Effect of peracetic acid on biofilms formed by Staphylococcus aureus and Listeria monocytogenes isolated from dairy plants

Abstract

This research investigated the removal of adherent cells of 4 strains of Staphylococcus aureus and 1 Listeria monocytogenes strain (previously isolated from dairy plants) from polystyrene microtiter plates using peracetic acid (PAA, 0.5%) for 15, 30, 60, and 120 s, and the inactivation of biofilms formed by those strains on stainless steel coupons using the same treatment times. In the microtiter plates, PAA removed all S. aureus at 15 s compared with control (no PAA treatment). However, L. monocytogenes biofilm was not affected by any PAA treatment. On the stainless steel surface, epifluorescence microscopy using LIVE/DEAD staining (BacLight, Molecular Probes/Thermo Fisher Scientific, Eugene, OR) showed that all strains were damaged within 15 s, with almost 100% of cells inactivated after 30 s. Results of this trial indicate that, although PAA was able to inactivate both S. aureus and L. monocytogenes monospecies biofilms on stainless steel, it was only able to remove adherent cells of S. aureus from polystyrene microplates. The correct use of PAA is critical for eliminating biofilms formed by S. aureus strains found in dairy plants, although further studies are necessary to determine the optimal PAA treatment for removing biofilms of L. monocytogenes.

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

“…Similar results were observed by Lee et al (2016), indicating that PAA (0.5%) was able to inactivate the biofilm of L. monocytogenes formed on stainless steel. Our results are also in agreement with those reported by Ibusquiza, Herrera and Cabo (2011), who observed that PAA treatment for 10 min was effective in eliminating L. monocytogenes biofilms.…”

“…Importantly, no treatment was able to completely reduce the BFI value of the biofilm producers evaluated, with percentage reduction varying from 29.3 to 62.3%. Lee et al (2016) also reported that PAA was not effective for removing adherent cells of a L. monocytogenes strain isolated from brine on polystyrene microplates.…”

“…Planktonic cells and the medium were removed, and each well was rinsed three times with 250 µL of phosphate buffer saline (PBS) to remove loosely attached cells. Then 250 µL of PAA (0.5%, pH: 2.3) (Dinâmica, Brazil) was added and allowed to react for 60, 120 and 180 s. The concentration of PAA (0.5%) used was the same as described by Lee et al (2016), who showed that PAA was able to inactivate biofilms formed by a L. monocytogenes strain isolated from brine on stainless steel. At the end of each treatment period, the disinfectant was removed and 250 µL of sodium thiosulfate 0.1 M (Chemco, Brazil) was added to each well for 5 min to stop the reaction.…”

“…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).…”

“…Several studies have demonstrated that PAA was efficient in removing adhered cells of L. monocytogenes (Belessi et al, 2011;Ibusquiza, Herrera, Cabo, 2011;Stoporth et al, 2002). Lee et al (2016) also found that PAA at 0.5% was able to inactivate biofilms formed by a L. monocytogenes strain isolated from brine on stainless steel, but was not effective for removing their adherent cells on polystyrene microplates. Thus, the present study aimed to evaluate the effect of PAA at different contact times on biofilms produced on polystyrene microplates and stainless steel coupons by L. monocytogenes strains previously isolated from the environment of a Brazilian cheese plant.…”