AIM:To assess the safety of Bifidobacterium longum (B.longum) JDM301 based on complete genome sequences.METHODS:The complete genome sequences of JDM301 were determined using the GS 20 system.Putative virulence factors,putative antibiotic resistance genes and genes encoding enzymes responsible for harmful metabolites were identified by blast with virulence factors database,antibiotic resistance genes database and genes associated with harmful metabolites in previous reports.Minimum inhibitory concentration of 16 common antimicrobial agents was evaluated by E-test.RESULTS:JDM301 was shown to contain 36 genes associated with antibiotic resistance,5 enzymes related to harmful metabolites and 162 nonspecific virulence factors mainly associated with transcriptional regulation,adhesion,sugar and amino acid transport.B.longum JDM301 was intrinsically resistant to ciprofloxacin,amikacin,gentamicin and streptomycin and susceptible to vancomycin,amoxicillin,cephalothin,chloramphenicol,erythromycin,ampicillin,cefotaxime,rifampicin,imipenem and trimethoprim-sulphamethoxazol.JDM301 was moderately resistant to bacitracin,while an earlier study showed that bifidobacteria were susceptible to this antibiotic.A tetracycline resistance gene with the risk of transfer was found in JDM301,which needs to be experimentally validated.CONCLUSION:The safety assessment of JDM301 using information derived from complete bacterial genome will contribute to a wider and deeper insight into the safety of probiotic bacteria. AIM: To assess the safety of Bifidobacterium longum (B. longum) JDM301 based on complete genome sequences. METHODS: The complete genome sequences of JDM 301 were determined using the GS 20 system. Puterative virulence factors, putative antibiotic resistance genes and genes encoding enzymes for harmful metabolites were identified by blast with virulence factors database, antibiotic resistance genes database and genes associated with harmful metabolites in previous reports. Minimal inhibitory concentration of 16 common antimicrobial agents was evaluated by E-test. RESULTS: JDM 301 was shown to contain 36 genes associated with antibiotic resistance, 5 enzymes related to harmful metabolites and 162 nonspecific virulence factors primarily associated with transcriptional regulation, adhesion, sugar and amino acid transport. B. longum JDM301 was intrinsically resistant to ciprofloxacin, amikacin, gentamicin and streptomycin and susceptible to vancomycin, amoxicillin, cephalothin, chloramphenicol, erythromyci n, ampicillin, cefotaxime, rifampicin, imipenem and trimethoprim-sulphamethoxazol.JDM 301 was moderately resistant to bacitracin, while an earlier study showed that bifidobacteria were susceptible to this antibiotic. A tetracycline resistance gene with the risk of transfer was found in JDM 301, which needs to be experimentally validated. CONCLUSION: The safety assessment of JDM301 using information derived from complete bacterial genome will contribute to a wider and deeper insight into the safety of probiotic bacteria.