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

J Appl Microbiol. 2001 Apr;90(4):614-21. doi: 10.1046/j.1365-2672.2001.01287.x.


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.

Conclusion: 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • DNA, Bacterial / analysis
  • Food Microbiology*
  • Immunomagnetic Separation / methods*
  • Listeria monocytogenes / genetics
  • Listeria monocytogenes / isolation & purification*
  • Meat Products / microbiology*
  • Polymerase Chain Reaction / methods*
  • Quality Control


  • DNA, Bacterial