Recovery and Survival of Aerosolized Escherichia coli and Enterococcus faecium on Food-Grade Rubber, HDPE Plastic, Stainless Steel, and Waxed Cardboard

Contamination of food contact surfaces by airborne transmission of pathogens from the environment has contributed to disease outbreaks. Therefore, this study evaluated the survival and recovery of aerosolized generic Escherichia coli and Enterococcus faecium from four food contact surfaces (food-grade silicone rubber, high-density polyethylene [HDPE] plastic, stainless steel, and waxed cardboard), after four contact times (10, 20, 40, and 60 min), two relative humidity (RH) levels (high: 80%–90%, low: 40%–50%), three distances from aerosolization source (0, 36.5, and 73 cm; E. coli only), and with and without airflow (E. coli only). ANOVA test with Tukey's HSD at α = 0.05 was used to determine how treatment combinations influenced recovery. At high humidity, E. coli recovery on all materials after 40 min was ~1.0 log lower than recovery after 10 min, and further reduced by 1.0 log at 60 min. At lower humidity, E. coli recovery on all materials was ~1.0 log lower at 10 and 20 min compared with high humidity. Distances exerted no significance, whereas airflow presence lowered E. coli recovery. E. coli survival on all materials declined from ~5.0 log CFU/coupon at 0 h to 3.5 log CFU/coupon at 6 h, and 2.0 log CFU/coupon at 24 h post-inoculation. E. coli recovery was significantly lower (p < 0.05) on waxed cardboard. Low RH and longer contact time reduced E. coli recovery but not E. faecium. E. faecium recovery was consistent across treatment combinations, with changes < 0.5 log CFU/coupon. The findings are relevant for the survival of bacteria on common food contact surfaces and the potential of transmission to food products.