Distribution of antimicrobial-resistant bacteria isolated from retail seafood in Japan

<p>[Introduction] Since about 1980, the emergence of new antimicrobial-resistant bacteria, caused by inappropriate use of antibiotics and other factors, has become a problem on a global scale. Antimicrobial-resistant bacteria have also been reported to contaminate food products, thus a one-health approach is required. There are many opportunities for vegetables and fish to eat raw, so antimicrobial resistance spreads in the human body and new antimicrobial-resistant bacteria are born. Clarifying this risk is extremely important for food hygiene. In this study, we investigated the distribution of antimicrobial-resistant Gram-negative bacteria and Vibrio spp. in retail seafood. </p><p>[Materials and Methods] 25 g each was collected from 50 retail available seafood samples, after treatment with APW (alkaline peptone water), standard plate counts, direct smear culture and selective isolation were performed after enrichment culture. MacConkey agar and X-VP agar (selective isolation agar for Vibrio spp.) were used for direct smears, and supplemented medium with ampicillin 100 µg/ml was also used. LB medium (with NaCl added as needed) for enrichment culture, and supplemented medium with ampicillin 100 µg/ml was also used. For selective isolation, MacConkey agar and X-VP agar were used, and antibiotics were colistin (4 µg/ml), ampicillin (100 µg/ml), cefotaxime (4 µg/ml) and meropenem (4 µg/ml).</p><p>[Results and Discussion] 10²-10⁶ CFU/g of viable bacteria were present in retail seafood. Direct smear culture results showed that ampicillin-resistant Gram-negative bacteria and Vibrio spp. appeared from 44 and 7 samples, respectively. Selective isolation results showed that 52 strains of Vibrio spp. and 236 strains of Gram-negative bacteria appeared from 22 and 48 samples, respectively. In the future, we will carry out biochemical tests and resistance gene analysis of each strain to elucidate antimicrobial-resistant bacteria derived from retail seafood.</p>