Microbial Infection and Pathogenesis - Pathogenicity, Virulence, and Attenuation

4 important questions on Microbial Infection and Pathogenesis - Pathogenicity, Virulence, and Attenuation

Define virulence and explain how it relates to pathogenicity.

Virulence is the relative ability of a pathogen to cause disease. It measures the overall pathogenicity of a pathogen, considering factors such as adherence, colonization, invasion, and the presence of virulence factors.

What is the LD50, and how does it help quantify the virulence of a pathogen?

The LD50 (lethal dose) is the number of pathogen cells or virions required to kill 50% of the host population in a test group. It quantifies virulence, especially for lethal pathogens, and illustrates the severity of the infection.

Describe the significance of the capsule in Streptococcus pneumoniae regarding virulence.

The capsule in S. pneumoniae is a major virulence factor that helps the bacterium evade immune surveillance. Strains with capsules are highly virulent, as demonstrated by Frederick Griffith's work on mouse mortality.
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What is attenuation, and why does it occur in laboratory cultures?

Attenuation is the decrease or loss of virulence in a pathogen. It often occurs in laboratory cultures because nonvirulent or weakly virulent mutants may grow faster in the absence of selective pressure for virulence.

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