Surveillance And Analysis On The Antibiotic Resistance Of Salmonella From Poultry

Eighty-nine isolates of Salmonellae from poultry were identified by biochemical and serological tests. By serotyping, 17 S.enteritidis, 1 S.newport, 6 S.typhimurium and 65 S.pullorum were idientified among the isolates.The broth microdilution method for surveillance of Enterobacteriaceae strains resistance was established by using 18 antimicrobials including 12 antibiotics and 6 quinolones. A total of 89 Salmonella strains were isolated from poultry from Beijing, Tianjin, Shandong etc. The resistance to 12 antimicrobial drugs and 6 fluoroquinolones were detected and analyzed by the broth microdilution method. The results indicated that all isolates exhibited a susceptibility to amikacin and ceftriaxon, and 67 isolates showed a greater or lesser degree resistance to streptomycin, kanamycin, gentamicin, ampicillin, tetracycline, chloramphenicol, florfenical, cefotaxime, cephalothin and ceftiofur, to which 22 isolates exhibited a susceptibility. Some isolates showed resistance to multiple antibiotics and displayed a highest level resistance to streptomycin with a frequency of 43.8%, followed by tetracycline with a frequency of 30.3%. Nineteen isolates among 89 isolates showed a lower resisance to nalidixic acid, ciprofloxacin, sarafloxacin, enrofloxacin, orbifloxacin and levofloxacin, and the remainder were susceptible.PCR was used for the amplification of Intregron gene of all the salmonella isolates. Three kinds of Integron were detected from 7 S.typhimurium with a size of 638bp, 1913bp and 2013bp respectively. The products were cloned and sequenced. The results showed that they contained two aadA2 gene, one dhfrXII gene associated with the resistance.The quinolone resistance-determining region (QRDR) of gyrA gene of 19 resistance isolates was amplified by PCR, sequenced and their amino acid mutations were analyzed. The results revealed that 9 isolates contained a mutation in gyrA of a serine at position 83 (Ser83) to a phenylalanine, and 1 isolate exhibited a mutation of Ser83 to a tyrosine, and 6 isolates that were resistant to more than six kinds of fluoroquinolones showed a mutation Asp87 to Asparagine at the same time. It was shown that there was a relationship between the degree of quinolone-resistance to clinical poultry Salmonella and the amino acid mutations in QRDR of the gyrA gene.