Many strains showed high resistant rates (more than
40%) to furazolidone, penicillin G, and rifampin. A total of 285 strains from farming seawater and oysters
were resistant to more than three antibiotics. Several strains showed resistance to more than nine
antibiotics. Furthermore, the peak resistant rates of the seawater-derived strains to multiple antibiotics
overlapped in April, June, September, and November, and those of oyster-derived strains overlapped
during April, July, and September. The multi-resistant rate patterns of strains from farming seawater and
oyster intestines were similar.