Comparison of chromogenic agar media for recovery of Listeria monocytogenes from ready-to-eat meat and poultry products

The objective of this study was to compare the sensitivity and specificity of esculin- and chromogen- containing agars for the recovery of Listeria monocytogenes front artificially contaminated ready-to-eat meat and poultry products. Listeria innocua, Listeria ivanovii and Listeria seeligeri were inoculated (1-10 cfu/25 g) onto samples (n = 180) in addition to L. monocytogenes at 1-10 (LM level 1), 100 (LM level 2) or 1,000 (LM level 3) cfu/25 g. Three esculin-containing agars (oxford, modified Oxford and PALCAM) and two chromogenic agars (Rapid'L. mono [RLM] and CHROMagar Listeria) were evaluated for the recovery of Listeria spp. With LM level 1, L. innocua overgrew the other three Listeria spp., and L. monocytogenes was recovered from only 6.7 and 1.7% of samples on CHROMagar and RLM, respectively, and front no samples on the esculin-containing agars. At LM level 2 and 3, chromogenic agars recovered L. monocytogenes better than the three esculin-containing agars (P < 0.05). The highest sensitivity and specificity values were obtained with RLM and CHROMagar These results indicate that chromogenic media could replace or supplement the current preferred media of the United States Department of Agriculture and Food and Drug Administration Bacteriological Analytical Manual methods to detect and isolate L. monocytogenes more rapidly with higher sensitivity without tedious confirmation tests.