Variations of CHROMagar Acinetobacter to detect imipenem-resistant Acinetobacter baumannii-calcoaceticus complex

Background: Acinetobacter baumannii-calcoaceticus complex (ABC) isolates are often multidrug-resistant, including to carbapenems. Chromogenic media can facilitate the rapid detection of Gram-negative bacteria, often with the addition of supplements to a base chromogenic medium to detect resistance. We examined various combinations of available media to detect imipenem resistance among 107 ABC clinical isolates. Methods: CHROMagar Orientation, CHROMagar KPC, and CHROMagar Acinetobacter, by itself, with Acinetobacter supplement, with KPC supplement, or CHROMagar Acinetobacter with increasing concentrations (1, 2.5, and 5 ml/l) of a new CR102 supplement, were examined. Results: Sensitivity for the detection of isolates was high (> 98%) for all formulations. Specificity was high for CHROMagar Acinetobacter with 2.5 ml/l and 5 ml/l of the CR102 supplement, at 95.3% and 97.7%, respectively, with positive predictive values of 97% and 98.5%. Negative predictive values of these 2 formulations were 100%. Conclusions: CHROMagar Acinetobacter with the addition of the CR102 supplement at 2.5 ml/l and 5ml/l is highly sensitive and specific for the detection of imipenem-resistant ABC, and may be useful for the rapid detection of imipenem-resistant ABC in clinical samples.