Purpose: This study aims to quantify the cross contamination rates of transient bacteria between fresh-cut produce and hands.
Methods: A food-grade strain of nalidixic acid-resistant Enterobacter aerogenes was used as a surrogate for transient hand-associated pathogens. A validation study showed no significant difference between E. aerogenes and Salmonella cross contamination (P > 0.05). Samples were collected using the glove juice method, where volunteers’ hands were massaged for ~1 min inside a nitrile glove containing 20 ml of phosphate buffered saline (PBS). Produce was sampled by homogenization in PBS. Samples were plated onto MacConkey agar containing nalidixic acid. Data were compiled, log transformed, and plotted as frequency distribution histograms. The log percent transfer rates were also analyzed using a Tukey range test to determine if multiple means were significantly different.
Results: Inoculated hands will transfer ~30% of the bacteria to carrots, and ~10-30% to celery and to cantaloupe samples. The Tukey range test showed a significant difference between the transfer rates to carrot and to cantaloupe. Samples of inoculated carrots, inoculated celery, and inoculated cantaloupe transferred ~0.3-1% of bacteria to hands. The Tukey range test showed no significant difference in transfer rates from the three items to hands.
Significance: Direction of transfer plays the largest role in determining transfer rates, followed by difference in produce type. Understanding transfer rates to and from fresh-cut produce will allow for better assessment and management of microbial food safety risks in the home.