Potential of oxygen and nitrogen reactive intermediates to disperse Listeria monocytogenes from biofilms

Abstract

Studying biofilm dispersal is important to prevent Listeria monocytogenes persistence in food processing plants and to avoid finished product contamination. Reactive oxygen and nitrogen intermediates (ROI and RNI, respectively) may trigger cell detachment from many bacterial species biofilms, but their roles in L. monocytogenes biofilms have not been fully investigated. This study reports on ROI and RNI quantification in Listeria monocytogenes biofilms formed on stainless steel and glass surfaces; bacterial culture and microscopy combined with fluorescent staining were employed. Nitric oxide (NO) donor and inhibitor putative effects on L. monocytogenes dispersal from biofilms were evaluated, and transcription of genes (prfA, lmo 0990, lmo 0807, and lmo1485) involved in ROI and RNI stress responses were quantified by real-time PCR (qPCR). Microscopy detected the reactive intermediates NO, peroxynitrite, H 2 O 2 , and superoxide in L. monocytogenes biofilms. Neither NO donor nor inhibitors interfered in L. monocytogenes growth and gene expression, except for lmo0990, which was downregulated. In conclusion, ROI and RNI did not exert dispersive effects on L. monocytogenes biofilms, indicating that this pathogen has a tight control for protection against oxidative and nitrosative stresses.

Properties of the Extracellular Polymeric Substance Layer from Minimally Grown Planktonic Cells of Listeria monocytogenes

“…Suggestions on how to stop EPS and biofilm formation include the potential use of oxygen and nitrogen reactive intermediates [ 68 ], the application of photodynamic food-grade photosensitisers [ 69 ], the use of combined enzyme-benzalkonium chloride treatments [ 70 ], surface programming of EPS production [ 71 ] and inhibition by bacteriocin producing bacteria [ 72 , 73 , 74 ]. The increasing trend in the food industry of Listeria monocytogenes biofilm formation is attributed to its easy survival on contact surfaces, resistance to disinfectants or antibiotics and growth under the stringent conditions used for food processing and preservation [ 75 ].…”