Passive oral immunization with O-antiserum was found to protect guinea pigs against fatal enteric cholera. The number of vibrios recoverable from the intestines of infected animals was not noticeably reduced by active and oral passive immunization.
Passive immunization by the intraperitoneal route was not protective even though high titers of circulating antibody were obtained shortly after injection. Oral administration of H-antiserum also had no protective effect.
Introduction of E. coli into the intestinal tract increased the resistance of guinea pigs to fatal enteric cholera.