[S. typhi strains which produce "beta" type of hemolysis]

S. typhi strains were isolated from the blood of one, and from the faeces cultures of the other of two brothers, which showed the classical biochemical and serological characteristics except for the Vi antigen. These strains produced "beta type" of hemolysis in their first isolation when grown on brain heart infusion agar media. This ability was lost after two or three subculturing on the same media. The cause of this phenomenon is thought to be a plasmid. However, this reason is still under investigation. Both patients were treated with classical methods plus ampicillin successfully.