Antibiotics are useful only for treating infections caused by which organisms?

• A. Bacteria
• B. Viruses
• C. Fungi
• D. Parasites

Answer: (A)

Antibiotics work by targeting features that stand out in bacterial cells, such as their cell wall, bacterial ribosomes, or specific bacterial metabolic pathways. Because these features are not present in viruses, fungi, or parasites, antibiotics don’t effectively treat infections caused by those organisms. For example, some antibiotics weaken bacterial cell walls or stop bacteria from making proteins, while others block DNA replication in bacteria. Viruses lack their own ribosomes and cell walls and rely on host cells to replicate, so attacking bacterial processes won’t stop a viral infection. Fungi and parasites have different cellular structures and life cycles, so they require antifungal or antiparasitic drugs designed for those organisms. In short, antibiotics are useful only for bacterial infections, and choosing them for viruses, fungi, or parasites won’t work and can contribute to resistance.