Which organism is rod-shaped, a strict aerobe, and causes pseudomembranes?

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Multiple Choice

Which organism is rod-shaped, a strict aerobe, and causes pseudomembranes?

The main idea is matching a pathogen's shape, growth needs, and the classic clinical lesion it causes. Corynebacterium diphtheriae is a slender, rod-shaped bacterium that grows with oxygen (aerobe) and is responsible for diphtheria, which classically produces a pseudomembrane in the throat. That pseudomembrane is a layer of necrotic cells, fibrin, and bacteria that can block the airway, and it results from the diphtheria toxin damaging mucosal tissue. The other organisms don’t fit all three clues together. Neisseria gonorrhoeae is a gram-positive? No, it’s a gram-negative diplococcus, not rod-shaped, and it doesn’t cause throat pseudomembranes. Bacillus anthracis is rod-shaped and aerobic but forms spores and causes anthrax with different clinical features (eschar, fulminant illness) rather than a classic throat pseudomembrane. Staphylococcus aureus is rod-shaped? No, it’s cocci in clusters, and it doesn’t produce the diphtheria pseudomembrane. So the combination of rod shape, strict aerobe growth, and the characteristic pseudomembrane points to Corynebacterium diphtheriae.

The main idea is matching a pathogen's shape, growth needs, and the classic clinical lesion it causes. Corynebacterium diphtheriae is a slender, rod-shaped bacterium that grows with oxygen (aerobe) and is responsible for diphtheria, which classically produces a pseudomembrane in the throat. That pseudomembrane is a layer of necrotic cells, fibrin, and bacteria that can block the airway, and it results from the diphtheria toxin damaging mucosal tissue.

The other organisms don’t fit all three clues together. Neisseria gonorrhoeae is a gram-positive? No, it’s a gram-negative diplococcus, not rod-shaped, and it doesn’t cause throat pseudomembranes. Bacillus anthracis is rod-shaped and aerobic but forms spores and causes anthrax with different clinical features (eschar, fulminant illness) rather than a classic throat pseudomembrane. Staphylococcus aureus is rod-shaped? No, it’s cocci in clusters, and it doesn’t produce the diphtheria pseudomembrane.

So the combination of rod shape, strict aerobe growth, and the characteristic pseudomembrane points to Corynebacterium diphtheriae.

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