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Food poisoning

Definition 
  • Illness caused by ingestion of food or water contaminated with:
    • bacteria and/or their toxins
    • viruses
    • parasites
    • chemicals
  • Contamination usually arises from improper handling, preparation, or storage of food or drinks
Risk Factors 
  • older people, children, and pregnant women
  • chronic disease
  • recent hx of travel
  • immunocompromised state
  • hx of contact food poisoning
  • improper food handling and storage
  • consumption of undercooked meat
    • Associated with Salmonella, Campylobacter, Shiga toxin-producing E coli, and Clostridium perfringens
  • consumption of raw seafood
    • Associated with Norwalk-like virus, Vibrio organism, or hepatitis A
  • consumption of homemade canned foods
    • Associated with Clostridium botulinum
  • consumption of unpasteurised soft cheeses
    • Associated with Listeria,Salmonella, Campylobacter, Shiga toxin-producing E coli, and Yersinia
  • consumption of deli meats
    • Associated with listeriosis
  • consumption of unpasteurised milk or juice
    • Associated with Salmonella, Campylobacter, Shiga toxin-producing E coli, and Yersinia
  • consumption of raw eggs
    • Associated with Salmonella
Differential diagnosis
  • Acute viral syndromes
    • Very difficult to differentiate
    • Lack of exposure to specific foods or absence of specific behaviours may help in differentiating
  • Crohn's disease
    • May present with fatigue, diarrhoea, abdominal pain, weight loss, fever, and rectal bleeding
    • Other signs may include:
      • presence of oral ulcers, perianal skin tags, fistulae, abscesses, and sinus tracts
      • abdominal exam may reveal a palpable mass in the ileocaecal area
      • no mass present on digital rectal examination
  • Ulcerative colitis
    • May present with:
      • bloody diarrhoea
      • hx of lower abdominal pain
      • faecal urgency
      • presence of extraintestinal manifestations (e.g., erythema nodosum, acute arthropathy)
      • hx of primary sclerosing cholangitis
    • No mass present on digital rectal examination
  • Food allergies/intolerance
    • History of exposure to certain foods known to cause intolerance or allergies (milk, lactose, gluten) 
    • Relapsing symptoms with challenge
  • Irritable bowel syndrome (IBS)
    • Total duration of symptoms should be more than 6 months
    • Specific criteria of combination of:
      • abdominal bloating or pain relieved by defection
      • association with change in stool frequency and/or consistency 
      • without evidence of alarm signs or symptoms
    • Physical examination reveals a healthy non-toxic appearance without evidence of dehydration. 
  • Microscopic colitis 
    • Typically present in older persons, long duration symptoms, and lack of haematochezia or blood in stool
  • Acute appendicitis
    • Localised right lower quadrant pain and peritoneal irritation are classic (guarding)
    • CT scan of the abdomen is diagnostic.
  • Acute cholecystitis
    • Localised pain in RUQ and a positive Murphy sign are classic symptoms
  • Acute pancreatitis
    • Epigastric pain radiating to the back
    • History of excessive alcohol consumption in alcohol induced pancreatitis
  • Acute hepatitis
    • Jaundice is usually present
    • Risk factors for acute hepatitis B and C include unprotected sex and IV drug use
    • History of excessive alcohol consumption in alcoholic hepatitis
    • History of hepatotoxic medication use or overdose in drug induced hepatitis
    • Neurological signs and Kayser-Fleischer ring in Wilson's disease
  • Malabsorption syndromes 
    • Chronic symptoms and significant malnourishment
    • History of intestinal surgery 
    • Extraintestinal manifestations of malnourishment and malabsorption are usually present
  • Large bowel obstruction
    • Distention is the more common presenting symptom
    • Vomiting, including vomiting of fecal matter, occur later in the course of the illness
  • Small bowel obstruction
    • Presents with abdominal distension and vomiting earlier on in course of the illness
    • May be history of abdominal surgery
  • Radiation enteritis 
    • Patients have a history of receiving radiation therapy
  • Mesenteric ischaemia
    • Sudden onset of diffuse abdominal pain 
    • Chronic symptoms of vague, diffuse abdominal pain may also be indicative of chronic mesenteric ischaemia
    • In contrast, ishaemic colitis may cause focal or diffuse abdominal pain 
      • Often has a more insidious onset, over several hours or days
  • Medication and drugs side-effects/toxicity
    • History of drugs ingestion/use
  • Diverticulitis
    • Leukocytosis and fever in an older patient. 
  • Systemic vasculitis
    • Multisystem involvement (skin, joints, blood) and chronic presentation
    • Biopsy shows vasculitis pattern (leukocytoclastic, necrotising)
Epidemiology
  • In 1995, foodborne diseases caused in England and Wales an estimated:
    • 2,366,000 illnesses
    • 21,138 hospital admissions
    • 718 deaths 
  • By 2000, this had fallen to 1,338,772 cases, 20,759 hospital admissions, and 480 deaths
  • The most important pathogens identified were:
    • Campylobacter
    • Salmonella
    • Clostridium perfringens
    • Verocytotoxin-producing Escherichia coli
  • The annual incidence of foodborne disease in the US is estimated to be 1 case per 4 persons
Aetiology 
  • Ingestion of food or water contaminated with bacteria and/or their toxins, viruses, parasites, or chemicals
  • Contamination usually arises from improper handling, preparation, or storage of food or drinks
Clinical features
  • Key common features:
    • Diarrhoea
    • Vomiting
      • Staphylococcus aureus, Bacillus cereus, or norovirus is suspected when vomiting is the major presenting symptom
  • Other features:
    • Abdominal pain (common)
    • Fever (common)
    • Blood or mucous in stool (common)
    • Dehydration (common)
    • Profuse rice-water stool (uncommon) 
      • Suggests cholera or a similar process
    • Reactive arthritis (uncommon) 
      • Can be seen with Salmonella, Shigella, Campylobacter, and Yersinia infections
    • Skin rash (uncommon) 
      • Rose spot macules on the upper abdomen and hepatosplenomegaly may be seen in Salmonella typhi infection
      • Erythema nodosum and exudative pharyngitis are suggestive of Yersinia infection
      • Patients with Vibrio vulnificus or V alginolyticus may present with cellulitis and otitis media
    • Symptoms of botulism
      • Diplopia (uncommon)
      • Slurred speech (uncommon)
      • Poor muscle tone (uncommon)
      • Difficulty swallowing (uncommon)
Pathophysiology
  • Diarrhoea results from the action of enterotoxins on the secretory mechanisms of the mucosa of the small intestine
    • May be preformed before ingestion or produced after ingestion
    • May occur:
      • Without invasion (non-inflammatory)
      • In the large intestine, with invasion and destruction (inflammatory)
  • In some types of food poisoning vomiting is caused by a toxin acting on the CNS
    • Staphylococci, Bacillus cereus
  • The clinical syndrome of botulism results from the inhibition of acetylcholine release in nerve endings by the botulinum toxin
  • The pathophysiological mechanisms that result in acute GI symptoms from some of the non-infectious causes of food poisoning are not well known
    • e.g. naturally occurring substances such as mushrooms and toadstools and heavy metals such as arsenic, mercury, and lead
Investigations
  • Stool microscopy for WBC and RBC
    • Easy, inexpensive, and widely available.
    • Helps to differentiate invasive or inflammatory from non-invasive disease.
    • Stool microscopy for WBCs and RBCs should be done in cases of:
      • Patients presenting with blood in stool
      • Fever
      • Suspected invasive pathogens (such as Escherichia coli O157:H7)
      • When other diagnoses are considered (such as inflammatory bowel disease, ischaemic or infectious colitis)
      • With prolonged symptoms (3 days or more)
      • Dark-field microscopy can be done to identify Vibrio cholera
  • Stool culture
    • Bacterial culture for enteric pathogens such as Salmonella, Shigella, and Campylobacter organisms becomes mandatory:
      • In any patient with grossly bloody stools
      • If a stool sample shows positive results for WBCs or blood
      • If patient has fever or symptoms persisting for longer than 3 to 4 days
    • If symptoms persist and the pathogen is isolated, specific treatment should be initiated
  • Stool O+P
    • Microscopic examination of the stool for ova and parasites
  • FBC with differential
    • Helps to assess the inflammatory response and the degree of haemoconcentration
    • Additionally, may detect evidence of haemolytic uraemic syndrome (HUS) when Shiga toxin-producing E coli (e.g., O157:H7) is suspected
    • Results:
      • High WBC with most inflammatory/invasive pathogen associated diarrhoea
      • Low WBC are associated with typhoid fever and some viruses
  • Anaemia
    • High Hb and haematocrit could reflect haemoconcentration
  • Serum creatinine and electrolytes
    • Should be done to rule out electrolyte abnormalities and renal dysfunction:
      • In all patients with evidence of moderate or severe dehydration
      • In those with severe vomiting or diarrhoea or symptoms without improvement after 24 hours
    • Results:
      • HUS suspected when uraemia present
      • Hypokalaemic metabolic acidosis secondary to diarrhoea
      • Hyper- or hyponatraemia and elevated blood urea nitrogen secondary to dehydration
  • Stool/serum botulinum toxin detection test
    • If patient has symptoms/signs of botulism, stool or serum should be sent for toxin identification/confirmation
  • Blood culture
    • Blood culture is performed to exclude bacteraemia if the patient is notably febrile (e.g., temperature >101°F [38.5°C]) and there are signs of sepsis
      • Tachycardia, hypotension, poor capillary refill, tachypnea, acute mental confusion, decreased urine output
    • Signs of sepsis are difficult to differentiate from signs of severe dehydration
  • Amylase and lipase
    • Helps to distinguish food poisoning from acute pancreatitis
  • LFTs
    • Helps to distinguish food poisoning from acute cholecystitis or acute hepatitis
    • May be elevated in patients with wild mushroom toxicity or invasive pathogens associated with systemic illness
      • Particularly Salmonella and Campylobacter
    • May show hypoalbuminaemia secondary to malnourishment or as an acute-phase reactant
  • Hepatitis A IgM antibodies
    • Performed when history or occupation (daycare, nursing) suggestive of exposure to hepatitis A or if LFTs abnormal
  • Acute abdominal series
    • Flat and upright abdominal radiographs should be obtained urgently if the patient experiences severe pain or obstructive symptoms, or if perforation is suspected
  • Sigmoidoscopy/colonoscopy
    • Sigmoidoscopy/colonoscopy is considered in cases where:
      • Bloody diarrhoea in whom no enteric pathogen has been identified
      • Bloody diarrhoea persists or increases in severity
      • Patients whose clinical picture and tests results are incompatible with a diagnosis of foodborne illness
    • Can be useful in diagnosing inflammatory bowel disease, antibiotic-associated diarrhoea, shigellosis, and amoebic dysentery
    • Colonoscopy is more expensive, requires full preparation and sedations, and should be performed in a special setting (endoscopy suite)
    • Careful colonoscopy is indicated in patients with persistent symptoms or not responding well to initial treatment
  • Other possible investigations
    • Oesophagogastroduodenoscopy
      • Immunocompromised patients
      • Patients receiving chemotherapy
      • Patients with persistent, severe symptoms lasting more than 5 days or not responding well to initial treatment
    • Biopsy
      • Considered when performing endoscopy
      • May distinguish inflammatory bowel disease from acute infectious enteritis or colitis
        • Presence of crypt architectural changes such as crypt branching or sparsity
      • However, these features take several weeks to develop and are not likely to be present in an infectious colitis
    • Duodenal aspirate
      • Considered in immunocompromised patients, patients receiving chemotherapy, and patients with persistent symptoms or not responding well to initial treatment
    • PCR of stool
      • PCR may be useful when available to detect Campylobacter,Salmonella, and Shiga toxin-producing E coli O157 but is not widely available
Management

a) conservative
  • Oral hydration
    • A simple oral rehydration solution (ORS) may be composed of 1 teaspoon of salt and 4 teaspoons of sugar added to 1 litre of water
    • ORS promotes co-transport of glucose, sodium, and water across the gut epithelium, a mechanism unaffected in cholera
    • The WHO recommends a solution containing 3.5 g of sodium chloride, 2.5 g of sodium bicarbonate, 1.5 g of potassium chloride and 20 g of glucose per litre of water
b) medical
  • Antiperistaltics
    • Can be offered to patients with uncomplicated watery diarrhoea whose diarrhoea interferes with their ability to work or those with traveller’s diarrhoea
    • Antiperistaltics (opiate derivatives) should not be used:
      • In patients with fever, systemic toxicity, or bloody diarrhoea
      • In patients whose condition either shows no improvement or deteriorates
  • Antidiarrhoeals
    • The value of non-prescription antiperistaltics or antidiarrhoeals (e.g., loperamide) in patients with mild-to-moderate diarrhoea is under discussion
    • They can be offered to patients whose diarrhoea interferes with their ability to work or those with traveller’s diarrhoea
    • Adsorbents (e.g., aluminium hydroxide) help patients have more control over the timing of defecation but do not alter the course of the disease or reduce fluid loss
    • Antisecretory agents (e.g., bismuth) may be useful
    • In mild cases, loperamide is safe and effective
    • When invasive pathogens are suspected, antidiarrhoeals that target motility should be generally avoided
    • Decrease in intestinal motility in patients taking diphenoxylate/atropine may be detrimental to those with diarrhoea resulting from Shigella or Salmonella organisms.
  • IV rehydration
    • Intravenous solutions are indicated in patients who are severely dehydrated or who have intractable vomiting
    • Rehydrate can generally be done rapidly without complication
      • For example, if there is 10% dehydration in a 75 KG adult, and the fluid deficit is 5 to 7 L, the volume can be administered over 2 to 4 hours (i.e., 2-4 L/hr)
    • Potassium may be added but not to exceed 10 mEq/hour with IV administration
  • Botulin antitoxin
    • Notifiable, discussion with local authority/CDC for provision of antitoxin
    • Antitoxin works to block the toxin produced by Clostridium botulinum
  • Antibiotics
    • Shigella species
      • fluoroquinolone or trimethoprim/sulfamethoxazole
    • Non-typhi species of Salmonella
      • fluoroquinolone or trimethoprim/sulfamethoxazole
    • Escherichia coli species (excluding enterohaemorrhagic [Shiga toxin-producing])
      • fluoroquinolone
    • Campylobacter species
      • erythromycin
    • Yersinia species
      • fluoroquinolone or doxycycline or aminoglycoside
    • Vibrio cholerae + Vibrio parahaemolyticus
      • fluoroquinolone or doxycycline or tetracycline or trimethoprim/sulfamethoxazole or azithromycin
    • Giardia species
      • antiparasitics
    • Cryptosporidium species
      • paromomycin or nitazoxanide
    • Cystoisospora belli
      • trimethoprim/sulfamethoxazole or pyrimethamine and folinic acid
    • Microsporidium species and immunocompromised
      • albendazole
    • Entamoeba histolytica
      • metronidazole + paramomycin or diiodohydroxyquinoline
    • Listeria monocytogenes
      • ampicillin or trimethoprim/sulfamethoxazole
c) surgical
  • n/a
Prognosis
  • Because most cases of food poisoning are self-limited, prolonged follow-up care is not required
  • Stool cultures should be monitored in individuals working in settings such as hospitals, food establishments, and daycare centres who are infected with:
    • Shiga toxin-producing Escherichia coli (e.g., O157:H7) or Salmonella or Shigella organisms
    • Continue until they become culture-negative without antibiotics
    • These people should not return to work until that time
  • Mortality is relatively rare (<0.1%) but more likely in very young, elderly or immunocompromised persons
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