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Virulence factor
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<p>Virulence factors (preferably known as pathogenicity factors or effectors in <a href="/facts/Botany/PaIRoxnb">botany</a>) are cellular structures, molecules and regulatory systems that enable microbial pathogens (<a href="/facts/Bacteria/wC8xSCsU">bacteria</a>, <a href="/facts/Virus/mf88Bcbl">viruses</a>, <a href="/facts/Fungi/BHo5DP59">fungi</a>, and <a href="/facts/Protozoa/JczTf25H">protozoa</a>) to achieve the following: </p> <ul><li>colonization of a niche in the host (this includes movement towards and attachment to host cells)</li> <li>immunoevasion, evasion of the host's immune response</li> <li><a href="/facts/Immunosuppression/22GHUHkr">immunosuppression</a>, inhibition of the host's immune response (this includes <a href="/facts/Leukocidin/QAJlvTo4">leukocidin</a>-mediated cell death)</li> <li>entry into and exit out of cells (if the pathogen is an intracellular one)</li> <li>obtain nutrition from the host</li></ul> <p>Specific pathogens possess a wide array of virulence factors. Some are <a href="/facts/Chromosome/FRGf11FC">chromosomally</a> encoded and intrinsic to the bacteria (e.g. capsules and <a href="/facts/Endotoxin/Ch967TXw">endotoxin</a>), whereas others are obtained from <a href="/facts/Mobile_genetic_elements/cmVCkbA7">mobile genetic elements</a> like <a href="/facts/Plasmid/yf59JVlA">plasmids</a> and <a href="/facts/Bacteriophage/L2Ll0T3q">bacteriophages</a> (e.g. some exotoxins). Virulence factors encoded on mobile genetic elements spread through <a href="/facts/Horizontal_gene_transfer/FPyUIsf2">horizontal gene transfer</a>, and can convert harmless bacteria into dangerous pathogens. Bacteria like <i><a href="/facts/Escherichia_coli_O157:H7/4d2BjhD0">Escherichia coli O157:H7</a></i> gain the majority of their <a href="/facts/Virulence/TYmX1Fa6">virulence</a> from mobile genetic elements. <a href="/facts/Gram-negative_bacteria/S1PbVtp4">Gram-negative bacteria</a> secrete a variety of virulence factors at <a href="/facts/Host%E2%80%93pathogen_interface/seV2tLTk">host–pathogen interface</a>, via <a href="/facts/Membrane_vesicle_trafficking/mX8USWA0">membrane vesicle trafficking</a> as <a href="/facts/Bacterial_outer_membrane_vesicles/7tlfVmeh">bacterial outer membrane vesicles</a> for invasion, nutrition and other cell-cell communications. It has been found that many pathogens have converged on similar virulence factors to battle against <a href="/facts/Eukaryote/SkwyPLMA">eukaryotic</a> host defenses. These obtained bacterial virulence factors have two different routes used to help them survive and grow: </p> <ul><li>The factors are used to assist and promote colonization of the host. These factors include <a href="/facts/Bacterial_adhesin/GXFLgd56">adhesins</a>, <a href="/facts/Invasin/nFbPGbt4">invasins</a>, and <a href="/facts/Antiphagocytic/eBrv2XKV">antiphagocytic</a> factors. <a href="/facts/Bacterial_flagella/nvQRcbgJ">Bacterial flagella</a> that give motility are included in these virulence factors.</li> <li>The factors, including <a href="/facts/Toxin/11oUNk7n">toxins</a>, <a href="/facts/Hemolysin/VFXR9Exg">hemolysins</a> and <a href="/facts/Protease/G1ASdVat">proteases</a>, bring damage to the host.</li></ul>