A Survey of the Microbiome Sampled from Surfaces of Supermarket Shopping Carts and Grocery Baskets

Introduction:  Supermarkets microbiological assessments are typically performed on food, and little information is available about carts and baskets used for grocery shopping. Studies on shopping carts contamination express concerns mostly associated with infants’ exposure to pathogens; however, there is the potential of food contamination due to carts and baskets.

Purpose: To identify the microbial contamination present in supermarkets shopping carts and baskets.

Methods: A total of 97 samples were collected from 21 supermarkets at eight different towns located in West Texas. Shopping cart handles, shopping cart grills, and grocery baskets were sampled using 25 ml BPW swabs. Microbial analyses were performed to enumerate aerobic plate count (APC), yeast and molds (YM), Enterobacteriaceae (EB), coliforms (CF), and Escherichia coli (EC). The prevalence of Listeria spp., Salmonella spp., Staphylococcus aureus, Enterobacteriaceae, and E. coli O157 was determined. Petrifilm, BAX system, and conventional selective agar media were used for the analyses.

Results: APC, EB, CF, and EC were at higher levels on handles (2.45, 4.43, 6.43, and 1.44 log CFU/cm², respectively), followed by baskets (2.03, 3.67, 5.55, and 0.7 log CFU/cm², respectively). YM was highest on baskets (3.01 log CFU/cm²). Cart grills had less than 10 CFU/cm² of APC, YM, CF and EC, but 2.38 log CFU/cm² of EB. The overall prevalence for the three type of samples was found to be: Salmonella 7.2%, E. coli O157 6.2%, S. aureus 61.8%, Listeria spp. 76.3%, (8.5% confirmed L. monocytogenes), and Enterobacteriaceae 51.5%.

Significance: Bacterial contamination of shopping carts and grocery baskets should be treated as a major public health threat. Fruits and vegetables are often placed on carts and baskets without protection; similarly, meat and other foodstuffs are wrapped in bags not properly sealed during grocery shopping. The presence of foodborne pathogens on such surfaces pose a risk of food contamination and a potential cause of illness.