Questions and Answers
What is the primary reason for spore formation in bacteria?
Which of the following bacteria is NOT a Gram Positive Rod?
What is the primary component responsible for the remarkable resistance of the spore?
Which of the following is NOT a medically important Gram Positive Rod?
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What is the characteristic of a bacterial spore?
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Which of the following bacteria does NOT form spores?
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What happens to the coat of a bacterial spore when it is exposed to water and the appropriate nutrients?
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What is the characteristic shape of a Bacillus anthracis cell?
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What is the composition of the capsule of Bacillus anthracis?
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Where can Bacillus anthracis spores be found?
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What is the main virulence factor of Bacillus anthracis?
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What is the typical lesion of cutaneous anthrax?
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What is the main symptom of gastrointestinal anthrax?
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Who was the first to isolate Bacillus anthracis in pure culture?
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What is the primary symptom of pulmonary anthrax?
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What is the diagnostic criterion for pulmonary anthrax?
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What is the morphology of B. anthracis?
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What is the laboratory diagnosis method for B. anthracis?
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What is the treatment for pulmonary anthrax?
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How can people at high risk of pulmonary anthrax be protected?
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What is the main characteristic of B. cereus?
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What is the mode of transmission of B. cereus?
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Study Notes
Gram Positive Rods
- Medically important GPR: Bacillus, Clostridium, Listeria, Corynebacterium, Actinobacteria, Streptomyces, Nocardia, and Mycobacterium
Spore Forming Bacteria
- Bacillus and Clostridium are spore-forming bacteria
- Spores are highly resistant structures formed in response to adverse conditions
- Spore formation occurs when nutrients such as carbon and nitrogen sources are depleted
- Spores contain bacterial DNA, a small amount of cytoplasm, cell membrane, peptidoglycan, and a thick keratin-like coat
- The keratin-like coat is responsible for the spore's remarkable resistance to heat, dehydration, radiation, and chemicals
- Dipicolinic acid, a calcium ion chelator, may mediate the spore's resistance
- Spores have no metabolic activity and can remain dormant for many years
- Upon exposure to water and nutrients, specific enzymes degrade the coat, water and nutrients enter, and germination into a potentially pathogenic bacterial cell occurs
Bacillus
- Characteristics: large gram-positive rod with square ends, capsule, central endospore, and non-motile
- Reservoir: hoof stock (sheep, cattle, goats), textile workers, and soil contaminated with spores
- Virulence factors: capsule, spore, and exotoxin (anthrax toxin)
- Exotoxin causes necrosis and edema
Bacillus anthracis
- Can cause gastrointestinal, cutaneous, and inhalation anthrax
- Cutaneous anthrax: painless ulcer with a black eschar, local edema, and a malignant pustule
- Gastrointestinal anthrax: vomiting, abdominal pain, and bloody diarrhea
- Inhalation anthrax: nonspecific respiratory symptoms, dry cough, and substernal pressure, progressing to hemorrhagic mediastinitis, bloody pleural effusions, septic shock, and death
- Laboratory diagnosis: gram-positive rod with square ends, nonhemolytic colonies on blood agar, and PCR
- Treatment: ciprofloxacin or doxycycline
- Prevention: immunization with cell-free vaccine and incinerating animals that die of anthrax to prevent soil contamination
Bacillus cereus
- Characteristics: aerobic, non-encapsulated, motile, and spore-forming
- Virulence factors: spores, enterotoxins, hemolysins, and lecithinase (pLC)
- Causes food poisoning through contaminated rice
- Pathogenesis: produces two enterotoxins, one with a mode of action similar to cholera toxin and the other a superantigen
- Clinical findings: two syndromes, one characterized by abdominal cramps, diarrhea, and vomiting, and the other by a more severe syndrome resembling staphylococcal food poisoning
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Description
A quiz on Gram Positive Rods, specifically Bacillus, as part of Microbiology studies. Based on the 13th edition of Warren Levinson's Review of Medical Microbiology and Immunology.
