Topic 1-8 (Lecture 8) Flashcards
What is pathogenicity?
The qualitative ability of a bacterium to cause disease
e.g. it can, it can’t
What is a pathogen?
A bacterium that is capable of harming a normal host (normal meaning no compromise in immune system)
Capable does NOT mean ALWAYS will cause harm, it just CAN cause harm
What is an opportunistic pathogen?
A bacterium that harms a compromised host
What is virulence?
The QUANTITATIVE measure of the pathogenicity of a microorganism (expressed it number ocells that will cause disease (ID50) and will kill (LD50))
What are commensals?
Bacteria of the microbiota
What is do commensals and opportunistic pathogens lack?
They lack an inherent ability to cause disease (lack a genetic component to cause disease/harm host)
What does pathogenicity indicate?
The ability of an organism to cause disease
What does virulence indicate?
The extent of a disease cause by an organism
What are some factors affecting virulence?
Route of entry
Susceptibility/general health of host
Ability to multiply within the host
What are the two extremes of virulence?
Highly virulent - causing disease in most individuals
Avirulent - rarely causing disease (if ever)
What are virulence factors?
Factors that allow a microorganism to enter and colonize in a host, resist the immune defences of a host, and cause damage in the host
What are the different classification of bacterial infections?
Primary Secondary Subclinical nosocomial local infection systemic/generalized focal
What is a primary infection?
The initial, acute infection of bacteria
What is a secondary infection?
The later, “second” infection caused by an opportunistic organisms after the primary infection has weakened the host defences
What is a subclinical infection?
An infection in which the host has no apparent symptoms
What is a nosocomial infection?
An infection which is acquired as a consequence of hospitalization
What is a local infection?
An infection restricted to a small area of the body (usually caused by non-invasive organisms)
What is a systemic/generalized infection?
An infection which spreads throughout the body (usually caused by invasive organisms, often via the blood)
What is a focal infection?
An infection that begins in a restricted area then spreads throughout the body
What is invasiveness?
The ability of an organism to invade/spread beyond the original site of entry into a host’s body
What influences the interaction between microorganisms and the host?
The virulence of the microorganisms
The anti-bacterial defenses of the host
What factors can compromise the immune defence?
Underlying disease/infection
Stress
Poor nutrition (body can’t fight if it doesn’t have the energy)
Immunosuppressive therapy (ex. during maintenance of transplanted organs)
Age (underdeveloped immune defences in newborn and infants make them weak; degeneration of immune defences when old also make them weak)
Genetics (some individuals are more resistant or more susceptible; think of HLA’s for MHC proteins)
What do bacteria rely on to cause disease?
Virulence factors
What is pathogenesis dependent on?
Having multifactotrial bacteria; bacteria with multiple virulence factors
