Poultry manure and vegetables as vehicles for antimicrobial resistance determinants distribution in some Farms in Delta State, Nigeria

Antimicrobial resistance has become a major threat to human health globally. One of the reasons for this increase is the abuse and misuse of antibiotics in the poultry industry as a growth promoter. This practice has resulted in the rise of the spread of antimicrobial resistance within the environment as poultry waste is used as manure in the growth of vegetables. With reduced enthusiasm on the part of the pharmaceutical industries to embark on developing new antimicrobial agents in the face of increasing resistance evolution, few options are available in the armamentarium to combat bacterial infections. The study aimed to determine if domestically grown leafy vegetables and soil amended with poultry manure constitute a possible reservoir of antibiotic resistance and assessed their ability to transfer resistance via conjugation experiment. Twenty-seven leafy vegetable samples and poultry manure-enriched soils were collected from some Delta State, Nigeria farms under aseptic conditions. Standard bacteriological methods were used to isolate and identify isolates, then examined for their susceptibility to fifteen antibiotics and potential for resistance transfer via conjugation experiment. Of the 76 bacterial isolates recovered, 52 originated from vegetables, while 24 were from poultry manure-enriched soil. Escherichia coli (14.5%) and Bacillus subtilis (7.9%) were the most prevalent isolates in vegetables and soil, respectively. The antibiotic resistance profiles of the isolates indicated very high resistance levels in Gram-negative isolates obtained from the soil to all tested antibiotics. The resistance profile of Gram-positive isolates from both vegetables and soil showed ≥ 50% resistance in tetracycline. Also, high level of resistance of between 50% to 100% was detected in Bacillus spp. and Enterococcus spp. to erythromycin, tetracycline, and chloramphenicol. Multidrug-resistant (MDR) isolates served as donor cells, while standard Escherichia coli, Pseudomonas aeruginosa, Bacillus spp. and Staphylococcus aureus served as recipient strains. The rate of antibiotic resistance transfer was generally high, particularly for tetracycline (57.1%) and chloramphenicol (61.9%). The high rate of antibiotic resistance transfer observed in this study highlights the risk of MDR spreading through poultry manure use.