Acid tolerance response of Listeria monocytogenes: Bioenergetics and mechanisms of resistance to the antimicrobial nisin.
Bacterial infections caused by Listeria monocytogenes target mainly newborn, pregnant, elderly and immunocompromised individuals, and are associated with mortality rates around 25%. Control of L. monocytogenes in foods is difficult due to its widespread presence in nature and ability to grow at refrigeration temperatures. The responses of L. monocytogenes to acid, osmotic and thermal stresses contribute to the problem, since they increase pathogen resistance and virulence beyond constitutive levels. The Acid Tolerance Response (ATR) is defined as the abnormal resistance to lethal acid after exposure to mild acidic conditions. The specific acid, rather than the medium's pH, is critical for ATR induction.