Purpose: The purpose of this study was to evaluate the antimicrobial efficacy of a novel commercial sanitizing solution (CX) for preventing cross-contamination of USDA-certified organic produce including, cherry tomatoes, baby spinach, and romaine lettuce during washing.
Methods: Pathogens used were cocktails of Escherichia coli (EC) O157:H7 or Salmonella enterica (SE) resistant to nalidixic acid (NAR). A microbroth dilution assay was used to determine minimum inhibitory concentration (MIC) of CX against EC or SE. Wild type and NAR strains were compared to confirm similar resistance characteristics to CX. Produce samples were inoculated with EC or SE and were placed into an aqueous solution at 0%, 0.5% and 0.75% CX (v/v) with and without 1.0% organic load (OL). To determine if cross-contamination occurred in the treatment liquids, un-inoculated produce was introduced to the same CX solutions after inoculated produce. After washing, produce was hand-massaged and rinsate plated on CT-SMAC or TSAN (TSA + Nalidixic acid) to enumerate survivors.
Results: The MICs for all strains of EC and SE were the same at 0.75%. For all produce samples at the initial sampling, CX solutions had little effect on reducing survival of EC or SE. However for the un-inoculated produce, cross contamination by EC or SE was eliminated (< 2 log CFU/ml rinsate) by CX compared to the control (ca. 4 - 5 log CFU/ml of rinsate). OL had no effect on CX inactivation.
Significance: Results indicate that the commercial sanitizer at 0.5% and 0.75% had efficacy in eliminating cross-contamination on organic produce in a model wash system.