Application of the hydrothermally treated oxytetracycline fermentation residue in agriculture: concentrations of antibiotic and resistance genes in soil and plant

PurposeThe treated antibiotic fermentation residues free of antibiotics but containing a high level of nutrients might be used as organic fertilizers. However, their impact on the development of antibiotic resistance in the soil and plant tissue has not been explored.MethodsIn this study, the effects of thermally treated oxytetracycline fermentation residue (OFR) free of antibiotics on the dissemination of antibiotic resistance in the rhizosphere of spinach (Spinacia oleracea), changes in the rhizobacterial communities, and contamination of plant tissue were investigated in a pot experiment under greenhouse condition. Raw OFR, animal manure-based compost sourced from a commercial company, and untreated soil (control) were used as control. The experiment was conducted over a period of 2 months, and soil samples were collected at intervals of 15 days. Plant tissues were analyzed at harvest for the presence of tet genes and the concentration of antibiotics.ResultsThe quantification of tet genes including tetA, tetL, tetQ, and tetX indicated that treated OFR did not significantly promote these genes over the control. The accumulation of antibiotics and tet genes in spinach tissues was not significantly different from the control (untreated soil), suggesting the potentiality of the treated OFR as an organic source for agricultural application.ConclusionThe findings of this study indicated that hydrothermally treated OFR can be used as an organic fertilizer in agricultural applications without the promotion of antibiotic resistance in the soil and plant tissue.