Gram-Positive Bacilli: Anthrax & Diphtheriae

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Questions and Answers

Which microscopy technique is utilized for identifying Corynebacterium diphtheriae by observing its characteristic appearance?

  • Negative stain
  • Methylene Blue stain
  • Gram stain (correct)
  • Acid-fast stain

What is the primary mode of transmission for Bacillus anthracis?

  • Aerosolized spores (correct)
  • Insect bites
  • Consumption of contaminated food
  • Contact with infected individuals

What distinguishes Listeria monocytogenes from Corynebacterium diphtheriae?

  • It forms spores
  • It is cold-tolerant (correct)
  • It is non-motile
  • It does not cause food poisoning

What differentiates the pathogenicity of Bacillus cereus from that of Bacillus anthracis?

<p>Bacillus cereus causes gastrointestinal diseases, while Bacillus anthracis causes inhalation anthrax. (A)</p> Signup and view all the answers

Which condition is primarily caused by Listeria monocytogenes, especially in newborns?

<p>Neonatal meningitis (D)</p> Signup and view all the answers

In the context of Corynebacterium diphtheriae, which test is considered the most common assay for determining its toxigenicity?

<p>Elek’s test (D)</p> Signup and view all the answers

Which clinical manifestation is NOT associated with inhalation anthrax?

<p>Local pseudomembrane formation (C)</p> Signup and view all the answers

What type of disease is associated with Bacillus anthracis in zoonotic contexts?

<p>Cutaneous anthrax from handling contaminated animal products (B)</p> Signup and view all the answers

Which bacteria are primarily responsible for the majority of neonatal meningitis cases?

<p>Listeria monocytogenes and Escherichia coli (A)</p> Signup and view all the answers

Which diagnostic specimen is crucial for confirming diphtheria?

<p>Throat swab from the pseudomembrane (B)</p> Signup and view all the answers

What characteristic morphology is observed in a Gram stain of Corynebacterium diphtheriae?

<p>Bacilli with a Chinese letters appearance (C)</p> Signup and view all the answers

Which medium is best known for providing the best morphological characteristics for isolating Corynebacterium diphtheriae?

<p>Loeffler's serum (D)</p> Signup and view all the answers

Which of the following tests is specifically used to confirm the toxigenicity of Corynebacterium diphtheriae?

<p>Elek’s test (C)</p> Signup and view all the answers

What specimen is primarily used for confirming the diagnosis of diphtheria?

<p>Throat swab from the pseudomembrane (D)</p> Signup and view all the answers

What is a common characteristic feature seen in methylene blue stained smears of Corynebacterium diphtheriae?

<p>Metachromatic granules (D)</p> Signup and view all the answers

Which of the following is a characteristic clinical sign of diphtheria?

<p>Local pseudomembrane (A)</p> Signup and view all the answers

What type of colonies would be expected on blood tellurite agar when culturing Corynebacterium diphtheriae?

<p>Grey/black colonies (A)</p> Signup and view all the answers

What complication is associated with diphtheria that affects the heart?

<p>Toxic myocarditis and heart failure (D)</p> Signup and view all the answers

What method is primarily used to diagnose diphtheria aside from laboratory confirmation?

<p>Clinical examination (C)</p> Signup and view all the answers

What describes Corynebacterium diphtheriae's morphology under the microscope?

<p>Club-shaped arranged in acute angles (C)</p> Signup and view all the answers

What is the primary specimen used for laboratory confirmation of diphtheria diagnosis?

<p>Throat swab from the pseudomembrane (C)</p> Signup and view all the answers

Which symptom is not typically associated with diphtheria?

<p>Severe abdominal pain (A)</p> Signup and view all the answers

Which of the following is a clinical feature of diphtheria?

<p>Local pseudomembrane (C)</p> Signup and view all the answers

What complication can arise from diphtheria affecting the respiratory system?

<p>Toxic myocarditis and heart failure (A)</p> Signup and view all the answers

What type of infection does diphtheria primarily cause?

<p>Upper respiratory tract infection (B)</p> Signup and view all the answers

What is the primary microscopic characteristic observed in a Gram-stained smear of Corynebacterium diphtheriae?

<p>Clubbing-shaped bacilli (D)</p> Signup and view all the answers

Which method is specifically used to visualize meta-chromatic granules in Corynebacterium diphtheriae?

<p>Methylene Blue stain (B)</p> Signup and view all the answers

Which culture medium is best known for providing the optimal morphology of Corynebacterium diphtheriae?

<p>Loeffler’s serum medium (C)</p> Signup and view all the answers

Which test is primarily used to assess the toxigenicity of Corynebacterium diphtheriae?

<p>Elek’s test (A)</p> Signup and view all the answers

What kind of colonies would be expected on blood tellurite agar when culturing Corynebacterium diphtheriae?

<p>Grey/black colonies (B)</p> Signup and view all the answers

Corynebacterium diphtheriae can be cultured on MacConkey's agar.

<p>False (B)</p> Signup and view all the answers

The Elek's test is used to determine the toxigenicity of Corynebacterium diphtheriae.

<p>True (A)</p> Signup and view all the answers

Blood tellurite agar is a simple medium used for isolating Corynebacterium diphtheriae.

<p>False (B)</p> Signup and view all the answers

Corynebacterium diphtheriae is typically observed as Gram-positive cocci arranged in chains.

<p>False (B)</p> Signup and view all the answers

Lowenstein-Jensen medium is the preferred culture medium for Corynebacterium diphtheriae.

<p>False (B)</p> Signup and view all the answers

Corynebacterium diphtheriae is identified as Gram-negative club-shaped bacilli under microscopic examination.

<p>False (B)</p> Signup and view all the answers

The Elek's test is a common assay used to detect the presence of toxin produced by Corynebacterium diphtheriae.

<p>True (A)</p> Signup and view all the answers

Methylene Blue stain is used to identify Corynebacterium diphtheriae by visualizing its meta-chromatic granules.

<p>True (A)</p> Signup and view all the answers

Blood agar is the primary medium used for the best morphological characterization of Corynebacterium diphtheriae.

<p>False (B)</p> Signup and view all the answers

Chinese letters appearance is a characteristic morphology seen in Gram-stained smears of Corynebacterium diphtheriae.

<p>True (A)</p> Signup and view all the answers

Corynebacterium diphtheriae is a non-motile organism commonly identified in bacterial cultures.

<p>True (A)</p> Signup and view all the answers

Detecting Gram-negative bacilli arranged in angles and palisades is indicative of Listeria monocytogenes.

<p>False (B)</p> Signup and view all the answers

Corynebacterium diphtheriae can be confirmed by analyzing a throat swab from the pseudomembrane.

<p>True (A)</p> Signup and view all the answers

Methylene blue staining is used to give Corynebacterium diphtheriae a smooth appearance under a microscope.

<p>False (B)</p> Signup and view all the answers

Blood agar is a culture medium that is utilized to grow Corynebacterium diphtheriae.

<p>True (A)</p> Signup and view all the answers

The characteristic morphology of Corynebacterium diphtheriae includes being club-shaped and arranged in parallel lines.

<p>True (A)</p> Signup and view all the answers

Diphtheria can only be diagnosed through laboratory confirmation, and clinical diagnosis is not applicable.

<p>False (B)</p> Signup and view all the answers

Corynebacterium diphtheriae is a non-spore forming gram-positive bacillus.

<p>True (A)</p> Signup and view all the answers

Loeffler’s serum is the least effective medium for obtaining the best morphology of Corynebacterium diphtheriae.

<p>False (B)</p> Signup and view all the answers

A throat swab is not useful in diagnosing diphtheria due to the nature of the infection.

<p>False (B)</p> Signup and view all the answers

Blood tellurite agar yields grey to black colonies when culturing Corynebacterium diphtheriae.

<p>True (A)</p> Signup and view all the answers

The presumption of diphtheria generally involves only serological testing without any clinical evaluation.

<p>False (B)</p> Signup and view all the answers

The indicative morphology of Corynebacterium diphtheriae under a Gram stain is characterized by ______ letters appearance.

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

The Elek's test is primarily used to assess the ______ of Corynebacterium diphtheriae.

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

Microscopic examination of Corynebacterium diphtheriae reveals it as a Gram-positive ______-shaped bacilli.

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

To visualize meta-chromatic granules in Corynebacterium diphtheriae, a ______ stain is utilized.

<p>methylene blue</p> Signup and view all the answers

Cultivation of Corynebacterium diphtheriae on ______ agar is utilized to obtain grey or black colonies.

<p>blood tellurite</p> Signup and view all the answers

Corynebacterium diphtheriae is primarily diagnosed through a throat swab from the ________.

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

Laboratory confirmation of diphtheria usually involves analyzing a ________ sample.

<p>throat swab</p> Signup and view all the answers

The diagnosis of diphtheria is mainly ________, though laboratory confirmation is also necessary.

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

Corynebacterium diphtheriae can cause an upper respiratory tract infection and is transmitted via ________.

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

Corynebacterium diphtheriae is characterized by a local ________ in the throat during diphtheria infections.

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

What type of infection is primarily caused by Corynebacterium diphtheriae?

<p>Diphtheria, which is an upper respiratory tract infection.</p> Signup and view all the answers

What is the primary specimen used for laboratory confirmation of diphtheria?

<p>A throat swab from the pseudomembrane.</p> Signup and view all the answers

What are the characteristic colony colors observed on blood tellurite agar when culturing Corynebacterium diphtheriae?

<p>Grey/black colonies.</p> Signup and view all the answers

What morphological feature is characteristic of Corynebacterium diphtheriae under the microscope?

<p>Corynebacterium diphtheriae appears as club-shaped bacilli arranged at acute angles, resembling Chinese letters.</p> Signup and view all the answers

Which culture medium provides the best morphology for isolating Corynebacterium diphtheriae?

<p>Loeffler’s serum is the best medium for obtaining the best morphological characteristics.</p> Signup and view all the answers

Name one diagnosis method that detects the toxin gene in Corynebacterium diphtheriae.

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

In the microscopic examination of Corynebacterium diphtheriae, what morphology is typically observed?

<p>Gram-positive club-shaped bacilli arranged like Chinese letters.</p> Signup and view all the answers

What complications can arise from a diphtheria infection?

<p>Possible complications include airway obstruction, toxic myocarditis, heart failure, and nerve paralysis.</p> Signup and view all the answers

What staining method is used to visualize the meta-chromatic granules of Corynebacterium diphtheriae?

<p>Methylene Blue stain.</p> Signup and view all the answers

What does a positive Elek’s test indicate in relation to Corynebacterium diphtheriae?

<p>It indicates the presence of toxin production.</p> Signup and view all the answers

Which of the following complications is associated with diphtheria?

<p>Toxic myocarditis and heart failure (A)</p> Signup and view all the answers

Which staining method is used specifically to visualize meta-chromatic granules in Corynebacterium diphtheriae?

<p>Methylene Blue stain (A)</p> Signup and view all the answers

Corynebacterium diphtheriae is a spore-forming bacterium.

<p>False (B)</p> Signup and view all the answers

Corynebacterium diphtheriae is identified microscopically as Gram-positive club-shaped bacilli arranged in chains.

<p>False (B)</p> Signup and view all the answers

What is the primary specimen used for laboratory confirmation of diphtheria diagnosis?

<p>Throat swab from the pseudomembrane</p> Signup and view all the answers

Corynebacterium diphtheriae is known to produce a _____, which is a virulence factor.

<p>diphtheria exotoxin</p> Signup and view all the answers

What type of colonies would you expect to see on blood tellurite agar when culturing Corynebacterium diphtheriae?

<p>Grey/black colonies</p> Signup and view all the answers

Match the following symptoms of diphtheria with their description:

<p>Local pseudomembrane = Membrane forming in the throat Toxemia = Presence of toxin in the bloodstream Airway obstruction = Difficulty in breathing Nerve paralysis = Loss of nerve function in muscles</p> Signup and view all the answers

The isolated organism from diphtheria testing is __________.

<p>Corynebacterium diphtheriae</p> Signup and view all the answers

Match the following tests with their purpose in identifying Corynebacterium diphtheriae:

<p>Elek’s test = Detect toxigenicity PCR = Detect toxin gene ELISA = Detect toxin from culture Gram stain = Identify morphology</p> Signup and view all the answers

Flashcards

Corynebacterium diphtheriae

A Gram-positive, club-shaped bacterium that can cause diphtheria.

Diphtheria Toxin

A toxin produced by some strains of Corynebacterium diphtheriae that causes serious illness.

Elek's test

A test used to detect the presence of diphtheria toxin.

Corynebacterium diphtheroids

Gram-positive bacteria that resemble C. diphtheriae but are not pathogenic (non-disease causing).

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Listeria monocytogenes

A Gram-positive, rod-shaped bacterium that can cause listeriosis, especially in pregnant women and newborns, and is also linked to food poisoning from contaminated dairy or meat products.

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Listeria Morphology

Gram-positive rods (or coccobacilli) arranged in short chains, non-capsulated, motile bacteria.

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Listeriosis Symptoms

Can cause abortion, premature birth, sepsis in pregnancy, neonatal meningitis, or sepsis and meningitis in immunocompromised adults. Possibly foodborne.

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Gram-positive bacilli

A type of bacteria characterized by a positive Gram stain, and a rod shape.

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Gram Stain

A staining technique used to differentiate bacteria based on their cell wall structure.

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Gram-positive bacilli

Bacteria with a thick peptidoglycan layer that retains the crystal violet stain during Gram staining.

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Capsule formation

Some Gram-positive bacteria, like Bacillus anthracis, have a protective capsule that helps them evade the host's immune system.

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Spore formation

Certain gram-positive bacteria, such as Bacillus species, can form endospores, resistant structures that survive harsh environmental conditions.

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Metachromatic granules

Characteristic dark-staining bodies found within Corynebacterium diphtheriae cells, appearing as granules.

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Corynebacterium diphtheriae

Gram-positive bacillus, causing diphtheria, club-shaped, arranged in Chinese letters, with metachromatic granules.

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Diphtheria Exotoxin

Virulence factor of Corynebacterium diphtheriae that causes the characteristic symptoms of diphtheria.

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Diphtheria

Upper respiratory tract infection caused by Corynebacterium diphtheriae, characterized by a pseudomembrane and toxemia.

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Specimen for Diphtheria diagnosis

Throat swab from the pseudomembrane.

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Gram-positive bacilli

Bacteria with a thick peptidoglycan layer that retains crystal violet stain.

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Capsule formation

Some gram-positive bacteria develop a protective layer to evade the immune system.

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Spore formation

Certain gram-positive bacteria produce resistant structures that survive harsh conditions.

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Metachromatic granules

Dark-staining bodies in Corynebacterium diphtheriae cells.

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Corynebacterium diphtheriae

Gram-positive bacillus causing diphtheria, with club-shaped cells and metachromatic granules.

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Diphtheria Exotoxin

Harmful toxin from Corynebacterium diphtheriae causing severe illness.

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Diphtheria

Upper respiratory infection caused by Corynebacterium diphtheriae, characterized by a pseudomembrane and toxemia.

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Diagnosis speciment

Throat swab from the pseudomembrane

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Gram-positive bacilli

Rod-shaped bacteria that stain purple in a Gram stain.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacteria that cause diphtheria; often arranged in "Chinese letters" patterns.

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Diphtheria

An upper respiratory infection caused by Corynebacterium diphtheriae.

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Metachromatic granules

Dark-staining structures seen in Corynebacterium diphtheriae cells, key for identification.

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Elek's test

Tests if a bacteria Corynebacterium diphtheriae produces a toxin.

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Listeria monocytogenes

Gram-positive, rod-shaped bacteria that can cause food poisoning and severe infections, particularly in newborns, and pregnant women.

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Listeria Morphology

Gram-positive, rod-shaped bacteria that are often arranged in short chains and are motile.

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Gram Stain

A laboratory technique to distinguish bacteria based on their cell wall composition.

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Specimen for Diphtheria Diagnosis

Throat swab taken from the affected area (pseudomembrane).

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet stain in a Gram stain.

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Corynebacterium diphtheriae

A Gram-positive, club-shaped bacterium that can cause diphtheria.

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Diphtheria

An upper respiratory tract infection caused by Corynebacterium diphtheriae .

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Elek's test

A test used to detect the presence of diphtheria toxin.

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Metachromatic granules

Unique, dark-staining structures within Corynebacterium diphtheriae cells.

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Listeria monocytogenes

A Gram-positive, rod-shaped bacterium causing Listeriosis.

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Listeria Morphology

Gram-positive rods arranged in short chains, motile bacteria.

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Listerioisis

Infection caused by Listeria monocytogenes, often severe in pregnant women and newborns.

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Gram stain

A staining technique used to categorize bacteria based on their cell wall structure.

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Gram-positive bacilli

Bacteria that have a thick peptidoglycan layer in their cell wall, retaining the crystal violet stain during Gram staining.

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Capsule formation

Some gram-positive bacteria produce a protective outer layer (capsule) that helps them avoid the host's immune system.

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Spore formation

Certain gram-positive bacteria can create highly resistant structures (endospores) that survive harsh conditions.

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Metachromatic granules

Unique granules found in Corynebacterium diphtheriae; these are dark-staining bodies, appearing as granules within the cell.

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Corynebacterium diphtheriae

A gram-positive bacillus causing diphtheria, with a distinctive club shape and characteristic metachromatic granules.

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Diphtheria Exotoxin

A harmful toxin produced by Corynebacterium diphtheriae that causes the severe symptoms associated with the disease.

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Diphtheria

An upper respiratory tract infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and toxin related symptoms.

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Diagnosis speciment

A throat swab taken from the pseudomembrane to confirm the presence of Corynebacterium diphtheriae and other diphtheria related infections.

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet stain in a Gram stain.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacteria causing diphtheria; often arranged in "Chinese letters" patterns.

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Diphtheria

An upper respiratory infection caused by Corynebacterium diphtheriae.

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Metachromatic granules

Unique, dark-staining structures within Corynebacterium diphtheriae cells.

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Elek's test

A test to determine if Corynebacterium diphtheriae produces a toxin.

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Listeria monocytogenes

Gram-positive, rod-shaped bacteria causing Listeriosis.

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Listeria Morphology

Gram-positive rods arranged in short chains, motile bacteria.

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Listerioisis

Infection caused by Listeria monocytogenes, often severe in pregnant women and newborns.

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Gram stain

A staining technique to distinguish bacteria based on their cell wall composition.

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Gram-Positive Bacilli

Rod-shaped bacteria that stain purple in a Gram stain, possessing a thick peptidoglycan layer.

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Gram Stain

A lab technique that differentiates bacteria based on their cell wall structure, using dyes.

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Peptidoglycan Layer

Thick layer in the cell wall of Gram-positive bacteria.

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Capsule Formation

Some Gram-positive bacteria produce a protective outer layer, helping them avoid the host's immune responses.

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Spore Formation

Some Gram-positive bacteria produce dormant structures that resist harsh conditions.

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Metachromatic Granules

Unique, dark-staining structures found in some Gram-positive bacteria, like Corynebacterium diphtheriae.

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Corynebacterium diphtheriae

A gram-positive bacillus causing diphtheria, with a club shape and metachromatic granules that appear in distinctive arrangements.

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Diphtheria Exotoxin

Harmful toxin produced by Corynebacterium diphtheriae; causes severe illness.

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Diphtheria

An upper respiratory tract infection caused by Corynebacterium diphtheriae.

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Diagnosis Specimen

Throat swab from the pseudomembrane for diphtheria.

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Neonatal meningitis cause (case)

Listeria monocytogenes is the most likely cause of neonatal meningitis in this case.

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Listeria monocytogenes Transmission

Listeria monocytogenes is a foodborne pathogen that can contaminate dairy products (like unpasteurized milk and soft cheeses), undercooked meat, and refrigerated foods.

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Listeria monocytogenes Morphology

Gram-positive, rod-shaped bacteria, often in short chains, and can be motile.

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Listeria Resistance

Listeria monocytogenes resists drying, heating, and freezing without forming spores; this makes food contamination a significant concern.

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Blood Tellurite agar

A selective and differential medium used for culturing Corynebacterium diphtheriae.

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Elek's test

A test that identifies the presence of diphtheria toxin produced by Corynebacterium diphtheriae .

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C. diphtheriae Morphology

Gram-positive, club-shaped bacilli; they are often described as having a "Chinese lettering" arrangement.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacterium causing diphtheria, often arranged in 'Chinese letters'.

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Diphtheria

Upper respiratory infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and the toxin it produces.

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Elek's test

An assay to detect diphtheria toxin, an important virulence factor of Corynebacterium diphtheriae.

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet stain in a Gram stain.

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Listeria monocytogenes

Gram-positive, rod-shaped bacteria that can cause food poisoning and severe infections, particularly in newborns or pregnant women.

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Listeria Morphology

Gram-positive rods arranged in short chains, motile bacteria.

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Metachromatic granules

Unique, dark-staining structures within Corynebacterium diphtheriae cells.

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Blood tellurite agar

A selective and differential medium used for culturing Corynebacterium diphtheriae.

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Gram stain

A laboratory technique to distinguish bacteria based on their cell wall composition.

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet dye in Gram staining, due to a thick peptidoglycan layer.

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Capsule formation

Some gram-positive bacteria create a protective outer layer that helps them evade the host's immune system.

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Spore formation

Certain gram-positive bacteria produce resistant structures (endospores) that survive harsh environmental conditions.

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Metachromatic granules

Dark-staining inclusions within Corynebacterium diphtheriae cells.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacteria arranged in characteristic "Chinese letters" patterns, a key cause of diphtheria.

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Diphtheria Exotoxin

A harmful toxin produced by Corynebacterium diphtheriae, causing severe symptoms.

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Diphtheria

Upper respiratory tract infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and toxemia.

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Diagnosis Specimen

Throat swab from the pseudomembrane for diphtheria diagnosis.

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Blood tellurite agar

A selective medium used to cultivate Corynebacterium diphtheriae.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacillus causing diphtheria, often arranged in "Chinese letters" patterns.

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Diphtheria

An upper respiratory infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and the toxin it produces.

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Elek's test

An assay to detect diphtheria toxin, an important virulence factor of Corynebacterium diphtheriae.

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet stain in a Gram stain.

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Listeria monocytogenes

Gram-positive, rod-shaped bacteria that can cause food poisoning and severe infections, particularly in newborns or pregnant women.

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Listeria Morphology

Gram-positive rods arranged in short chains, motile bacteria.

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Metachromatic granules

Unique, dark-staining structures within Corynebacterium diphtheriae cells.

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Blood tellurite agar

A selective medium used to cultivate Corynebacterium diphtheriae.

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Diagnosis Specimen (Diphtheria)

Throat swab from the pseudomembrane for diphtheria diagnosis.

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Gram-positive Bacilli

Rod-shaped bacteria retaining crystal violet dye in Gram staining, due to a thick peptidoglycan layer.

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Capsule Formation

Some gram-positive bacteria develop a protective outer layer to avoid the immune system.

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Spore Formation

Gram-positive bacteria creating resistant structures (endospores) that withstand harsh conditions.

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Metachromatic Granules

Unique dark-staining inclusions within Corynebacterium diphtheriae cells.

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Corynebacterium diphtheriae

Gram-positive bacteria, club-shaped, often arranged in "Chinese letters," causing diphtheria.

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Diphtheria Exotoxin

Harmful toxin from Corynebacterium diphtheriae, causing serious illness.

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Diphtheria

Upper respiratory infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and toxemia.

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Diagnosis Specimen

Throat swab from the pseudomembrane for diphtheria diagnosis.

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Blood Tellurite Agar

Selective medium for culturing Corynebacterium diphtheriae.

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Elek's test

Assay detecting diphtheria toxin produced by Corynebacterium diphtheriae.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacterium causing diphtheria, often arranged in "Chinese letters" patterns.

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Diphtheria

Upper respiratory infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and the toxin it produces.

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Elek's test

Assay to detect diphtheria toxin, an important virulence factor of Corynebacterium diphtheriae.

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet stain in a Gram stain.

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Listeria monocytogenes

Gram-positive, rod-shaped bacteria that can cause food poisoning and severe infections, particularly in newborns and pregnant women.

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Listeria Morphology

Gram-positive rods arranged in short chains, motile bacteria.

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Metachromatic granules

Dark-staining inclusions within Corynebacterium diphtheriae cells.

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Blood tellurite agar

A selective medium used to cultivate Corynebacterium diphtheriae.

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Gram Stain

A laboratory technique to distinguish bacteria based on their cell wall structure.

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Gram-positive bacilli

Rod-shaped bacteria that retain the crystal violet stain in a Gram stain, due to a thick peptidoglycan layer.

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Capsule formation

Some gram-positive bacteria create a protective outer layer that helps them evade the host's immune system.

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Spore formation

Certain gram-positive bacteria produce resistant structures (endospores) that survive harsh environmental conditions.

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Metachromatic granules

Dark-staining inclusions within Corynebacterium diphtheriae cells.

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Corynebacterium diphtheriae

Gram-positive, club-shaped bacteria arranged in characteristic "Chinese letters" patterns, a key cause of diphtheria.

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Diphtheria Exotoxin

A harmful toxin produced by Corynebacterium diphtheriae, causing severe symptoms.

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Diphtheria

An upper respiratory tract infection caused by Corynebacterium diphtheriae, marked by a pseudomembrane and toxemia.

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Diagnosis Specimen

Throat swab from the pseudomembrane for diphtheria diagnosis.

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Blood tellurite agar

A selective medium used to cultivate Corynebacterium diphtheriae.

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Study Notes

Gram-Positive Bacilli: Anthrax and Corynebacterium Diphtheriae

  • Gram-positive bacteria possess a thick peptidoglycan layer that retains crystal violet stain during Gram staining.
  • Some species, like Bacillus anthracis, have a capsule, a protective layer that helps them evade the host's immune system.
  • Certain gram-positive bacteria, such as Bacillus species, can form endospores, resistant structures that survive harsh environmental conditions.
  • Corynebacterium diphtheriae, the causative agent of diphtheria, has metachromatic granules, appearing as dark-staining granules within cells.

Gram-Positive Bacilli: Morphology

  • Gram-positive bacilli are club-shaped and arranged at acute angles or parallel to each other, resembling "Chinese letters" under a microscope.
  • They often display metachromatic granules.
  • They are often non-spore forming.

Corynebacterium diphtheriae

  • Certain species are part of normal skin and mucous membrane flora.
  • Corynebacterium diphtheriae is a medically important species.
  • Corynebacterium diphtheriae colonies, as visible under a microscope, display a beaded appearance when stained with methylene blue.

Corynebacterium diphtheriae: Culture Characters

  • Corynebacterium diphtheriae grows aerobically.
  • Good growth is seen on blood agar.
  • Loeffler's serum provides the best morphology.
  • Blood tellurite agar is a selective and differential medium, yielding grey-to-black colonies.

Corynebacterium diphtheriae: Virulence Factors

  • Corynebacterium diphtheriae produces diphtheria exotoxin.

Corynebacterium diphtheriae: Disease

  • Diphtheria is an upper respiratory tract infection transmitted via droplets.
  • A defining characteristic of diphtheria is the presence of a local pseudomembrane.
  • Toxemia is also a common symptom.
  • Complications include airway obstruction, toxic myocarditis (inflammation of the heart muscle), and nerve paralysis.

Diagnosis of Corynebacterium diphtheriae

  • Diagnosis is mainly clinical.
  • A throat swab from the pseudomembrane is a specimen for laboratory confirmation.
  • Microscopic examination (Gram stain) shows gram-positive bacilli with Chinese-letter appearance.
  • Microscopic examination (methenamine blue stain) reveals metachromatic granules.
  • Loffler's serum is used for the best morphology.
  • Blood tellurite agar distinguishes Corynebacterium diphtheriae by yielding gray to black colonies.

Listeria monocytogenes: Morphology and Culture

  • Listeria is gram-positive bacilli, in short chains.
  • Listeria are non-capsulated.
  • Listeria form no spores.
  • Listeria is non-motile and has the motility characteristics of being motile. Listeria is cold tolerant and can grow in refrigerated food/drink.

Listeria monocytogenes: Culture and Identification

  • Listeria monocytogenes readily grows on blood agar; colonies exhibit a zone of hemolysis comparable to that of Group B Streptococcus.
  • Shows positive catalase test. Positive tumbling motility is seen at 25°C, displaying a “umbrella” appearance.
  • Direct smears of specimens reveal gram-positive bacilli.

Listeria monocytogenes: Diseases

  • Listeriosis encompasses diseases including neonatal meningitis, adult listeriosis (meningitis and gastroenteritis), abortion, premature delivery, or sepsis during the peripartum, and septicaemia. Symptoms may include meningitis in immunocompromised adults.
  • Food poisoning linked to dairy and undercooked meats.

Listeria monocytogenes: Neonatal Meningitis

  • Neonatal meningitis caused by Listeria is typically seen in newborns.
  • Other causes include Group B Streptococcus and E. coli K1.

Listeria monocytogenes: Contracting Listeriosis

  • Listeria is a foodborne infection.
  • It survives drying, heating, and freezing without spore formation.
  • Common sources include unpasteurized milk and dairy products, soft cheeses, and undercooked meats (e.g., chicken, hot dogs).
  • Refrigerated foods can also be contaminated.

Bacillus Anthracis: General Characteristics

  • Bacillus anthracis is a facultative anaerobic, gram-positive, rod-shaped bacterium that forms spores.
  • Anthrax primarily affects herbivores, but humans can contract it via contact with infected animals/products or contaminated soil.

Bacillus Anthracis: Clinical Manifestations

  • Cutaneous anthrax manifests as a painless skin lesion progressing to a black eschar.
  • Inhalation anthrax typically begins with flu-like symptoms, progressing to severe respiratory distress.
  • Gastrointestinal anthrax arises from the ingestion of contaminated meat, causing abdominal pain, nausea, and vomiting.
  • Injection anthrax is a rarer form, associated with drug use. Symptoms often resemble those of cutaneous anthrax, spreading quickly.

Bacillus Anthracis: Diagnosis

  • Diagnosis typically relies on a combination of clinical symptoms and laboratory findings.
  • Microscopic examination using Gram staining reveals large, square-ended, spore-forming bacilli.
  • Culture of Bacillus anthracis on suitable media, like blood agar, provides a definitive identification.
  • Serological tests identify specific antibodies against anthrax toxin.

Bacillus Anthracis, Listeria, Corynebacterium: Relevant Testing

  • Elek's test: Detects the production of diphtheria toxin by Corynebacterium diphtheriae.
  • PCR (Polymerase Chain Reaction): Detects the presence of toxin genes or Listeria/Bacillus species.
  • ELISA (Enzyme-Linked Immunosorbent Assay): Detects the toxin produced by Corynebacterium diphtheriae.

Review Questions: Species Identification and Culture

  • C. diphtheriae is cultured on Loffler's serum.
  • Blood tellurite agar is a selective and differential medium.
  • An Elek's test is a toxigenicity test for C. diphtheriae.
  • C. diphtheriae morphology is gram-positive club-shaped bacilli.
  • A 1-week-old newborn with meningitis, and past unpasteurized cheese consumption, likely means Listeria monocytogenes as the etiological factor.

Potential Bioterrorism Concerns

  • Bacillus anthracis spores are highly stable and can survive for an extended period.
  • Bacillus anthracis can be transmitted by aerosolization.
  • Corynebacterium diphtheriae is a highly contagious bacterium that forms an exotoxin-causing severe disease and death.

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