Isolation and characterization of the aadA aminoglycoside‐resistance gene from Salmonella choleraesuis

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Abstract
The streptomycin- and spectinomycin-resistance gene of Salmonella choleraesuis was cloned and its nucleotide sequence determined. The gene is 789 bases long, encoding a protein of a predicted size of 29353 Da. The gene product inactivated streptomycin and spectinomycin by an adenylation modification. It is homologous (c. 40% total identity) to streptomycin adenylyltransferase, a 3′ (9)-O-nucleotidyltransferase (AAD(3′)(9)), which is encoded by the aad A gene in Escherichia coli, Agrobacterium tumefaciens, Kiebsiella pneumonia, and Serratia marcescens. The AadA protein of S. choleraesuis differs significantly from the other AadA proteins, indicating that it may have diverged from the other members of this family earlier in evolution. Southern hybridization analysis revealed that homologous aad A sequences were also present in other streptomycin-resistant Salmonella species.