Why can antibiotics worsen fungal infections?

• A. They kill normal bacteria → fungi lose competition and overgrow
• B. They directly promote fungal growth
• C. They reduce host immunity
• D. They have no effect on fungi

Answer: (A)

Antibiotics don’t target fungi; they wipe out bacteria. Normal bacterial communities on our skin, gut, and mucous membranes compete with fungi for nutrients and space, and they can even produce substances that help keep fungi in check. When a broad-spectrum antibiotic reduces these bacteria, that competition is removed, allowing fungi such as Candida to overgrow. This overgrowth can then cause things like oral thrush or vaginal yeast infections, depending on the site affected. The key idea is the disruption of normal flora and the resulting loss of colonization resistance, not a direct promotion of fungal growth by the antibiotic itself.