Ready-to-Eat Sandwich Microbiota: Diversity, Antibiotic Resistance, and Strategies to Enhance Food Safety

Ready-to-eat (RTE) sandwiches are consumed globally due to their convenience, availability, and affordability. Sandwich processing practices and their ingredients expose the sandwiches to various sources of contamination, which can enhance their microbial diversity and introduce certain pathogenic and spoilage bacteria, thereby affecting their safety and quality. Sandwiches may not receive safe cooking temperatures sufficient to destroy food poisoning bacteria, as they are often cooked and served quickly to meet high consumer demand. Improper storage temperatures can enhance microbial growth, and frequent improper handling makes this food a good vehicle for various pathogens such as Escherichia coli, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and norovirus. Many pathogenic sandwich-associated bacteria, such as L. monocytogenes, showed resistance to clinically important antibiotics. Sandwich microbiota have been investigated; however, their diversity, antimicrobial resistance, and importance to sandwich safety and quality have been rarely reviewed. Therefore, this review elucidates the diversity of sandwich microbiota as an impact of ingredients, handling practices, and storage, with emphasis on the importance of this diversity on sandwich safety and quality. It also discusses strategies, control measures, and recommendations to reduce the risk of contamination of sandwiches with pathogenic bacteria or their antibiotic resistance genes, thereby safeguarding public health.