BIOFILM DEVELOPMENT AND SANITIZER INACTIVATION OF LISTERIA-MONOCYTOGENES AND SALMONELLA-TYPHIMURIUM ON STAINLESS-STEEL AND BUNA-N RUBBER

Biofilm formation by seven strains of Listeria monocytogenes and one s train of Salmonella typhimurium on stainless steel and Buna-n rubber w as examined under two nutrient conditions. The type of surface, nutrie nt level, and organism influenced biofilm development and production o f extracellular materials. Buna-n had a strong bacteriostatic effect o n L monocytogenes, and biofilm formation on Buna-n under low nutrient conditions was reduced for four of the seven strains tested. Buna-n wa s less bacteriostatic toward S. typhimurium. It inhibited the growth o f several other pathogens to varying degrees. An ethylene propylene di amine monomer rubber was less inhibitory than Buna-n, and Viton rubber had no effect. The effectiveness of sanitizers on biofilm bacteria wa s examined. Biofilms were challenged with four types of detergent and nondetergent sanitizers. Resistance to sanitizers was strongly influen ced by the type of surface. Bacterial biofilm populations on stainless steel were reduced 3-5 log by all the sanitizers, but those on Buna-n were resistant to these sanitizers and were reduced less than 1-2 log . In contrast, planktonic (suspended) bacteria were reduced 7-8 log by these sanitizers. Chlorine and anionic acid sanitizers generally remo ved extracellular materials from biofilms better than iodine and quate rnary ammonium detergent sanitizers. Scanning electron microscopy demo nstrated that biofilm cells and extracellular matrices could remain on sanitized surfaces from which no viable cells were recovered.