Mouse Anti-E. coli K99 Pilus Monoclonal antibody. K99 pilus antigen is frequently associated with enterotoxigenic strains of E. coli isolated from the intestine of calves, sheep and pigs. Pilus antigens have been shown to be the main attachment mechanism whereby EPEC attach to and colonize the small intestine of neonatal animals. Any mechanism which will interfere with this attachment and colonization process is capable of reducing the intestinal colonization, diarrhoea and mortality associated with K99 EPEC infections.