| Salmon is a fresh,nutritious and delicious raw aquatic product,accounting for 20%of the world’s total fish trade and being the most valuable commodity in the global aquatic product trade chain.Traditionally,salmon usually refers to Atlantic salmon(Salmo salar),but according to research reports,some of the salmon circulating in the Chinese market are rainbow trout(Oncorhynchus mykiss).Therefore,the China Aquatic Products Processing and Marketing Association(CAPPMA)proposed and organized the drafting of a group standard for "raw salmon" in 2018,unifying the definition of salmon species such as Atlantic salmon and rainbow trout as "salmon",which has attracted widespread attention in society.Therefore,there is an urgent need to develop a scientific and reasonable evaluation technology to carry out targeted risk assessment of the raw food hazards of salmon aquatic products.Due to the overuse of antibiotics,antibiotic-resistant bacteria and antibiotic resistance genes(ARGs)are widely present in food.This article reviews the relevant research on microbial resistance in food and related environments from 2011 to 2021,and finds that antibiotic-resistant bacteria and ARGs are widely present and can spread through the food chain,seriously endangering food safety and human health.Salmon,as a commonly used raw aquatic product,lacking heat processing can directly ingest antibiotic-resistant bacteria and ARGs.However,there is currently no scientific risk assessment system established for the raw food risk of Atlantic salmon and rainbow trout,and research on the risk assessment of microbiology and microbial resistance is particularly lacking,with most studies focused on the analysis of parasitic hazards.Based on this,this study proposes for the first time the concept of "Food Resistomes" and focuses on the highly concerned Atlantic salmon and rainbow trout as research objects.Through metagenomic sequencing,the microbial community characteristics of Atlantic salmon and rainbow trout were analyzed,and the existence and differential features of resistance genes in Atlantic salmon and rainbow trout were further explored from the perspective of resistomics.For the first time,a food resistance grading evaluation framework was constructed to scientifically evaluate the resistance risk level of Atlantic salmon and rainbow trout.The specific research content and results are as follows:1.Microbial community structure of Salmo salar and Oncorhynchus mykissThis study focuses on Atlantic salmon(Salmo salar)and rainbow trout(Oncorhynchus mykiss)as research objects.Using metagenomic sequencing technology and based on the NCBI Nucleotide database and NCBI Ref Seq database,Kraken 2 was used to compare,annotate,and classify all effective sequences in the samples.Abundance clustering analysis,LEf Se biomarker analysis,and multiple comparison Dunn Test analysis were conducted based on species abundance tables and functional abundance tables.The results showed that the main microorganisms in Atlantic salmon and rainbow trout were bacteria and fungi,accounting for 99.22% of the total microbial community.At the bacterial level,the core bacterial groups of Atlantic salmon were Vibrio,Shewanella,and Phocaeicola,while the core bacterial groups of rainbow trout were Vibrio,Lactoccoccus,and Shewanella.At the fungal level,the core fungi of Atlantic salmon and rainbow trout were both Aspergillus.In the rainbow trout samples,10 species with statistical differences were found at the class level,while in the Atlantic salmon samples,5 species with statistical differences were found at the class level.14 specific biomarkers were found at the class level between Atlantic salmon and rainbow trout samples.Planctomycetes was the most significant differential biomarker between Atlantic salmon and rainbow trout samples.This study systematically analyzes the microbial community in Atlantic salmon and rainbow trout,which helps to fully understand the distribution characteristics,relative abundance,and intergroup differences of the microbial community in aquatic products,laying the foundation for the study of antibiotic-resistant risks of foodborne pathogens in aquatic products.2.Antimicrobial Resistomes analysis in Salmo salar and Oncorhynchus mykissThis study further analyzed the distribution characteristics of ARGs and MGEs in Salmo salar and Oncorhynchus mykiss.After quality control and host removal,the sequences of each sample were compared with the CARD database using DIAMOND software.Based on the comparison results,the number of fragments of each sample that matched each ARG reference sequence was counted.From the ARG abundance,abundance bar chart display,abundance clustering heatmap display,abundance distribution circle chart display,inter-group difference analysis,and correlation analysis were performed.The analysis found that the high abundance resistomes in Salmo salar were nov A,msb A,van HM,APH(3’)-Ia,tet B(46),and CRP.The high abundance resistomes in Oncorhynchus mykiss were nov A,msb A,van HM,tet A(46),Mex K,efr B,tet B(46),and efr A.LEf Se differential analysis showed that Pmr F,Mex F,Mux C,and tet A(46)were specific biomarkers of ARGs between Salmo salar and Oncorhynchus mykiss.The resistomes network analysis of Salmo salar and Oncorhynchus mykiss with bacteria indicated that Escherichia was the major resistant host in salmon samples.In addition,Vibrio and Acinetobacter were also major source microbial communities of the resistomes.This study aimed to raise national,scientific,and consumer awareness of the Antimicrobial Resistomes as a new food safety hazard factor and provide a basis for developing a foodborne pathogen resistance risk grading system for subsequent analysis.3.Establishment of a classification assessment framework and grade assessment of food-borne pathogen resistance risk in Salmo salar and Oncorhynchus mykissAntimicrobial Resistance Risk Assessment(AMR-RA)is an emerging food safety risk assessment tool,which is based on traditional Microbial Risk Assessment(MRA).Its purpose is to assess the risk of resistant microorganisms and resistant determinants spreading through food on human health,and to provide appropriate risk management measures to reduce such risks.This study is based on resistome analysis of foodborne pathogens,following key steps such as hazard identification,hazard characterization,exposure assessment,and risk characterization.Combining risk assessment practice experience and referencing related literature,ARG-related environment,ARG mobility,and the pathogenicity of ARG host bacteria were used as evaluation criteria.The relevant risk level ratings were listed in detail from eight dimensions(NIDSMOFE),and a grading framework for the assessment of foodborne pathogen resistance risk was established,providing semi-quantitative and accurate assessment of the resistance risk of foodborne pathogens.Taking Salmo salar and Oncorhynchus mykiss as examples of risk grading assessment,both accumulated scores were 5,the hazard scenario was IME,and the resistance risk of foodborne pathogens was rated as high risk.This reminds consumers to pay attention to the issue of food resistance when consuming salmon,properly handle and cook food ingredients,and reduce the intake and spread of resistant organisms in the body.The establishment of this framework aims to guide professionals to carry out objective and accurate assessments of foodborne pathogen resistance when evaluating risk,providing reliable evaluation strategies for the effective control of resistant foodborne pathogens in China,and effectively ensuring food safety and human health. |
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