Study On Mechanism Of β-lactam Antibiotic Resistance In Enteropathogenic E.coli From Chicken

Escherichia coli is one of the common pathogenic bacterium in medical science and veterinarian clinical infection. The serological type of it is multiple, so there was no ideal vaccine to prevent (it is difficult to prevent).When it breaks out, we treated it with antibiotics. But with the generally. persistently and unreasonably use of the antibiotics, the quantity of persister of E.coli increased unceasingly. Since the mechanism resistance diversified frequently, sometimes we could not find out an effective antibiotic. In recent years, the occurrence of the colibacillosis of chicken presented upgrade tendency, thus it caused large loss chicken farming. Therefore, the study on the drug resistance of enteropathogenic E.coli from chicken is significance to theory and practice.In this study, the enteropathogenic E.coli was isolated from sick chicken and those drug resistances were investigated by drug sensitivity experiment. Then, 13 strains were selected and examined by the rate of producingβ-lactamases,the rate of producing AmpCβ-lactamases and extended-spectrumβ-lactamase was determined. Strains was examined by minimal inhibitory concentration (MIC) test toβ-lactam antibiotics. The drug resistance gene relatedβ-lactam antibiotics ompFA and ompCA were investigated in the experiment with polymerase chain reaction (PCR), cloning and sequencing to analyze the relationship between them with the drug resistance level.The result indicated that the rate of producingβ-lactamases of Escherichia coli was 53.85%, respectiverly, AmpCβ-lactamase was 28.57%, extended-spectrumβ-lactamase was 71.43%. The strains of AmpCβ-lactamase-producing was multi drug resistant. Most Escherichia coli were poorly susceptible to Ampicillin,Amoxicillin, Ciprofloxcin and third-generation cephalosporins. Most Escherichia coli were susceptible to Gentamicin and Aztreonam. The MIC of 7 strains was from 1μg/ml to 256μg/ml. The result of sequencing of the masculine clone plasmid showed, to contrast with the reference sequence in GeneBank: the ompFA gene and the ompCA gene encoding outer membrane protein (OMP) had many mutation basic group and corresponding many changed amino acids, that lead to raising the drug tolerance level.The results also indicated that the drug-resistance of E.coli which isolated in clinic from chicken was very serious. therefore, it is essential to detect the drug tolerance of pathogenic bacteria before treatment; the change of PBP and OMP'permeability often caused the low level drug tolerance, the drug tolerance level of the E.coli in study was very high. We concluded that the drug resistance of these E.coli have relation with the change of OmpF and OmpC. the change of PBP and OMP'permeability often caused the low level drug tolerance,but caused extensive drug resistance.The change of gene was not to be ignored.