An organism described as "highly virulent" has which of these characteristics?

• A. It is unable to survive outside a host.
• B. It can only infect immunocompromised individuals.
• C. It causes severe disease in a host.
• D. It is always resistant to antibiotics.

Answer: (C)

Verified step by step guidance

1. Understand the term 'virulence' in microbiology: Virulence refers to the degree of pathogenicity or the ability of a microorganism to cause disease in a host.
2. Recognize that 'highly virulent' means the organism has a strong capacity to cause disease, often leading to severe symptoms or damage in the infected host.
3. Evaluate each option based on the definition of virulence: - Being unable to survive outside a host relates to survival, not virulence. - Infecting only immunocompromised individuals relates to opportunistic infection, not necessarily virulence. - Causing severe disease directly relates to high virulence. - Antibiotic resistance is about treatment difficulty, not virulence.
4. Conclude that the characteristic most aligned with 'highly virulent' is the ability to cause severe disease in a host.
5. Remember that virulence is about the severity and harmfulness of the disease caused, not about survival outside the host or antibiotic resistance.