Microbiology
Summary
Bacillus anthracis and Bacillus cereus are two distinct species of bacteria known for their rod-shaped morphology and ability to form chains. While they share certain characteristics, they exhibit different pathogenic behaviors. B. anthracis is known for its association with cutaneous anthrax, which is characterized by a black eschar or necrotic cutaneous lesion surrounded by an erythematous ring. This bacterium has unique features, such as being a spore-former, an obligate aerobe, and having a capsule made of poly-D-glutamate. Bacillus anthracis produced multiple toxins, two of which are edema factor (EF) and lethal factor (LF). EF functions as an adenylate cyclase, which increases cAMP intracellularly and causes edema, while LF is an exotoxin that acts as a protease and cleaves mitogen-activated protein kinase (MAPK), leading to tissue necrosis.
On the other hand, Bacillus cereus is associated with food poisoning, often linked to reheated rice. Like B. anthracis, B. cereus is also an aerobic and spore-forming microbe.
Lesson Outline
Don't stop here!
Get access to 128 more Microbiology lessons & 13 more medical school learning courses with one subscription!
FAQs
Bacillus anthracis and Bacillus cereus are both gram-positive rods, but they cause different diseases. B. anthracis is the causative agent of anthrax, a severe, potentially lethal infection. The symptoms of anthrax can include pulmonary symptoms (Woolsorter's disease), cutaneous symptoms, and gastrointestinal manifestations. B. cereus is a common cause of foodborne illness, which usually results in self-limiting gastrointestinal symptoms, such as vomiting and diarrhea. Unlike B. anthracis, B. cereus rarely causes life-threatening infections.
The black eschar is a characteristic lesion found in cases of cutaneous anthrax caused by Bacillus anthracis. The lesion begins as a small, itchy bump, which rapidly progresses to a painless ulcer with necrosis. The necrotic tissue eventually forms a black eschar, composed of dead skin and debris, surrounded by edema.
Pulmonary anthrax, also known as inhalational anthrax, is a severe form of anthrax caused by the inhalation of Bacillus anthracis spores. Historically, Woolsorter's disease was the term used to describe pulmonary anthrax specifically among workers who sorted wool, as they were frequently exposed to B. anthracis spores through their occupation. Since the spores were often present in the wool, workers who inhaled these spores would develop Woolsorter's disease.
Early diagnosis and treatment are crucial for the effective management of anthrax infections. Antibiotics, such as fluoroquinolones (e.g., ciprofloxacin), doxycycline, and amoxicillin, are effective in treating anthrax if initiated early in the course of infection. In severe cases, additional supportive care, including intravenous fluids, oxygen, and other life-sustaining measures, may be required. Treatment duration varies depending on the severity of the infection and the type of anthrax (cutaneous, gastrointestinal, or inhalational). In cases of suspected or confirmed exposure to B. anthracis spores, prophylactic antibiotic treatment may be implemented to prevent infection.
