The effects of surface type on the removal of Bacillus cereus and Pseudomonas fluorescens single and dual species biofilms

Abstract

The aim of this work was to assess the effectiveness of the biocide benzyldimethyldodecyl ammonium chloride (BDMDAC) on the removal of single and dual species biofilms of Bacillus cereus and Pseudomonas fluorescens formed in a rotating cylinder reactor (RCR), using AISI316 stainless steel (SS) and polymethyl methacrylate (PMMA) as adhesion surfaces. Additional tests were performed to understand the adhesion of B. cereus and P. fluorescens to the selected surfaces.Predictions of the adhesion potential according to the thermodynamic theory showed more favourable adhesion on SS than on PMMA, for both species.Thermodynamically, adhesion was more favourable for B. cereus. After BDMDAC treatment, thermodynamic adhesion ability was favoured for P. flurescens and decreased for B. cereus, mainly on PMMA. Both bacteria had negative surface charge and the exposure to BDMDAC increased the charge to less negative values. In vitro adhesion results were, for most cases, contradictory to those predicted by the thermodynamic theory. Single and dual species biofilms were formed in the RCR for 7 days. Afterwards, the biofilms were exposed to the chemical (use of BDMDAC) and to hydrodynamic stresses (use of increasing Reynolds number of agitation), alone and combined. The applications of BDMDAC or hydrodynamic stress, when applied alone, were insufficient to remove the biofilms from the surfaces. The combined effects of BDMDAC with a series of increasing Reynolds number of agitation promoted additional biofilm removal. This effect was dependent on the surface used. For PMMA, the hydrodynamic stress was more effective on the removal of BDMDAC-treated dual species biofilms. For SS, the synergy of the chemical and hydrodynamic stresses removed more B. cereus and dual species biofilms. The overall results 2 demonstrate that the species association was not advantageous in biofilm resistance to removal when compared with the single species biofilms, particularly those of P. fluorescens. In general, removal by hydrodynamic stress, alone and preceded by the BDMDAC treatment, was higher for biofilms formed on SS. However, even the combined action of BDMDAC and the exposure to a series of increasing Reynolds number of agitation were not effective to obtain biofilm-free surfaces.

The action of chemical and mechanical stresses on single and dual species biofilm removal of drinking water bacteria

“…The presence of S. maltophilia in a significantly higher extent in dual species biofilms was not advantageous in increasing resistance to removal. Lemos et al (2015), using the rotating cylinder reactor with stainless steel and polymethyl methacrylate surfaces for biofilm formation, also found that the association of B. cereus and P. fluorescens did not increase biofilm resistance to chemical and mechanical treatments. These biofilms were treated with the quaternary ammonium compound benzyldimethyldodecyl ammonium chloride.…”

“…A rotating cylinder reactor was used for the first time in DW biofilm studies. This bench top laboratorial reactor was already successfully used in studies of chemical and mechanical control of industrial biofilms (Lemos et al, 2015;Simões et al, 2005Simões et al, , 2009. PVC is commonly found in DWDS and was used as model substratum for biofilm formation (Lemos et al, 2015;Simões et al, 2007).…”

“…The control (untreated biofilm) was carried out with 0.2 M phosphate buffer instead of NaOCl. Biofilm exposure to NaOCl solutions was carried out at constant shear stress (1 Pa, the same used for biofilm formation) for 30 min (Lemos et al, 2015). After treatment, the disinfectant solutions were removed and the biofilms on the PVC cylinders were rinsed twice by immersion in 0.5% (w/v) sodium thiosulfate (Merck, VWR) for 10 min to quench the activity of the disinfectant and finally one time in 0.2 M phosphate buffer.…”

Bacillus cereus hazard and control in industrial dairy processing environment

“…Traditionally, chlorine (sodium hypochlorite)-based sanitizers have been used, however, a wide variety of sanitizers including quaternary ammonium compounds, anionic acids, iodophores and chlorine-based compounds are currently in use or being evaluated for use in CIP systems. The combined effects of the biocide, benzyldimethyldodecyl ammonium chloride with a series of increasing Reynolds number of agitation promote B. cereus biofilm removal from stainless steel surfaces (Lemos, Gomes, Mergulhão, Melo, & Simões, 2015).…”

The impact of material properties, nutrient load and shear stress on biofouling in food industries

“…Total bacterial counts were obtained by direct staining with 4',6-diamidino-2-phenylindole (DAPI), as previously described by Lemos et al (2014). Cells were visualized under an epifluorescence microscope (Eclipse LV100, Nikon, Japan) equipped with a filter block sensitive to DAPI fluorescence (359-nm excitation filter in combination with a 461-nm emission filter).…”