title: Decreased susceptibility to 4'-deoxy-6'-N-methylamikacin (BB-K311) conferred by a mutant plasmid in Escherichia coli.
abstract: Escherichia coli MP6 contains a plasmid that encodes aminoglycoside 3'-phosphotransferase II, which phosphorylates kanamycin and confers high-level kanamycin resistance, Amikacin is a minor substrate of this enzyme, but MP6 is susceptible to amikacin. Strain MP10 has a spontaneous mutation in the plasmid of MP6 that increases the aminoglycoside 3'-phosphotransferase II activity not only against kanamycin but also against amikacin. This mutation is also responsible for the appearance of resistance to amikacin in MP10. Resistance to 4'-deoxy-6'-N-methylamikacin (BB-K311) by enzymatic modification has not been reported previously. As with amikacin, MP6 was susceptible to BB-K311 and its aminoglycoside 3'-phosphotransferase II did not phosphorylate this amikacin derivative appreciably. We found that the plasmid-borne mutation in MP10, however, localized by being cloned with a 3.7-megadalton HindIII fragment containing the aminoglycoside 3'-phosphotransferase II gene, resulted in increased phosphorylation of BB-K311 and resistance to it. Thus, the mutation distinguishing MP6 and MP10 has increased the activity of an existing aminoglycoside-modifying enzyme and produced new bacterial resistance to two previously minor substrates of the enzyme.
mesh_terms: D000583:Amikacin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D005798:Genes, Bacterial; D007612:Kanamycin / Q000031:analogs & derivatives*; D019868:Kanamycin Kinase; D009154:Mutation; D010770:Phosphotransferases / Q000235:genetics; D011815:R Factors
chemical_list: D007612:Kanamycin; C030518:4'-deoxy-6'-N-methylamikacin; D000583:Amikacin; D010770:Phosphotransferases; D019868:Kanamycin Kinase