Decreased biofilm formation by planktonic cells of Listeria monocytogenes in the presence of sodium hypochlorite

Authors: BANSAL,, M - Mississippi State University; DHOWLAGHAR, N - Mississippi State University; NANNAPANENI, R - Mississippi State University; KODE, D - Mississippi State University; CHANG, S - Mississippi State University; SHARMA, C - Mississippi State University; MCDANIEL, C - Mississippi State University; KIESS, A - Mississippi State University

Submitted to: Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/4/2020
Publication Date: 12/16/2020
Citation: Bansal,, M., Dhowlaghar, N., Nannapaneni, R., Kode, D., Chang, S.C., Sharma, C.S., Mcdaniel, C., Kiess, A. 2020. Decreased biofilm formation by planktonic cells of Listeria monocytogenes in the presence of sodium hypochlorite. Food Microbiology. 96. Article 103714. https://doi.org/10.1016/j.fm.2020.103714.
DOI: https://doi.org/10.1016/j.fm.2020.103714

Interpretive Summary: Listeria monocytogenes is regularly exposed to different kind of stresses in the food processing environment. It can adapt to homologous or heterologous stresses and enhance its persistence in the harsh environmental conditions. Along with stress adaptation, biofilm formation by L. monocytogenes is another form of survival mechanism, which makes bacterial elimination from food contact surfaces a serious challenge. There is limited information on the effect of subinhibitory NaOCl (a source of chlorine) stress on planktonic cells and on its subsequent biofilm formation ability. It is evident that NaOCl at subinhibitory concentrations induces formation of reactive NaOCl species (RCS) which causes oxidative stress to pathogens. In the present study, we determined the effect of subinhibitory concentrations of NaOCl on L. monocytogenes planktonic cells to form biofilm and its effect on the genes critical for surface attachment and biofilm synthesis. In addition, we investigated if adaptation to subinhibitory NaOCl concentrations can modulate the biofilm formation ability of L. monocytogenes grown in culture medium in order to mimic the presence of organic matter on food-contact surfaces. Our findings show that chlorine, a commonly used disinfectant, decreased L. monocytogenes biofilm formation on polystyrene surface at subinhibitory concentration level. Such antibiofilm effect of NaOCl was found to be associated with the reduced attachment on polystyrene surface, decreased expression of genes, which control biofilm-forming ability and changes in cell wall of L. monocytogenes strains at subinhibitory NaOCl levels observed by electron microscopes.

Technical Abstract: The objective of this study was to determine if the adaptation at planktonic stage to subinhibitory concentrations (SIC) of sodium hypochlorite (NaOCl) could modulate the biofilm forming ability of five Listeria monocytogenes strains V7, Scott A, FSL-N1-227, FSL F6-154 and ATCC 19116 representing serotypes 1/2a, 4b and 4c. Biofilm formation by NaOCl nonadapted and adapted L. monocytogenes planktonic cells was measured in the presence or absence of SIC of NaOCl. The biofilm formation ability of NaOCl nonadapted and adapted L. monocyotgenes planktonic cells was reduced only in the presence of NaOCl (P < 0.05). Scanning electron microscopy revealed that the continuous exposure of NaOCl induced morphological changes in the L. monocytogenes biofilm structure and reduced its attachment to polystyrene surface. The qRT-PCR results also showed that the subinhibitory NaOCl reduced biofilm formation related gene expression such as motility and quorum sensing signals (P < 0.05). These findings indicate that subinhibitory NaOCl can reduce the ability of L. monocytogenes planktonic cells to form biofilms on polystyrene surface.