By using the Imipenem-EDTA disk method, a very high percentage of imipenem resistant Acinetobacter spp. (97%) and Pseudomonas aeruginosa (100%) isolates showed metallo-β-lactamase activity. This finding is consistent with reports from other tertiary care hospitals, [10] giving the evidence that acquired MBLs can rapidly emerge and establish a condition of endemicity in certain epidemiological settings. A majority of our isolates also showed resistance to other important groups of antibiotics including third generation cephalosporin, aminoglycoside and quinolone, which is a characteristic of majority of metallo-β-lactamases producing isolates. [11] A number of MBLs producers in both organisms showed significant difference between zone of inhibition by imipenem and imipenem plus EDTA disk. When compared with non-MBL producers the average zone difference for the MBL producers was 15 mm versus 2 mm for the non-MBL producers, thus making this test reliable for initial screening of the MBL production in clinical isolates.