In aquaculture, bacterial infections in sea animals are treated using antimicrobials. As seafood is frequently consumed in its raw form, seafood contaminated with water-borne antimicrobial-resistant bacteria presents a potential transmission route to humans and can influence food safety. In this study, we aimed to determine the abundance of water-borne bacteria in retail raw seafood and to characterize their antimicrobial resistance profiles. In total, 85 retail raw seafood samples (32 fish, 26 shellfish, 25 mollusks, and two crustaceans) were purchased from supermarkets in Japan, and water-borne bacteria were isolated. The isolated bacterial species predominantly included Vibrio spp. (54.1%) and Aeromonas spp. (34.1%). Vibrio or Aeromonas spp. were isolated from more than 70% of the seafood samples. Tetracycline-, sulfamethoxazole-, and/or trimethoprim/sulfamethoxazole-resistant Vibrio or Aeromonas spp. isolates were detected in seven (21.9%) fish samples (two wild-caught and five farm-raised) harboring tet, sul, and/or dfr genes. Sulfamethoxazole- and trimethoprim/sulfamethoxazole-resistant isolates were only detected in farm-raised fish. Tetracycline and sulfamethoxazole are commonly used in aquaculture. These results suggest that water-borne bacteria like Vibrio and Aeromonas spp. should be the primary focus of antimicrobial-resistant bacteria monitoring to effectively elucidate their spread of bacteria via seafood.

Food Safety Commission of Japan (FSCJ) conducted a risk assessment of isotianil (CAS No. 224049-04-1), an isothiazole agent for induced resistance to blast disease. This evaluation was requested from Ministry of Agriculture, Forestry and Fisheries (MAFF) on the reevaluation article of Agricultural Chemicals Regulation Act. Additional information including the fate in livestock (goats and chickens) and genotoxicity, and also the list of published scientific literature were newly submitted from the MAFF. The following data were used in the assessment; fate in plants (including paddy rice and potatoes), residues in crops, fate in livestock (goats and chickens), residues in livestock products, fate in animals (rats), subacute toxicity (rats, mice and dogs), chronic toxicity (rats and dogs), carcinogenicity (rats and mice), two-generation reproductive toxicity (rats), developmental toxicity (rats and rabbits), and genotoxicity. Major adverse effects of isotianil were observed in the stomach (mucosal epithelium hyperplasia of the forestomach limiting ridge in rats), the liver (including organ weight gain), and the kidney (including chronic nephropathy). No adverse effects were observed on carcinogenicity, fertility, teratogenicity, and genotoxicity. The lowest no-observed-adverse-effect level (NOAEL) obtained from the studies described above was 2.83 mg/kg bw per day in a one-year chronic toxicity study in rats. FSCJ specified an acceptable daily intake (ADI) of 0.028 mg/kg bw per day based on the NOAEL after applying a safety factor of 100. An acute reference dose (ARfD) was judged unnecessary to be specified, based on the results of a single oral administration of isotianil and other related tests.

Food Safety Commission of Japan (FSCJ) updated the risk assessment of marbofloxacin (MBFX) (CAS No. 115550-35-1), an antibacterial fluoroquinolone. For the application of cattle injection (Forcyl) containing MBFX as an active ingredient, the pharmacokinetics and residue studies on cattle were newly submitted and reviewed for the current version (2^nd edition). Adverse effects were detected in the general findings, hematology/blood biochemistry, articular cartilage, and also other observations in subacute toxicity studies in rats and dogs. The lowest no-observed-adverse-effect level (NOAEL) was judged to be 4 mg/kg bw per day. The lowest NOAEL obtained from all the studies was 4 mg/kg bw per day. The ADI was thus specified as 0.004 mg/kg bw per day in considering the lack of chronic and carcinogenic tests. Meanwhile, a microbiological ADI was calculated as 0.0072 mg/kg bw per day by the VICH. The lower value (0.004 mg/kg bw per day) was taken for the ADI of MBFX. FSCJ concluded that an ADI of MBFX should be 0.004 mg/kg bw per day.