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Chapter 4: Gastrointestinal infections 149

Aetiology and pathophysiology severity of each symptom and a careful history of food
Bacillus cereus has an incubation period of 30 min- intake over the past few days may point in the direction

utes to 6 hours. This most commonly causes acute of a cause.
self-limiting vomiting due to pre-formed enterotoxin
particularly associated with rice and pulses. Ingested
Investigations
spores (which are resistant to boiling) may cause diar-
Microscopy and culture of stool is used to identify cause.
rhoea from production of a different toxin. Recovery
All forms of bacterial food poisoning are notifiable to
occurs within a few hours.
allow contact tracing and investigation of source.
Staphylococcal food poisoning is caused by ingestion

of heat stable enterotoxins A, B, C, D and E. The onset
oftheclinicaldiseaseoccurs2–6hoursafterconsump- Management
tion of the toxins. Canned food, processed meats, milk In most cases the important factor is fluid rehydration
and cheese are the main source. The main character- preferablywithoralrehydrationsolution.Antibioticsare
istic feature is persistent vomiting, sometimes with a not used in simple food poisoning unless there is ev-
mild fever. There may be diarrhoea. Recovery occurs idence of systemic spread. Ciprofloxacin is a common
within a few hours. first-line antibiotic, until an organism is identified.
Campylobacter has an incubation period of 16–48

hours. There is a large animal reservoir (cattle, sheep, Bacilliary dysentery
rodents, poultry and wild birds). Patients present with
fever, headache and malaise, followed by diarrhoea, Definition
sometimes with blood and abdominal pain. Recovery Bacilliary dysentery is a diarrhoeal illness caused by
occurs within 3–5 days. Shigella infection.
Clostridium perfringens Type A producesanentero-

toxin which causes watery diarrhoea and cramping
Aetiology
abdominal pain as the main symptoms. It has an in-
There are four species of Shigella known to cause diar-
cubation period of 12–24 hours and recovery occurs
rhoeal illness:
within 2–3 days.
Shigella sonnei (75% of UK infections) cause most of
Salmonella has an incubation period of 16–48 hours.

the mild infections.
There are more than 2000 species on the basis of
Shigella flexneri and Shigella boydii (travellers) cause
antigens, which can help in tracing an outbreak.
intermediate infections.
Salmonella enteritidis (one common serotype is called
Shigella dysenteriae is the most serious.
Salmonella typhimurium)isfound in both animals
and humans. The main reservoir of infection is poul-
try, though person to person infection may occur. Di- Pathophysiology
arrhoea results from invasion by the bacteria result- Shigella is a human pathogen without an animal reser-
ing in inflammation. The condition is generally mild voir. Spread is by person-to-person contact, faecal–oral
with fever, malaise, cramping abdominal pain, bloody route or contaminated food. The incubation period is
diarrhoea and vomiting. Systemic disease may occur usually 2 days. The organism attaches to the mucosal
in those predisposed individuals, e.g. children, ter- epithelium of the distal ileum and colon causing inflam-
minally ill patients, sickle cell anaemia patients. The mation and ulceration.
organisms cause septicaemia causing osteomyelitis,
pneumonia or meningitis. Recovery may occur within Clinical features
days, but may take up to 2 weeks. Acutewaterydiarrhoeawithsystemicsymptomsoffever,
malaise and abdominal pain develops into bloody di-
Clinical features arrhoea. Other features include nausea, vomiting and
As outlined above the cardinal features of food poison- headaches. Complications include colonic perforation,
ing are diarrhoea, vomiting and abdominal pain. The septicaemia, arthritis and convulsions.