| Tibetan chicken, a precious resource, is mainly found on 2200 m-4100 m above sea level in Qinghai-Tibet Plateau, and has become an unique breed resource to develop the poultry industry in the highlands in China. In recent years, Salmonellosis is the common bacterial disease to Tibetan chicken, causing serious losses for Tibetan chicken. And antibacterials contributed to an important increase to resistance reducing the effectiveness of treatments.In this study we have collected the 196 samples of blood in heart, liver, spleen, lung, ovary (or testis) and intestinal contents of 28 sick Tibetan chicken from 4 farms in Ganzi. Sichuan. Through biochemical tests and PCR. total of 42 Salmonella isolates were identified. The diagnosis results indicate that the 42 Salmonella isolates were serotyped into 6 distinct serotypes. including Salmonella Typhimurium (14), Salmonella Gallinarum (10). Salmonella Pullorum (8), Salmonella Enteritidis (6), highestly.The sensitivity tests of 42 Salmonella to 21 kinds of antibacterials were performed by Kirby-Bauer method. The results indicated that strains were resistant to 21 kinds of antimicrobials. The highest resistant rates were observed by amoxicillin (90.48%) and carbenicillin (90.48%), followed by ampicillin (88.10%), rifampicin (88.10%), sulphame-thoxazole (76.19%). tetracycline (69.05%). doxycycline (59.52%), florfenicol (54.76%), cefazolin sodium (47.62%). kanamycin (47.62%) and streptomycin (42.86%). Resistant rates to gentamicin and amikacin were under 10%. It meants that 97.62% (41/42) of strains showed MDR.The results indicated that 26 kinds of resistance genes could be detected from 42 strains by PCR. ?-Lactam resistance genes included blaTEM, blaCTX-M, blaSHV, blaOXA, blaPSE and blaCMY-2, and the highest gene was blaTEM (90.48%). Aminoglycoside resistance genes included addAl, addA2, addB, AacC2, aac(3)-? and Aph(3')-?a, and the highest gene was addA2 (85.71%). Tetracycline resistance genes included tetA, tetB and tetC for genes, and the highest gene was tetA (83.33%). Chloramphenicol resistance genes included catAl, floR and CmlA, and the highest gene was CmlA (57.14%). Sulfa resistance genes included sull and sul2, and the highest gene was sul2 (83.33%). Fluoroquinolone resistance genes included qnrA, qnrB, qnrS, aac(6')-Ib-cr, oqxA and oqxB, and the highest gene was aac(6')-Ib-cr (59.52%).The mobile genetic elements in 41 multidrug-resistance strains were detected by PCR. And 9 kinds of mobile genetic elements could be detected by PCR, including traA, trbC, merA, tnpA/Tn3, tnpU, tnp513, n1721, IS26 and intI1. To our knowledge, traA and trbC of Salmonella isolated in China was described at the first time. Strains were detected to carry at the least 3 kinds of mobile genetic elements. Moreover, the resistance genes and mobile genetic elements were transferred from 57.14%(8/14) of the MDR Salmonella strains into the E.coli J53 recipient strain by conjugation experiments.Conclusion:The isolation rate of Salmonella isolates was 21.43%(42/196) in the of 196 Tibetan chicken samples.42 Salmonella isolates were serotyped into 6 distinct serotypes, including Salmonella Typhimurium, Salmonella Gallinarum, Salmonella Pullorum, Salmonella Enteritidis, highestly. Isolates were differently resistant to commonly used 21 antimicrobials, and 97.62% of strains showed MDR. Additionally, these resistance genes and mobile genetic elements were widely distributed among MDR isolates tested, and there was correlation between the resistance genes and mobile genetic elements. |
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