identifying C. diff toxin
  • Cell cytotoxicity neutralisation assay (CCNA) slow but sensitive and specific
  • Toxigenic culture is slow but sensitive and specific
  • Enzyme immunoassays for toxins A and B highly specific but low sensitivity (should not be used alone)
  • NAAT for toxins highly specific and sensitive
• Testing must be performed on unformed stools only
• Do not repeat testing during same episode of diarrhoea or for test of cure
• Asymptomatic colonisation is common under 2yo

Antibiotic-associated diarrhoea

• Treatment
  • Discontinue antibiotics if able
  • Mild-moderate: Metronidazole 400mg PO TDS for 10 days
    • Can use IV if not tolerated orally
  • Severe disease (WCC > 15, severe abdo pain, elevated creatinine, raised lactate, low serum albumin, high fever, organ dysfunction)
    • Vancomycin PO 125mg q6h for 10 days
    • Add metronidazole 500mg IV q8h if in shock, ileus or megacolon
    • May require colectomy for toxic megacolon so get early surgical referral
  • Stool transplant for intractable recurrent disease

Gastroenteritis in aged-care facilities

• Diagnosis can be difficult
• Criteria:
  • 3 or more loose bowel motions above baseline over 24 hours
  • 2 or more episodes of vomiting over 24 hours
  • Symptoms with identified pathogen on stool testing
• Take stool specimens from symptomatic patients during epidemics, implement infection control and notify public health if >2 cases in 72 hours

Traveller’s diarrhoea

• 20-50% of travellers to developing nations
• ETEC is most common
• Norovirus most common on cruise ships
• Salmonella and Campylobacter increasing in Asia
• Cholera vaccine not proven to prevent ETEC and not licensed for this in Australia
• Treatment
  • Mild disease: Supportive
  • Moderate to severe: Norfloxacin 800mg PO stat
  • If fever or bloody stools: Norfloxacin 400mg PO BD for 2-3 days

Persistent diarrhoea in returned traveller

• Postinfectious IBS, lactose intolerance, coeliac disease or ongoing infection
• Need stool testing
• Serology for amoebiasis, schistosomiasis, strongyloidiasis
• Empirical therapy for giardia may be reasonable if no cause identified

Diarrhoea in immunocompromised hosts

• The usual + CMV, Cryptosporidium, Isospora and microsporidia
• Test for above in addition to usual
• If any suggestion of bacterial infection, empirical Ab’s recommended
• CMV colitis
  • Diagnosis requires demonstration of CMV on biopsy tissue
  • Ganciclovir 

Ciguatera poisoning

• GI within 1 hour followed by neurological
• Abdo pain, vomiting, diarrhoea, paraesthesias, reversal of hot/cold sensation, hypotension, bradycardia
• GI resolves within days but neurological sequelae may last months to years
• Reef fish contamined by dinoflaggelate Gambierdiscus toxicus, which produces ciguatoxin
• Ciguatoxin acts on sodium channels to induce membrane depolarisation
• Can last days to months
• From large reef fish typically
• Clinical diagnosis and supportive care

Tetrodotoxin

• Paraesthesias, headache, vomiting, diarrhoea, abdo pain, ascending paralysis, respiratory failure and death
• Death in 4-6 hours
• From puffer fish
• Supportive care

Scrombroid

• Flushing, rash, burning sensation, dizziness, paraesthesias
• Histidine metabolised by bacteria into histamine
• Improper temperature control leads to bacterial proliferation and high levels of histamine in fish when consumed
• Symptoms within 30 minutes to 24 hours after ingestion
• Lasts 3-6 hours
• From pelagic fish
  • Scrombridae family tuna, mackerel, bonito
  • Non-Scrombidae mahi-mahi, bluefish, herring, sardines
• Antihistamines and supportive care

Shellfish toxins

• Diarrhoea, vomiting, abdominal pain, fever, numbness, dizziness, myalgias, confusion, memory loss, coma
• Lasts 2h to 3 days
• From shellfish, muscles, clams esp. Gulf of Mexico
• Supportive care

Chronic sequelae of foodborne illness

• Salmonella, Shigella, Campylobacter associated with seronegative reactive arthritis in 2% of patients
• Campylobacter associated with GBS in up to 40% of cases
  • Typically 7-21 days after diarrhoeal illness
• MS, RA, psoriasis and Graves may also be associated
• HUS linked to shiga-toxin E. coli O157:H7, ETEC, Campylobacter, Shigella, Citrobacter, Salmonella, Yersinia
• E. coli O157:H7 also associated with TTP

Last Updated on October 2, 2020 by Andrew Crofton