There is a variety of protocols for Listeria spp detection in foods and other sources. Therefore, the decision on which method to be used becomes very difficult. Conventional isolation methodologies indicate different pre-enrichment and enrichment broths as well as different isolation media. The comparison between the efficiency of PALCAM (PAL), lithium chloride-phenylethanol-moxalactam (LPM) and haemolitic ceftazidime-lithium chloride (HCLA) agars was carried out. A total of 413 samples from different sources, collected from a chicken nuggets processing plant, was pre-enriched in Half Fraser broth followed by enrichment in BLEB. They were streaked onto LPM, PAL and HCLA plates and typical colonies were submitted to biochemical identification. L. monocytogenes (Lm) was isolated from 60.1% of the samples when HCLA was used and from approximately 47.9% when PAL and LPM were considered. The difference between the efficiency of HCLA and the other two media was statistically significant (p<0.05) for all samples but food handlers. For food handler samples all three media showed the same efficiency. The combined use of HCLA and PAL allowed the identification of the highest number of Lm positive samples indicating that these media can be a good choice.
L. monocytogenes; isolation; HCLA; PALCAM; LPM
