Effect of Sanitizers on Listeria Biofilm on Contact Surfaces

Abstract

The effectiveness of sanitizers on biofilms of Listeria monocytogenes (NCTC 1994) developed on stainless steel and plastic (high density polyethylene, HDPE) surfaces was studied. There was more biofilm formation on the surface of stainless steel than on plastic with the latter being more resistant to the sanitizers than the former. Upon exposure to 100 ppm hypochlorite and 10 ppm iodophor for five minutes, there was a three to four log decrease in counts on the stainless steel surfaces, while on plastic surfaces, the reduction was one to two log cycles. Hypochlorite was more effective than iodophor in inactivating biofilm cells grown on both the surfaces. Two hundred ppm hypochlorite for five minutes. completely inactivated the adherent microcolony cells on stainless steel surfaces but failed to do so on plastic surfaces. Total inactivation of planktonic cells of L. monocytogenes was achieved using permitted concentrations of hypochlorite (10 ppm) and iodophor (1 ppm) for five minutes.