In vitro activity of fosfomycin against blaKPC-containing Klebsiella pneumoniae isolates, including those nonsusceptible to tigecycline and/or colistin.

In vitro activity of fosfomycin was evaluated against 68 bla(KPC)-possessing Klebsiella pneumoniae (KpKPC) isolates, including 23 tigecycline- and/or colistin-nonsusceptible strains. By agar dilution, 93% of the overall KpKPC were susceptible (MIC(50/90) of 16/64 microg/ml, respectively). The subgroup of 23 tigecycline- and/or colistin-nonsusceptible strains showed susceptibility rates of 87% (MIC(50/90) of 32/128 microg/ml, respectively). Notably, 5 out of 6 extremely drug-resistant (tigecycline and colistin nonsusceptible) KpKPC were susceptible to fosfomycin. Compared to agar dilution, disk diffusion was more accurate than Etest.