Effects of Different Fertilization Treatments on the Antibiotic Concentrations and Resistance in the Paddy Soils.

Tetracycline (TCs) and sulfonamides (SAs) are widely used in livestock production to serve as disease prevention and growth promotion.Because these compounds are not completely metabolized in animals, substantial amounts of TCs and SAs are excreted in feces and urine. These antibiotics are released either directly to the environments without any treatments or indirectly to the edible soils while applying TCs and SAs-containing manure or sludge as fertilizers. Once the antibiotics enter the environments, they may alter the populations and normal functions of pristine microbes. Even worse, the antibiotic resistance genes may be induced and spread out that can be a potential hazard to the ecosystems or human health. In the study, TCs (tetracycline, oxytetracycline, chlortetracycline) and SAs (sulfadiazine, sulfadimethoxine, sulfaquinoxaline) concentrations and microbial resistances in the paddy soils receiving organic or chemical fertilizer were determined. The results showed that no antibiotics were detected in these paddy soils. The resistances of bacteria in the tested paddy soils are less than 4% for these antibiotics. The multiple-resistances and mono-resistances of bacteria to the six antibiotics were less than 1 and 3 %, respectively. The preliminary results suggested that the antibiotic residue and resistance were low even if the soil was applied manure-based organic fertilizers. Because of the presence of only trace amount of antibiotics in the fertilizers, it was not surprised that no antibiotics were accumulated in the paddy soils. However, the percentage of bacteria antibiotic resistance was relatively low, affecting probably by the sampling time and the redox potential which merit further study.