The activity of ACHN-490 was evaluated against 493 meticillin-resistant Staphylococcus aureus (MRSA) isolates collected in 2009-2010 from 23 US hospitals. The MIC(50) and MIC(90) values (minimal inhibitory concentrations for 50% and 90% of the organisms, respectively) for ACHN-490 were 1 and 2 μg/mL compared with 8 and 32 μg/mL for amikacin, 0.5 and 1 μg/mL for gentamicin and 2 and >16 μg/mL for tobramycin. The gene encoding the aminoglycoside-modifying enzyme APH(2″)-Ia/AAC(6')-Ie was present in 12% of the subset of 84 isolates examined by polymerase chain reaction (PCR), whilst the gene encoding ANT(4')-Ia was present in 89% of isolates. ACHN-490 activity was not affected by either enzyme.
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