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Questions and Answers
Which characteristic of Mycoplasma pneumoniae directly contributes to its pleomorphic nature?
Which characteristic of Mycoplasma pneumoniae directly contributes to its pleomorphic nature?
- The presence of a rigid cell wall composed of peptidoglycan.
- The presence of cholesterol in its cell membrane.
- The absence of a cell wall, resulting in a flexible cell membrane. (correct)
- The production of hydrogen peroxide.
What is the primary mechanism by which Mycoplasma pneumoniae causes damage to the respiratory tract?
What is the primary mechanism by which Mycoplasma pneumoniae causes damage to the respiratory tract?
- Inhibition of ciliary action and necrosis of ciliated bronchial cells via binding to sialic acid-rich glycolipids. (correct)
- Direct invasion and destruction of lung parenchyma.
- Activation of complement pathways leading to acute lung injury.
- Secretion of exotoxins that induce a strong inflammatory response.
A 20-year-old college student presents with a persistent dry cough, headache, and mild fever. A chest X-ray reveals patchy interstitial pneumonia. Given the likely pathogen, why is the cold agglutinin test sometimes unreliable for diagnosing this infection?
A 20-year-old college student presents with a persistent dry cough, headache, and mild fever. A chest X-ray reveals patchy interstitial pneumonia. Given the likely pathogen, why is the cold agglutinin test sometimes unreliable for diagnosing this infection?
- Cold agglutinins are specific to _Mycoplasma pneumoniae_ and rarely cause false positives.
- The test has low sensitivity and frequently misses _Mycoplasma pneumoniae_ infections.
- False-positive results can occur with other infections such as influenza and adenovirus. (correct)
- Cold agglutinins are only produced in severe cases of pneumonia.
Why are antibiotics like penicillin, which target cell wall synthesis, ineffective against Mycoplasma pneumoniae?
Why are antibiotics like penicillin, which target cell wall synthesis, ineffective against Mycoplasma pneumoniae?
What contributes to the 'walking pneumonia' presentation typical of Mycoplasma pneumoniae infections?
What contributes to the 'walking pneumonia' presentation typical of Mycoplasma pneumoniae infections?
A researcher is studying the adhesion properties of Mycoplasma pneumoniae. Which specific structure on the bacterium is most critical for its attachment to host cells?
A researcher is studying the adhesion properties of Mycoplasma pneumoniae. Which specific structure on the bacterium is most critical for its attachment to host cells?
How does the production of hydrogen peroxide by Mycoplasma pneumoniae contribute to its pathogenicity?
How does the production of hydrogen peroxide by Mycoplasma pneumoniae contribute to its pathogenicity?
Why does Mycoplasma pneumoniae require lipids in its growth medium in a laboratory setting?
Why does Mycoplasma pneumoniae require lipids in its growth medium in a laboratory setting?
Following a Mycoplasma pneumoniae infection, a patient develops mild hemolytic anemia. What is the likely mechanism behind this complication?
Following a Mycoplasma pneumoniae infection, a patient develops mild hemolytic anemia. What is the likely mechanism behind this complication?
If a new strain of Mycoplasma pneumoniae emerged with a mutation that significantly reduces its superantigen activity, what would be the most likely clinical consequence?
If a new strain of Mycoplasma pneumoniae emerged with a mutation that significantly reduces its superantigen activity, what would be the most likely clinical consequence?
Flashcards
Mycoplasma Characteristics
Mycoplasma Characteristics
Smallest free-living organism without a cell wall, making them pleomorphic and Gram stain poorly. Their membrane contains cholesterol.
P1 Protein Function
P1 Protein Function
A membrane protein of Mycoplasma pneumoniae that binds to sialic acid-rich glycolipids on ciliated bronchial cells, inhibiting ciliary action and causing necrosis.
P1 Protein Action
P1 Protein Action
Inhibits ciliary action and causes necrosis of cells in the respiratory tract.
"Walking Pneumonia"
"Walking Pneumonia"
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Chest Radiography Findings
Chest Radiography Findings
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Best Diagnostic Procedure
Best Diagnostic Procedure
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Cold Agglutinins
Cold Agglutinins
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Treatment for Mycoplasma pneumoniae
Treatment for Mycoplasma pneumoniae
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Study Notes
- Mycoplasma pneumoniae is the smallest free-living organism without a cell wall so Gram staining is not effective.
- Its flexible cell membrane allows it to take on various shapes (pleomorphic).
- The cell membrane contains cholesterol, typical of eukaryotic cells.
- This is pathogenic only to humans, spread through respiratory droplets, and more common in winter.
- It is a common cause of pneumonia in young adults and outbreaks occur in places with close contact.
- Only about 10% of those infected develop pneumonia.
- It accounts for 5-10% of community-acquired pneumonia cases.
Virulence Factors and Pathogenesis
- Its membrane protein P1 acts as a cytoadhesin, binding to sialic acid-rich glycolipids on ciliated bronchial cells.
- This inhibits ciliary action and kills these cells.
- It produces hydrogen peroxide, damaging ciliated cells and has superantigen activity.
Clinical Features
- Mycoplasma pneumoniae causes primary atypical pneumonia, also known as "walking pneumonia", which presents with less severe symptoms than typical pneumonia.
- Tracheobronchitis and pharyngitis can be present.
- Symptoms start gradually with headache, fever, chills, sore throat, and malaise.
- A dry or mildly productive cough develops after 2-4 days.
- Earache can occur.
- Rare complications include central nervous system issues, rash, and mild hemolytic anemia.
Diagnosis
- Mycoplasmas need lipid-supplemented media to grow in the lab and it takes at least a week for a colony to form.
- Colonies often have a "fried egg" appearance.
- Chest X-rays show patchy, diffuse interstitial pneumonia in one or more lobes, or patchy bronchopneumonia.
- The X-ray results can look worse than the actual clinical symptoms.
- PCR assays to find Mycoplasma pneumoniae-specific nucleic acids in sputum or respiratory secretions is the best diagnostic procedure.
- A cold agglutinin titer of 1:128 or higher suggests recent infection.
- Cold agglutinins are IgM antibodies against type O red blood cells, agglutinating at 4°C but not at 37°C.
- The cold agglutinin test is non-specific, with potential false positives in influenza and adenovirus infections.
Treatment
- Macrolides like erythromycin or azithromycin, or tetracyclines like doxycycline, are used as antibiotics.
- The illness typically resolves on its own in 3-10 days without specific treatment.
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