Antimicrobial food packaging involves packaging the foods with antimicrobials to protect them from harmful microorganisms. In general, antimicrobials can be integrated with packaging materials via direct incorporation of antimicrobial agents into polymers or application of antimicrobial coating onto polymer surfaces. The former option is generally achieved through thermal film‐making technology such as compression molding or film extrusion, which is primarily suitable for heat‐stable antimicrobials. As a nonthermal technology, surface coating is more promising compared to molding or extrusion for manufacturing food packaging containing heat‐sensitive antimicrobials. In addition, it also has advantages over direct incorporation to preserve the packaging materials’ bulk properties (e.g., mechanical and physical properties) and minimize the amount of antimicrobials to reach sufficient efficacy. Herein, antimicrobial food packaging films achieved through surface coating is explored and discussed. The two components (i.e., film substrate and antimicrobials) consisting of the antimicrobial‐coated films are reviewed as plastic/biopolymer films; and synthetic/naturally occurring antimicrobials. Furthermore, special emphasis is given to different coating technologies to deposit antimicrobials onto film substrate. Laboratory coating techniques (e.g., knife coating, bar coating, and spray coating) commonly applied in academic research are introduced briefly, and scalable coating methods (i.e., electrospinning/spraying, gravure roll coating, flexography coating) that have the potential to bring laboratory‐developed antimicrobial‐coated films to an industrial level are explained in detail. The migration profile, advantages/drawbacks of antimicrobial‐coated films for food applications, and quantitative analyses of the reviewed antimicrobial‐coated films from different aspects are also covered in this review. A conclusion is made with a discussion of the challenges that remain in bringing the production of antimicrobial‐coated films to an industrial level.

Background: Food antimicrobial compounds are naturally present or purposefully added in food systems to retard microbial growth or cause microbial death to improve food safety and quality. Directly added antimicrobial compounds to food products may face several major challenges: (1) poor solubility in aqueous systems; (2) limited stability against chemical or physical degradation; (3) uncontrolled release, and (4) possible adverse effects on food sensory qualities. One approach to address these problems is the use of delivery systems. Scope and approach: In this review, antimicrobial compounds are categorized into synthetic and naturally occurring. They are briefly reviewed with their properties and applications. Considering their structural and physicochemical aspects, three types of delivery system are discussed: (1) emulsion-based, (2) nanosized carrier-based, and (3) film or coating-based. Applications of antimicrobial delivery systems in food are discussed. Key findings and conclusions: Compared with the direct addition of antimicrobial compounds, the use of delivery systems may protect active compounds from degradation, improve their solubility in aqueous phase, decrease their impact on food sensory qualities, and control their release. Although numerous delivery systems have shown efficacies under in vitro conditions, their antimicrobial performances need to be verified in real food systems. The availability of low-cost, food-grade carrier materials and the knowledge of interactions between delivery systems and other food components are essential to achieving industrial success for the design and use of delivery systems of antimicrobial compounds.

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Within-host evolution of S. Typhimurium may lead to pathovars adapted to specific hosts.

Wild birds are common reservoirs of Salmonella enterica. Wild birds carrying resistant S. enterica may pose a risk to public health as they can spread the resistant bacteria across large spatial scales within a short time. Here, we whole-genome sequenced 375 S. enterica strains from wild birds collected in 41 U.-S. states during 1978-2019 to examine bacterial resistance to antibiotics and heavy metals. We found that Typhimurium was the dominant S. enterica serovar, accounting for 68.3% (256/375) of the bird isolates. Furthermore, the proportions of the isolates identified as multi-antimicrobial resistant (multi-AMR: resistant to at least three antimicrobial classes) or multi-heavy metal resistant (multi-HMR: resistant to at least three heavy metals) were both 1.87% (7/375). Interestingly, all the multi-resistant S. enterica (n = 12) were isolated from water birds or raptors; none of them was isolated from songbirds. Plasmid profiling demonstrated that 75% (9/12) of the multiresistant strains carried resistance plasmids. Our study indicates that wild birds do not serve as important reservoirs of multi-resistant S. enterica strains. Nonetheless, continuous surveillance for bacterial resistance in wild birds is necessary because the multi-resistant isolates identified in this study also showed close genetic relatedness with those from humans and domestic animals.