Inactivation of Listeria monocytogenes biofilms by electrolyzed oxidizing water

This study investigates the resistance of Listeria monocytogenes biofilms o n stainless steel surfaces to electrolyzed oxidizing (EO) water. A direct a gar overlay method was used to estimate the attached bacteria on stainless steel coupons after an EO water treatment. A scraping method was also used to quantify the adherent cell populations after the EO water treatment. The stainless steel surface allowed IO to 15% of the surface area to be covere d by Listeria biofilm when the inoculated stainless steel coupon was incuba ted in 10% tryptic soy broth (TSB) at 23C for 48 h. When the stainless stee l coupons containing adherent cells were treated with EO water (56 mg/L of residual chlorine) for 10, 30, 60, 180, and 300 s, adherent cell population s (10.3 log(10) CFU/coupon) were reduced with increasing treatment rime. Al though the direct agar overlay methods do not quantify survival of single b acteria, only one to five cell clumps per coupon survived after 300 s of th e EO water treatment. Using the scraping method, the adherent cell populati on on the stainless steel coupons was reduced by about 9 log cycles after 3 00 s of EO water treatment.