Frequency of aminoglycoside 6'-N-acetyltransferase among Serratia species during increased use of amikacin in the hospital

The incidence of tobramycin-resistant, gentamicin-susceptible Serratia species at the Minneapolis Veterans Administration Medical Center decreased from an average 42.1 to 2.5% (P<0.001) during a 4.5-year period despite the predominant use of amikacin. These organisms were shown to express a 6'-N-acetyltransferase-modifying enzyme (EC 2.3.1.82). Resistance was not shown to be plasmid mediated.