DETECTION OF VIABLE AND DEAD LISTERIA-MONOCYTOGENES BY PCR

Non-culturable Listeria monocytogenes are defected by polymerase chain reaction (PCR) after treatment with a variety of disinfectants and af ter different heat conditions. The sensitivity of this PCR detection i s strongly dependent on the treatment applied. Dissolving L. monocytog enes cells in pure ethanol for 30 days only reduced the PCR sensitivit y 100 times compared with untreated cells. Treatment with 1% HCl and s terilization at 124 degrees C for 15 min prevented PCR detection after 1 h. The non-culturable L. monocytogenes cells, obtained after a chee se pasteurization of 63 degrees C for 30 min are dead and not in a via ble but non-culturable state as was established by reverse transcripti on (RT) PCR on L. monocytogenes RNA. (C) 1997 Academic Press Limited.