Variability of protection against different strains induced by a culture filtrate (CF) obtained from Salmonella enteritidis

Cross-protective ability against the challenge of different strains of culture filtrate (CF) obtained from Salmonella enteritidis was investigated. Immunization with CF from various smooth strains with the exception of strain 3551 which is a rough strain of S. enteritidis induced protective immunity against challenge with strains 2547 and 116M. However, when strains 2822, 3551 and 3975 were used as the challenge strain, no protective effect was observed. The agglutination titers against whole cells of strain 2547 or 2822 of sera taken from the 2547 CF-immunized mice were almost the same as those of sera from the 2822 CF-immunized mice. Furthermore, delayed footpad reactivity was observed when heat-killed cells of strain 2547 or 2822 were transferred into the footpad of 2547 CF- or 2822 CF-immunized mice. These results show that the capability of inducing protective immunity is similar between the 2547 CF and 2822 CF, and protection against infection with S. enteritidis differs in accordance with different challenge strains.