Bacterial levels and diversity in kitchen sponges and dishwashing brushes used by consumers

Abstract

Aims:The purpose of the work was to investigate bacterial levels and diversity as well as survival of Salmonella in used dish washing sponges and brushes and identify consumer practices that can potentially explain bacterial status of these items. Methods and Results:Used washing up utensils were collected from consumers.The bacterial numbers (TVC) were very variable with an extremely high median level (10.3 log cfu/item) in Portuguese sponges and lower levels in Norwegian items (7.3 and 7.0 cfu/item for sponges and brushes). No self-reported practices or household composition could explain differences found in TVC levels among the collected sponges. Lower mean TVC levels were found in unworn brushes and brushes regularly cleaned with soap, but the differences were modest (1.5 log or less). A common set of bacteria was found in brushes and sponges, dominated by Acinetobacter, Chryseobacterium, Enhydrobacter, Enterobacteriaceae and Pseudomonas. There was no difference in TVC or bacterial diversity between conventional and antimicrobial sponges containing silver after 4 weeks of use. For used brushes inoculated with Salmonella and allowed to dry overnight, a significant reduction in Salmonella numbers was observed. No reduction was observed for brushes stored in humid conditions (in a plastic bag) or for sponges regardless of storing conditions. Conclusions: Overall, lower bacterial levels were observed in used brushes than in sponges, and Salmonella died more rapidly in brushes. A common set of nonpathogenic bacteria dominated in brushes and sponges. Significance and Impact of Study:The study demonstrates that the use of brushes may be more hygienic than the use of sponges.

Mapping the Kitchen Microbiota in Five European Countries Reveals a Set of Core Bacteria across Countries, Kitchen Surfaces, and Cleaning Utensils

“…Although the households in the current study had considerable differences with respect to kitchen standards (households with and without running water, indoor sink, and dish washing machine), food preparation routines, and dietary habits ( 23 – 25 ), we still found a set of core bacteria resident in the kitchen environment. Also, similar bacteria were found in European kitchens as were previously found in other kitchen surfaces and kitchen sponge studies ( 2 , 7 , 12 – 15 ).…”

“…We found that Acinetobacter was present in all countries and samples and that its relative abundance was high (especially in humid samples such as sponges, cloths, and sinks) and not significantly different between countries. We have previously also reported that Acinetobacter was among the most dominant bacteria in used sponges and brushes across different countries in Europe ( 12 ), and Adams et al ( 2 ) reported that Acinetobacter was abundant in kitchens regardless of geographic location (South Korea, Colorado, North Carolina). One explanation for the dominance of Acinetobacter in kitchens could be that it probably enters the kitchen daily, since it is highly occurrent on vegetables, meat, fish, and milk and appears to be persistent in drinking water systems ( 29 – 31 ).…”

“…Kitchen sponges absorb microorganisms, food soils, and humidity during use and dry slowly ( 11 ), which leads to growth of bacteria to high levels. Foodborne illness has also been associated with sponges transferring pathogens to food or hands ( 12 – 14 ), and we have previously reported high survival of Salmonella added to used sponges ( 11 ). Although previous studies of kitchen sponges have reported dominance of nonpathogenic bacteria, there have been reports of taxonomic relationships to risk group 2 species (moderate individual risk, low community risk) such as Acinetobacter johnsonii , Acinetobacter pittii , Acinetobacter ursingii , Chryseobacterium hominis , and Moraxella osloensis ( 1 , 14 ).…”

“…Although previous studies of kitchen sponges have reported dominance of nonpathogenic bacteria, there have been reports of taxonomic relationships to risk group 2 species (moderate individual risk, low community risk) such as Acinetobacter johnsonii , Acinetobacter pittii , Acinetobacter ursingii , Chryseobacterium hominis , and Moraxella osloensis ( 1 , 14 ). We have previously reported a common set of bacteria in brushes and sponges across two countries (Norway and Portugal) despite the total bacterial levels varying by several magnitudes ( 12 ). Many of the same genera also dominated in sponges in two German studies ( 13 , 14 ).…”

“…Many of the same genera also dominated in sponges in two German studies ( 13 , 14 ). Based on this, we suggested that there may be a set of common bacteria, with Acinetobacter , Enhydrobacter , Pseudomonas , and Chryseobacterium as the most dominant, in used sponges and brushes across different countries in Europe ( 12 ).…”