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Questions and Answers
What is the primary virulence factor of Listeria monocytogenes that allows it to evade immune detection?
What is the primary virulence factor of Listeria monocytogenes that allows it to evade immune detection?
Which symptom is typically associated with late onset listeriosis in neonates?
Which symptom is typically associated with late onset listeriosis in neonates?
Which group has the highest risk of severe outcomes from Listeria monocytogenes infection?
Which group has the highest risk of severe outcomes from Listeria monocytogenes infection?
What is a common laboratory diagnosis method for identifying Listeria monocytogenes?
What is a common laboratory diagnosis method for identifying Listeria monocytogenes?
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What is a potential complication of listeriosis in pregnant women?
What is a potential complication of listeriosis in pregnant women?
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What type of movement does Listeria monocytogenes utilize to spread between host cells?
What type of movement does Listeria monocytogenes utilize to spread between host cells?
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What is one preventive measure that could reduce the risk of listeriosis in pregnant women?
What is one preventive measure that could reduce the risk of listeriosis in pregnant women?
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Which of the following describes the typical clinical presentation of healthy individuals infected with Listeria monocytogenes?
Which of the following describes the typical clinical presentation of healthy individuals infected with Listeria monocytogenes?
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What indicates a positive reaction in the diphtheria skin test?
What indicates a positive reaction in the diphtheria skin test?
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Which of the following correctly describes a false positive reaction in the diphtheria test?
Which of the following correctly describes a false positive reaction in the diphtheria test?
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What is the primary mode of transmission for Listeria monocytogenes?
What is the primary mode of transmission for Listeria monocytogenes?
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Which characteristic is NOT true regarding Listeria monocytogenes?
Which characteristic is NOT true regarding Listeria monocytogenes?
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What clinical symptom does a negative reaction in the diphtheria test indicate?
What clinical symptom does a negative reaction in the diphtheria test indicate?
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Which statement concerning the Listeria monocytogenes entry into host cells is correct?
Which statement concerning the Listeria monocytogenes entry into host cells is correct?
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What describes a 'combined reaction' in the diphtheria skin test?
What describes a 'combined reaction' in the diphtheria skin test?
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Which group is most at risk for severe infections caused by Listeria monocytogenes?
Which group is most at risk for severe infections caused by Listeria monocytogenes?
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What type of bacteria is Corynebacterium diphtheriae?
What type of bacteria is Corynebacterium diphtheriae?
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What two properties determine the virulence of toxigenic strains of Corynebacterium diphtheriae?
What two properties determine the virulence of toxigenic strains of Corynebacterium diphtheriae?
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How does the diphtheria exotoxin inhibit protein synthesis in eukaryotic cells?
How does the diphtheria exotoxin inhibit protein synthesis in eukaryotic cells?
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What is a common clinical manifestation in patients infected with Corynebacterium diphtheriae?
What is a common clinical manifestation in patients infected with Corynebacterium diphtheriae?
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What type of transmission is primarily associated with Corynebacterium diphtheriae?
What type of transmission is primarily associated with Corynebacterium diphtheriae?
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Which factor is least relevant in the epidemiology of Corynebacterium diphtheriae infections?
Which factor is least relevant in the epidemiology of Corynebacterium diphtheriae infections?
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Which of the following best describes a preventive measure against diphtheria?
Which of the following best describes a preventive measure against diphtheria?
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Which characteristic is true of non-toxigenic strains of Corynebacterium diphtheriae?
Which characteristic is true of non-toxigenic strains of Corynebacterium diphtheriae?
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Study Notes
Medical Microbiology - 4th Year
- Gram-Positive Rods: Divided into spore-forming and non-spore-forming categories.
- Non-spore Forming: Includes Corynebacterium diphtheriae and Listeria monocytogenes,
- Spore-Forming: Includes Bacillus anthracis and Bacillus cereus.
- Aerobic Non-Spore Forming: Corynebacterium diphtheriae is a gram–positive rod, non-motile, with a beaded appearance.
- Properties: Transmitted via respiratory droplets, a disease of childhood.
- Toxigenic Strains: Diphtheria exotoxin consists of fragment A (catalytic), inhibits elongation factor 2, and fragment B, binds to the cell surface.
- Virulence Factors: Diphtheria exotoxin’s ability to colonize the nasopharynx and produce toxin.
- Pathogenesis: Infection starts in the nose, spreading to the pharynx, forming a pseudo-membrane. Can lead to life-threatening systemic complications affecting the heart and nervous system.
- 1-in Nasopharyngeal Diphtheria: Symptoms include fever, enlargement of cervical lymph nodes. Rare cases lead to pharyngeal necrosis.
- 2-in Cutaneous Diphtheria: Skin lesions covered with a gray-brown pseudomembrane. Diagnosed by throat swab stained with Gram stain, or grown on Loffler's, and McLeod's media.
- Laboratory Diagnosis: Elek's test (in vitro) distinguishes toxigenic from non-toxigenic varieties. Guinea pig inoculation is also part of the test.
- Treatment: includes Antitoxin, penicillin or erythromycin, tracheotomy (laryngeal diphtheria).
Listeria monocytogenes
- Characteristics: Facultative intracellular, catalase-positive, beta-hemolytic.
- Epidemiology: Foodborne pathogen, grows at refrigerator temperatures. Transmitted via the fecal-oral route.
- Virulence Factors: Ability to survive harsh environments, surface proteins (internalins A and B) to attach to host cells, and cytotoxic protein (listeriolysin O). The bacterial protein ActA is involved in host actin polymerization.
- Pathogenesis: Can move from cell-to-cell without antibody exposure. Can infect neonates and cause meningitis.
- Diagnosis: Blood or cerebrospinal fluid analysis, gram stain showing small gram-positive rods, motility test and culture on blood agar.
Anaerobic Non-Spore Forming Gram-Positive Bacilli
- Propionibacterium species: Members of the normal skin flora.
- Pathogenesis: P. acnes causes Acne vulgaris via production of lipases.
- Important Considerations: Pregnant women and immunocompromised adults can experience severe Listeria infections.
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Description
This quiz explores the characteristics of gram-positive rods, focusing on both spore-forming and non-spore-forming bacteria. Key pathogens such as Corynebacterium diphtheriae and Bacillus anthracis are examined, including their virulence factors and pathogenesis. Test your knowledge on these crucial microbiological concepts relevant to medical practice.
