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Improved detection of Listeria monocytogenes in soft mould-ripened cheese

  1. T. Johansson1,
  2. H. Ahola-Luttila2,
  3. T. Pirhonen1,
  4. A.-M. Taimisto2,
  5. H. Haario3,
  6. M. Laine3,
  7. M. Salkinoja-Salonen4

Article first published online: 25 DEC 2001

DOI: 10.1046/j.1365-2672.2000.01030.x

Issue

Journal of Applied Microbiology

Journal of Applied Microbiology

Volume 88, Issue 5, pages 870–876, May 2000

Additional Information

How to Cite

Johansson, T., Ahola-Luttila, H., Pirhonen, T., Taimisto, A.-M., Haario, H., Laine, M. and Salkinoja-Salonen, M. (2000), Improved detection of Listeria monocytogenes in soft mould-ripened cheese. Journal of Applied Microbiology, 88: 870–876. doi: 10.1046/j.1365-2672.2000.01030.x

Author Information

  1. 1

    Department of Food Microbiology, National Veterinary and Food Research Institute,

  2. 2

    Research and Development Centre, Valio Ltd,

  3. 3

    Department of Mathematics, University of Helsinki and

  4. 4

    Department of Applied Chemistry and Microbiology, University of Helsinki, Finland

* T. Johansson, Department of Food Microbiology, National Veterinary and Food Research Institute, PO Box 368, FIN-00231 Helsinki, Finland (e-mail: tuula.johansson@eela.fi).

Publication History

  1. Issue published online: 25 DEC 2001
  2. Article first published online: 25 DEC 2001
  3. 7424/10/99: received 12 October 1999, revised 14 January 2000 and accepted 18 January 2000

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In comparison with standard methods, enrichment in half-Fraser broth for 24 h at 30 °C, followed by plating out onto Listeria monocytogenes blood agar (LMBA) and PALCAM medium combined with an additional streak proved to be the most rapid and specific method for the detection of indigenous L. monocytogenes populations from soft mould-ripened cheese. This procedure, with a high sensitivity (93%) and a low detection limit (1–10 cfu 25 g−1), provided negative and presumptive positive results within 2–3 d. Differences between LMBA, PALCAM and Oxford medium turned out to be highly significant (at 99% significance level); plating on LMBA after standard enrichment protocols giving the best overall results. An improvement in detection was also obtained by modifying the confirmation procedure. A loopful of culture (an additional streak) from PALCAM or Oxford medium was streaked on non-selective medium in addition to streaking only separate colonies as specified in the standards.

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