Genotypes of TEM-type and CTX-M-type extended-spectrum β-lactamases produced by Escherichia coli isolated from the fowl.

【Objective】The genotypes and subtypes of ESBLs produced by Escherichia coli isolated from the fowl were detected to elucidate their distributions in Henan Province.【Method】Twenty-eight ESBL-producing Escherichia coli were collected from different chicken farms of seven districts in Henan Province,and were amplified by PCR using the primers of TEM,SHV and CTX-M,respectively.Their PCR products were cloned and then the cloned fragments were sequenced.The nucleotide sequences were analyzed by DNAStar software and GenBank database.【Result】Twenty-one strains were TEM-type,two isolates were CTX-M-type,and two genotypes were detected in five strains,including TEM-type and CTX-M-type.No SHV-type was found. TEM-1 variant was the most common subtype,and the sequences of 26 isolates shared 98%-99%homology with that of AY293072(TEM-1β-lactamase) .Except a silent mutation of 18T→C of all,the sequences of C3,X2,and F4 were characterized by another nucleotide base variations(783G→A,21T→A,and 269G→A,respectively) ,and only the last variation led to the shift of amino acid(92Gly→Asp) .These three sequences were submitted to Genbank database and obtained the accession No(FJ405207,FJ405208,and FJ405211,respectively) .The CTX-M-type of ESBLs included two subtypes:three isolates(F2,X3,and B5) CTX-M-gene sequences were identical with EF158299(CTX-M-14) ,the others(C2,C3,C4,and K1) CTX-M-gene belonged to CTX-M-65 type(FJ405191,FJ405192,FJ405212,and FJ405214,respectively) .【Conclusion】The predominant genotype of ESBLs is TEM-1 variant in chicken farms of Henan Province,and then are CTX-M-65 and CTX-M-14.