Detection of viable and dead Listeria monocytogenes on gouda-like cheeses by real-time PCR
Article first published online: 28 FEB 2005
Letters in Applied Microbiology
Volume 40, Issue 4, pages 301–306, April 2005
How to Cite
Rudi, K., Naterstad, K., Drømtorp, S.M. and Holo, H. (2005), Detection of viable and dead Listeria monocytogenes on gouda-like cheeses by real-time PCR. Letters in Applied Microbiology, 40: 301–306. doi: 10.1111/j.1472-765X.2005.01672.x
- Issue published online: 28 FEB 2005
- Article first published online: 28 FEB 2005
- 2004/0970: received 23 August 2004, revised 26 November 2004 and accepted 10 January 2005
- DNA diagnostics;
- ethidium monoazide bromide;
- Listeria monocytogenes;
- real-time PCR;
- viable but not culturable;
- viable/dead diagnostics
Aims: Surface contamination by Listeria monocytogenes of gouda-like cheeses during processing represents a potential public health problem. The aim of this work was to develop novel real-time PCR diagnostics to detect the presence of viable, dead or viable but not culturable (VBNC) cells on gouda-like cheeses.
Methods and Results: We used ethidium monoazide bromide (EMA)-PCR for direct quantification of viable and dead cells, while semiquantitative detection of culturable cells below the PCR detection limit (c. 100 CFU g−1) was obtained by combining growth and real-time PCR. We were able to quantify the fraction of >0·5% viable cells in a background of dead cells by EMA-PCR, given that the viable cell concentration was above the PCR detection limit. The combined growth and real-time PCR complemented the EMA-PCR, and enabled semiquantitative detection of low levels of culturable cells (10 and 100 CFU g−1).
Significance and Impact of the Study: The significance of this work is that we have developed a novel concept for detection of viable and potentially infectious L. monocytogenes.