| To gudie the resistance surveillance and know epidemiological study of plasmid-mediated β-lactams resistance genes in Salmonella isolated food-animals, which can guide therational use of β-lactams antibiotics in clinical care. The conventional identification and slide agglutination method were used to detect the serotype of 710 Salmonella isolates from different animals in 2003-2013. Results A total of 15 serotypes were identified, including S.Pullorum (n= 405,50.04%), S.Derby (n= 50,7.04%), S. Give (n = 37,5.21%), S. Fyris (n= 30,4.23%) and S. Enteritidis (n= 11,1.55%). Different animals haroured different kinds of serotype, followed by poultry main to S.Pullorum, pigs to S.Derby and cows to S. Give.The MICs of Salmonella to 21 kinds of antimicrobial agents was examined by using the broth microdilution method. The results indicated that the resistant rate to all antimicrobial agents was more than 10%, among β-lactams,60.56% were resistant to Amoxicillin/Clavulanic acid, followed by resistance to Ampicillin (50.42%), Aztreonam (50.14%), Cefazolin (49.72%), Ceftiofur (47.76%), Ceftriaxone (28.45%), Cefotaxime (24.51%), Ceftazidime (22.25%), Cefepime (15.07%), Cefoxitin (13.66%) and among non-β-lactams 91.83% were Trimethoprim/sulfamethoxazole, fowlled by resistance to Sulfafurazole (67.61%), Tetracycline (45.63%), Doxycycline (45.21%), Streptomycin (30.14%), Florfenicol (18.45%), Chloramphenicol (16.76%), Kanamycin (16.2%), Ciprofloxacin (14.93%), Gentamicin (10.85%) and Amikacin (10.7%). The resistant rates of isolates from swins and cattles were higher than that from poultry; there is no correlation between resistance of drugs and year, but the whole resistant rates to each drug increased with the increasing of time; the incidence of resistance has a certain correlation with the pathogenicity of strains.98.13% strains showed Multidrug resistance, the multidrug profile was very complex and most isolates exhibited multidrug-resistance to 4 and 5 antimicrobial agents, furthermore the 99% isolates from swines and cattles showed Multidrug resistance and was main to 12 and 13 antimicrobial agents, the poultry was resistance main to 1 and 4 antimicrobial agents.PCR and PCR-sequencing were used to detect the β-lactams resistance genes (TEM, CTX-M, SHV and CMY) of in 430 amoxacilline/clavullinic acid-resistant Salmonella isolates. The results of PCR indicated that CTX-M, SHV and CMY genes were not detected in 430 Salmonella, 48.14%(207/430) TEM gene was found. There were different rates of genotypes harboured strains from different sources, for example TEM-positive rate in strains from swine(75%) and cows (62.14%) was higher than that of poultry(42.54%). The results of sequencing showed blaTEM-1B was main sub-genotype in strains. The plasmid profiling of 207 TEM-positive strains was divided into seven type(Plasmid size from >1000 to> 15000) and the strains from pigs harboured small plasmids (< 15000) more than that of poultry. The resistance rate of TEM-positive strains to Ampicillin, Cefepime, Aztreonam, Streptomycin, Kanamycin, Amikacin, Gentamicin, Chloramphenicol, Florfenicol, Tetracycline and Ciprofloxacin was significant or highly significant higher than that of TEM-negetive strains (0.01<P<0.05 or P<0.01), but there was no significant difference between two groups resistance to first/second/third cephalosporin, Doxycycline and Trimethoprim/sulfamethoxazole(P>0.05).Transconjugation test was used to ebaluation the transitibity of resistance gene between different strains. Results The TEM gene of 207 strains located on the plasmid. The results of transconjugation test showed that there were 118 transconjugants (Transfer rate 57.01%,118/207). The conjugation frequency of the plasmid was from 3.8×10-2 to 5.75×10-2 in poultry strains and was from 4.77×10-8 to 7.15×10-8 in pig and cow strains. The plasmid profiling of transconjugation from chicken and cow strains only contained one R plasmid and from the pigs was at least two R plasmids. The MICs of transconjugation showed that the MICs of transconjugation to 21 drugs from different sources had some difference, especially Cefazolin, Cefoxitin, Cefepime and Aztreonam.Our results indicated that the multiple-serptype of 710 Salmonella strains from food-animals were exhibited and these strains showed serious multi-drug resistance. β-lactams must be prudently used in veterinary clinical medicine. The serotype and resistance in Salmonella from food-animals were enhanced to detect. Antibacterial agents must be prudently used in veterinary clinical medicine and breeding industry. TEM was main epidemiological genotype in 430 amoxacilline/clavullinic acid-resistant strains of Salmonella. The gene located on the removable R plasmid and can transfer from donor to the recipient in interspecies with horizontal transmission accompanying R plasmid. |
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