Environmental and Public Health Impact of Sub- Therapeutic Antibiotic Use in the Poultry Industry- A Pilot Study

Introduction: Poultry industry in India is a fast growing and dynamic subsector of agriculture.
Extensive use of antibiotics as growth promoters in poultry farms will select for antimicrobial
resistance genes among bacterial isolates of broiler origin and may spread to environment and
individuals in close contact thereby posing a threat to human health.
Methods: To study the effects of sub-therapeutic usage of antibiotics, soil samples were collected
from different poultry farms in various districts of Tamil Nadu to detect the percentage of antibiotic
resistance and the resistance determinants in soil. Environmental and carrier staphylococcal isolates
were studied for their resistant characteristics.
Results: Bacteria resistant to tetracycline and erythromycin were detected in soil samples of eight
different farms. Mean resistance levels were highly variable ranging between 59-93% for tetracycline
and 23-78% for erythromycin respectively. The most frequent gene was erm(A) (56.2%) followed by
tet(K) (43.7%) and erm(C) (32.2%). Higher tetracycline and macrolide resistance determinants were
observed inside the farms compared to outside. erm (A) (100%) was the resistance gene most
commonly found in environmental staphylococcal isolates from farm H followed by msr (A) (75%), tet
K (62.5%) and erm (C) (25%).
Conclusion: To conclude, presence of the resistance determinants could make that poultry farm a
potential reservoir of tetracycline and erythromycin resistance and thereby cause environmental
contamination.