[An oral enteritis-vaccine composed of twelve heat-inactivated Enterobacteriaceae 3. Communication: studies on efficacy tests in mice protection tests (author's transl)].

The polyvalent vaccine consists of twelve heat-inactivated species of Enterobacteriaceae (six strains of Salmonellae, two strains of Shigellae, four strains of Dyspepsia coli). The above vaccine is administered orally (6) to man for prophylactic purposes against local infections. The present communication describes the efficacy results of the vaccine obtained for different parameters by the mouse protection test. For this purpose, seven different infection models were used: oral infection with a strain of S. typhimurium and a strain of S. enteritidis, respectively, and intraperitoneal infection with the following five strains: S.l typhimurium, S. panama, S. enteritidis, Sh. flexneri 2a, or E. coli 2380. For 10 days the mice were daily immunized with the twelve-fold vaccine orally administered by means of a probang. On the 10th day after the last orally applied antigen, the animals were challenged with the seven strains mentioned above. The success of vaccination was determined by the difference of mortality between vaccinated and non-vaccinated mice. The results show (Table 1) following the vaccination that a significant effect could be observed and statistically be evaluated for 6 models of infection. Optimal values showing the highest consistency rate were found for the model of intraperitoneal infection with the strain of E. coli 2380. Which is why, studies were made for the following parameters by using the latter mode of infection. The efficacy of the oral immunization depends on the dosage of the vaccine (Table 2). Even at a dilution of 1 : 1000, the effect of the vaccine was still sufficient. Only a dilution of 1 : 10 000 made the vaccination almost ineffective. - The content of humidity of the lyophilized vaccine in a range of 4% to 12% did not influence the immunogenicity (Table 3). - The protection obtained by vaccination was found to last unexpectedly long. The vaccinated mice were still well protected even one year after the oral vaccination (Table 4), which means - when referred to the life-span of mice - that protection is effected for almost a life-time. The lyophilized vaccine does not even loose its immunogenicity after storage at 22 degrees C and 40 degrees C over a period of 3 years (Table 5). These polyvalent lyophilized vaccine are, therefore, storable even under tropical conditions without cooling. This is a further great advantage of this vaccine.