Download Methods by which pathogens cause disease

Methods by which pathogens cause disease:
• Adhesion: bacteria must bind to the cell surfaces
• Colonization: bacteria produce proteins and colonize parts of
the host body
• Invasion: bacteria produce proteins that allow bacteria to
enter cells by through
either
the paper
disruption of host cell
Draft
VFO-Toxins
membranes or the stimulation of endocytosis (cells absorbing
material) into host cells
• Immune response inhibitors: bacterial produce proteins that
inhibit the host's immune system defenses, such as binding
host antibodies
• Toxins: bacteria produce proteins that poison the host cells
and cause tissue damage
Virulence Factors are specific adaptations that allow pathogen to:
1. attach selectively to host tissues
2. gain access to nutrients by invading or destroying host tissues
3. avoid host defenses
Lecture on Virulence Factors:
http://www.sp.uconn.edu/~terry/229sp03/lectures/pathogens_intro.html
Virulence factors refer to the properties (i.e., gene products) that enable a microorganism
to establish itself on or within a host of a particular species and enhance its potential to
cause disease.
VFDB: http://www.mgc.ac.cn/VFs/main.htm
Virulence factors include:
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•
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bacterial toxins
cell surface proteins that mediate bacterial attachment
cell surface carbohydrates and proteins that protect a bacterium
hydrolytic enzymes that may contribute to the pathogenicity of the bacterium
Adherence and colonization factors : to enable the pathogen to attach and replicate,
to get past the host barrier, e.g. mucosal surface of gut or respiratory tract
Invasins: act extracellularly, affecting physical barriers, such as cell membranes or tissues
Capsules and surface components: act to protect the pathogen from phagocytosis using surface
components that prevent the attachment and engulfment of macrophages and other host cellular
immune responses.
Endotoxins: Possessed solely by Gram negative organisms; endotoxin or lipopolysaccharide (LPS)
activates the host complement pathway, and is a potent inducer of inflammation.
Exotoxins: Secreted by viable pathogenic cells. Some bacterial protein exotoxins act on host cell
surfaces, while the majority (A/B toxins) bind to the target membrane with a receptor (B subunit) and
deliver a second moiety (A subunit) directly in to the cytoplasm
Siderophores : scavenges bound iron from the host via high binding constants.