The Microbial Community of Kitchen Sponges: Experimental Study Investigating Bacterial Number, Resistance and Transfer

There are over 48 million episodes of foodborne illnesses in the U.S each year, 3,000 of which result in death (CDC, 2018). Many of these cases may have been prevented with improved sanitation techniques. Previous studies results suggest that kitchen sponges are reservoirs for pathogens and can serve as vector of cross-contamination (Rossi et al., 2013). This hypothesis proposes that the moist, porous nature of kitchen sponges not only provides microbes the perfect physical and nutritional environment, but it also provides a vehicle that allows potential pathogens to move from place to place. The goal of this 12-week research study was to quantify the bacterial number in and on typical household kitchen sponges and to test the effectiveness of common household sanitation techniques on bacterial number. In addition, the transfer of bacteria from sponge to surface was also investigated. To do this, five sponges were distributed to five participants of the Assumption College community who agreed to partake in this study. Every 7 days for a total of 28 days, a square centimeter from each sponge was removed and the bacterial load was quantified in triplicate using colony forming units (CFU) per cm3 on nutrient agar media. Out of the 14 samples, 3 samples reached a log value \u3e1x109 CFU/cm3 (\u3e9 log CFU/cm3). Surprisingly, a significant correlation between the bacterial load and the amount of time the sponge was used was not observed as there was only a 0.4% increase in log10 in the bacterial abundance from week two to week three suggesting consistent bacterial loads after two weeks of use. To determine the most effective strategies for decontamination, sponges that had been used for 28 days were subjected to various treatments. Bacterial abundance was significantly reduced with the use of all sanitation methods apart from the use of hot soapy water as a cleaning technique. Bleach and ethanol treated sponges both showed a 99.9% log CFU/cm3 decrease in bacterial growth. Lastly to test the ability sponges to transfer bacteria, a four-week old sponge was scrubbed against a benchtop and the surface was quantified for bacterial number. The results showed an average of 5.12% bacterial transfer from sponge to surface. These data support previous studies which suggest that kitchen sponges provide a hospitable environment for microbial growth. Moreover, our data provides a clear protocol on how to properly eliminate bacterial contamination in kitchen sponges