Purpose: To measure the impact of swab-type and surface on swabbing effectiveness.
Methods: Four types of swab ([1] cotton; [2] polyesterurethane foam (PU foam); [3] sponge; and [4] gauze swab) were used to recover pathogens (Salmonella Typhimurium, Staphylococcus aureus, Escherichia coli and Listeria monocytogenes) from stainless steel and polyesterurethane (wet and dry) coupons. Additionally, the efficiency of bacterial release from the different swab types was evaluated by inoculating 5 log CFU/ml of a bacterial suspension directly onto each swab type and measuring the amount of bacteria released.
Results: Sponge, PU foam and gauze swab showed higher release efficiency (average range of 4 pathogens: 94.09-99.34%) compared to cotton swab (80.76-87.17%). Swabbing on a wet surface using sponge (80.12-98.19%), PU foam (87.30-98.54%) and gauze (77.93-100.78%) yielded no significant difference of recovery efficiency, but the cotton swab was significantly lower (79.01-92.49%). For swabbing on dry surfaces, the sponge showed the highest recovery efficiency (52.31-78.40%), while cotton swab exhibited the lowest recovery (33.85-63.31%). Swabbing on dry surfaces decreased bacterial recovery efficiency of all swab types to 33.85-78.40%. The efficiency of each swab to recover bacterial biofilm from surfaces was also determined. Sponge (47.68-54.97%) and PU foam (48.29-55.16%) showed higher percentage recovery of bacterial biofilm than cotton (45.10-50.09%) and gauze swab (48.29-55.16%).
Significance: The results of this study clearly show that swab and surface types and conditions can affect bacterial recovery efficiency. Therefore, choosing appropriate swab-types can increase bacterial recovery efficiency from surfaces and achieve more accurate estimations of the actual contamination.