FIG. 5.
Differential carbapenem susceptibility of N. cyriacigeorgica and synergistic activity of amikacin and imipenem. (A) Antimicrobial susceptibility and synergy were evaluated for amikacin (upper right), imipenem (upper left/lower right), and meropenem (lower left) by disk diffusion. (B) MICs of imipenem (left) and meropenem (right) were determined by Etest. Results for type VI strain ATCC 14759T are shown and are representative of all N. cyriacigeorgica clinical isolates. N. cyriacigeorgica strains also produced a brown pigment when grown on Mueller-Hinton agar that was clearly visible on the plate reverse (not shown). Note that, based upon preliminary testing, disks were spaced at a nonstandard 3.5-cm distance apart in order to best illustrate synergy between amikacin and imipenem.