BACTERICIDAL EFFECT OF FRESH SERUM AGAINST MUTABILE-TYPE VARIANT (MURASE) AND ITS DERIVATIVES OF SALM. TYPHI-MURIUM

Abstract

1. Mutabile-type variant Murase (M) and its derivatives such as MT, DM₁, DMT₁, “MT-like”, Mucoid RT and RT were obtained by mutation. The wild type and one of the above mutants were inoculated simultaneously into 1 ml of fresh horse serum. After an incubation period of varying lengths from O min, to 24 hours, 0.01ml of the mixture was plated onto a plane agar plate or Galactose agar plate for the counting of each colony.
The results showed that the wild type and RT, which is a so-called back mutant of M to the wild type, were resistant to the serum. All the other mutants were equally sensitive to the serum and disappeared within 2.5 hours of incubation.
While, the resistant strains survived and increased showing numerous colonies even after 24 hours of incubation.
2. Utilizing TTC reagent, the bactericidal effects of the serum against M and its derivatives were also investigated.
The results obtained showed that the wild type and RT produced red formazane within 4 hours of incubation, demonstrating the survival of the wild type or RT in the serum. While, all the other variants produced no formazane within 4 hours of incubation, indicating the organisms were killed by the serum.
3. The wild type and RT, both of which were resistant to the serum were highly virulent for mice.
Whereas, all the other sensitive strains were either very weak in virulence or almost lost their ability to produce typhoid disease in mice.