View source for 27. Epidemiology and prevention of enteric bacterial infections

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

[[Category:Public health 4 - Preventive medicine]]