Potential of oxygen and nitrogen reactive intermediates to disperse Listeria monocytogenesfrom biofilms

Studying biofilm dispersal is important to prevent Listeria monocytogenespersistence 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. monocytogenesbiofilms have not been fully investigated. This study reports on ROI and RNI quantification in Listeria monocytogenesbiofilms 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. monocytogenesdispersal 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, H2O2, and superoxide in L. monocytogenesbiofilms. Neither NO donor nor inhibitors interfered in L. monocytogenesgrowth and gene expression, except for lmo0990, which was downregulated. In conclusion, ROI and RNI did not exert dispersive effects on L. monocytogenesbiofilms, indicating that this pathogen has a tight control for protection against oxidative and nitrosative stresses.