Occurrence and distribution of tetracycline resistance determinants and their pollution profile in the aquaculture environment in Sri Lanka

Tetracyclines (TET) have been extensively used in aquaculture for chemotherapy against various fish diseases. The occurrence of tetracycline contamination levels in the aquaculture farms in Sri Lanka were analyzed using High Performance Liquid Chromatography (HPLC). The presence of antibiotic-resistant bacteria was identified using the 16SrRNA gene sequencing and the corresponding antibiotic resistance genes (ARGs) were screened at each location using PCR method. The concentration of TET in aquaculture farms ranged between 0.001± 0.001 - 0.112± 0.017 ppm whereas Bacillus and Staphylococcus were the most dominant bacterial genera as TET resistant bacteria. Acinetobacter sp., Achromabacter sp., Staphylococcus sp., Micrococcus sp. were also identified as the resistant bacteria. In the present study, tet (M) and tet (A) were abundant resistance genes (11/16 isolates), followed by tet (S) (5/16) and tet (B) (4/16). It was found that tet (M) is one of the most widely distributed tetracycline resistance determinant in the aquatic environment in Sri Lanka.