Studies On The Resistance Of β-lactamas Antibiotics And The Efficacy Against E.coli From Chicken

This paper studied the resistance of E.coli from chicken - the characterization of β -lactamases in E.coli clinical from chicken and the therapeutic experiment in vivo using E.coli infection models to investigate the current situation and the mechanisms of resistance of E.coli clinical isolated from Henan province. The contents of the studies included four parts: the drug susceptibility of E.coli clinical and standard,the detection of β -lactamase(BLA) and the induction of the extended-spectrum of β -lactamases(ESBLs), the stabilization of β -lactamases, the therapeutic experiment in vivo using E.coli infection models.The results of drug susceptibility in vitro showed that the third Cephalosporin (Ceftriaxone, Cefotaxime and Ceftiofur) had potent activity against all kinds of clinical and standard strains: the MICs were in the range of 0.0125-6.4ug/ml. Amoxicillin and Ampicillin had potent activity to E.coli O78 standard, but inpotent activity to E.coli clinical with the MIC50 were both above 128ug/ml, at the same time , 90% of E.coli clinical had produced resistance. Lincomycin, Spectinomycin and Fluoroquinolone( Ciprofloxacin , Gatifloxacin, Levofloxacin) had stronger activity to E.coli O78 standard than E.coli clinical, 60% of E.coli clinical had produced resistance. Aminoglycosides(Gentamicin and Amikacin) had potent activity to E.coli 078 standard and E.coli clinical. Though there were some strains which produced resistance, there were 60% and 86.7%of stains that were sensitive to Gentamicin and Amikacin respectively.The results of the detection of BLA and ESBLs showed that al 1 the 14 E.coli clinical strains had produced BLA by nitrocefin disc test, but none of which was ESBLs and AmpC BLA producing by double-disc synergy method. ESBLs was found when one E.coli clinical strain was induced to the twentieth generation with ceftriaxone whose concentration was 1/2 MIC to the strain. At the same time the MICs of β -lactamas to which became bigger. But the strain did not produce ESBLs either when it was cultured for 5 generations continuously without ceftriaxone, and the MICs reconverted in some extent. AmpC β -lactamase was found when one E.coli...