Molecular Koch's Postulates and Pathogenesis

What is the best definition of disease?

• The presence of microbes in the body.

• The process by which microbes cause damage to a host.

• Damage to the host caused by infection, often accompanied by symptoms.

• The body’s response to bacterial invasion.

What does virulence describe?

• The rate at which a microbe reproduces in a lab setting.

• The capacity of a microorganism to cause disease.

• The genetic variability of a pathogen.

• The environmental survivability of bacteria.

Which of the following is a virulence factor?

• Bacterial motility

• Host immune response

• A toxin produced by bacteria that damages host tissues

• Antibiotic resistance genes in humans

Pathogenesis refers to:

• A) The body’s defense against microbial invasion.

• B) The process by which microbes colonize the environment.

• C) The mechanisms by which microbes cause disease in a host.

• D) The resistance of a host to bacterial infection.

What factor does NOT influence pathogenesis?

• Host immune system.

• Environmental conditions.

• Virulence factors of the microbe.

• The presence of antibiotics in the environment.

What is the first step in Koch’s postulates?

• The microorganism must be isolated and grown in pure culture.

• The microorganism must be found in all cases of the disease and absent in healthy individuals.

• The microorganism must cause disease when introduced into a healthy host.

• The microorganism must be re-isolated from the experimental host.

Koch’s second postulate requires:

• The microorganism to be present in diseased tissues only.

• The microorganism to cause disease in a susceptible host.

• The microorganism to be isolated in pure culture.

• The microorganism to be eliminated with antibiotics.

Which postulate demonstrates causality in disease?

• The first postulate.

• The second postulate.

• The third postulate.

• The fourth postulate.

A caveat to the second postulate is that:

• Some pathogens cannot be grown in pure culture.

• Disease symptoms may not always be present.

• Pathogens may not be transmissible to animals.

• Re-isolation of pathogens is difficult.

Koch’s fourth postulate involves:

• Observing symptoms in an infected host.

• Growing the microorganism in a lab setting.

• Re-isolating the microorganism from the experimentally infected host.

• Detecting the pathogen with molecular tools.