| Antibiotics resistace has increasing emerged among bacteria during the widespread clinical use of antibiotics. Escherichia.coli is so far a leading pathogen of hosipital acquired infections and community acquired infections. The dissemination of Multidrug-resistance bacteria make us face the severe trouble in therapy.Quinolons has been excellent antibiotics activity, however, Quinolons resistance has increasing emerged among E.coli in recent year, which severely limits its application. The mechanism of quinolons-resistance involve target gene mutations and active efflux of the agents.There are more than seven efflux systems in Escherichis coli that can export structurally unrelated antibiotics. AcrAB is a major, constitutively expressed, multidrug efflux pump from E.coli. It recognizes and expels from the cells an unusually broad range of antimicrobial agents. The acrAB operon codes for two proteins, the efflux transporter AcrB and the periplasmic lipoprotein AcrA, the outer membrane channel TolC is the third component of this transporter. One of its physiological roles may be protection of E. coli from lipophilic inhibitors occurring in ets natural habitat, such as bile salts and fatty acids. There is nearly perfect correlation between antibiotics resistance and overexpression of the AcrAB efflux system, this study investigate the phenotype of resistance to antibiotics of 367 clinical isolate E.coli. In order to detect the clinical contribution of multidrug efflux pump, detect the level of mRNA expressions of acrA in clinical isolates.Part 1 Investigate on Resistant Phenotype of Clinical Isolatesin Escherichia.coli. Object: Investigate the phenotype of resistance to 17 antibiotics in 367clinical isolates of Escherichis coli from 2001-3 to 2002-3 from eight hospitals in Tianjing. Analysis risk factor about hospital acquired infection and multidrug-resistant bacteria.Method: MIC values of antibacterial agents were determined with agardilution method and disk diffusion (K-B)method.Result: (1) Rate of ciprofloxacin resistance of clinical isolates inEscherichia coli is 68.7% in our city. Ampicillin resistance rate is high, strains are relatively sensitive to cephalosporins and very sensitive to imepenem. Moreover, rate of amikacin resistane is 9.7%. Among 367 clinical isolates, the percent of multidrug-resistant isolates is 51.8%. (2)the percent of hospital acquired infection isolates is 27.0% hi all of clinical strains. (3) multidrug-resistant isolates is common in urinary tract, ICU hospital room, patient of chronic disease, the old, Quinolone-resistant, and so on.Conclusion: With increasing rate of ciprofloxacin resistance ,Quinolone-resistant bacteria and multidrug-resistant bacteria are compact correlation, More attention should be drawn in multidrug-resistant Escherichia coli, on the basis of the result of susceptibility testing , use objective therapy.Part 2 Expression of active efflux pump acrAB in clinical isolates of multidrug-resistant Escherichia.coliObjective: to study the mechanism of multidrug resistance in clinicalisolates of Escherichia coli and discuss the role of active efflux pump AcrAB-TolC in clinical isolates.Methods: use CCCP inhibit testing detect the existence of pump mechanismin clinical isolates, the level of mRNA expressions of acrA in clinical strains of Escherichia.coli was determined by RT-PCR.Results: Among 20 clinical Quinolone -resistant isolates, 12 were foundMIC be down after inhibited by CCCP. Among them, MIC of 8 isolates is down more than 9 times, near the AG102. 2 isolates descent about 4-5 times. Another 2 isolates is down 2 times. Quinolone-susciptible strains and AG100 don't change their MIC. Moreover, mRNA of acrA were overexpression in 11 of 12 isolates which susceptible to CCCP, involve in 4 Mar strains.Conclusions: 1 Overexpression of active pump AcrAB-TolC is a importantproportion in membrane-induced multidrug-resistant clinical strains of E.coli. 2... |
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