(A) Samples of an enrichment culture of Listeria monocytogenes were diluted and subjected to the mechanical (bead) lysis protocol of the mericon DNA Bacteria Plus Kit and the thermal (boiling) lysis protocol of the mericon DNA Bacteria Kit to evaluate lysis efficiency. For this Gram-positive bacterium, mechanical lysis delivered a more effective extraction, most evident at very low bacterial concentrations. (B) Diluted and undiluted samples of an enrichment culture of Salmonella enterica in milk and hazelnut spread were subjected to the mechanical and thermal lysis protocols. Overall, the efficiency of DNA extraction from Gram-negative bacteria is similar with both preparation protocols.
Detection of pathogens was highly sensitive, even in difficult food matrices, such as peanut butter. Peanut butter was homogenized in buffered peptone water, spiked with <5 cfu of salmonella, and enriched for 20 h at 37°C. DNA was extracted from serially diluted samples of the enrichment culture using the mericon DNA Bacteria Kit and then tested with the mericon Salmonella Kit. Although the original inoculation was small, salmonella was still reliably detected at a dilution factor of 1:100,000.
Delivering sensitive and highly specific results, real-time PCR analysis is also faster than conventional pathogen detection methods. Besides taking longer, immunoassays and traditional culture methods are less sensitive and more labor intensive.