Comparison of Oxford Agar, PALCAM and Listeria monocytogenes Blood Agar for the recovery of L-monocytogenes from foods and environmental samples

This work had as the main objective a comparison between Listeria monocytog enes Blood Agar (LMBA) and the conventional selective agar media, Oxford an d PALCAM, relative to its efficacy in the detection of L monocytogenes in n aturally contaminated food and environmental samples. 173 environmental sam ples and 272 samples of foods were analysed. A higher sensitivity for detec tion of L. monocytogenes was verified for LMBA than for PALCAM and Oxford. In LMBA L monocytogenes could be distinguished from other Listeria spp. by detection of hemolysis. In Oxford and PALCAM this distinction was not possi ble. The higher growth rate of L. innocua cf. L. monocytogenes in selective liquid media could result in a high number of false negatives (nondetectio n of the target organism on plates, although its presence was observed by o ther tests, eg. mini-VIDAS LMO). The need for specific media for the detect ion of L. monocytogenes in food was confirmed. LMBA could be an alternative medium to use together with PALCAM or Oxford. (C) 2001 Elsevier Science Lt d. All rights reserved.