A comparison of solid and liquid media for measuring the sensitivity of heat‐injured Salmonella typhimurium to selenite and tetrathionate media, and the time needed to recover resistance

Abstract

Sensitivity of heat‐injured Salmonella typhimurium to selenite and tetrathionate media was measured by viable counts in liquid and on agar‐solidified versions of these media and on nutrient media. All solid media, including the supposedly non‐inhibitory nutrient agar, were more inhibitory to injured cells than the corresponding liquid media. Catalase or pyruvate increased counts on nutrient agar to the level obtained in nutrient broth. Therefore nutrient agar plus pyruvate was the most suitable reference medium against which to compare recoveries on other media. Although recoveries of injured cells varied widely depending on the composition and physical state of the medium, this had a minor effect on estimates of repair time because resistance to all selective media was regained by the end of the lag phase.

Resuscitation of ‘non-culturable’ cells from aged cultures of Campylobacter jejuni

“…Similar observations have been reported for cells injured by heat or other stresses (Mackey & Derrick, 1982). However, recovery of C. jejuni in liquid media was further enhanced by adding mucin.…”

Towards a maximal cell survival in convective thermal drying processes

“…Viable cell count is a traditional approach to evaluate the viability of cells after a stress treatment. It allows a cell that has been damaged but not to a lethal extent to repair its structure, and regain the capability to reproduce after repairing (Mackey & Derrick, 1982;Montville & Matthews, 2007). As a result, on a rich medium both intact and injured cells are able to reproduce, with probably the injured cells having a longer lag time due to the repair process.…”

“…For such methods relying on the cell's ability to grow to an observable level, it should be noted that cell growth is significantly affected by the environmental conditions used to culture them (Mackey & Derrick, 1982). While the use of the same media to culture microbial cells before and after drying provides an estimation of the change in viable cell number, the evaluation of cell survival in an environment simulating the target destination may be more meaningful.…”

The Effect of Catalase on Recovery of Heat-injured DNA-repair Mutants of Escherichia coli

“…The recovery of several species of bacteria following heat injury is improved by incorporating catalase in recovery media, implying that heated cells are sensitive to hydrogen peroxide (BairdParker & Davenport, 1965;Brewer et al, 1977;Rayman et al, 1978;Mackey & Derrick, 1982). Hydrogen peroxide causes several types of damage to DNA, therefore peroxide, or oxygencontaining radicals derived from it, could constitute an indirect mechanism of DNA damage in heated cells.…”