| Antibiotics, which have the function of killing and inhibiting microorganisms, are widely applied in the prevention and treatment of human and animal infections diseases. However, antibiotics has selection effect on pathogenic microorganisms and will improve their drug resistance.Tetracycline as a kind of broad spectrum antibiotic is currently one of the most frequently used antibiotics in livestock breeding industry. According to some researches, livestock feces has become the main source of tetracycline resistant bacteria and tetracycline resistant genes which might lead to an increased abundance and transferability of tetracycline-resistance determinants. The pollution issue of tetracycline resistant genes is increasingly serious. In this paper, traditional method of cultivation was applied to analysis the percentage of the tetracycline resistant Lactose-fermenting Enterobacteriaceae(TR-LFE) separated from boar feces, sow feces, soil, chicken feces and composts of chicken feces. In addition, qualitative PCR was carried out to detect the diversity and abundance of tetracycline resistance genes (tet-R gene) in the Lactose-fermenting Enterobacteriaceae(LFE. Besides, all samples were subjected to qualitative and quantitative PCR for the detection of tet-R genes.There was great difference among the proportions of the TR-LFE in different samples. The research results showed that the percentages in pig feces were between 25.00% and 66.87%; in soil of pig farm, the rates were among 8.56%～11.51%; composts of chicken feces, the numbers are 12.17%～13.45%; and the proportions of TR-LFE in chicken feces were among 4.86%-8.01%.In the test,255 of the 449 strains of LFEs were detected to be tet-R gene positive, accounting for 56.79%. The rates of tet-R gene positive LFE were in the range of 3.12%-96.87%. And the numbers in the pig feces were between 78.12%-96.87% followed by chicken feces (12.90%～62.07%), while soil of pig farm (25.00%～46.88%) and composts of chicken feces (3.12%～30.56%) contained much less tet-R genes. Based on the detection frequency of tet-R genes, the general rank of tet-R genes was set out as follows:tet (A), tet (B), tet (M) and tet (G) and tet (C) and tet (D) and tet (S). All the samples were not detected to harbor genes coding the ribosomal protection protein:tet (O) and tet (X). And tet (A) and tet (B) were the most prevalent genes in tet-R gene positive LFEs. Among the multiple tet-R gene positive LFEs, most of the detected tet-R genes belong to the efflux genes, namely, tet (A) and tet (B), tet (C), tet (D) and tet (G), and tet (A) and tet (B) were the most frequently detected. Most of the multiple tet-R gene positive LFEs were separated from boar feces and sow feces.In the detection of tet-R genes in bacteria, LFEs in the pig samples were detected to contain the most kinds of tet-R genes, the numbers of detected tet-R genes in compost of chicken feces were less, followed by soil of pig farm and chicken feces. From September to January, the detection rates of tet-R genes in LFEs were on the decline.The diversity of tet-R genes in all samples was higher than that in the LFEs. For instance, one sample of soil was detected to contain six kinds of tet-R genes, less than that in other samples. The occurrence of each tet-R gene (except the tet(D)) was quite frequent, and the detection results did not vary significantly along with the seasons.According to the results of quantitive PCR, the number of tet(A) gene in bore feces and sow feces were among 103～104 copies/ng DNA, more than that in soil of pig farm and chicken feces, their copy numbers of tet(A) were among 102～103 copies/ng DNA. The quantities of tet(A) in compost of chicken feces turned out to be the least, significantly less than that in the pig feces. |
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