Microbiology: Gram Positive Rods and Bacillus

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Questions and Answers

What is the primary reason for spore formation in bacteria?

To adapt to favorable environmental conditions

To increase metabolic activity

To increase cell size

In response to depleted nutrients (correct)

Which of the following bacteria is NOT a Gram Positive Rod?

Clostridium

Mycobacterium (correct)

Bacillus

Streptomyces

What is the primary component responsible for the remarkable resistance of the spore?

Cytoplasm

Dipicolinic acid (correct)

Cell membrane

Peptidoglycan

Which of the following is NOT a medically important Gram Positive Rod?

Actinobacteria Signup and view all the answers

What is the characteristic of a bacterial spore?

Highly resistant structure Signup and view all the answers

Which of the following bacteria does NOT form spores?

Listeria Signup and view all the answers

What happens to the coat of a bacterial spore when it is exposed to water and the appropriate nutrients?

It is degraded by specific enzymes Signup and view all the answers

What is the characteristic shape of a Bacillus anthracis cell?

A large gram-positive rod with square ends Signup and view all the answers

What is the composition of the capsule of Bacillus anthracis?

D-glutamate Signup and view all the answers

Where can Bacillus anthracis spores be found?

In contaminated soil, hoof stock, and textile workers Signup and view all the answers

What is the main virulence factor of Bacillus anthracis?

All of the above Signup and view all the answers

What is the typical lesion of cutaneous anthrax?

A painless ulcer with a black eschar Signup and view all the answers

What is the main symptom of gastrointestinal anthrax?

Abdominal pain and bloody diarrhea Signup and view all the answers

Who was the first to isolate Bacillus anthracis in pure culture?

Koch Signup and view all the answers

What is the primary symptom of pulmonary anthrax?

Dry cough Signup and view all the answers

What is the diagnostic criterion for pulmonary anthrax?

Mediastinal widening on chest X-ray Signup and view all the answers

What is the morphology of B. anthracis?

Large gram-positive rod with square ends Signup and view all the answers

What is the laboratory diagnosis method for B. anthracis?

PCR Signup and view all the answers

What is the treatment for pulmonary anthrax?

Ciprofloxacin Signup and view all the answers

How can people at high risk of pulmonary anthrax be protected?

Immunization with cell-free vaccine Signup and view all the answers

What is the main characteristic of B. cereus?

Motile Signup and view all the answers

What is the mode of transmission of B. cereus?

Contaminated food Signup and view all the answers

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.