Abstract: 【Objective】 The genotypes of five ESBLs-producing shigella flexneri clinical isolates and a standard ESBLs-producing shigella flexneri induced by Ceftifur were detected ,at the same time ,we studied the molecular involvement mechanism of the shigella flexneri ESBLs production.【Method】The standard shigella flexner was induced by Ceftifur with 0.5MIC concentration and detected βlactamase every ten times.After induced shigella flexner had produced ESBLs, the plasmides of it and 5 ESBLs-producing clinical shigella flexneri were amplified by PCR using the primers of TEM,SHV, CTX-M,respectively, their PCR products were cloned and then the cloned fragments were sequenced. The nucleotide sequence obtained were analyzed using DNASTAR software.The search for homologous sequences was done in the GenBank database using FAST software through the Internet. 【Results】 There were the same TEM- type and SHV- type sequences in the plasmids of the five shigella flexneri clinical isolates.The sequence of the TEM-type was characterized by two nucleotide mutations (G157A,C409T) compared with the sequence of AY903309(TEM-116).The mutation of nucleotide 409 was aslient mutation,the mutation of nucleotide 157 leaded to the mutation of amino acid( Gly53Ser) and the mutation didn't exist in the published ESBLs sequences.Therefore, the TEM-type was a new genotype,named TEM-1V type.The sequence of SHV-type was the same as that of the AY826418(SHV-12), therefore the obtained sequence was the SHV-12 type. For the standard shigella flexneri,when it was induced to the tenth times by Ceftiofur, its gene sequence of the produced β-lactamase was the TEM-1 type, when induced to the fifth times,the gene sequence of the produced ESBLs was the TEM-1V type. 【Conclusion】(1)The shigella flexneri clinical isolates harbored TEM-1V type and SHV-12 type ESBLs.(2) when it was induced to the tenth times by Ceftiofur, the standard shigella flexneri's gene sequence of the produced β-lactamase was the TEM-1 type, when induced to the fifth times,the gene sequence of the produced ESBLs was the TEM-1V type.