Drug resistance and genotype of extended spectrum beta-lactamases(ESBLs) producing escherichia coli strains

[Objective] To investigate the antibiotic resistance and genotype of extended spectrum beta-lactamase(ESBL) producing Escherichia coli amid clinical isolates from dalian municipal central hospital.[Methods] A total of 40 ESBL producing E.coli,isolates between Nov.2005 and Feb.2006,were screened out by phenotype confirmatory tests according to the procedures of Committee of Laboratory Standards Institute(CLSI).ESBL genes in those producing isolates were detected by PCR with primers specific for blaTEM,blaSHV,blaCTX-M-Ⅰ,blaCTX-M-Ⅱ,blaCTX-M-Ⅲ and blaCTX-M-Ⅳ respectively,and then the PCR products were analyzed by capillary electrophoresis.Their antibiotic resistance was determined by K-B tests.[Results] According to capillary electrophoresis results,only 1 of the 40 strains(2.50%) was SHV carrier,7(17.50%) were CTX-M-Ⅰ,7(17.50%) were CTX-MⅡ,2(5.00%) were CTX-M-Ⅲ,4(10.00%)were CTX-M-Ⅳ.18 of the 39 strains(46.15%) carried two or more kinds of genes,and CTX-M usually combined with TEM or SHV genes.K-B tests showed these strains were higher resistant to beta-lactam antibiotics and were most susceptible to Carbapenems(imipenem and meropenem).[Conclusions]The most common ESBL type in E.coli is CTX-M.Most of the studied strains isolated from our hospital usually carry more than one type of ESBL genes.Carbapenems is the most effective antibiotic to treat infections caused by ESBL producing E.coli.