Microbiology: Gram Positive Rods and Bacillus
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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?

    <p>Actinobacteria</p> Signup and view all the answers

    What is the characteristic of a bacterial spore?

    <p>Highly resistant structure</p> Signup and view all the answers

    Which of the following bacteria does NOT form spores?

    <p>Listeria</p> 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?

    <p>It is degraded by specific enzymes</p> Signup and view all the answers

    What is the characteristic shape of a Bacillus anthracis cell?

    <p>A large gram-positive rod with square ends</p> Signup and view all the answers

    What is the composition of the capsule of Bacillus anthracis?

    <p>D-glutamate</p> Signup and view all the answers

    Where can Bacillus anthracis spores be found?

    <p>In contaminated soil, hoof stock, and textile workers</p> Signup and view all the answers

    What is the main virulence factor of Bacillus anthracis?

    <p>All of the above</p> Signup and view all the answers

    What is the typical lesion of cutaneous anthrax?

    <p>A painless ulcer with a black eschar</p> Signup and view all the answers

    What is the main symptom of gastrointestinal anthrax?

    <p>Abdominal pain and bloody diarrhea</p> Signup and view all the answers

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

    <p>Koch</p> Signup and view all the answers

    What is the primary symptom of pulmonary anthrax?

    <p>Dry cough</p> Signup and view all the answers

    What is the diagnostic criterion for pulmonary anthrax?

    <p>Mediastinal widening on chest X-ray</p> Signup and view all the answers

    What is the morphology of B. anthracis?

    <p>Large gram-positive rod with square ends</p> Signup and view all the answers

    What is the laboratory diagnosis method for B. anthracis?

    <p>PCR</p> Signup and view all the answers

    What is the treatment for pulmonary anthrax?

    <p>Ciprofloxacin</p> Signup and view all the answers

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

    <p>Immunization with cell-free vaccine</p> Signup and view all the answers

    What is the main characteristic of B. cereus?

    <p>Motile</p> Signup and view all the answers

    What is the mode of transmission of B. cereus?

    <p>Contaminated food</p> 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.

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