['To investigate the induction of the acid tolerance response (ATR) in Listeria monocytogenes and to assess the persistence of the pathogen in broth fermented using a nisin-producing starter culture.', 'Lactic, acetic and hydrochloric acids were used to induce the ATR in L. monocytogenes growing at early exponential phase. Cells were then challenged in medium acidified to pH 3.5 with the same acid. Only lactic acid induced a detectable ATR. ATR+ cells maintained their initial numbers after 1 h exposure while ATR- were reduced by c. 4 log10 CFU. ATR+ or ATR- cells were also inoculated in M17G broth fermented with nisin-producing (nis+) or control (nis-) Lactococcus lactis. When exposed to nisin, the numbers of ATR+ cells were c. 2 log10 CFU higher than non detectable ATR- cells at day 3. In the absence of nisin (nis- culture), L. monocytogenes was recovered from all ATR+ and ATR- samples after 30 days. In contrast, no L. monocytogenes were recovered from any nis+ATR- samples but four of five nis+ATR+ samples were positive for L. monocytogenes after 30 days.'] Do acid-tolerant Listeria monocytogenes persist in a model food system fermented with nisin-producing bacteria?