Numerical index of the discriminatory ability of biotyping for strains of Salmonella typhimurium and Salmonella paratyphi B.

An index of discrimination was used to assess the discriminatory power of biotyping for salmonellas of selected serotypes. Three collections of phage-typed strains of Salmonella typhimurium and Salmonella paratyphi B, previously tested for biotype, were examined. The results established that the discrimination index was high when full biotyping alone was used for differentiation of strains from international series. When biotyping was combined with phage typing, the discrimination achieved was greater than for either method used alone. These findings confirm that biotyping affords excellent discrimination of strains of S. typhimurium and S. paratyphi B and indicate that the results obtained from biotyping can be interpreted with confidence.