Microbiology -- Chapter 25 – Virulence factors
25.1 Microbial adherence
Infection; colonization and growth of microorganism on or
in the host
Disease; damage to the host that disrupts the normal
functioning of the host, actual tissue damage
Pathogenicity; the potential (ability) of a micro-organism to
cause harm to the host.
Virulence; the extent (mate) to which a pathogen is able to harm the
host. Depends on abilities to adhere, colonize and invade.
Virulence factors; substances produced by the pathogen that directly
or indirectly enhance invasiveness and host damage
Attenuation; decrease or loss of virulence of a pathogen
If a pathogen (ziekteverwekker) gain access to tissues it infects and
disease will follow.
Infection process takes place in 5 steps;
Step 1; adherence (aankleving)
Ability of a microorganism to attach to a cell or a surface, via receptor molecules on
the surface of the pathogen (adhesins) and host cell (glycoproteins)
Pathogen adheres to epithelial cells
Pathogen gain access to host tissue by way of portal of entry (wounds, cuts, insect
bites). The place where they entry is crucial, in the stomach killed by strong acidity, in
the respiratory tract they could trigger a fatal case.
Capsule; Some pathogens contain this, the capsule contains specific receptors that
facilitate adherence to host tissue. Capsule may help with attachment but is not
required.
Fimbriae (small) and pilli (longer); cell surface protein structures that function in
attachment.
Flagella; facilitate adherence of bacterial cells to host cells
Step 2; invasion (invasive)
Invasion; ability of a pathogen to enter into host cell or tissues, they spread and
cause disease.
Some pathogens remain localized after entry. Other pathogens enter the
bloodstream, from where they can travel to other parts of the body.
25.1 Microbial adherence
Infection; colonization and growth of microorganism on or
in the host
Disease; damage to the host that disrupts the normal
functioning of the host, actual tissue damage
Pathogenicity; the potential (ability) of a micro-organism to
cause harm to the host.
Virulence; the extent (mate) to which a pathogen is able to harm the
host. Depends on abilities to adhere, colonize and invade.
Virulence factors; substances produced by the pathogen that directly
or indirectly enhance invasiveness and host damage
Attenuation; decrease or loss of virulence of a pathogen
If a pathogen (ziekteverwekker) gain access to tissues it infects and
disease will follow.
Infection process takes place in 5 steps;
Step 1; adherence (aankleving)
Ability of a microorganism to attach to a cell or a surface, via receptor molecules on
the surface of the pathogen (adhesins) and host cell (glycoproteins)
Pathogen adheres to epithelial cells
Pathogen gain access to host tissue by way of portal of entry (wounds, cuts, insect
bites). The place where they entry is crucial, in the stomach killed by strong acidity, in
the respiratory tract they could trigger a fatal case.
Capsule; Some pathogens contain this, the capsule contains specific receptors that
facilitate adherence to host tissue. Capsule may help with attachment but is not
required.
Fimbriae (small) and pilli (longer); cell surface protein structures that function in
attachment.
Flagella; facilitate adherence of bacterial cells to host cells
Step 2; invasion (invasive)
Invasion; ability of a pathogen to enter into host cell or tissues, they spread and
cause disease.
Some pathogens remain localized after entry. Other pathogens enter the
bloodstream, from where they can travel to other parts of the body.
