Effect of swabbing techniques on the efficiency of bacterial recovery from food contact surfaces

Abstract

Four types of swab (cotton, gauze, polyurethane foam (PU foam) and cellulose sponge) were used to recover four food-borne pathogens (Salmonella Typhimurium, Staphylococcus aureus, Escherichia coli and Listeria monocytogenes) from stainless steel and polyester urethane (old and new) surfaces under wet and dry surface conditions. Characteristics of swabs and swab surfaces were analyzed. The cellulose sponge swab showed the highest bacterial release efficiency, followed by the PU foam, gauze and cotton swabs. The bacterial Gram type affected the efficiency of bacterial recovery on dry surfaces, but the surface type had no apparent effect on the swab efficiency. Swabbing on wet surfaces using PU foam or cellulose sponge yielded a higher efficiency than with gauze or cotton swabs. Swabbing on dry surfaces with cellulose sponge and cotton swabs showed the highest and lowest swab efficiency, respectively. Swabbing on a dry surface decreased the efficiency of all swab types to 30%. For recovery from bacterial biofilms, the swab efficiency was 40% lower than those of wet surfaces. The cellulose sponge and PU foam swabs had a higher percentage recovery of biofilm than gauze and cotton swabs. Thus, the swab type and surface condition can affect the swab efficiency, and choosing the appropriate type of swab for the surface condition will increase the swab efficiency.