Antibiotic Resistance Profile of Bacteria from Abattoir Wastewater and Environmental Media in Ado-Ekiti, Nigeria

The slaughter of livestock continues to rise due to the growing demand for meat and its products. Antimicrobials have played a central role in the fight to reduce infectious diseases for most of the past century. Soil and wastewater samples were collected from Ado Ekiti abattoir in Ekiti State. The antibiotic susceptibility of the bacterial isolates was determined using the Kirby-Bauer disk diffusion method on Mueller-Hinton Agar. The antibiotics tested included β-lactams, specifically ampicillin (10 µg) and cefotaxime (30 µg); aminoglycosides, represented by gentamicin (10 µg); fluoroquinolones, with ciprofloxacin (5 µg); tetracyclines, including tetracycline (30 µg); and sulfonamides, tested as trimethoprim-sulfamethoxazole (25 µg). The findings revealed varying levels of susceptibility, with Bacillus spp., Staphylococcus aureus, Streptococcus spp., and Listeria spp. showing the highest susceptibility across all tested antibiotics. Similarly, Escherichia coli, Salmonella spp., Shigella spp., Vibrio spp., Klebsiella pneumoniae, Enterobacter spp., and Proteus spp. were generally sensitive to most antibiotics, with inhibition zones of 25 mm or more for ciprofloxacin, cefotaxime, gentamicin, and chloramphenicol. However, Pseudomonas aeruginosa exhibited notable resistance, especially to ampicillin (10.5 mm), cefotaxime (12.3 mm), tetracycline (9.8 mm), erythromycin (8.9 mm), and trimethoprim-sulfamethoxazole (10.7 mm), highlighting its multidrug-resistance. Notably, resistance to erythromycin was observed in E. coli, Salmonella spp., Vibrio spp., Proteus spp., and Pseudomonas aeruginosa, suggesting limited efficacy of this antibiotic against these pathogens. These findings emphasise the importance of continuous surveillance and prudent antibiotic use to reduce the risks of antimicrobial resistance in abattoir environments.