1. 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 disruption of host cell 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 Draft VFO-Toxins paper

2. Lecture on Virulence Factors: http://www.sp.uconn.edu/~terry/229sp03/lectures/pathogens_intro.html 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 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: 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

3. 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.