Influence of pH, Salt, and Temperature on Nisin Resistance in Listeria monocytogenes ^†

The influence of pH (5.0, 5.5, and 6.0), salt (0.5, 2.0, and 3.5%) and temperature (10,20, and 30°C) on the frequency of nisin resistance in Listeria monocytogenes Scott A was evaluated. At 20 and 30°C, resistance frequencies of around 1 in 10⁵ were obtained regardless of salt concentration or pH. At 10°C the frequency of nisin resistance dropped with decreasing pH and decreasing salt concentration. At pH 5.5 and 0.5% NaCl it became impossible to generate nisin-resistant isolates. Low salt (2 to 3.5%) appeared to playa protective role, allowing L. monocytogenes to better survive nisin at low temperature (l0°C).