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Treatment with disinfectants may induce an increase in viable but non culturable populations of Listeria monocytogenes in biofilms formed in smoked salmon processing environments
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International audience. The objectives of this study were 1) to evaluate the impact of two industrial disinfectants on the viability ofListeria monocytogenespopulations in biofilm and 2) to investigate the viability state ofL. monocytogenescellspresent on contact surfaces in the smoked salmon processing environment. In thefirst step, we cultured monospecies and mixed species biofilms containingL. monocytogeneson stainless steel or polyvinyl chloride (PVC) at8 °C for 48h. The biofilms were then exposed to quaternary ammonium- and hydrogen peroxide-based disin-fectants. Residual total populations ofL. monocytogeneswere measured by qPCR, and viable culturable (VC) cellpopulations were quantified using standard microbiological culture-based techniques and by a quantitative PCR(qPCR) assay coupled with a propidium monoazide treatment. Decreases in VC populations and the appearanceof viable but non culturable (VBNC) populations were observed in response to treatment with the disinfectants.An 8 month sampling campaign in 4 smoked salmon processing plants was also carried out to detectL. mono-cytogenesin environmental samples. VBNC cells were detected mainly after the cleaning and disinfection op-erations. This study showed that industrial disinfectants did not inactivate allL. monocytogenescells on inertsurfaces. The presence of VBNC populations ofL. monocytogenesin the smoked salmon processing environment isa public health concern.1.
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