title: [Aspects of the interrelationship between the infected host and the pathogenic agent].
abstract: The severity of an infection is related to the disequilibrium in the complex relationship between the infected host and the pathogenic agent. The bacterial factors include the size of the inoculum, the pathogenicity and particular virulence of certain strains which, because of their antigenic structures (capsular antigen, lipopolysaccharide, exotoxins), may escape the bactericidal defence mechanisms of the serum, phagocytosis and intracellular bacterial destruction. The principal host factor, which also determines the prognosis of the infection, is the subject's immune status which can be affected in its non-specific elements (complement system) and in its specific elements (humoral and cellular immunity). Thus, in the normal host, only extremely virulent bacteria are capable of causing severe infections, while in the immunodepressed patient, even non-pathogenic organisms which are usually commensual are capable of being invasive.
mesh_terms: D000907:Antibodies, Bacterial / Q000276:immunology; D001424:Bacterial Infections / Q000276:immunology* / Q000382:microbiology; D006090:Gram-Negative Bacteria / Q000472:pathogenicity*; D006094:Gram-Positive Bacteria / Q000472:pathogenicity*; D006801:Humans; D018805:Sepsis / Q000503:physiopathology; D014774:Virulence
chemical_list: D000907:Antibodies, Bacterial
vernacular_title: Aspects de l'interrelation entre l'hôte infecté et son agent pathogène.