Microbiology
Summary
Mycoplasma pneumoniae is a gram-indeterminate bacterium that uniquely lacks a cell wall, preventing its visualization using Gram stain. Mycoplasma has developed an adaptation by incorporating cholesterol molecules into its cell membranes.
Infections caused by Mycoplasma tend to affect young adults, particularly in settings with close contact, including military recruits. This infection often presents as atypical pneumonia, earning it the colloquial term "walking pneumonia" because unlike typical pneumonia cases, individuals with walking pneumonia can often continue their daily activities. While chest X-rays might reveal a patchy infiltrate, the patients generally don't appear severely ill. To diagnose the infection, the cold agglutinins test is employed. This test prompts certain antibodies called IgM molecules to bind to the surface of red blood cells, causing them to clump together, or agglutinate, in vitro, particularly at low temperatures. To culture Mycoplasma, a specific medium known as Eaton's agar is essential. When it comes to treatment, macrolides like erythromycin or azithromycin are utilized due to the lack of a cell wall in Mycoplasma.
Lesson Outline
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FAQs
Mycoplasma pneumoniae is a type of bacteria that causes infections in the respiratory system, most commonly, a lung infection known as 'walking pneumonia'. This particular strain of pneumonia is termed 'walking' because while it is a serious lung infection, its symptoms are often mild enough that individuals can continue to function, or 'walk about'. Mycoplasma pneumoniae adheres to and damages the lining of the respiratory tract, eliciting an inflammatory response which leads to the symptoms of walking pneumonia.
Unlike most bacteria, Mycoplasma pneumoniae lack a rigid cell wall, which leaves them with a pleomorphic form. Instead, they have a unique plasma membrane that is rich in cholesterol. The absence of a cell wall makes them resistant to many common antibiotics like penicillin, that target cell wall synthesis. The cholesterol in the membrane, a sterol usually found only in eukaryotic cells, provides stability to the organism and helps it survive in various environments.
Atypical pneumonia caused by Mycoplasma pneumoniae often presents clinically with gradual onset of symptoms like low-grade fever, dry cough, and fatigue, which is quite different from typical pneumonia's sudden onset. The X-ray findings also show a patchy infiltrate, a diffuse and spread out pattern of inflammation in the lung tissues, as opposed to the localized consolidation visible in typical pneumonia.
The demographic at most risk of contracting Mycoplasma pneumoniae infections are school-aged children, military recruits, and people living in crowded conditions like dormitories. This is due to the fact that Mycoplasma pneumoniae spreads through respiratory droplets in the air, and these environments facilitate close contact and quickly spread the bacteria.
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