Aminoglycoside Resistance Genes aph(2")-Ib and aac(6′)-Im Detected Together in Strains of both Escherichia coli and Enterococcus faecium

AUTOR(ES)

Chow, Joseph W.

FONTE

American Society for Microbiology

RESUMO

Escherichia coli SCH92111602 expresses an aminoglycoside resistance profile similar to that conferred by the aac(6′)-Ie-aph(2")-Ia gene found in gram-positive cocci and was found to contain the aminoglycoside resistance genes aph(2")-Ib and aac(6′)-Im (only 44 nucleotides apart). aph(2")-Ib had been reported previously in Enterococcus faecium SF11770. aac(6′)-Im had not been detected previously in enterococci and was found to be present also 44 nucleotides downstream from aph(2")-Ib in E. faecium SF11770. aph(2")-Ib and aac(6′)-Im are separate open reading frames, each with its own putative ribosome binding site, whereas aac(6′)-Ie-aph(2")-Ia appears to be a fusion of two genes with just one start and one stop codon. The deduced AAC(6′)-Im protein exhibits 56% identity and 80% similarity to the AAC(6′)-Ie domain of the bifunctional enzyme AAC(6′)-APH(2"). Our results document the existence of a member of the aph(2") family of genes in gram-negative bacteria and provide evidence suggesting the horizontal transfer of aph(2")-Ib and aac(6′)-Im as a unit between gram-positive and gram-negative bacteria.

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