Bacterial food poisoning is common and can be caused by a number of different organisms.
Bacillus cereus has an incubation period of 30 minutes to 6 hours. This most commonly causes acute self-limiting vomiting due to preformed enterotoxin particularly associated with rice and pulses. Ingested spores (which are resistant to boiling) may cause diarrhoea from production of a different toxin. Recovery occurs within a few hours.
Staphylococcal food poisoning is caused by ingestion of heat stable enterotoxins A, B, C, D and E. The onset of the clinical disease occurs 2–6 hours after consumption of the toxins. Canned food, processed meats, milk and cheese are the main source. The main characteristic feature is persistent vomiting, sometimes with a mild fever. There may be diarrhoea. Recovery occurs within a few hours.
Campylobacter has an incubation period of 16–48 hours. There is a large animal reservoir (cattle, sheep, rodents, poultry and wild birds). Patients present with fever, headache and malaise, followed by diarrhoea, sometimes with blood and abdominal pain. Recovery occurs within 3–5 days.
Clostridium perfringens Type A produces an entero-toxin which causes watery diarrhoea and cramping abdominal pain as the main symptoms. It has an incubation period of 12–24 hours and recovery occurs within 2–3 days.
Salmonella has an incubation period of 16–48 hours. There are more than 2000 species on the basis of antigens, which can help in tracing an outbreak.Salmonella enteritidis (one common serotype is called
Salmonella typhimurium) is found in both animals and humans. The main reservoir of infection is poultry, though person to person infection may occur. Di-arrhoea results from invasion by the bacteria resulting in inflammation. The condition is generally mild with fever, malaise, cramping abdominal pain, bloody diarrhoea and vomiting. Systemic disease may occur in those predisposed individuals, e.g. children, terminally ill patients, sickle cell anaemia patients. The organisms cause septicaemia causing osteomyelitis, pneumonia or meningitis. Recovery may occur within days, but may take up to 2 weeks.
As outlined above the cardinal features of food poisoning are diarrhoea, vomiting and abdominal pain. The severity of each symptom and a careful history of food intake over the past few days may point in the direction of a cause.
Microscopy and culture of stool is used to identify cause. All forms of bacterial food poisoning are notifiable to allow contact tracing and investigation of source.
In most cases the important factor is fluid rehydration preferably with oral rehydration solution. Antibiotics are not used in simple food poisoning unless there is evidence of systemic spread. Ciprofloxacin is a common first-line antibiotic, until an organism is identified.