Which of the following correctly lists the organisms in order from most resistant to least resistant to antimicrobial agents?

• A. Viruses with lipid envelopes, gram-positive bacteria, gram-negative bacteria, mycobacteria, bacterial endospores, prions
• B. Bacterial endospores, prions, mycobacteria, gram-negative bacteria, gram-positive bacteria, viruses with lipid envelopes
• C. Prions, bacterial endospores, mycobacteria, gram-negative bacteria, gram-positive bacteria, viruses with lipid envelopes
• D. Gram-positive bacteria, gram-negative bacteria, mycobacteria, bacterial endospores, prions, viruses with lipid envelopes

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the concept of microbial resistance to antimicrobial agents. Resistance refers to how well an organism can survive exposure to disinfectants, antiseptics, or antibiotics. Some organisms have structural or biochemical features that make them more resistant than others.
2. Step 2: Recognize that prions are the most resistant infectious agents because they are misfolded proteins without nucleic acids, making them extremely difficult to inactivate.
3. Step 3: Identify bacterial endospores as highly resistant structures formed by some bacteria (e.g., Bacillus and Clostridium species) that protect the bacterial genome under harsh conditions, making them very resistant to antimicrobial agents.
4. Step 4: Understand that mycobacteria have a waxy, lipid-rich cell wall containing mycolic acid, which provides them with increased resistance compared to typical gram-positive and gram-negative bacteria.
5. Step 5: Know that gram-negative bacteria are generally more resistant than gram-positive bacteria due to their outer membrane, which acts as a barrier to many antimicrobial agents, while viruses with lipid envelopes are the least resistant because their envelopes are easily disrupted.