Salmonella paratyphi A is more genetically homogeneous than Salmonella typhi, as indicated by pulsed-field gel electrophoresis.

We analyzed 18 Salmonella Paratyphi A and 12 Salmonella Typhi isolates from domestic and imported cases in Aichi, Japan, using pulsed-field gel electrophoresis. Paratyphoid fever cases have increased and outbreaks of Salmonella Paratyphi A occasionally occur in Japan, but S. Paratyphi A has not been extensively analyzed. Our study suggests significant genetic homogeneity among Salmonella Paratyphi A belonging to different phage types, which is in contrast to the genetic heterogeneity of Salmonella Typhi. These results suggest that a limited number of clones are responsible for paratyphoid fever.