Antibiotic Susceptibility, Clonality, and Molecular Characterization of Carbapenem-Resistant Clinical Isolates of Acinetobacter baumannii from Washington DC

Figure 4

(a) Phenotypic tests to detect MBL production. The upper left panel shows the negative combined disk diffusion test (CDDT) and the upper right panel is a positive CDDT with increase in zone diameters of imipenem disks (≥4 with imipenem/0.1 M EDTA and ≥7 with imipenem/0.5 M EDTA). The lower left panel shows a negative EDTA-disk synergy test (DST) while the lower right panel shows a positive DST with a synergistic inhibition zone between imipenem disk and imipenem with 0.5 M EDTA. (b). Colony PCR amplification for blaVIM gene. Lanes 1-28 represent isolates A1, A2, A3, A5, A7, A8, A10, A11, A14, B1, B2, B3, B4, B8, B9, B10, B14, B16, C4, C5, C9, C11, C20, C22, C24, H4, H8, and H11, respectively. M is a 100 bp size marker ladder (HyperLadder™, Bioline).

(a)

(b)