Objective To describe the distribution of antibiotic resistance genes (ARGs) and heavy metals in soil of selected agricultural areas.
Methods Sixteen mixed soil samples were collected from seven observation farmlands near an industrial zone (14 samples) and two control farmlands (2 samples). Total DNA in soil samples was extracted by soil DNA kit after pretreated with humic acid removal agent. Fifteen kinds of ARGs (sulⅠ, sulⅡ, tetA, tetC, tetE, tetM, tetQ, tetW, CTX-M-1, bla-TEM, SHV, strA, qnrA, qnrB, and qnrS) were detected by polymerase chain reaction (PCR). Positive productions of PCR were out-sourced to be sequenced and using BLAST to compare sequences to Genbank. Mercury in soil samples was determined by atomic absorption spectrophotometry, arsenic by atomic fluorescence spectrometry, lead and zinc by inductively coupled plasma atomic emission spectrometry, as well as cadmium, chromium, nickel, and copper by inductively coupled plasma mass spectrometry.
Results Nine kinds of ARGs (sulⅠ, sulⅡ, tetC, tetA, tetM, bla-TEM, tetE, tetW, and strA) were found positive in the soil samples from the observation farmlands. Besides, the concentrations of seven heavy metals, except chromium, in the soil samples from the observation farmlands exceeded the relevant standard values by varied degrees; specifically, the maxmium concentrations of cadmium and lead were 72.7 and 6.5 times of the corresponding standard values respectively. In control area soil samples, no ARGs or heavy metals with any concentration exceeding standard were found. The exceeding-standard rate of cadmium was 100% in the ARGs positive soil samples, whereas none of the heavy metals was found exceeding standard in the ARGs negative soil samples.
Conclusion ARGs such as tetC and bla-TEM are prevalent in the agricultural soil near the industrial zone in Henan where cadmium and lead are the dominant heavy metal pollutants.
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