Effectiveness of Sustained Antimicrobial Packaging on Control of Escherichia coli O157:H7 on Iceberg Lettuce

Introduction: Leafy green vegetables contaminated with bacterial pathogens such as E. coli O157:H7 have been linked to several outbreaks of infections. An antimicrobial intervention that would be effective, economical, and adoptable by the fresh produce industry for control of pathogen contamination is in great demand. 

Purpose: The objective of this study was to evaluate the efficacy of sustained antimicrobial packaging on control of E. coli O157:H7 on artificially-contaminated lettuce.

Methods: Commercial iceberg lettuce was inoculated with a three-strain mixture of E. coli O157:H7 at 10¹ or 10³ CFU/g. The contaminated lettuce and un-inoculated controls were placed in each of four different antimicrobial packaging structures. Traditional, non-antimicrobial structure was included in the study as controls. The packaged lettuce was stored at 4 or 10 °C for 3 weeks. The lettuce was sampled twice a week for the population of E. coli O157:H7.

Results: Results showed that E. coli O157:H7 was not detectable from samples inoculated with 1 log E. coli O157:H7 and stored at 4 °C including the samples in the non-antimicrobial packaging structure.  Lettuce inoculated with 3 log E. coli O157 and stored at 4 °C  and all samples stored at 10 °C in packaging structures with the CO₂ generator, O₂ scavenger, or chlorine dioxide generator tested negative for E. coli O157H7 except for samples inoculated with 3 log E. coli O157:H7 in packaging structures with the CO₂ generator at 10 °C.  The populations of E. coli O157:H7 in the control packaging structure had 1.85 – 5.32 log CFU/g of E. coli O157:H7.  The packaging structure with the AIT generator was ineffective in inhibiting the growth of E. coli O157:H7 and the populations of the pathogen ranged from 1.30 to 5.89 log CFU/g. 

Significance: The research suggests that some of the antimicrobial packaging structures evaluated in the study were effective in inhibiting the growth of E. coli O157:H7 on iceberg lettuce.