Effect of residual antibiotics in soil and water on plant growth -

Abstract

Antibiotics such as oxytetracycline, enrofloxacin, tylosin and gentamicin are extensively used in Lebanon as a mean to prevent and treat illnesses in animals, promote growth and increase feed efficiency. They are mainly excreted via animal defecates used as fertilization mean on agricultural lands and found in the environment as their parent compound or metabolite. Researchers have identified that most of these antibiotics are absorbed and accumulated by plants via roots and leaves; however, studies are still lacking on antibiotics effect on plant growth and persistence in soil and water. The aim of this study is to evaluate the uptake and accumulation sites of antibiotics by plants grown in soil and nutrient solution and their effect on plant growth, as well as study the antibiotic persistence in soil. Antibiotic analysis was done using the Enzyme Linked Immunosorbent Assay (ELISA). A pot experiment was conducted in the greenhouse of the American University of Beirut where lettuce and cucumbers were grown in two growing media (soil without and soil with 5percent manure), administered with gentamicin and enrofloxacin at 4 different antibiotic levels (0, 5, 10 and 20 mg-kg). In nutrient solution, lettuce and radish were grown in 3 different levels of enrofloxacin, oxytetracycline and tylosin at 0, 5 and 10 mg-kg. Lastly, the persistence of enrofloxacin, oxytetracycline and tylosin was investigated in a pot experiment at 5 mg-kg and extracted with water. In the pot experiment, results demonstrated that gentamicin and enrofloxacin mainly accumulated in cucumber leaves and manured soil increased the uptake of antibiotics. In nutrient solution, enrofloxacin, oxytetracycline and tylosin were absorbed by lettuce and radish plants; in radish bulbs (edible part) it accumulated at an average of 67.7 ng-g, 30.98 ng-g and 407.45 ng-g respectively. In lettuce, enrofloxacin was translocated all over the crop, tylosin accumulated the most in leaves (343.83 ng-g) and oxytetracycline the most in lettuce roots (20.43 ng-g). Enrofloxaci