Bacillus anthracis
Overview
Bacillus anthracis is a Gram-positive rod that can cause anthrax, an acute infection that may affect the skin (cutaneous anthrax), the lungs (inhaled anthrax) or the gastrointestinal tract. It is spread by infected carcasses.
It is also known as Woolsorter’s disease due to its association with people who work in wool mills where they may inhale spores from infected animals.
Features
- Painless, black eschar without pus:
- These are firm, black, scabs made of necrotic tissue
- Skin oedema – due to the bacteria producing a protein called oedema factor
- Fever, chills, dyspnoea, cough – in inhalation anthrax, usually seen weeks-months after exposure
- Gastrointestinal bleeding, abdominal pain, diarrhoea – in gastrointestinal anthrax
Bacillus cereus
Overview
Bacillus cereus is a Gram-positive rod associated with food poisoning and nosocomial infection in immunocompromised people. It is found in soil and nearly everywhere in nature.
The classic presentation of infection is gastroenteritis shortly after eating under-cooked or reheated rice. It occurs because the exotoxin cereulide can withstand high temperatures.
Significant exposures to B. cereus occur most commonly in the context of food poisoning. Under-cooked or reheated rice is most classically associated with B. cereus. The bacterial exotoxin cereulide is stable for short periods of very high temperatures such as in stir frying.
Features
Bacillus cereus infection can cause two food poisoning syndromes:
- Emetic syndrome – due to ingesting contaminated food and the cereulide toxin. Vomiting occurs within 6 hours of ingestion and may have associated diarrhoea.
- Diarrhoeal syndrome – due to ingesting contaminated food and other toxins. Crampy abdominal pain and diarrhoea usually happen 8-16 hours after ingestion.
In both cases, symptoms usually resolve within 24 hours.
In people who are immunosuppressed, more serious infections can occur including sepsis, infective endocarditis, meningitis and encephalitis, and musculoskeletal infections.
