Listeria phage and phage tail induction triggered by components of bacterial-growth media (phosphate, LiCl, nalidixic acid and acriflavine)

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Lemaître, Jean-Paul, J.-P. | Duroux, Amandine | Pimpie, Romain | Duez, Jean-Marie | Milat, Marie Louise

Edité par CCSD ; American Society for Microbiology -

SPE MERS CT3. International audience. The detection of Listeria monocytogenes from food is currently carried out using a double enrichment. For the ISO methodology, this double enrichment is performed using Half-Fraser and Fraser broths, in which the overgrowth of Listeria innocua can occur in samples when both species are present. In this study, we analysed the induction of phage and phage tails of Listeria spp. in these media and in two BHI broths (Brain Heart Infusion) [BioMérieux (BHIM) and Biokar (BHIK)] to identify putative effectors. It appears that Na2HPO4 at concentrations ranging from 1 to 40 g/L with initial pH= 7.5 can induce phage or phage tail production of Listeria spp., especially with 10 g/L of Na2HPO4 and pH= 7.5, conditions used in Half-Fraser and Fraser broths. An exposure to LiCl in BHIM (18 to 21 g/L) can also induce phage and phage tail release but in Half-Fraser and Fraser broths, the concentration of LiCl is much lower (3 g/L). Low phage titers were induced by acriflavine and/or nalidixic acid. We also show that the production of phages and phage tails can occur in Half-Fraser and Fraser broths. This study points out that induction of phages and phage tails could be triggered by compounds present in enrichment media. This could lead to a false negative result for the detection of L. monocytogenes in food products.

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