Use of 3M Molecular Detection Assay for the Recovery of Salmonella and Listeria Species from the Surface of Avocados

Introduction: Salmonella and Listeria species are ubiquitous microorganisms. The presence of these pathogens in fruits increases the risk of illness. Outbreaks of Salmonella and Listeria monocytogenes have in the past been linked to produce. Fast and accurate results on pathogen determination are key in food safety management. Use of technologies such the 3M Molecular Detection Assay (3M MDA) combines isothermal DNA amplification and bioluminescence detection providing real-time detection and next-day results.

Purpose: The purpose of this study was to evaluate the performance of 3M MDA for the recovery of Listeria species and Salmonella from avocado’s surface. 

Methods: Salmonella Enteritidis (ATCC 13076) and Listeria monocytogenes (ATCC 19115) were used to artificially contaminate avocados (0.4-4.0 CFU/avocado) by dipping. Thirty avocados were contaminated and five were used as a negative control for each microorganism. Each avocado was placed in enrichment broth (3M Buffered Peptone Water-ISO for Salmonella and 3M Modified Listeria Recovery Broth and Supplement for Listeria) at a 1:1.5 w:v ratio and incubated during 24 h at 35°C. All the samples were culture confirmed. 

Results: A total of 35 avocados were analyzed for each test. Sensitivity was 96.7% for Listeria and 100% for Salmonella assays. Statistically significant differences were not detected (P>0.05) when these rapid tests were compared with the respective traditional methods for the recovery of Salmonella or Listeria species. All the avocados used as control were negative. 

Significance: Use of MDA assays for the detection of Salmonella or Listeria species on avocado surfaces provide fast and accurate results that are equivalent to the traditional method.