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

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.

Particle laden fluid interfaces: dynamics and interfacial rheology.

We review the dynamics of particle laden interfaces, both particle monolayers and particle+surfactant monolayers. We also discuss the use of the Brownian motion of microparticles trapped at fluid interfaces for measuring the shear rheology of surfactant and polymer monolayers. We describe the basic concepts of interfacial rheology and the different experimental methods for measuring both dilational and shear surface complex moduli over a broad range of frequencies, with emphasis in the micro-rheology methods. In the case of particles trapped at interfaces the calculation of the diffusion coefficient from the Brownian trajectories of the particles is calculated as a function of particle surface concentration. We describe in detail the calculation in the case of subdiffusive particle dynamics. A comprehensive review of dilational and shear rheology of particle monolayers and particle+surfactant monolayers is presented. Finally the advantages and current open problems of the use of the Brownian motion of microparticles for calculating the shear complex modulus of monolayers are described in detail.

Salt effects on the air/solution interfacial properties of PEO-containing copolymers: equilibrium, adsorption kinetics and surface rheological behavior.

Lithium cations are known to form complexes with the oxygen atoms of poly(oxyethylene) chains. The effect of Li(+) on the surface properties of three block-copolymers containing poly(oxyethylene) (PEO) have been studied. Two types of copolymers have been studied, a water soluble one of the pluronic family, PEO-b-PPO-b-PEO, PPO being poly(propyleneoxyde), and two water insoluble ones: PEO-b-PS and PEO-b-PS-b-PEO, PS being polystyrene. In the case of the pluronic the adsorption kinetics, the equilibrium surface tension isotherm and the aqueous/air surface rheology have been measured, while for the two insoluble copolymers only the surface pressure and the surface rheology have been studied. In all the cases two different Li(+) concentrations have been used. As in the absence of lithium ions, the adsorption kinetics of pluronic solutions shows two processes, and becomes faster as [Li(+)] increases. The kinetics is not diffusion controlled. For a given pluronic concentration the equilibrium surface pressure increases with [Li(+)], and the isotherms show two surface phase transitions, though less marked than for [Li(+)]=0. A similar behavior was found for the equilibrium isotherms of PEO-b-PS and PEO-b-PS-b-PEO. The surface elasticity of these two copolymers was found to increase with [Li(+)] over the whole surface concentration and frequency ranges studied. A smaller effect was found in the case of the pluronic solutions. The results of the pluronic solutions were modeled using a recent theory that takes into account that the molecules can be adsorbed at the surface in two different states. The theory gives a good fit for the adsorption kinetics and a reasonably good prediction of the equilibrium isotherms for low and intermediate concentrations of pluronic. However, the theory is not able to reproduce the isotherm for [Li(+)]=0. Only a semi-quantitative prediction of the surface elasticity is obtained for [pluronic]≤1×10(-3) mM.