S1B4 - Study Questions 03 - Intro to Infectious Disease

Question 1

What factors generally determine whether an infection becomes serious enough to produce symptoms?

Answer 1

• *Multiplication/spread**: The expansion of the infection and pathology. Factors include:
  1. Inoculum size: the potential for infection increases with number of organisms that gain entry
  2. Multiplication vs. the immune system: this contest often determines the state of the infection

Question 2

What is convalescence?

Answer 2

Convalescence is the time-period following the illness. A convalescent individual may still harbor the pathogen and be a carrier, i.e., a source for reinfection (e.g., malaria), or infection (e.g., typhoid fever).

Question 3

What is a fulminant infection?

Answer 3

A fulminant infection is when symptoms appear suddenly and intensely; explosive.

Question 4

What is a retrograde infection?

Answer 4

A retrograde infection is when a microbial invasion proceeds through a tube or duct against the direction of fluid-flow. This is a common problem in urinary tract infections.

Question 5

What is a pyogenic infection?

Answer 5

A pyogenic infection is a pus forming infection.

Question 6

What are frank or strict pathogens? What are some examples?

Answer 6

Frank or strict pathogens are organisms not known to inhabit humans without causing disease. In all cases, the ability of bacteria to cause disease is regulated to some degree by the innate and adaptive immune systems. The presence of IgG in the serum (an “elevated” titer) is good proof of pathogenicity.

Examples:

• rabies virus
• Shigella
• Salmonella
• Vibrio
• Neisseria gonorrhoeae
• Plasmodium
• Yersinia pestis
• Bacillus anthracis
• Francisella tularensis

Question 7

What is virulence?

Answer 7

Virulence is the ability to produce an infection, i.e., highly virulent pathogens need only a few bacteria to successfully overcome immune systems; low virulence pathogens require large numbers of organisms, or special situations, e.g., immunosuppression, trauma, cystic fibrosis (predisposes to Pseudomonas and Staphylococcus)

Question 8

What is pathogenicity?

Answer 8

Pathogenicity is the ability to cause disease or pathology. Highly pathogenic organisms cause very serious or destructive disease.