Salmonella Typhimurium internalization is variable in leafy vegetables and fresh herbs

Area of Science:

• Food Microbiology
• Plant Pathology
• Food Safety

Background:

• Outbreaks linked to leafy greens persist despite decontamination.
• Understanding contamination routes is crucial for produce safety.
• Internalization into plant tissues protects pathogens from sanitizers.

Purpose of the Study:

• To investigate Salmonella Typhimurium internalization in various leafy vegetables and herbs.
• To quantify the incidence of internalization across different plant species.
• To identify plant susceptibility and factors influencing bacterial internalization.

Main Methods:

• Examined Salmonella Typhimurium incidence on leaf surfaces and beneath the epidermis.
• Utilized GFP-tagged bacteria for visualization and quantification.
• Surveyed seven types of vegetables and fresh herbs over two years.

Main Results:

• Salmonella internalization varied significantly among plant types.
• Iceberg lettuce (81%) and arugula (88%) showed the highest incidence.
• Romaine (16%) and red-lettuce (20%) had significantly lower internalization rates.

Conclusions:

• Salmonella internalization occurs in multiple leafy vegetables and herbs, not just iceberg lettuce.
• Internalization levels differ significantly between plant species and even within crops.
• Identifying susceptible plants and influencing factors is vital for mitigating contamination risks.