Study On Detection Of Tetracycline Resistance Gene(tetC) Of Pathogenic Salmonella From Swine By PCR And Nucleic Acid Probe

The MIC values of tetracycline, oxytetracycline and chlortetracycline of the 16 pathogenic Salmonella strains from swine were detected by disc dilution method. Using NCCLS guidelines hi America hi 1990, all strains showed resistance. In the 16 strains, thirteen strains showed high level of resistance to tetracyclines, and three strains showed low level of resistance.According to the tetC sequences published, a pair of primers were designed and synthesized. The tetC of 16 salmonella strains was amplified by polymerase chain reaction. Twelve strains were positive, and the gene located on plasmids. There is no correlation between tetC and serotype, between tetC and MIC, between tetC and origin of strain. The PCR products of two strains (SLPS1-3 and DYPS1) were sequenced and analysed. Comparing the nucleotide sequences of tetC in Salmonella with pBR322 reported (GenBank accession No: J01749), the percent identity ranged from 97.7% to 98.7%.The PCR product of SLPS1-3 was labelled with photo-biotin. Colony hybridization with the probe was applied. The result indicated that 13 strains were positive, 3 strains were negative. Compared with the result of PCR, The method obtained 93.75% concordance in positive rate. The method can be used for the detection of tetC precisely, sensitively and quickly.In the study, two methods of PCR and nucleic acid probe were established on the base of optimized conditions. By them, the tetC of salmonella would be detected, and molecular epidemiology of tetracyclines-resistance would be investigated.