Activity of a novel aminoglycoside, ACHN-490, against clinical isolates of Escherichia coli and Klebsiella pneumoniae from New York City.

OBJECTIVES Reports of Enterobacteriaceae resistant to all commonly used antimicrobial agents, including β-lactams, fluoroquinolones and aminoglycosides, are increasing in hospitals worldwide. The activity of ACHN-490, a next-generation aminoglycoside, was examined against clinical isolates of Escherichia coli and Klebsiella pneumoniae from hospitals in New York City, an area where multidrug-resistant organisms are endemic. METHODS Unique patient isolates of E. coli and K. pneumoniae were gathered from 16 hospitals located in New York City in 2009 and underwent susceptibility testing to aminoglycosides and ACHN-490. Subsets of isolates were characterized by PCR for the presence of genes encoding aminoglycoside-modifying enzymes, ribosomal methylases and KPC-type carbapenemases. RESULTS Although most isolates of E. coli were susceptible to the aminoglycosides, the MIC(90) values of gentamicin, tobramycin and amikacin were 32, 8 and 4 mg/L, respectively. The MIC(90) of ACHN-490 was 1 mg/L. Multidrug resistance, including resistance to aminoglycosides and the presence of bla(KPC), was much more common in isolates of K. pneumoniae. However, the MIC(90) of ACHN-490 for K. pneumoniae was also 1 mg/L. The MICs of ACHN-490 did not correlate with the presence of commonly recovered aminoglycoside-modifying enzymes. Bactericidal activity was evident in most isolates at concentrations 4× the MIC. CONCLUSIONS The novel aminoglycoside ACHN-490 retains activity against most isolates of E. coli and K. pneumoniae, including multidrug-resistant strains. Additional studies examining the roles of efflux systems and outer membrane permeability alterations are recommended in isolates with reduced susceptibility to this agent.