Antimicrobiotic Resistance And Genotpyes Of Extended-spectrum β-lactamase Producing Extraintestinal Pathogenic Escherichia Coli

Objective: to understand the antimicrobial resistance of Extraintestinal pathogenic Escherichia coli (ExPEC)to the antimicrobiotics used commonly in clinical in FuJian Province; to investigate the incidence of extended-spectrumβ-lactamases(ESBLs) of ExPEC in the area and establish a fast test which can detect ESBLs conveniently and usefully; to identify the genotypes and characteristics of ESBLs coding gene and build up a groundwork for molecular epidemiological screening methods and clinical diagnosis methods of ESBLs producing ExPEC. Methods: All strains of ExPEC collected between 2003 and 2005 in 7 hospitals in FuJian Province were tested for resistance to antimicrobiotics by agar dilution test. ESBLs producing strains screening test was performed by substrates Ceftazidime or Cefotaxime with a working concentration of 1μg/ml. Strains growing in either of substrates were confirmed whether they were producing ESBLs or not by ESBLs phenotypic confirmatory test recommended by Clinical and Laboratory Standards Institute (CLSI). At the same time, broth microdilution method to confirm ESBLs producing strains was designed. To verify its reliability, Two International Standard Strains Escherichia coli ATCC 25922 (non-ESBLs producing strain) and Klebsiella pneumoniael ATCC 700603 (ESBLs producing strain) were tested for 40 times. Then 59 isolates of ESBLs producing ExPEC and 33 isolates of non-ESBLs producing ESBLs were tested. Refer to the results of ESBLs phenotypic confirmatory test recommended by CLSI as standard, the validity of the method the research established was verified. Pulsed-field Gel Electrophoresis was performed to detect the plasmid profiles of ESBLs producing strains. A pair of conserved primers was designed to amplify a 544bp fragment of blaCTX-M gene which can produce ESBLs and PCR was performed. To...