Oral Immunization with Polyvalent Streptomycin-Dependent Escherichia coli Vaccine1

Streptomycin-dependent Escherichia coli serotypes O 111, O 55 and O 26 were used to vaccinate young patas monkeys against these organisms by the oral route. Five administrations of 10 10 cells in 3-day intervals gave almost full protection to the animals against challenge with 9 to 11 minimal infective doses of homologous virulent organisms for at least 1 month, whether the three serotypes were administered singly or simultaneously.