EM Notes – Foodborne Illness
Causative Agents
**Source and Clinical Features
Pathogenesis
**Diagnosis and Treatment
Staphylococci
Improperly stored foods with high salt or sugar content favour growth of staphylococci
Intense vomiting and watery diarrhoea start 1–4 hours after ingestion and last as long as 24–48 hours.
Enterotoxin acts on receptors in gut that transmit impulses to medullary centers.
Symptomatic treatment
B cereus
Contaminated fried rice (emetic). Meatballs (diarrheal)
Emetic: Duration is 9 hours, vomiting and cramps
Diarrheal: Lasts for 24 h
Mainly vomiting after 1–6 hours and mainly diarrhoea after 8–16 hours after ingestion; lasts as long as 1 day
Emetic enterotoxin (short incubation and duration) – Poorly understood
Diarrheal enterotoxin (long incubation and duration) – Increasing intestinal secretion by activation of adenylate cyclase in intestinal epithelium
Symptomatic treatment
C perfringens
Inadequately cooked meat, poultry, or legumes
Acute onset of abdominal cramps with diarrhoea starts 8–24 hours after ingestion.
Vomiting is rare. It lasts less than 1 day.
Enteritis necroticans associated with C perfringens type C in improperly cooked pork (40% mortality)
Enterotoxin produced in the gut, and food causes hypersecretion in the small intestine.
Culture of clostridia in food and stool
Symptomatic treatment
C botulinum
Canned foods (e.g., smoked fish, mushrooms, vegetables, honey)
Descending weakness and paralysis start 1–4 days after ingestion, followed by constipation.
Mortality is very high.
Toxin absorbed from the gut blocks the release of acetylcholine in the neuromuscular junction.
Toxin present in food, serum, and stool.
Respiratory support
Intravenous trivalent antitoxin from CDC
Listeria monocytogenes
Raw and pasteurized milk, soft cheeses, raw vegetables, shrimp
Systemic disease associated with bacteraemia
Intestinal symptoms precede systemic disease
Can seed meninges, heart valves, and other organs
Highest mortality among bacterial food poisonings
Highly motile, heat-resistant, gram-positive organism
CSF or blood culture
Must treat with antibiotics if bacteraemic
Enterotoxic E coli (e.g., traveller’s diarrhoea)
Contaminated water and food (e.g., salad, cheese, meat)
Acute-onset watery diarrhoea starts 24–48 hours after ingestion.
Vomiting and abdominal cramps may be present. Lasts 1–2d
Enterotoxin causes hypersecretion in small and large intestine via guanylate cyclase activation.
Supportive treatment
No antibiotics
Enterohaemorrhagic E coli (e.g., E coli O157:H7)
Improperly cooked hamburger meat and previously spinach
Commonest pathogen in bloody diarrhoea starts 3–4d after ingestion.
Usually progresses from watery to bloody diarrhoea. It lasts for 3–8 days
May be complicated by HUS or TTP
Cytotoxin results in endothelial damage and leads to platelet aggregation and microvascular fibrin thrombi
Diagnosis with stool culture
Supportive treatment
No antibiotics
Enteroinvasive_E coli_
Contaminated imported cheese
Usually watery diarrhoea (some may present with dysentery)
Enterotoxin produces secretion
Shiga-like toxin facilitates invasion.
Supportive treatment
No antibiotics
Enteroaggregative E coli
Implicated in traveller’s diarrhoea in developing countries
Can cause bloody diarrhoea
Bacteria clump on the cell surfaces
Ciprofloxacin may shorten duration and eradicate the organism
V cholera
Contaminated water and food
Large amount of nonbloody diarrhoea starts 8–24 hours after ingestion. It lasts for 3–7 days.
Enterotoxin causes hypersecretion in small intestine.
Infective dose usually is 107 –109 organisms.
Positive stool culture
Prompt replacement of fluids and electrolytes (oral rehydration solution)
Tetracycline (or fluoroquinolones) shortens the duration of symptoms and excretion of Vibrio.
Causative Agents
Source and Clinical Features
Pathogenesis
Diagnosis and Treatment
V parahaemolyticus
Raw and improperly cooked seafood (i.e., molluscs and crustaceans)
Explosive watery diarrhoea starts 8–24 hours after ingestion. It lasts for 3–5 days.
Enterotoxin causes hypersecretion in small intestine.
Haemolytic toxin is lethal.
Infective dose usually is 107 –109 organisms.
Positive stool culture
Prompt replacement of fluids and electrolytes
Sensitive to tetracycline, but unclear role for antibiotics
V vulnificus
Wound infection in salt water or consumption of raw oysters
Can be lethal in patients with liver disease (50% mortality)
Polysaccharide capsule
Growth correlates with availability of iron (esp. transferrin saturation >70%)
Culture of characteristic bullous lesions or blood
Immediate antibiotics if suspected (e.g., doxycycline and ceftriaxone)
C jejuni
Domestic animals, cattle, chickens
Faecal-oral transmission in humans
Foul-smelling watery diarrhoea followed by bloody diarrhoea
Abdominal pain and fever also may be present. It starts 1–3 days after exposure and recovery is in 5–8 days.
Uncertain about endotoxin production and invasion
Culture in special media at 42°C
Erythromycin for invasive disease (fever)
Shigella
Potato, egg salad, lettuce, vegetables, milk, ice cream, and water
Abrupt onset of bloody diarrhoea, cramps, tenesmus, and fever starts 12–30 hours after ingestion.
Usually self-limited in 3–7 days
Organisms invade epithelial cells and produce toxins.
Infective dose is 102 –103 organisms.
Enterotoxin-mediated diarrhoea followed by invasion (dysentery/colitis)
Polymorphonuclear leukocytes (PMNs), blood, and mucus in stool
Positive stool culture
Oral rehydration is mainstay.
Trimethoprim-sulfamethoxazole (TMP-SMX) or ampicillin for severe cases
No opiates
Salmonella
Beef, poultry, eggs, and diary products Abrupt onset of moderate-to-large amount of diarrhoea with low-grade fever; in some cases, bloody diarrhoea
Abdominal pain and vomiting also present, beginning 6–48 hours after exposure and lasts 7–12 days
Invasion but no toxin production
Positive stool culture
Antibiotic for systemic infection
Yersinia
Pets; transmission in humans by faecal-oral route or contaminated milk or ice cream
Acute abdominal pain, diarrhoea, and fever (enterocolitis)
Incubation period not known Polyarthritis and erythema nodosum in children
May mimic appendicitis
Gastroenteritis and mesenteric adenitis
Direct invasion and enterotoxin
PMNs and blood in stool
Positive stool culture
No evidence that antibiotics alter the course but may be used in severe infections
Aeromonas
Untreated well or spring water
Diarrhoea may be bloody.
May be chronic up to 42 days in the United States
Enterotoxin, haemolysin, and cytotoxin
Positive stool culture
Fluoroquinolones or TMP/SMX for chronic diarrhoea
Parasitic Food Poisoning
Source and Clinical Features
Pathogenesis
Diagnosis and Treatment
E histolytica
Contaminated food and water
90% asymptomatic
10% dysentery
Minority may develop liver abscesses
Invasion of the mucosa by the parasites
Criterion standard is colonoscopy with biopsy
Ova and parasites may be seen in the stool but has low sensitivity
Luminal amebicides (e.g., paromomycin) Tissue amebicides (e.g., metronidazole)
G lamblia
Contaminated ground water
Faecal-oral transmission in humans
Mild bloody diarrhoea with nausea and abdominal cramps starts 2–3 days after ingestion; lasts for 1 week
May become chronic
Unknown
Highest concentration in the distal duodenum and proximal jejunum
Initial diagnostic test is stool ELISA
Duodenal aspiration or small bowel biopsy
Cyst in the stool
Metronidazole
Seafood/Shellfish Poisoning
**Source and Clinical Features
Pathogenesis
**Diagnosis and Treatment
Paralytic shellfish poisoning
Temperate costal areas
Source – Bivalve molluscs
Onset usually is 30–60 minutes.
Initial symptoms include perioral and intraoral paraesthesia.
Other symptoms include paraesthesia of the extremities, headache, ataxia, vertigo, cranial nerve palsies, and paralysis of respiratory muscles, resulting in respiratory arrest.
Fish acquires toxin-producing dinoflagellates
General observation for 4–6 hours
Maintain patent airway.
Administer oxygen, and assist ventilation if necessary.
For recent ingestion, charcoal 50–60 g may be helpful.
Neurotoxic shellfish poisoning
Coastal Florida
Source – Molluscs
Illness is milder than in paralytic shellfish poisoning.
Fish acquires toxin-producing dinoflagellates
Symptomatic
Ciguatera
Hawaii, Florida, and Caribbean
Source – Carnivorous reef fish
Vomiting, diarrhoea, and cramps start 1–6 hours after ingestion and last from days to months.
Diarrhoea may be accompanied by a variety of neurologic symptoms including paraesthesia, reversal of hot and cold sensation, vertigo, headache, and autonomic disturbances such as hypotension and bradycardia.
Chronic symptoms (e.g., fatigue, headache) may be aggravated by caffeine or alcohol
Fish acquires toxin-producing dinoflagellates
Toxin increases intestinal secretion by changing intracellular calcium concentration
Symptomatic
Anecdotal reports of successful treatment of neurologic symptoms with mannitol 1 g/kg IV
Tetrodotoxin poisoning
Japan
Source – Puffer fish
Onset of symptoms usually is 30–40 minutes but may be as short as 10 minutes. It includes lethargy, paraesthesia, emesis, ataxia, weakness, and dysphagia. Ascending paralysis occurs in severe cases. Mortality is high.
Neurotoxin is concentrated in the skin and viscera of puffer fish.
Symptomatic
Scombroid
Source – Tuna, mahi-mahi, kingfish
Allergic symptoms such as skin flush, urticaria, bronchospasm, and hypotension usually start within 15–90 minutes.
Improper preservation of large fish results in bacterial degradation of histidine to histamine.
Antihistamines (diphenhydramine 25–50 mg IV)
H2 blockers (cimetidine 300 mg IV)
Severe reactions may require IM adrenaline (0.3–0.5 mL of 1:1000 solution).
Heavy Metal Poisoning
Source
Symptoms
Treatment
Mercury
Ingestion of inorganic mercuric salts
Causes metallic taste, salivation, thirst, discoloration and oedema of oral mucous membranes, abdominal pain, vomiting, bloody diarrhoea, and acute renal failure
Consult a toxicologist.
Remove ingested salts by emesis and lavage, and administer activated charcoal and a cathartic.
Dimercaprol is useful in acute ingestion.
Lead
Toxicity results from chronic repeated exposure.
It is rare after single ingestion.
Common symptoms include colicky abdominal pain, constipation, headache, and irritability.
Diagnosis is based on lead level (>10 mcg/dL)
Other than activated charcoal and cathartic, severe toxicity should be treated with antidotes (edetate calcium disodium [EDTA] and dimercaprol).
Arsenic
Ingestion of pesticide and industrial chemicals
Symptoms usually appear within 1 hour after ingestion but may be delayed as long as 12 hours.
Abdominal pain, watery diarrhoea, vomiting, skeletal muscle cramps, profound dehydration, and shock may occur.
Gastric lavage and activated charcoal
Dimercaprol injection 10% solution in oil (3–5 mg/kg IM q4–6h for 2 d) and oral penicillamine (100 mg/kg/d divided qid for 1 wk)