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Comparison of the performance of the biofilm sampling methods (swab, sponge, contact agar) in the recovery of Listeria monocytogenes populations considering the seafood environment conditions
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International audience. Aims:The aim of this study was to evaluate the performance of sampling methods [contact plates, sponges, andswabs] in the recovery of biofilmListeria monocytogenespopulations considering the seafood environmentconditions (nature of conditioning, of materials and bacterial species).Methods and results:Different materials (stainless steel, polyvinyl chloride, polyurethane) were conditioned withtwofishfiltrates, the ready-to-eat the most consumed in Europe (smoked salmon, cod). After, we added thesuspension ofListeria monocytogenes, alone or withPseudomonasfluorescensorCarnobacteriumstrains, and in-cubated for 48 h at 8 °C. Then, the 48 h-biofilms were sampled with different methods (contact plates, sponges,and swabs). The cultivable bacterial populations were enumerated on agar, while theL. monocytogenestotal andviable populations were quantified by qPCR and propidium monoazide-qPCR (PMA-qPCR), respectively. Theamount ofL. monocytogenesin biofilms was affected only by the nature of the conditioning with lowest adherentbacteria with cod versus with smoked salmon conditioning. Considering the amount of total population, theswab displayed the lowest values versus the sponges and the contact plates. An explanation was that the ob-servations of the swab by microscopy showed the bacteria trapped within it. The recovery of cultivable bacterialpopulations was not significantly different with the three sampling methods. On the contrary, we showed thatthe VBNC populations were only detached by two of three methods (contact plates, sponges) while for the deadpopulations, those were contact plates and swabs.Conclusions:The nature of the conditioning influenced the amount of the bacteria in biofilms. And the perfor-mance of the recovery of the bacterial populations (dead, VBNC, cultivable) was dependent on the methods used.Significance and impact of the study:This study showed that the seafood environmental conditions influenced thebiofilm formation and the assessment of the efficiency of cleaning and disinfectant operations could be sig-nificantly affected by the used sampling methods.
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