Fig 1.

MALDI-TOF MS spectra showing the most representative imipenem peaks. Spectra were determined with the incubation solution alone (0.46% NaCl) (A), imipenem-cilastatin solution (B), an OXA-24-like-producing Acinetobacter strain (C), and an IMP-8-producing Acinetobacter strain (D). Peaks represent [thienamycin-H⁺] at m/z 274, imipenem at m/z 300, cilastatin-Na⁺ at m/z 381, and imipenem–α-cyano-hydroxy-cinnamic acid at m/z 489. Arrows and asterisks show peaks due to imipenem-cilastatin addition that were nonresponsive to resistant Acinetobacter incubation. au, arbitrary units.