Microbial Infection and Pathogenesis - Genetics of Virulence and the Compromised Host

5 important questions on Microbial Infection and Pathogenesis - Genetics of Virulence and the Compromised Host

Define virulence and explain how it can be encoded by both chromosomal genes and mobile genetic elements.

Virulence is the relative ability of a pathogen to cause disease. It can be encoded by chromosomal genes or highly mobile genetic elements. For example, Bordetella pertussis has chromosomal genes for pertussis toxin, while some bacterial pathogens exchange virulence genes through horizontal gene exchange.

Describe the significance of Salmonella pathogenicity islands (SPI1 and SPI2) in the context of virulence.

Salmonella pathogenicity islands (SPI1 and SPI2) contain genes responsible for promoting virulence, invasion, and systemic disease. SPI1 includes genes like invH, involved in surface adhesion, and SPI2 contributes to resistance against host defenses.

Explain how plasmids contribute to the transfer of virulence factors in Salmonella and other enteric bacteria.

Plasmids in Salmonella and other enteric bacteria encode virulence factors, including antibiotic resistance genes. Pathogenicity islands and plasmids facilitate the rapid transfer of these virulence factors between bacterial species through horizontal gene exchange.
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What is virulence attenuation, and why is it valuable in vaccine development?

Virulence attenuation is the decrease or loss of virulence in a pathogen, often occurring in laboratory cultures. Attenuated strains are valuable for vaccine development as they can stimulate an immune response without causing disease. Examples include the rabies vaccine and vaccines for measles, mumps, rubella, chickenpox, shingles, and yellow fever.

Discuss the concept of compromised hosts and provide examples of factors that can compromise host resistance.

Compromised hosts are individuals with reduced resistance to infections, making them more susceptible to diseases. Factors include hospitalization, ongoing infectious diseases like AIDS, physiological conditions (old age, immune suppression), lifestyle choices (intravenous drug use, tobacco, alcohol), and genetic diseases affecting the immune system.

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