Abstract
The built environment (BE) and in particular kitchen environments harbor a remarkable microbial diversity, including pathogens. We analyzed the bacterial microbiome of used kitchen sponges by 454–pyrosequencing of 16S rRNA genes and fluorescence in situ hybridization coupled with confocal laser scanning microscopy (FISH–CLSM). Pyrosequencing showed a relative dominance of Gammaproteobacteria within the sponge microbiota. Five of the ten most abundant OTUs were closely related to risk group 2 (RG2) species, previously detected in the BE and kitchen microbiome. Regular cleaning of sponges, indicated by their users, significantly affected the microbiome structure. Two of the ten dominant OTUs, closely related to the RG2-species Chryseobacterium hominis and Moraxella osloensis, showed significantly greater proportions in regularly sanitized sponges, thereby questioning such sanitation methods in a long term perspective. FISH–CLSM showed an ubiquitous distribution of bacteria within the sponge tissue, concentrating in internal cavities and on sponge surfaces, where biofilm–like structures occurred. Image analysis showed local densities of up to 5.4 * 1010 cells per cm3, and confirmed the dominance of Gammaproteobacteria. Our study stresses and visualizes the role of kitchen sponges as microbiological hot spots in the BE, with the capability to collect and spread bacteria with a probable pathogenic potential.
Highlights
IntroductionHumans spend up to 90% of their lifetime within built environments (BEs)[1]
In industrialized countries, humans spend up to 90% of their lifetime within built environments (BEs)[1]
No bacteria could be detected in a collection of newly bought, i.e. unused kitchen sponges, using 16S rRNA gene PCR, FISH or cultivation (Supplementary Figures S1 and S2)
Summary
Humans spend up to 90% of their lifetime within built environments (BEs)[1]. Further works showed the presence of specific pathogenic bacteria in kitchen sponges, including Campylobacter spp.[15], Enterobacter cloacae[16, 17], Escherichia coli[14, 17, 18], Klebsiella spp.[14, 16,17,18], Proteus spp.[17], Salmonella spp.[19], and Staphylococcus spp.[14, 16, 17] This evidence, as well as the common perception of kitchen sponges as collectors of microorganisms, initiated the development of commercial products and devices for effective sanitation of kitchen sponges (for example, Martz (2001)[20]). Our work closes a gap in the knowledge of the BE microbiome, and provides new and important information for an effective domestic hygiene awareness
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