title: Survey of modifying enzymes and plasmids in amikacin-resistant Serratia marcescens.
abstract: Forty amikacin-resistant strains of Serratia marcescens isolated from four different hospitals (A, B, C, and D) were examined for modifying enzymes and plasmids. Twenty-one of the isolates produced acetyltransferase that modified amikacin. Eighteen of the 21 acetyltransferase-bearing isolates were from different inpatients in hospital A and the other three were from hospital C. Amikacin resistance was mediated by conjugative plasmid of 24 megadaltons in 15 of the 18 acetyltransferase-bearing isolates of hospital A and by nonconjugative plasmids, derivatives of the 24-megadalton plasmids, in the remaining three isolates of the same hospital. The 24-megadalton plasmid determined aminoglycoside acetyltransferase (6') IV. This plasmid-borne enzyme conferred amikacin resistance on S. marcescens but not on Escherichia coli K12. The frequency of transfer of the 24-megadalton plasmid from the S. marcescens isolate to E. coli K12 by conjugation was approximately 10(-7) (transconjugants/donors) and was 0.1% of that between E. coli strains. In acetyltransferase-bearing isolates from hospital C, the enzyme was mediated by a nonconjugative plasmid in one case and could not be associated with a plasmid in the remaining two cases. Neither enzymes nor plasmids could be associated with amikacin resistance of the isolates of the other two hospitals.
mesh_terms: D000583:Amikacin / Q000494:pharmacology; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000235:genetics; D008826:Microbial Sensitivity Tests; D008970:Molecular Weight; D011815:R Factors; D012706:Serratia marcescens / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D014170:Transformation, Genetic
chemical_list: D004269:DNA, Bacterial; D000583:Amikacin