Occurrence of sul and tet(M) genes in bacterial community in Japanese marine aquaculture environment throughout the year: Profile comparison with Taiwanese and Finnish aquaculture waters.

The use of antibiotics in aquaculture causes selection pressure for antibiotic-resistant bacteria (ARB). Antibiotic resistance genes (ARGs) may persist in ARB and the environment for long time even after stopping drug administration. Here we show monthly differences in the occurrences of genes conferring resistance to sulfonamides (i.e. sul1, sul2, sul3), and tetracyclines (tet(M)) in Japanese aquaculture seawater accompanied by records of drug administration. sul2 was found to persist throughout the year, whereas the occurrences of sul1, sul3, and tet(M) changed month-to-month. sul3 and tet(M) were detected in natural bacterial assemblages in May and July, but not in colony-forming bacteria, thus suggesting that the sul3 was harbored by the non-culturable fraction of the bacterial community. Comparison of results from Taiwanese, Japanese, and Finnish aquaculture waters reveals that the profile of sul genes and tet(M) in Taiwan resembles that in Japan, but is distinct from that in Finland. To our knowledge, this work represents the first report to use the same method to compare the dynamics of sul genes and tet(M) in aquaculture seawater in different countries.