Surface Material, Temperature, and Soil Effects on the Survival of Selected Foodborne Pathogens in the Presence of Condensate

Abstract

The effects of surface type (stainless steel, acetal resin, and fiberglass reinforced plastic wall paneling [FRP]), soil, and temperature on the survival of Listeria monocytogenes, Salmonella spp., and Yersinia enterocolitica, in the presence of condensate were evaluated. Surface coupons—half soiled with sterile porcine serum—were exposed to cell suspensions made from individual five-strain cocktails composed of organisms from the same genus (107 CFU/ml) in Butterfield's phosphate buffer and incubated for 2 h at 25°C allowing attachment of cells to coupon surfaces. Coupons were rinsed to remove unattached cells, incubated at either 4 or 10°C under condensate-forming conditions, and sampled at six time intervals over a 15-day period. For enumeration, cells were removed from the coupons by vigorous shaking in 100 ml of Butterfield's phosphate buffer with 3 g of glass beads and plated on tryptic soy agar with 0.6% yeast extract. Stainless steel did not support the survival of Listeria as well as acetal resin or FRP. Acetal resin and stainless steel were less supportive of Salmonella than FRP. All surfaces supported the survival of Yersinia over the 15-day trial equally. Temperature had little effect on survival of all organisms across all surfaces with one exception. However, Yersinia displayed growth on FRP at 10°C, but death at 4°C. Serum had a protective effect on L. monocytogenes on all surfaces, with populations sustained at significantly (P ≤ 0.05) higher numbers over time than unsoiled coupons. Serum did not effect survival of Salmonella or Yersinia on stainless steel, acetal resin, or FRP.