Fungal infections are often difficult to treat because fungi:

• A. Are eukaryotic cells with many cellular structures similar to human cells, limiting selective toxicity of drugs
• B. Lack ribosomes, so antifungal drugs cannot inhibit protein synthesis
• C. Have cell walls made of peptidoglycan, which prevents penetration of most antifungal drugs
• D. Are obligate intracellular pathogens that cannot be targeted by systemic medications

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the nature of fungal cells by recognizing that fungi are eukaryotic organisms, meaning their cellular structure is similar to that of human cells, including having a nucleus and membrane-bound organelles.
2. Step 2: Recall that selective toxicity in antimicrobial treatment relies on differences between the pathogen and human cells; since fungi share many cellular features with human cells, it is challenging to target fungi without harming human cells.
3. Step 3: Evaluate the incorrect options by considering basic microbiology facts: fungi do have ribosomes, so the statement about lacking ribosomes is false; their cell walls are made of chitin, not peptidoglycan, which is found in bacteria; and fungi are not obligate intracellular pathogens, meaning they can be targeted by systemic medications.
4. Step 4: Conclude that the main reason fungal infections are difficult to treat is due to their eukaryotic nature and cellular similarity to human cells, which limits the selective toxicity of antifungal drugs.
5. Step 5: Summarize that effective antifungal drugs must target unique fungal components (like ergosterol in fungal membranes) to minimize harm to human cells, explaining why treatment is more complex compared to bacterial infections.