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Purpose: Veterinary antibiotics are physiologically highly active substances which are being used on a large scale as therapeutic drugs and as feed additives in modern agricultural practice. Major purposes of use of antibiotics are prevention and treatments of bacterial infections and for the improvements of growth rates of farm animals. Therefore, the present study was focused on quantification of some selected groups of antibiotics; tetracycline [Tetracycline (TET), Oxytetracycline (OTC)] and penicillin [Amoxicillin (AMX), Ampicillin (AMP)] in wastewater discharge drains in large-scale livestock and poultry farms and to isolate antibiotic resistant bacteria.
Methods: Twenty wastewater discharge drains in livestock and poultry farms were selected to collect samples for the study. Solid-Phase Extraction (SPE) was employed and antibiotic quantification was done by High Performance Liquid Chromatography (HPLC). Isolation of resistance (r) bacteria was done by standard pour plate method where Minimum Inhibitory Concentration (MIC) of bacteria was determined using the range of 60 to 720ppm concentrations of the antibiotics by agar dilution method.
Results: Oxytetracycline (55%), and tetracycline (38%) were recorded as most frequent antibiotics in samples and having concentrations of 0.005 ppm and 0.004 ppm respectively. The highest concentration of AMX was recorded as 0.003±0.004 ppm. However, AMP was not detected during the study period. Oxytetracycline and tetracycline resistance bacteria were identified as Enterococcus sp., E. faecium, E.coli and Clostridium sp. while, A. baumanii, E. clocae, A. lwoffii and H.pylori were identified as AMPr and AMXr bacteria by 16S rRNA sequencing. The MIC values of tetracycline (TET, OTC) resistant bacteria ranged from 360 ppm to 720 ppm whereas for penicillin (AMX, AMP) from 360 to 760 ppm.
Conclusion: The contamination of antibiotics leads to develop antibiotic resistance in environmental bacteria. Thus, the results of the study indicate that presence of antibiotic resistant bacteria may limit the effectiveness of antibiotics in treating animal illness, thereby causing a potential risk to the productivity of livestock and poultry farms.
