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Table 3 Common criteria generally considered as essential for the safety of NF/probiotic products (required for both novel food and health claim regulations)

From: A proposed framework for an appropriate evaluation scheme for microorganisms as novel foods with a health claim in Europe

  What How Why Comments and Propositions for improvement
Survival in GI tract conditions Resistance to intestinal stress In vitro Growth curves/Detection in feces after consumption Resistance to GI tract conditions may favor the beneficial effects Not valuable for all beneficial effects
Development of new protectors/encapsulators
Bile salt deconjugation High-performance liquid chromatography Large amounts of deconjugated bile salts may have undesirable effects on the human host Evaluation of property in vitro has poor relevance; assessment of bile salt deconjugation in vivo
Mass spectrometry   
Preservation of the homeostasis of gut barrier components Microbiota Perturbation of commensal consortium In vitro production of bacteriocins or antibiotics (AB) Bacteriocins and AB may perturb microbiota. Development of growth inhibitory references with major commensal bacteria
AB may interact with a patient’s treatment
Antibiotics (AB) resistance In silico *prediction and in vitro antibiogram AB resistance may be transmitted between bacteria Development of in vivo assessment (animal model) indicating the microbiota homeostasis (composition and activities) after probiotic consumption
Minimal inhibitory concentration test (MIC)
Minimal bactericidal concentration test (CMB) If plasmids are detected: the presence/absence of genes encoding the most common resistance determinants should be characterized
Presence of plasmids In silico *prediction or DNA extraction followed by analysis by gel electrophoresis Plasmids favor the transmission of antibiotic resistance Requirement to up-date the antibiotic list
Mucus Mucus degradation Mucin degradation test (agarose gel or liquid culture) Excessive mucus degradation may lead to intestinal barrier weakening The capacity to degrade mucus seems to be a poor criterion to estimate the protective or deleterious effect of bacteria on the intestinal barrier
Adhesion and translocation risk Intestinal/Mucosal adhesion Test bacterial strain adhesion to epithelial cell line Mucosal adhesion may interfere with pathogenic microorganisms, stimulate beneficial cellular processes, or favor bacterial translocation The intestinal/mucosal adhesion capacity can be either a beneficial or a deleterious criterion
Intestinal mucosa degradation Gelatinase activity assay Mucosal degradation may weaken the intestinal barrier It could be useful to evaluate in vivo translocation capacities
Hemolytic activity Blood agar culture Hemolysis damages red blood cells  
Metabolic activities D-Lactate production Colorimetric assay D-Lactate accumulation in blood leads to acidosis The production of D-lactate should be compared with the amount produced by usual strains (like in yoghurt)
Toxin production Protocol recommended by the European scientific committee of animal nutrition. Toxic molecules Establishment of threshold values relevant in humans
Biogenic amine production Colorimetric assay Immune responses such as allergic responses
Remote effects Platelet aggregation Aggregation test Risk of thrombosis Development of ex vivo protocols (explants, organoids)
Genotoxicity Toxicity testing on animals models (chronic and subchronic tests) Risk of cancer
Allergenicity   Allergic response
  1. (*: if the complete genome is available).