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The treatment of bacterial infections is increasingly complicated due to development of resistance to antimicrobial agents. The present study records, occurrence of tetracycline (TET) and oxytetracycline (OTC) resistance bacteria in the effluent waste water of Zoological garden, Sri Lanka. Moreover, corresponding antibiotics resistance genes of the isolated bacteria were screened.Four bacterial strains which were resistant to both TET and OTC were isolated by enrichment culture method following standard pour plate. Different concentrations of OTC and TET (0 900 ppm) were used to detect Minimum Inhibition Concentration (MIC) of isolated bacteria using standard pour plate and 96 well plate methods. Chromosomal DNA of the bacterial isolates was extracted and the presence of resistance genes (tetA, tet M, tet S) were identified by Polymerase Chain Reaction (PCR). Isolated bacterial strains were identified as Acinetobacter junii, Acinetobacter calcoaceticus, Staphylococcus aureus and Staphylococcus arlettae by 16S rRNA sequencing. The MICs of the A. junii (OTC=480ppm, TET= 540ppm), A. calcoaceticus (OTC= 540ppm, TET= 660ppm), S. aureus (OTC =780ppm, TET= 840ppm), and S. arlettae (OTC= 600ppm, TET= 540ppm) were detected respectively. It was identified that S. aureus bear tetA, tet S and tet M genes where tet A gene was detected fromA. junii, A. calcoaceticus. The resistant genes of tet M and tet S were detected in S. arlettae. Acinetobacter strains were commonly known for transmitting antibiotic resistance genes which are associated with urinary tract infections, pneumonia and wound infections. Thus, the finding of the present study shows the contamination status of antibiotics in the environment and it would lead to develop antibiotic resistance in most of the pathogenic bacteria. KeywordsA. junii, A. calcoaceticus, S. arlettae, S. aureus, Oxytetracycline, Tetracycline, antibiotic resistance, Minimum Inhibition Concentration (MIC)
