QuestionSBA
QuestionChoice
Escherichia coli can present in a similar way to C. Jejuni with bloody diarrhoea, fever, and abdominal pain in the context of food poisoning. It is important to remember the 0157: H7 strain which can trigger haemolytic uraemic syndrome. However, E. Coli is a gram negative rod, as opposed to spiral/comma shaped.
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c
Escherichia coli
QuestionChoice
Bacillus cereus is a gram positive rod presenting with rapid onset, toxin mediated food poisoning (within hours.) It is classically associated with takeaways or reheating rice. It is not associated with bloody diarrhoea. The incubation period in this case, findings on stool culture, and bloody diarrhoea point against Bacillus cereus.
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Bacillus cereus
QuestionChoice
C. jejuni is a spiral or comma-shaped gram negative organism, which commonly presents with a flu-like prodrome, crampy abdominal pain, and bloody diarrhoea. It is a common cause of food poisoning and has a long incubation period of around 5 days. It is associated with Guillain Barre syndrome, which presents with ascending, bilateral weakness in the lower limbs; this child is complaining of lower limb weakness, so this should raise clinical suspicion of this complication.
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Campylobacter jejuni
QuestionChoice
Entamoeba histolytica causes amoebic dysentery. It is associated with foreign travel and stool microscopy would show trophozoites.
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Entamoeba histolytica
QuestionChoice
Salmonella enteritidis can present in a similar way to C. Jejuni with bloody diarrhoea, fever, and abdominal pain in the context of food poisoning. However, it presents earlier than C. jejuni as the incubation period is shorter (around 12-48 hours.) Furthermore, Salmonella is a gram-negative rod rather than a spiral-shaped/comma-shaped organism.
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b
Salmonella enteritidis
QuestionComment
don't know my rods from my spirals

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Gabriel Magalhaes
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# Summary
 
Gastroenteritis is an enteric infection causing acute-onset diarrhoea, sometimes with additional symptoms. Food poisoning results from consuming contaminated substances, while acute diarrhoea involves three or more liquid or semi-liquid stools in 24 hours, lasting less than 14 days. Prolonged diarrhoea lasts over 14 days, and dysentery is acute infectious diarrhoea with blood and mucus. Infectious diarrhoea is commonly spread via the faeco-oral route and often caused by viruses like norovirus, rotavirus, and adenovirus. Bacterial causes include Campylobacter, E. coli, Salmonella, Cholera, Shigella, and Yersinia. Parasites like Cryptosporidium, Entamoeba histolytica, and Giardia can also cause prolonged diarrhoea. Symptoms include sudden-onset diarrhoea, nausea, vomiting, fever, and abdominal pain. Diagnosis often involves assessing hydration status and may require stool cultures or blood tests. Treatment includes rehydration and, in some cases, antimicrobials. Preventative measures include proper food hygiene and handwashing. Certain infections must be reported to health authorities. High-risk groups include young children, the elderly, immunocompromised individuals, and pregnant women, who may face complications such as dehydration, haemorrhagic colitis, and sepsis.
 
# Definition
 
 **Gastroenteritis:** an enteric infection causing acute-onset diarrhoea, with or without associated symptoms
 
 **Food poisoning:** illness caused by eating or drinking substances contaminated with disease-causing pathogens, toxins or chemicals.
 
 **Acute diarrhoea:** 3+ episodes liquid/semi-liquid stools in in a 24h period, lasting less than 14 days
 
 **Prolonged diarrhoea:** acute-onset diarrhoea lasting over 14 days
 
 **Dysentery:** is acute infectious diarrhoea with blood & mucus, often with associated symptoms
 
# Aetiology
 
Most cases of infectious diarrhoea are spread by the faeco-oral route and are caused by viruses. These include:
 
 - **Norovirus:** **most common** cause in the population, and often causes outbreaks. Typically causes projectile vomiting and non-bloody diarrhoea.
 - **Rotavirus:** the most common cause of gastroenteritis in children.
 - **Adenovirus:** typically causes respiratory tract infections but may cause gastrointestinal symptoms in children.
 
Bacteria causing infectious diarrhoea include:
 
 - **Campylobacter**: often associated with contaminated food & drink (in exams: a recent barbeque!), this is the most common cause of bacterial gastroenteritis in the UK. On microscopy, gram-negative rods are seen with characteristic 'seagull' shape, which release enterotoxin in the gut and invade the mucosa. Incubation period is 1 - 5 days and may cause bloody diarrhoea, though vomiting is rare.
 - **E. coli**: the most common cause of traveller's diarrhoea. In the UK, O157:H7 is the most common type and may cause bloody diarrhoea. Sources include improperly cooked meat. Associated complications include haemolytic uraemic syndrome, which typically affects the very young are old and can be fatal.
 - **Salmonella** is associated with consumption of contaminated foods, particularly poultry, eggs and milk. These are gram negative bacteria with an incubation of 16-48 hours. *Salmonella* can cause bloody diarrhoea and is associated with complications such as sepsis, endocarditis, mycotic aneurysm and osteomyelitis.
 - **Cholera** is associated with contaminated water supplies and causes very watery diarrhoea associated with dehydration.
 - **Shigella** and *Yersinia* tend to occur in children. The former can cause severe, bloody diarrhoea.
 - **Bacillus cereus** are gram-positive rods that produce two toxins causing diarrhoea and vomiting within hours of eating contaminated food (in exams, this is usually reheated rice).
 - **Staphylococcus aureus** produces a heat-stable enterotoxin that causes profuse vomiting with mild diarrhoea and abdominal pain. The incubation period is short (under 6 hours) after eating contaminated foods. The bacteria are usually introduced from the skin of the person preparing the food. Foods which do not require cooking carry greater risk.
 
Parasites can be spread by ingestion of contaminated food/drink or from person to person, and often associated with recent travel.
 
 - **Cryptosporidium**: a protozoal infection which may cause prolonged symptoms
 - **Entamoeba histolytica**: most cases are mild but severe cases cause dysentery
 - **Giardia**: causing diarrhoea, constitutional symptoms and bloating which may be prolonged
 
# Signs and Symptoms
 
Symptoms include:
 
 - Sudden-onset diarrhoea, with or without blood
 - Faecal urgency
 - Nausea & vomiting
 - Fever, malaise
 - Abdominal pain
 - Associated symptoms specific to the cause
 
 
# Differential Diagnosis
 
 - ***Clostridium difficile*** infection, causing antibiotic-associated (in particular, cephalosporins) diarrhoea. Patients usually have predisposing risk factors such as recent antibiotics, immunocompromise or PPI use. Typically causes foul-smelling diarrhoea and can cause severe systemic upset and GI complications.
 - Other causes of **diarrhoea**, including irritable bowel syndrome, inflammatory bowel disease, malignancy, endocrine conditions such as thyrotoxicosis. These usually have a more prolonged history and may be associated with other systemic symptoms (except IBS).
 - Other causes of **abdominal pain**, such as appendicitis, intestinal obstruction, diverticulitis, pancreatitis. These are associated with other symptoms such as absolute constipation and vomiting (obstruction) or pain relieved on leaning forward (pancreatitis). Often, there is also more systemic upset and deranged blood tests.
 
# Investigations
 
 - Often, infectious diarrhoea is a clinical diagnosis and, providing the patient is not systemically unwell, may not need further investigation. 
 - It is important to assess hydration status and consider whether the person can tolerate oral fluids.
 - A stool culture may be needed if there are any higher risk features. These include if the person is systemically unwell, is immunocompromised, presents with dysentery or prolonged diarrhoea, there is increased risk of transmission, food poisoning is suspected or symptoms are associated with recent travel.
 - If a person is unwell presenting to secondary care, consider performing blood tests to include FBC, U&Es, CRP, LFTs and TFTs. 
 - Consider a VBG, blood cultures and monitoring urine output if they appear septic.
 
 
# Management
 
 - If a person is systemically unwell, or severely dehydrated, adopt an A-E approach and consider initiating the sepsis six. Admit the patient and seek senior help early. They may need IV fluids, antiemetics or antibiotics.
 - Conservative: advise regular fluids, with or without rehydration salts, and safetynet for signs of dehydration. Antidiarrhoeal drugs are not routinely used, and should be avoided if the patient has symptoms of dysentery or suspected *E. coli 0157*.
 - Medical: antimicrobials are not routinely indicated, but clinical suspicion or positive cultures of the following may prompt initiation of antibiotics:
 
 - *Campylobacter*: macrolide e.g. clarithromycin
 - *Amoeba, Giardia*: anti-protozoal e.g. metronidazole
 - *Cholera*: tetracycline
 
 - If a patient is systemically unwell, immunosuppressed or elderly, consider empirical antibiotics following local pathways and microbiology advice.
 
 - Infectious diarrhoea can be prevented by avoiding foods that are undercooked or prepared in unsanitary conditions, and handwashing at appropriate times and hygiene measures. 
 - Enhanced precautions such as isolation and barrier nursing along with handwashing can prevent spread in clinical settings. People should not return to work until 48 hours after their symptoms have resolved.
 
The following are notifiable diseases, and should be reported to the local health protection scheme:
 
 - Food poisoning
 - Haemolytic uraemic syndrome
 - Dysentery
 - Enteric fever
 - Cholera
 
# Complications
 
Young children, elderly, people with comorbidities or immunocompromised and pregnant women are at highest risk of complications. These include:
 
 - Dehydration, electrolyte disturbance, acute kidney injury
 - Haemorrhagic colitis, haemolytic uraemic syndrome, thrombotic thrombocytopenic purpura
 - Reactive arthritis
 - Toxic megacolon
 - Sepsis
 
Longer-term complications include: faltering growth, irritable bowel syndrome and lactose intolerance.
 
Specific complications may occur depending on the causative organism.
 
# NICE Guidelines
 [NICE CKS: Gastroenteritis](https://cks.nice.org.uk/topics/gastroenteritis/)
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Quesmed Tutorial: Infectious Diseases 
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Campylobacter jejuni commonly causes food poisoning, presenting with crampy abdominal pain, bloody diarrhoea, and can lead to Guillain-Barré syndrome.
A 14-year-old boy presents to A&E with his dad complaining of abdominal pain. He describes it as crampy, which paracetamol has not relieved. Over the last 2 days, he is complaining of leg weakness, fever, and bloody diarrhoea. His dad is concerned that he may have ulcerative colitis. There is no travel history of note. They went to a barbecue 5 days ago where they ate chicken. On examination, the patient has a temperature of 39.8. A faecal sample is taken which shows a spiral shaped organism.

Which of the following organisms is the most likely cause?
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