Efficacy of a Sonicating Swab for Removal and Capture of Microorganisms from Experimental and Natural Contaminated Surfaces

Abstract

Enhancements in swabbing technology to increase sample collection efficacy would benefit the food industry. Specifically, these enhancements would assist the food industry in implementing the FDA Food Safety Modernization Act (FSMA) requirements by improving environmental monitoring effectiveness. A sonicating swab device, an example of an enhanced swabbing technology, was demonstrated previously to remove biofilm from stainless steel more efficiently than a standard cotton swab. Within this study, the performance of the sonicating swab was compared to that of the standard cotton swab for the recovery of Listeria monocytogenes from inoculated surfaces (plastic cutting board, wood cutting board, vinyl floor tile, and quarry clay floor tile). Additionally, we demonstrate the sonicating swab performance for collection of a microbiological sample from used commercial plastic cutting boards (noninoculated) in comparison to cotton swabs, foam swabs, and sponges. The sonicating swab captured significantly (P ≤ 0.05) more L. monocytogenes than the cotton swab for both the quarry tile and wood cutting board, while no significant differences were observed for the plastic cutting board or the vinyl floor tile. The sonicating swab consistently recovered significantly (P ≤ 0.05) more bacteria from the used cutting boards than did the standard cotton swab or the 3M Enviro swab, and it recovered significantly (P ≤ 0.05) more bacteria than the sponge swab for a majority of the time (4 of 6 trials). The results of this study indicate that swab technology can still be improved and that the sonicating swab is a viable technological enhancement which aids microbiological sample collection.IMPORTANCE Swabbing of surface areas for microbial contamination has been the standard for the detection and enumeration of microorganisms for many years. Inadequate surface sampling can result in foodborne illness outbreaks due to biotransfer of harmful microorganisms from food contact surfaces to foods. Swab material type, surface characteristics, and swabbing method used are a few of the factors associated with swabbing that can result in the variability of bacterial cell recovery for detection and enumeration. A previous study highlighted a sonicating swab prototype and its ability to recover cells from a stainless steel surface more efficiently and reliably than a standard swab method (T. A. Branck, M. J. Hurley, G. N. Prata, C. A. Crivello, and P. J. Marek, Appl Environ Microbiol 83:e00109-17, 2017, https://doi.org/10.1128/AEM.00109-17). This study expands upon the capabilities of the sonicating swab technology to recover cells from multiple surface types with increased performance over traditional swabbing methods as a tool to further assist in the prevention of foodborne illness outbreaks.

Keywords: capture; microorganisms; removal; sonicating; swab.

FIG 1

Comparison of the sonicating (sonic) swab to a standard cotton swab for the recovery of L. monocytogenes from food contact and non-food contact inoculated surfaces. *, boxplot significantly different (P ≤ 0.05) between the standard cotton swab and the sonicating swab.

FIG 2

Comparison trials of the sonicating swab to a standard cotton swab and the 3M Enviro foam swab for recovery of natural microflora from used commercial plastic cutting boards. (A to C) Boxplots of separate trials comparing the sonicating swab to the standard cotton swab. (D to F) Boxplots of separate trials comparing the sonicating swab to the 3M Enviro foam swab. *, significantly different (P ≤ 0.05) between the standard cotton swab and the sonicating swab; †, significantly different (P ≤ 0.05) between the 3M Enviro foam swab and the sonicating swab.

FIG 3

Comparison of the sonicating swab to a sponge swab for the recovery of natural microflora from used commercial plastic cutting boards. Boxplot of separate trials (A to F) comparing the sponge swab to the sonicating swab. *, significantly different (P ≤ 0.05) between the sponge swab and the sonicating swab.

FIG 4

Three-dimensionally rendered drawing of the sonicating swab adaptor in trimetric view. Components of the sonicating swab adaptor comprise a tightly fitted tube with a locking groove (A), a barbed tube suction port and an adjacent socket (B), a rigid pultruded carbon fiber tube (C), and a swab tip suction head (D). Inset, components of the swab suction head, with a rubber plug to hold in place 100 PPI reticulated polyurethane foam (E) and a swab head with three suction ports (F).