Antibiotics are frequently used in aquaculture for the treatment of bacterial diseases. In this study, bacteria were isolated from the spleen, liver and kidney of grouper from PCG and cobia from EMD and THOD in southern Taiwan. All isolates were cultured on TCBS agar, blood agar, and MacConkey agar. The results showed that the isolates from PCG were 83% (20/24) Vibrio and 13% (3/24) £]-hemolysis¡F76% (22/29) Vibrio and 24% (7/29) £]-hemolysis from EMD¡F100% (6/6) Vibrio and none of £]-hemolysis from THOD. The bacteria were tested for antibiotics resistance by the disc agar diffusion method. 70% bacteria resisted to penicillin, cephazolin, and streptomycin while double resistance to furazolidone/streptomycin increased to with time from 0% to 83% in PCG. In EMD, 70% bacteria resisted to streptomycin and furazolidone, and double resistance to furazolidone/streptomycin increased with time from 0% to 60%. In THOD, 50% bacteria resisted to £]-lactam drugs, 100% bacteria resisted to cephazolin, and 67% bacteria doubly resisted to ampicillin/amoxycillin, cephalexin/cephazolin, cephalexin/streptomycin and cephazolin/streptomycin. Further, the detection of tetB, tetD, tetM, tetS and tetX resistance, tetracycline resistance genes, in the chromosomal DNAs from 17 multiple resistance isolates were performed by PCR. The PCR products were confirmed by digestion of restriction enzymes. The data indicated that J39-1, J39-2, K26-4 and K27-2, strains from THOD, together with N18-5 and M35-2, from PCG, were identified as carrying tetB. From EMD, The tetB and tetM genes were detected in P19-1, P19-3, P32-1 and Q8-3, whereas strain O2-3 carried tetS gene.

This master thesis is focused on the role of horizontal gene transfer in disseminating tetracycline resistance among bacteria in farm soils. In the experimental part, plasmids carrying antibiotic resistance, were exogenously isolated in biparental matings with cattle manure and Escherichia coli K-12 CV601 gfp recipients.