Bacteriology: Pathogenicity and Virulence

Questions and Answers

Pathogenicity is the ability of any bacterial species to cause disease in a susceptible human host.

Opportunistic pathogens can cause disease primarily in immunocompromised individuals, whereas they rarely cause disease in healthy people.

Virulence refers to the degree to which a pathogen can cause disease, ranging from low to high levels.

Bordetella pertussis is highly virulent and causes whooping cough. Signup and view all the answers

Epidemic, pandemic, and endemic. Signup and view all the answers

The first stage of infection involves transmission from an external source into the portal of entry. Signup and view all the answers

Bacterial pili facilitate adherence to mucous membranes. Signup and view all the answers

An endemic disease is constantly present at a low level in a specific population. Signup and view all the answers

The host response involves both nonspecific and specific defenses against infection. Signup and view all the answers

Moderate virulence in E. coli occurs when it displaces to other sites, causing acute infection. Signup and view all the answers

Study Notes

Pathogenicity is the ability of a bacterial species to cause disease in a susceptible human host.
A pathogen is a bacterial species that can cause disease when presented with favorable circumstances.
Opportunistic pathogens are bacterial species that rarely cause disease in immunocompetent people but can cause serious infection in immunocompromised patients and are frequent members of the body's normal flora.

Virulence is a term that presumes pathogenicity and allows expression of degrees from low to extremely high.
Examples of virulence include:
- Low virulence: Streptococcus salivarius, which is universally present in the oropharyngeal flora of humans and can cause disease only in specific circumstances, such as when it lands on a damaged heart valve.
- Moderate virulence: Escherichia coli, which is universally found in the colon but can cause acute infection if displaced to other sites.
- High virulence: Bordetella pertussis, which is highly infectious and causes disease in almost every nonimmune person it contacts.

Epidemic: an infection that occurs more frequently than usual.
Pandemic: an epidemic with a worldwide distribution.
Endemic: an infection that is constantly present at a low level in a specific population.

Transmission: infection from an external source into the portal of entry.
Evasion: evasion of primary host defenses such as skin or stomach acid.
Adherence: adherence to mucous membranes, usually by bacterial pili.
Colonization: growth of the bacteria at the site of adherence.
Disease: disease caused by toxin production or invasion, accompanied by inflammation.
Host Response: host response with nonspecific and specific (immunity) defenses.
Progression or Resolution: progression or resolution of the disease.