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Obsolete term for a substance of microbial origin postulated to inhibit the resistance mechanisms of the host.
[L. agressor, an assailant, fr. ad-gredio, pp. -gressus, to attack]
aggressin(1) A nonspecific term for any product (antigen) secreted by pathogenic bacteria.
(2) Virulence factor.
substance or substances formed in the body by bacteria which enhance the bacteria's virulence. Include capsular material, enzymes and toxins. Called also virulin.