Characterization of the enzyme aac(3)-id in a clinical isolate of Salmonella enterica serovar Haifa causing traveler's diarrhea

Introduction: The objective of this investigation was to identify the mechanism of decreased susceptibility to gentamicin in a Salmonella clinical isolate, leading to the detection of a aminoglycoside acetyltransferase gene found in a class 1 integron. Methods: A multidrug-resistant Salmonella strain was recovered from feces of a traveler to Egypt. The antimicrobial susceptibility test to 12 antimicrobial agents was performed with the Kirby-Bauer method. The presence of class 1 integron was determined by PCR. The ampli.ed product was recovered and sequenced in order to establish the genes carried. In addition, susceptibility to gentamicin C_1a, gentamicin C₁, sisomicin, neomycin, dibekacin, kanamycin, tobramycin, amikacin, netilmicin, apramycin, dactimicin, spectinomycin, streptomycin, lividomycin and butirosin, was established. The Champion™ pET101 Directional TOPO® Expression Kit was used to clone and express the aac(3)-I gene. Results: The isolate was identi.ed as Salmonella enterica serovar Haifa, showing resistance to nalidixic acid, tetracycline and decreased susceptibility to gentamicin. One integron with a size circa 1,500 bp, encoding an aac(3)-Id plus aadA7 genes was observed. The analysis of the susceptibility to different aminoglycosides in the E. coli TOP10F' transformed with the vector carrying aac(3)-Id gene showed resistance to gentamicin C_1a, gentamicin C₁, and dactimicin, in accordance with the presence of this enzyme but, was susceptible to sisomicin. The homology of the amino acid and nucleotide sequences with the AAC(3)-Id enzyme was of 100%. Conclusion: The presence of the AAC(3)-Id enzyme was described for the first time in a S. Haifa.