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Tetracyclines (TET) and Oxytetracycline (OTC) have been extensively used in
aquaculture for chemotherapy against various fish diseases. The tetracycline (TET
and OTC) contamination levels in the 16 aquaculture farms in Sri Lanka were
analyzed by using High Performance Liquid Chromatography (HPLC). Antibioticresistant bacteria in samples were isolated by standard pour plate method and
identification was done by the 16s rRNA sequencing. The MIC o f resistance
bacteria was determined by an agar dilution method following CLSI guidelines. The
concentration o f OTC in aquaculture farms effluent water was ranged between
0.008± 0.012 - 0.234± 0.014ppm whereas TET concentration ranged from 0.001±
0.011- 0.112± 0.017 ppm. Bacillus and Staphylococcus were the most dominant
bacterial genera recorded as resistant to both OTC and TET bacteria. Acinetobacter
sp., Achromobacter sp., Staphylococcus sp., Micrococcus sp. were identified from
the samples as OTC and TET resistant bacteria. The MIC values o f TET resistance
bacteria ranged from 360 ppm to 720ppm and OTC range was from 360 to 760
ppm. The results of the study indicate that contamination with antibiotics (TET,
OTC) potentially lead to development of antibiotic resistance in environmental
bacteria and the presence o f antibiotic resistance bacteria may limit the
effectiveness o f antibiotics which are used to treat fish illness as well. This is an
alarming aquaculture industry is in a risk on wide range of pathogenic infection
diseases.
