Clonal nature of Salmonella typhi and its genetic relatedness to other salmonellae as shown by multilocus enzyme electrophoresis, and proposal of Salmonella bongori comb. nov

Abstract

Crude cell extracts of 26 isolates of Salmonella serotype typhi (S. typhi) and 48 other Salmonella isolates representing 28 serotypes and seven DNA hybridization subgroups were analyzed for electrophoretic variants of 24 metabolic enzymes by starch gel electrophoresis. All strains of S. typhi had identical isoenzyme patterns, indicating that they were a single clone. All of the enzymes detected in the remaining strains were polymorphic, and the degree of genetic variation was quite high. The average number of alleles per enzyme locus was 4.7, and the mean genetic diversity per locus was 0.556. Thirty-two distinct allele profiles, or electrophoretic types (ETs), were found in these 48 strains of Salmonella serotypes other than S. typhi. Analysis of the genetic relationships of the ETs to each other showed that, with one exception, the ETs formed subgroups that were consistent with the subgroupings based on DNA hybridization studies. ET profiles were not always linked to specific serologic patterns. These data show that multilocus enzyme electrophoresis has a potential application in epidemiologic and taxonomic studies of salmonellae, although it is not differential for S. typhi. We also propose a new species, Salmonella bongori comb. nov., a new combination based on the elevation of Salmonella choleraesuis subsp. bongori to the level of species.