Abstract:

【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-1 β-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.

Key words: Escherichia coli, extended-spectrum β-lactamases, TEM gene, CTX-M gene