The effect of incubation temperature and magnesium chloride concentration on growth of salmonella in home‐made and in commercially available dehydrated Rappaport‐Vassiliadis broths

Abstract

Growth rate of salmonellas in Rappaport-Vassiliadis broth (RV) decreased with higher temperature when incubated at 40, 42 and 43 degrees C. Home-made RV and RV-Merck were less inhibitory than RV-Oxoid and RV-lab m. At 43 degrees C growth of all strains of Salmonella dublin were almost completely inhibited in all types of RV. In home-made RV and RV-Merck incubated at 42 degrees C, Salm. dublin was not inhibited any more than other serotypes tested. Variations in growth rate between different types of RV could be explained by differences in concentration of MgCl2. RV with higher MgCl2-concentration were most inhibitory. It is proposed that RV should be incubated at 41.5 +/- 0.5 degrees C (42.0 +/- 0.1 degrees C in a waterbath) and that the amount of MgCl2.6H2O should be approximately 28.6 g/l of the ready-to-use medium, which corresponds to the formula in the original description.