Can Salmonella spp., Listeria monocytogenes, and Escherichia coli O157:H7 Survive on Fresh Produce Cardboard Boxes?

Introduction: Cross-contamination of foodborne pathogens from fomites to food surfaces has been an increasing issue in the food industry.  Communication with small farmers showed that produce boxes made from cardboard are constantly reused. This practice may increase the risk of cross-contamination of foodborne pathogens from produce to boxes and vice versa. 

Purpose: The purpose of this study was to demonstrate the ability of Salmonella spp., Listeria monocytogenes, and Escherichia. coli O157:H7 to survive over several days on cardboard produce boxes. 

Methods: Cardboard boxes used for produce were obtained from farms in Houston, TX. Coupons (10 x 10 cm) were created, packaged in aluminum foil, autoclaved at 121°C for 15 min. Salmonella Typhimurium, L. monocytogenes, and E. coli O157:H7 overnight culture cocktail was inoculated on the coupons (~ 6 log CFU/cm²) and samples were tested at days 0 (0 and 6 h), 1, 2, 5, 8, 11, 14, 17, 20, 23 and 29. The pathogens were plated on EMB and Palcam media and quantified. 

Results: The results demonstrated that the three foodborne pathogens can survive on produce boxes over time. Up to 1 log CFU/cm² E. coli O157:H7 and L. monocytogenes and 2 log CFU/cm² were observed on the coupons on day 17. E. coli O157:H7 and L. monocytogenes were below detection limit on day 20. However, 1.5 log CFU/cm² Salmonellaspp. was observed on day 20. All pathogenic microorganisms were below detection limit on days 23 and 29. Three biological replicates were carried out.

Significance: The results of this study show that produce boxes made from cardboard should not be reused since they can be a vector of foodborne pathogen transfer on fresh produce. An effective outreach program to communicate scientifically validated results may help reduce the risk of foodborne illness caused by fresh produce contamination and improve public health.