Comparison of the effects of sodium chloride, pH and temperature on the growth of Listeria monocytogenes on gradient plates and in liquid medium


  • The authors thank Mrs T. Kelly and Mr M. Truman for technical assistance.


Gradient plates provide a convenient means of assessing the effect of sodium chloride and pH in combination with different temperatures on the growth of microorganisms. The effects of these variables on the growth of Listeria monocytogenes in gradient plates at four temperatures are compared with growth in a micro-well system. The growth-limiting conditions in the two systems are in good agreement, and also compare favourably with data in the literature. The gradient plates gave a good illustration of the concentrations of sodium chloride required to inhibit growth at different temperatures and pHs, although incubation time is limited to 72 h.