In-vitro activity of arbekacin alone and in combination with vancomycin against gentamicin- and methicillin-resistant Staphylococcus aureus

In-vitro susceptibility studies were performed on 99 clinical Staphylococcu s aureus isolates. A total of 68 of 73 methicillin-resistant S. aureus and 2 of 26 methicillin-susceptible S. aureus were gentamicin-resistant (gentam icin MIC range 16 to 1,024 mu g/mL). All 70 gentamicin-resistant isolates c ontained the aac(6')-Ie-aph(2 ")-Ia aminoglycoside resistance gene, and non e possessed the aph(2 ")-Ic or aph(2 ")-Id aminoglycoside resistance genes. The arbekacin MIC for the 70 gentamicin-resistant isolates ranged from 0.2 5 to 4 mu g/mL. The combination of arbekacin plus vancomycin produced syner gistic killing against 12 of 13 gentamicin-resistant MRSA isolates. The com bination of gentamicin plus vancomycin produced synergistic killing against 7 of the same 13 isolates. Arbekacin may prove useful when used in combina tion with vancomycin in treating infections caused by gentamicin-resistant MRSA. (C) 2000 Elsevier Science Inc. All rights reserved.