ISSUE FOCUS FEED & ADDITIVE MAGAZINE February 2025 49 identification should combine morphological and DNA sequencing information. ANTIMICROBIAL RESISTANCE Antibacterial Resistance EFSA has introduced new workflows to distinguish between intrinsic and extrinsic resistance. Intrinsic resistance, which is naturally present in a microorganism’s species, is not considered a risk. However, extrinsic resistance, which arises from incorporation of DNA from external sources, requires additional evidence to evaluate risk to human and animal health. This is established through assessment of phenotypic susceptibility to confirm bacteria are still killed by the antibiotic at levels below the cutoff value. Antimycotic Resistance This category is a new addition that applies to yeasts and filamentous fungi. As horizontal transfer of resistance genes is uncommon in fungi, genomic analysis isn’t relevant. Instead, for active agents, phenotypic testing should be used. TOXIGENICITY AND PATHOGENICITY Yeasts and Filamentous Fungi To assess the potential pathogenicity of yeast and filamentous fungi and their ability to produce harmful metabolites, applicants should carry out a literature search on the species, and other closely related species. In addition, applicants should use WGS analysis to identify known metabolic pathways involved in toxigenicity and compare the data against at least one up-to-date curated database. The WGS database search must be no older than two years from the date of application submission. If either of the searches indicate potential harmful metabolites, the following should be conducted: • For active agents: phenotypic testing under relevant conditions • For production strains: quantitative analysis of hazardous metabolites Microalgae and Protists Microalgae and protists are another new addition to this section of EFSA’s guidance, which states that a literature search should be conducted to identify the capacity of the species to produce known harmful metabolites. If the search suggests potential risks, applicants should perform quantitative analyses of the relevant metabolites. Viruses and Bacteriophages Viruses and bacteriophages are a new addition to the EFSA guidance. For viruses, the infectivity and absence of adverse effects should be demonstrated using representative species. Plant virus assessments must confirm target specificity and lack of adverse effects on non-target plants. For bacteriophages, testing should be conducted on a representative set of strains for the target and closely related species. WGS-based analysis is required to interrogate the presence of genes coding for toxins, virulence factors, lysogeny, and genetic elements involved in transduction. As is the case with yeasts and filamentous fungi, the WGS analysis of
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