Conductance measurements of the lag phase of injured Salmonella typhimurium

Abstract
The duration of the lag phase of S. typhimurium injured by heating, freezing, acidification or drying was measured using the Malthus conductance meter. Results confirmed those previously obtained by viable counting and additionally, revealed the very wide variation in lag between and within populations and the extreme length of lag that can occur in some severely injured cells. In an extreme example, the measured lag times of low numbers of bacteria taken from the same heat-injured population ranged from 16-70 h. The implications for the detection of injured microorganisms in food are discussed.