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**K antigens prevent phagocytosis or mimic host antigens and resist complement
**K antigens prevent phagocytosis or mimic host antigens and resist complement
**Fimbriae permit adhesion to mucosal surfaces
**Fimbriae permit adhesion to mucosal surfaces
**May enter blood to cause septicaemia
*Clinical infections:
**Avian colibacillosis:
***Septicaemia in newly-hatched chickens
***Infection enters via faecal contamination of the egg surface or via the ovary of the hen
***Infection enters via the respiratory tract
***A bacteraemia develops
***Acute colisepticaemia, subacute fibrinopurulent serositis or chronic granulomatous disease of the viscera
***Occurs in older birds via inhalation of ''E. coli'' in dust; respiratory infection spreads to the blood to cause acute colisepticaemia
***Airsacculitis, pericarditis and perihepatitis during acute phase
***Often secondary to virus or mycoplamsa infection or environmental stress
**Colisepticaemia:
***Systemic disease in young calves, piglets, foals, lambs
***Penetration of intestinal mucosa and entrance into the blood
***Invasive strains survive the host defences
***Virulence related to adhesive properties, complement resistance and ability for iron aquisition
***Ammonia, dust, viral infections and temperature changes enhance likelihood of disease