ULTRA SENSITIVE DETECTION OF LISTERIA-MONOCYTOGENES IN MILK BY THE POLYMERASE CHAIN-REACTION (PCR)

The polymerase chain reaction (PCR) has been used to detect Listeria monocytogenes in whole milk at a level of 0.1 cfu per 30 ml. This high degree of sensitivity has been achieved following enzymatic digestion, polysulphonone membrane filtration and amplification of a nucleotide sequence within the promoter region of hlyA. Key elements of the procedure are the absence of enrichment culture and a complete solubilization of the membrane filter, ensuring total nucleic acid recovery. The simplicity of the protocol coupled with high sample volumes and exquisite sensitivity extends the relevance of PCR within food and environmental microbiology.