Efficiency and novelty of using environmental swabs for dry surface biofilm recovery

Abstract

Studies on the epidemiology of dry surface biofilms within healthcare has shown an almost universal distribution across frequently touched items. Despite a growing body of evidence for dry surface biofilms in hospitals little attention has been paid to the recovery capacity of techniques used to detect these microbial communities. Biofilms are inherently difficult to remove from surfaces due to adhesive substances within their matrix and may act as sources of infection but to what extent is largely unknown. In this study we evaluate the recovery efficiencies of commonly used environmental swabs against dry surface biofilms containing 7.24-Log10 Acinetobacter baumannii/cm2, using a drip flow reactor and desiccation cycle. Biofilm presence was visually confirmed using episcopic differential interference contrast microscopy combined with epifluorescence and quantified using sonicated viable plate counts. The swab materials used comprised of foam, viscose and cotton, all of which were pre-moistened using a buffer solution. The surfaces were vigorously swabbed by each material type and the resultant microbe populations for both swabs and remaining dry surface biofilms were quantified. Our results found foam tipped swabs to be superior, detecting on average 30% of the original dry surface biofilm contamination; followed by viscose (6%) and cotton (3%). However, no distinct difference was revealed in the concentration of microbes remaining on the surface after swabbing for each swab type suggesting there is variation in the capacity for each swab to release biofilm associated microorganisms. We conclude whilst environmental swabs do possess the ability to detect biofilms on dry surfaces; the reduced efficiencies are likely to cause an underestimation of the microbes present and should be considered during clinical application.

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Identifiers

ORCID for Sandra Wilks: orcid.org/0000-0002-4134-9415

ORCID for Bill Keevil: orcid.org/0000-0003-1917-7706

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