Prevalence of High-Level Aminoglycoside Resistance and Genes Encoding Aminoglycoside-Modifying Enzymes in Enterococcus faecalis and Enterococcus faecium Isolated in a University Hospital in Tokyo

[摘要] High-level aminoglycoside resistance (HLAR) limits treatment options for invasive enterococcal infections. We examined the prevalence of HLAR, carriage of genes encoding aminoglycoside-modifying enzymes, and production of β-lactamase using the disk diffusion method, polymerase chain reaction, and a nitrocefin-based test, respectively, in Enterococcus faecalis and Enterococcus faecium isolated from patients at a university hospital in Tokyo in 2010. Of the 100 E. faecalis isolates analyzed, 30 isolates had high-level resistance (HLR) to gentamicin, and 22 isolates had HLR to streptomycin. Of the 40 E. faecium isolates analyzed, 9 isolates had HLR to gentamicin, and 9 isolates had HLR to streptomycin. Of the 39 gentamicin-HLR enterococcal isolates, 24 isolates were non-HLR to streptomycin. All 39 isolates with HLR to gentamicin as well as 19 of 101 without HLR carried aac(6′)-Ie-aph(2′′)-Ia . Carriage of ant(6′)-Ia was confirmed in 25 of 31 streptomycin-HLR isolates. Production of β-lactamase was documented in none of the E. faecalis and E. faecium isolates. Whole-genome sequencing analysis revealed that all but one E. faecalis isolate that carried aac(6′)-Ie-aph(2′′)-Ia and ant(6′)-Ia belonged to sequence type (ST) 4 ( n = 8), ST16 ( n = 4), or ST179 ( n = 9). Nevertheless, most of the pairs of isolates had > 10 single-nucleotide polymorphisms even among the isolates of the same ST.

[学科分类] 传染病学