Cultivable soil bacteria antibiotic resistance induced by oxytetracycline pollution

Antibiotics enter agricultural soils by the use of animal excrements as fertilizers. However,it is scarcely known how these antibiotics affect the cultivable soil bacteria antibiotic resistance. Therefore,effect of antibiotic oxytetracycline (OTC) pollution on cultivable soil bacteria antibiotic resistance was studied by addition of different dose of OTC in the soil. Percentage of soil bacteria antibiotic resistance was evaluated by comparing cultivable bacteria number in culture medium spiked with or without OTC. The results showed that soil OTC pollution could increase the cultivable soil bacteria,which was related to the additional dose and times of OTC. The cultivable soil bacteria antibiotic resistance was significantly increased when soil was treated once with OTC at the dose of 4 mg·kg-1,or repeatedly treated twice at the dose of 3 mg·kg-1,or repeatedly treated five times at the dose of 2 mg·kg-1. But,no significant increase in the cultivable soil bacteria antibiotic resistance was found when soil was treated with OTC at the dose of 1 mg·kg-1. The results suggested that long-term application of antibiotics-containing animal manure could improve the development of soil bacteria antibiotic resistance.