Viability Discrimination of Bacterial Microbiomes in Home Kitchen Dish Sponges via Propidium Monoazide Treatment

Abstract

Dish sponges are known to support the survival and growth of human bacterial pathogens yet are commonly used by consumers to wash dishes and clean kitchen surfaces. Exposure to foodborne pathogens via sponge use may lead to foodborne illness, which is of particular concern among susceptible populations. Limitations associated with culture-independent or - dependent methods for bacterial community characterization have challenged the complete assessment of foodborne pathogen exposure risk presented by sponges. In this study, the bacterial microbiomes of five dish sponges were characterized to evaluate the presence of viable bacterial foodborne pathogens using propidium monoazide treatment, which is a novel approach in this medium. Total and viable sponge microbiomes were subsequently metataxonomically evaluated via targeted 16S rRNA sequencing. Select pathogen viability was confirmed using targeted selective enrichment. The comparison of total and viable sponge microbiome beta diversity indicated that sponge taxonomic abundance profiles did not vary significantly according to PMA treatment. The numbers of unique bacterial species (p-value = 0.0465) and unique bacterial foodborne pathogens (p-value = 0.0102) identified were significantly lower after PMA-treatment. A total of 20 unique bacterial foodborne pathogens were detected among sponge microbiomes regardless of PMA treatment. Three to six unique viable foodborne pathogens were identified in each sponge. Escherichia coli and Staphylococcus aureus were identified in all five viable sponge microbiomes evaluated. Viable E. coli were recovered from two of five sponges via targeted selective enrichment. These findings suggest that most sponge-associated bacterial communities may be viable and contain multiple viable bacterial foodborne pathogens. ImportanceBacterial pathogens may exist in the domestic kitchen environment, threatening both sanitation levels and the health of residents. Dish sponges are commonly used kitchen tools that can harbor foodborne pathogens as they present adequate conditions for the survival and growth of bacteria. Using a contaminated sponge may lead to foodborne illness through direct contact with pathogens or via cross-contamination with food or other surfaces. Although bacterial foodborne pathogens have been identified in sponges, previous limitations in methodology have prevented the complete understanding of sponge microbiomes. This study used a novel application of a chemical reagent coupled with targeted amplicon sequencing to identify sponge communities and differentiate between viable and non-viable bacteria. Insights into dish sponge microbiomes and potential risks of bacterial foodborne pathogen exposure can inform food safety education programs to aid in the prevention of home-acquired foodborne illness and cross-contamination events.