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.