Survival of Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes on the Skin and Sliced Kiwifruit

Introduction: Pathogens, such as Escherichia coli O157:H7 and Salmonella, have shown their capability to survive in low pH fruits such as pineapples, mangoes, and strawberries. However, no study has been done for kiwifruit. Two varieties of kiwifruit are available on the market now for consumers. One is the green-fleshed traditional kiwifruit and the other is the yellow-fleshed golden kiwifruit.

Purpose:  The objective of this study is to evaluate the survival of E. coli O157:H7, Salmonella spp., and L. monocytogenes cocktails on the skin and on sliced kiwifruit.

Methods: The green and golden kiwifruit were purchased from a local grocery store. They were proven to be E. coli O157:H7, Salmonella, and L. monocytogenes negative before inoculation following the FDA standard protocols. The whole kiwifruit were inoculated by dipping the entire fruit into the cocktail broth for 30 s then drying and storing them at room temperature for 30 days. The sliced kiwifruit were inoculated by adding 100 µl of each cocktail to the cut surface of every slice. The sliced inoculated kiwifruit were dried and stored at 4°C for 48 h. Selective agars were used to enumerate survived pathogens.

Results: Escherichia coli O157:H7 survived for 30 days on whole green kiwifruit while it survived only for 20 days on the golden kiwifruit. The numbers of Salmonella and L. monocytogenes were below the limit of detection after 15 days on green kiwifruit and 10 days on golden kiwifruit. The pH of cut kiwifruit was 3.48 for golden kiwifruit and 3.51 for green kiwifruit. Although the pH of cut kiwifruit was low, three pathogens survived for 48 hours in the refrigerator.

Significance:  This study highlights the importance of preventing contamination of pathogens on raw kiwifruit. Implementation of intervention and preventive control strategies is essential to the safety of fresh cut fruits.