The Drug Sensitivity Testing, Serotyping And Detecting Drug Resistance Genes By PCR Of E.coli From Chickens

A total of 76 samples were collected from the chickens died of Escherichia coli disease in 5 chicken fields of a group managed by a group of broiler in Shandong in september 2006. In the test, many identification experiments such as biochemistry test, pathogenicity test and so on were done and at last the 76 cases of bacterial strain were all appraised as avian pathogenic Escherichia coli. The strains isolatesd were also examined for their susceptibility to 24 antimicrobial agents.The antimicrobial susceptibility test was completed according to the standard procedure advised by NCCLS. The result showed , 24 kinds of medicines had low or no sensitivity to the 76 Escherichia coli. Resistance profiles suggest that penicilin and ampicillin may be the most resistant antimicrobial agents tested in this study. The followed antimicrobial agents were multiplicity amindan, ciprofloxacin, ambramycin, rifampicin, vancomycin, oxacillin, erythromycin,.the resistant rate of the 9 kinds of medicines were 100%. Then the followed antimicrobial agents were norfloxacin,amphemycin,furadantin,phytomycin,chanamyn,gentamicin,amikacin,ceftazidime,cefotaxime,cefuroxime。Cefoperazone,cefazolin and cefatrizine may be the most sensitivity antimicrobial agents tested in this study.Subsequently the identification of the O serotype were done with the help of Doctor Gao of Yang Zhou university. The E.coli strains included in this study fell into O41,O78,O29,O76,O5,O14,O104 and O63 groups,of which O41,O78 and O29 together accounted for 68% of the 76 isolates examined. 51 strains isolated were not serotyped. Otherwise serological type was different in different branch filed, and different serological types has been existed in the same chicken filed. So vaccine should be prepared to control E.coli disease according to ascendant serological type of different chicken filed.The strains which sustain Ampicil and ambramycin isolated from pathogenic E.coli was bolting out, then 4 pairs special primers was designed towards the two kinds of drug resistance. The drug resistance gene could be detected. Sequencing and analyzing the Sequences gained and the result shows 45 positive strains of TEM gene account 60.0%, 35 positive strains of CTX-M gene account 33.3%; 15 positive strains of tetA gene account 22.1%, 23 positive strains of tetD gene account 33.8%. Furthermore, the proportion on the positive strains of tetA gene and tetD gene accounts as high as 24.7%. Analyzing the sequences of the drug resistance gene showed that the autoploidy among the 4 drug resistance genes and the related genes in Genbank were all above 99.3%.And corresponding amino acids were unchanged which reflects unchanged characteristic of drug fast of E.coli. The result showed, E.coli has wide spectrum of drug resistance ,high level drug fast.The multi-drug resistant and the chiasm drug fast were generally,it was not easy to change with the charactreristic of drug fast.