Infections of the GI Tract

• What does the normal microbiome look like for the stomach, SI, & LI?

  Stomach- sterile, contains only a few organisms because of low pH and enzymes

  SI-streptococci, lactobacilli and yeasts, the proportions of which depend on dietary habits

  LI-dense population of varied flora:Strep faecalis,Bacteroides spp, enterobacteriaceae,Clostridium spp, anaerobic streptococci
• What is gastroenteritis, what is associated with it, and who commonly gets it?

  Acute gastrointestinalillness usually due to infection.

  You get vomiting and diarrhoea and it's often associated with food poisoning.

  Can occur at all ages, but infants principal group
• Where is gastroenteritis more common?

  More common in countries with poor hygiene standards, water sanitation problems
• What are some bacterial causes of gastroenteritis and their individual incubation periods?

  
• What are some other non-bacterial causes of gastroenteritis and their incubation periods?

  There are also viral and parasitic causes

  
• What are the main groups at risk of contracting gastroenteritis?

  Enteric hygiene difficulties

  Pre-school, creche children

  Food workers

  Health care staff
• What is the commonest bacterial gastroenteritis in the Western world?

  Gastroenteritis secondary toCampylobacter, with C. jejuni & C. colibeing some of the most common diarrhoea-inducing agents in the Western world
• What are the characteristics of campylobacter?

  Curved, slender, Gram negative bacilli
• What are the signs and symptoms associated with campylobacter gastroenteritis?

  -Incubation period which can be up to 4 days.

  
  

  -these can be fever, myalgia, malaise, abdominal pain, and headaches.

  
  

  -Diarrhoea occurs later & ranges from profuse, watery stools to bloody stools lasting up to one week.

  
  

  -Patients may have prolonged carriage, however a chronic carrier state is rare
• Can recurrent infection of campylobacter gastroenteritis occur?

  Yes, in up to 25% of patients
• Where can campylobacter be found?

  In the gut or oral cavity

  
  

  common sources are food (poultry; gut of bird), raw milk and dairy products

  
  

  It can also infect young animals, like kittens or puppies, and then spread to humans

  
  

  Caused by enterotoxins
• How do you diagnose campylobacter gastroenteritis?

  Via stool culture

  
  

  Selective media, low Ox, 43C
• Is treatment required for campylobacter gastroenteritis?

  Not normally since it's a self limiting infection

  
  

  Erythromycin recommended for symptoms lasting more than 1 week

  
  

  OR

  
  

  If patient presents with worsening symptoms, dysentery, pyrexia, bacteraemia, is pregnant, or at risk of complications

  
  

  (extremely young or elderly, immunocompromised, or those with liver cirrhosis)
• Are there any post-infectious complications with campylobacter gastroenteritis?

  It's very rare but can include:

  Guillain-Barré syndrome,reactive arthritis,or convulsions
• What is salmonellosis?


  Infection caused bysalmonella bacteria.

  This can cause a spectrum of diseases which can be divided into:

  non-typhoidal types(causing self-limiting gastroenteritis)

  typhoidal subtypes(like salmonella typhi, and salmonella paratyphi, which can cause typhoid fever)
• What is the incubation period, symptoms & signs, and source of salmonellosis (non-typhoid)?

  Incubation period :1-2 days

  Symptoms: Nausea, vomiting, diarrhoea, fever, abdominal pain and disseminated sepsis (severe sepsis)

  Source: ingestion of contaminated food/water.

  Also found in domestic animals and poultry e.g poultry, swine, cattle

  Or from handling exotic pets

  
• How long do the conditions caused by salmonella last and what are the possible outcomes?

  Duration: 1-7 days

  Gastroenteritisoccurs in 75% of infections

  Bacteraemiaoccurs in 5-10% of infections, often resulting in distant infections (e.g. CNS infections, endocarditis, or osteomyelitis)
• Which groups are mostly affected by salmonella?


  Infants, elderly and those with decreased stomach acid
• How do you diagnose salmonella?


  Stool culture

  
  

  Enrichment and selective media
• What is the treatment for salmonella infections?

  Rehydration(treatment rarely necessary and antibiotic therapy is generally contraindicated as it would prolong the carriage of the organism in the convalescent phase and cause resistance)

  Antibiotic therapyis only indicated for those with colitis, bacteraemia, haemoglobinopathies & immunocompromised states
• Does salmonella have a high secondary spread?

  Yes so it's important to have strict contact precautions & clinical surveillance of contacts
• Describe the sources, symptoms, incubation period, & treatment ofStaphylococcus aureus.

  Staphylococcus aureus- bacteria that can cause a range of infections of the skin, bone and heart valves.

  When infected, it can cause nausea, vomiting and diarrhoea (25% of cases)

  Usually due to cooked food not stored at 4 degrees/frozen immediately + food handler since organisms multiply in warm conditions

  
• What is the incubation/duration period of staphylococcus aureus? What treatment is given?

  Incubation: 1/2 - 6 hours.

  Duration: 1-24 hrs (rarely 48)

  Treatment: self-limiting, no treatment required
• What isBacillus cereus?


  Aerobic spore-forming gram-positive bacillus which can contaminate foods such as rice, cereals, raw, dried & processed foods

  
  

  It survives cooking/boiling by sporulation
• What does theBacillus cereustoxin cause?


  Two types of poisoning:emetic (vomiting)anddiarrhoeal(rare)

  Symptoms (nausea & vomiting) usually occur within 2 to 6 hours after ingestion of contaminated food

  Symptoms can last for 6 to 10 hours

  No treatment required; self limiting
• How can you prevent Bacillus cereus infection?

  Adequate food hygiene & correct storage of food
• What is Shigellosis and what can it cause?

  Most common species in developed countries producing mildest symptoms.

  
  

  Due to contaminated food + water

  
  

  Causes fever, malaise, self-limiting eatery diarrhoea (can have mucus, pus and blood)

  
  

  Incubation: 48hrs

  
  

  Locally invasive in large bowel

  
• Which species of Shigella is most likely to cause complications and how do you diagnose & treat this?

  S. dysenteriaeinfection is most likely to cause complications such as HUS, dysentery, and toxic megacolon

  Diagnosis-isolate organism on selective culture media

  Treatment- rehydrationAntibiotics indicated for most patients-ciprofloxacin
• What is cryptosporidiosis?


  A self limiting diarrhoeal illness in children that causes nausea & vomiting
• How is cryptosporidiosis acquired?

  By drinking contaminated water containing cysts ofCrypto parvumfound in infected cattle or humans and passed on in stools
• Why is elimination of cryptosporidiosis difficult?

  Because it's very resistant to chlorination

  
  

  A more severe illness results in those that are immunocompromised e.g. like in those that have AIDS
• How is cryptosporidiosis diagnosed?


  By finding cysts in stool (acid 'fast')There is no specific treatment
• What is


  Clostridium perfringensresponsible for?Gas gangrene and food poisoning
• How is


  Clostridium perfringenstransmitted?Heat resistant spores survive in contaminated foods during the heating procedure

  
  

  After food is ingested- sporulation occurs in the GUT and an enterotoxin is produced

  
  

  Also contamination of an open wound
• What are the symptoms, treatment, and prevention of

  Clostridium perfringens?Symptoms- abdominal pain and watery diarrhoea

  Treatment- symptomatic, no antibiotics

  Prevention- good food hygiene, adequate cooking of food to kill the organisms
• What are the principal causes of infantile gastroenteritis?

  Viral:-rotavirus (the most common cause)-noroviruses (Norwalk like)

  Bacterial:Escherichia coli

  Different strains are classified based on their serological and virulence properties:

  enteropathogenic; enterohaemorrhagic; enterotoxigenic; enteroinvasive
• What is the incubation period of viral gastroenteritis and what are the symptoms?

  Incubation period: 2-4 days

  
  

  Presents as acute diarrhoea of mild to moderate severity, may be vomiting

  
  

  Common in winter months
• How is viral gastroenteritis diagnosed & treated?

  Diagnosed by detection of rotavirus antigen in stool

  
  

  Treatment is supportive care as medication not necessary
• What can


  enteropathogenicE.coli cause (EPEC)?More than 20 (O) serotypes have been identified in outbreaks ofinfantile diarrhoea
• What can EPEC affect, how is it spread, and what are the symptoms, and how do you treat it?

  Small intestine affected (local destruction of intestinal epithelial cells)

  
  

  Spread by contaminated food

  
  

  Symptoms include fever, nausea, vomiting, non-bloody stools

  
  

  Self-limiting, supportive care, no specific antibiotic treatment