Main content area

Rapid detection of Listeria monocytogenes in ham samples using immunomagnetic separation followed by polymerase chain reaction

Hudson, J.A., Lake, R.J., Savill, M.G., Scholes, P., McCormick, R.E.
Journal of applied microbiology 2001 v.90 no.4 pp. 614-621
DNA, Listeria monocytogenes, bacteria, food industry, genes, ham, immunomagnetic separation, polymerase chain reaction, rapid methods, ribosomal RNA
Aims: To develop a 24-h system for the detection of Listeria monocytogenes in ham. Methods and Results: An immunomagnetic separation (IMS) of bacteria directly from ham followed by extraction of DNA and detection using a new multiplex polymerase chain reaction (PCR) was used. The PCR method used one primer pair targeted at the listeriolysin O gene of L. monocytogenes and the other pair for a region of the 23S rRNA genes of Listeria, giving products of 706 and 239 bp, respectively. The combined IMS/PCR was calculated to be capable of detecting as few as 1.1 L. monocytogenes cells g(-1) in a 25-g ham sample. Conclusions: The process produced acceptable results, but the IMS step is the main barrier to further improvement of sensitivity. The DNA isolation was the most time-consuming step in the process. Significance and Impact of the Study: A 24-h test for the presence of L. monocytogenes will be useful to the food industry and significantly assist in the timely investigation of outbreaks.