| Shigella called as dysenteriae bacillary is the main pathogen of shigellosis. It is an epidemic contagion throughout the world, especially in the countries with the laggard sanitation. These days, though our country has made a great achievement on the shigellosis of prevention and cure, the incidence of shigellosis was always high, because of much more population, underdevelopment economy in our country and because of the complex of the bacterial type, the easy variance and without the crossover immunity in Shigella. It is the familiar contagion in summer and autumn. Since antimicrobial agents were widely employed to treat shigellosis, antimicrobial resistance in Shigella spp .has been widely appeared and was multiple-antibiotic-resistance, which brought great hard to shigellosis of prevention and cure, consequently shigellosis spread and prevail. In 1996, Shigella spp. had been identified by the World Health Organization as one of the growing antibiotic-resistant bacteria posing a major threat to mankind. It is the important task increasing the level of shigellosis of prevention and cure to study the multiple-antibiotic-resistant mechanisms in Shigella spp.and to overcome multiple-antibiotic-resistance (Mar) of bacterial .The study on Escherichia coli.suggested that AcrAB-TolC multidrug efflux pump played a main role in multiple-antibiotic-resistance E.coli. This mechanism is called as active efflux pump system, which is multiple genes collaborateing phenotype and is regulated by chromosomal. It makes the level of mar gene expression increased, which can transport different drugs outside the cell and decrease drug accumulating density inside the cell, thus the bacterial bring about the resistance to multiple antibiotic. It was found that these multidrug efflux pump genes widely lie in enterobacteriaceae. In order to know the multiple-antibiotic-resistant mechanisms in clinical strains of Shigella spp.and quest for the track to solve this problem, this study was planned to amplify multidrug efflux pump genes acrAB-tolC by polymerase chain reaction (PCR), single strand conformational polymorphism analysis (SSCP) were applied to all PCR products and the level of mar gene expression were measured by Northern blots. This study identified the role of the inhibitors of efflux pumps (MC-207, 110) to the multiple-antibiotic-resistance strains of Shigella spp. Methods1. Filtrateing the Mar strains and WT: antimicrobial susceptibilities were tested by the agar doubling dilution method. The strains appearing resistance to Teracycline (TE), Chloramphenicol(C), Ampicillin (Am) and Pipemidic adcid (PI) or Ciprofloxacin (CIP) were called as Mar, susceptible called as wild type (WT).2. Accumulation of CIP in clinical isolates of Shigella spp.:accumulation of CIP in clinical isolates of Shigella spp. was measured by fluorometry. Test of accumulation was in the water of 37癈, the samples were resuspended in O.lmol/L (pH 3.0) ice-cold glycine hydrochloride. The concentration of CIP in Mar strains was shown with the CIP milligram in the cell per litre when the cell of ODeoo was 10.3. PCR-SSCP of multidrug efflux pump genes acrAB-tolC: acrAB-tolC genes were amplified by PCR, the products of which were digested (or undigested) with restriction endonuclease EcoR I (Alu I ), this can detect a single nucleotide change as well as the loss or insertion of oligonucleotide by electrophoresis.4. The label of the probe by random priming: the single DNA hybridized with random primer and the other single was synthesized with E. co/z'DNA polymerase I Klenow Fragment and DIG-11-dUTP was added to the new strand, the label of the probe was performed.5. Northern blots: the total RNA of the cell was in the denaturing formaldehyde agarose gel and transferred to nitrogen nylon membrane, the blot was hybridized with the labeled probe.Results1. Filtrateing the Mar strains and WT: antimicrobial susceptibilities of 141 clinical isolates were tested by the agar doubling dilution method. 64 clinical isolate...
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