Evaluation of the Removal and Destruction Effect of a Chlorine and Thiamine Dilaurylsulfate Combined Treatment on L. monocytogenes Biofilm

Abstract

The present study investigated the efficacy of single and combined treatment of both chlorine and thiamine dilaurylsulfate (TDS) on the reduction of Listeria monocytogenes biofilms in microtiter plate. The disinfectants used in this study were 50, 100, and 200 mg/L chlorine and 100, 500, and 1000 mg/L of TDS. Biofilm-forming index (BFI) and culturable cell count were used to evaluate the disinfectant assay. The highest BFI reduction was 0.80, achieved by the combination of 200 mg/L chlorine and 1000 mg/L TDS. In contrast, the highest culturable cell count reduction was 4.80 log colony-forming units/well by the combination of 200 mg/L chlorine and 100 mg/L TDS. The BFI was reduced in a concentration-dependent manner while culturable cell count was significantly reduced only when all chlorine concentration was combined with 100 mg/L TDS. However, when chlorine was combined with a higher concentration of TDS, the reduction decreased significantly. The result in this study showed that the combination of the 200 mg/L chlorine and 1000 mg/L TDS could be a practical application in removing L. monocytogenes biofilms from surfaces in food industry, and for the 200 mg/L chlorine and 100 mg/L, it can be used for killing the pathogen biofilms. However, more studies are still needed in order to show its efficacy on foods surfaces as well as to develop an even more effective treatment in both killing and removing biofilms.

Effect of peracetic acid on biofilms formed by Listeria monocytogenes strains isolated from a Brazilian cheese processing plant

“…However, it does not provide information on the biological status of the cells. On the other hand, culturable cell counts enable the evaluation of the bactericidal effect of the disinfectants on the biofilm (Srey et al, 2014). Destruction of existing biofilms can involve removing the intact biofilm from surfaces via mechanical action for instance, or dissolving the biofilm structure by chemical disruption of EPS, for example.…”

“…Assays were conducted in 4 replicates, as originally described by Srey et al (2014), with modifications proposed by Lee et al (2016). One loop of each isolate stored in TSB with 15% glycerol was added to 5 mL of freshly prepared TSB, incubated at 37 °C for 24 h and diluted until reaching 0.5 on the McFarland scale (approximately 10 8 cells/mL).…”

“…The efficiency of PAA against the biofilms was also evaluated by culturable cell counts in each well of the microplates, following the procedures recommended by Srey et al (2014). Another set of triplicate aliquots of 200 μL of each TSB bacterial suspension were transferred into 3 wells of a flat bottomed, 96-well polystyrene microplate and incubated statically at 35 °C for 48 h. After incubation, all planktonic cells and medium were removed and the wells were rinsed three times with 250 µL of PBS.…”

“…After the PAA contact times, the sanitizer was removed from each well and 250 µL sodium thiosulfate 0.1 M (Chemco, Brazil) was placed into each well. Then, a sterile cotton swab was pressed to the bottom of the well and rotated 50 times clockwise and another 50 times counterclockwise (Srey et al, 2014). Swabs were placed in test tubes containing sterilized PBS.…”

Effect of oleuropein and peracetic acid on suspended cells and mono-species biofilms formed by Staphylococcus aureus and Escherichia coli

“…The mono-species biofilms were prepared following the method of Srey et al [12]. An aliquot of 250 μL of each bacterial suspension in BHI was pipetted in triplicate into 96-well, flat bottomed polystyrene microtiter plates (TPP, Switzerland).…”