Aminoglycoside resistance in enterococci.

High-level aminoglycoside resistance in enterococci is mediated generally by aminoglycoside-modifying enzymes, which eliminate the synergistic bactericidal effect usually seen when a cell wall-active agent is combined with an aminoglycoside. Clinical microbiology laboratories currently screen for aminoglycoside resistance in enterococci by testing gentamicin and streptomycin susceptibility. If the recently detected aminoglycoside resistance genes, aph(2")-Ib, aph(2")-Ic, and aph(2")-Id, become more prevalent among clinical isolates, the approach for detecting susceptibility to aminoglycoside synergism in enterococci will require modification. More potent aminoglycosides need to be developed that will be resistant to modification by a broad spectrum of aminoglycoside-modifying enzymes present in enterococci.