27. Epidemiology and prevention of enteric bacterial infections

From greek.doctor

Enteric bacterial infections

  • Non-inflammatory diarrhoea (often watery)
    • Preformed toxin
      • Staphylococcus aureus
      • Bacillus cereus
    • Bacteria that produce toxin in the intestines
      • Enterotoxigenic E. coli (ETEC)
      • Vibrio cholerae
      • Clostridium botulinum
      • Clostridium perfringens
  • Inflammatory diarrhoea (often bloody)
    • Bacteria that produce cytotoxins
      • Enterohaemorrhagic E. coli (EHEC)
      • Clostridium difficile
    • Bacteria that invade the mucosa
      • Shigella
      • Salmonella
      • Campylobacter
      • Enteroinvasive E. coli
      • Yersinia enterocolitica

Clostridium botulinum

  • Causes botulism
  • Bacteria proliferates and produces toxin in improperly canned foods, preserved meat
  • Clinical features
    • Descending, flaccid paralysis
    • Toxin inhibits release of acetylcholine in the neuromuscular junction
  • Prevention
    • Proper heating of food before

Staphylococcus aureus

  • Bacterium enters food from the nasal discharge or skin of food handlers
  • Lives in salads, ham, eggs, dairy products
  • Produces toxin which is ingested
  • Clinical features
    • Diarrhoea
    • Vomiting

Clostridium perfringens

  • Toxin is found in meat which is not sufficiently cooked
  • Clinical features
    • Diarrhoea

Bacillus cereus

  • Produces spores which survive cooking
  • Food left too long in room temperature -> spores start to proliferate and produce toxin
  • Often associated with rice stored at room temperature
  • Clinical features
    • Diarrhoea
    • Vomiting
  • Prevention
    • Food should be cooked rapidly and then cooled rapidly, not allowed to remain warm for long itme

Campylobacter jejuni

  • Epidemiology
    • Outbreaks during summer
    • Common in EU
  • Bacteria ingested through
    • Contaminated food or water
    • Undercooked meat
    • Raw milk
  • Clinical features
    • Bloody diarrhoea
    • May cause Guillain-Barré syndrome
  • Prevention:
    • Thoroughly cooking the food
    • Pasteurizing milk

Salmonella

  • Most commonly salmonella enteritidis, typhimurium
  • Reservoir
    • Poultry
    • Pigs
    • Cattle
  • Ingested through undercooked or contaminated meat or eggs
  • Acid labile bacteria
    • Healthy adults need to ingest many bacteria to be infected

Enterohaemorrhagic E. coli (EHEC)

  • Most important serotype – O157:H7
  • Very similar bacterium: Shiga-toxin producing E. coli (STEC)
  • Reservoir
    • Cattle
    • Sheep
  • Ingested through
    • Person-to-person
    • Undercooked ground meat
    • Raw milk
  • Clinical features
    • Causes severe disease
    • Bloody diarrhoea
    • Fever
    • May cause haemolytic uraemic syndrome in children, elderly
  • Prevention
    • It’s heat-sensitive

Enterotoxigenic E. coli (ETEC)

  • Epidemiology
    • Major cause of infantile diarrhoea
    • Causes traveller’s diarrhoea in visitors to endemic countries
    • One of the top four pathogens causing severe diarrhoea in children < 5
  • Ingested through contaminated food or water
  • Clinical features
    • Self-limiting
    • Mild diarrhoea
    • Can cause dehydration in young children

Shigella

  • S. sonnei, S. dysenteriae, etc.
  • Epidemiology
    • Uncommon in EU, common in developing countries
    • 60% of deaths occur in children < 5
    • One of the top four pathogens causing severe diarrhoea in children < 5
  • Transmitted faecal-oral or via contaminated food or water
  • Clinical features
    • Produce Shiga toxin
    • Causes dysentery (mucoid-bloody diarrhoea)
    • High fever
    • Can cause haemolytic uraemic syndrome in children and elderly
  • No vaccine

Cholera

  • Vibrio cholerae
  • Affects both children and adults
  • Transmission by
    • Contaminated water
      • Due to non-segregated sewage and drinking water
    • Undercooked seafood
  • Clinical features
    • Produces cholera toxin
    • Can kill within hours
      • Mortality 80% untreated, 1% treated
    • Watery diarrhoea 20 – 30 times a day
  • Treatment
    • 80% of cases can be treated with oral rehydration + salts
  • Prevention
    • Acid-labile bacterium
    • Providing safe water and sanitation is the most important factor in preventing cholera
    • Having oral rehydration prepared in case of outbreak
    • Oral cholera vaccine
      • Should not replace the other preventative measures

Typhoid fever

  • Salmonella typhi or paratyphi
  • Epidemiology
    • Absent from industrialized countries
    • Big problem for poorer countries
  • Transmission
    • Spread faecal-orally
  • Clinical features
    • Persistent fever
    • Headache
    • Abdominal pain
    • Constipation or diarrhoea
    • GI bleeding
  • Vaccine
    • Exists for salmonella typhi but not for paratyphi
    • Oral and injectable