Dispersal of human and plant pathogens biofilms via nitric oxide donors at 4 °C

Abstract

Recent studies suggest that nitric oxide donors capable of manipulating nitric oxide-mediated signaling in bacteria could induce dispersal of biofilms. Encased in extracellular polymeric substances, human and plant pathogens within biofilms are significantly more resistant to sanitizers. This is particularly a problem in refrigerated environments where food is processed. In an exercise aimed to study the potential of nitric oxide donors as biofilm dispersal in refrigerated conditions, we compared the ability of different nitric oxide donors (SNAP, NO-aspirin and Noc-5) to dislodge biofilms formed by foodborne, human and plant pathogens treated at 4 °C. The donors SNAP and Noc-5 were efficient in dispersing biofilms formed by Salmonella enterica, pathogenic Escherichia coli and Listeria innocua. The biomasses were decreased up to 30 % when compared with the untreated controls. When the plant pathogens Pectobacterium sp. and Xanthomonas sp. were tested the dispersion was mainly limited to Pectobacterium carotovorum biofilms, decreasing up to 15 % after exposure to molsidomine. Finally, the association of selected nitric oxide donors with sanitizers (DiQuat, H2O2, peracetic acid and PhenoTek II) was effective in dispersing biofilms. The best dispersal was achieved by pre-treating P. carotovorum with molsidomine and then peracetic acid. The synergistic effect was estimated up to ~35 % in dispersal when compared with peracetic acid alone. The association of nitric oxide donors with sanitizers could provide a foundation for an improved sanitization procedure for cleaning refrigerate environments.

Keywords: Biofilm dispersal; Biofilms; MAHMA NONOate; Nitric oxide donors; Salmonella enterica; Sanitization.

Fig. 1

Dispersal of different preformed biofilms by the nitric oxide donors SNAP, Noc-5 and NO-aspirin on polypropylene during exposure at 4 °C. Salmonella and E. coli cocktails: see “Materials and methods” section for details about the strains. Concentrations of the nitric oxide donor are on the x-axis. Residual biofilms were quantified by staining with crystal violet. Error bars are standard errors. Asterisk (*) represents significant different mean when compared with the PBS treatment only (p = 0.05)

Fig. 2

Dispersal of different preformed biofilms by the nitric oxide donors SNAP, Noc-5 and NO-aspirin on polystyrene during exposure at 4 °C. Concentrations of the nitric oxide donor are on the x-axis. Residual biofilms were quantified by staining with crystal violet. Error bars are standard errors. Asterisk (*) represents significant different mean when compared with the PBS treatment only (p = 0.05)

Fig. 3

Dispersal of different preformed plant pathogens biofilms by molsidomine and NO-aspirin at 4 °C. Concentrations of the nitric oxide donors are on the x-axis. Residual biofilms were quantified by staining with crystal violet. Error bars are standard errors. Asterisk (*) represents significant different mean when compared with the PBS treatment only (p = 0.05)

Fig. 4

Additive effect of different sanitizers in association with nitric oxide donors. MAHMA NONOate: 6-(2-hydroxy-1-methyl-2-nitrosohydrazino)-N-methyl-1-hexanamine; Noc-5: 3-(aminopropyl)-1-hydroxy-3-isopropyl-2-oxo-1-triazene; NO-aspirin: 2-(acetyloxy)benzoic acid 4-(nitroxymethyl)phenyl ester. Bars represent the standard error. Asterisk (*) represents the significant synergistic effect of the nitric oxide donor in association with the sanitizer compared with the sanitizer only