High-level amikacin resistance in Pseudomonas aeruginosa associated with a 3'-phosphotransferase with high affinity for amikacin.
This work describes the characterization of the phosphotransferase enzymatic activity responsible for amikacin resistance in two clinical Pseudomona aeruginosa strains, isolated from a hospital that used amikacin as first-line aminoglycoside. Amikacin-resistant P. aeruginosa PA40 and PA43 (MIC: 128 mg/l) were shown to have APH activity with a substrate profile similar to that of APH(3')-VI. The enzyme from P. aeruginosa PA40 was purified to > 70% homogeneity. The Km of amikacin for this enzyme was 1.4 microM, the Vmax/Km ratio for amikacin was higher than for the other aminoglycosides tested and PCR and DNA sequencing ruled out the presence of aph(3')-IIps. Amikacin resistance in this strain was, therefore, associated with APH(3')-VI and the high affinity of this enzyme for amikacin could explain the high-level resistance that we observed.
Department of Biochemistry and Molecular Biology, University of La Rioja, Logroño, Spain. carmen.torres@daa.unirioja.es
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D000583:Amikacin / Q000378:metabolism / Q000494:pharmacology*; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001483:Base Sequence; D015139:Blotting, Southern; D017931:DNA Primers; D004352:Drug Resistance, Microbial; D007700:Kinetics; D008826:Microbial Sensitivity Tests; D010770:Phosphotransferases / Q000302:isolation & purification / Q000378:metabolism*; D016133:Polymerase Chain Reaction; D011550:Pseudomonas aeruginosa / Q000187:drug effects* / Q000201:enzymology; D013379:Substrate Specificity
D000900:Anti-Bacterial Agents; D017931:DNA Primers; D000583:Amikacin; D010770:Phosphotransferases