A total number of 63 samples represent 7 different inactivated veterinary vaccines each type was represented by 3 different batches and experimentally contaminated with 5, 20 and 100 CFU Salmonella Typhimurium reference strain /bottle then examined for sterility. Two ml from each batch was tested in comparison with different volumes of the same bottle ranging
from 2ml up to 25 ml related to final vaccine volume as referenced by OIE. Further dilution of vaccines was done in a ratio of 1:10, 1:15 and 1:20 which might be attributed to formalin residues. Statistical analysis indicates no significant difference for the effect of two volumes on the validity of final results by all formalized and non-formalized vaccines, while there is
significant difference between direct inoculation of test vaccine and different dilutions. Finally, it could be concluded that, the test method is appropriate for testing sterility of most inactivated vaccine types but some vaccines need further dilution before being tested.