Growth and survival of Shigella sonnei and S. flexneri in minimal processed vegetables packed under equilibrium modified atmosphere and stored at 7°C and 12°C Original Research Article

The growth and survival of Shigella flexneri and Shigella sonnei at 7°C and 12°C was evaluated in culture media (BHI and LB) and in three minimal processed vegetables (mixed lettuce, grated carrots and chopped bell peppers) packed in optimized EMA packages. In BHI and LB growth was observed at 12°C for Shigella sp. and both species survived at 7°C although it was noted that S. flexneri was more sensitive to temperature reduction. Growth and survival in EMA-packaged vegetables stored at 7°C and 12°C was variable depending upon the type of vegetable mix used. In the mixed lettuce the total aerobic plate count dominated spoilage and Shigella sp. maintained high numbers (≥105 cfu g−1) throughout the shelf life (7 days). In grated carrots and in chopped bell peppers spoilage was dominated by lactic acid bacteria leading to a pH drop and a gradual die-off of the inoculum after 7 days of storage but low numbers of Shigella sp. may still be present (<102–104 cfu g−1) and in view of the low infective dose of the pathogen they may pose a hazard.