Background: The purpose of this study was to evaluate a new rapid colorimetric method for detection of ESBL producing Klebsiella pneumoniae. This method is capable to detect ESBL producing bacteria, by a color change in the colorimetric medium within 5 to 6 hours, which is due to metabolic activity of growing bacteria. The method is based on CLSI standard disk diffusion method performed on the colorimetric medium.
Methods: Fifty-four clinical isolates of Klebsiella pneumoniae obtained from Pasteur Institute of Iran and Iran University of Medical science were used for evaluation of this medium. 25 ESBL positive and 29 ESBL isolates were compared by CLSI disk diffusion ESBL (phenotypic confirmatory test) criteria by Mueller Hinton and colorimetric medium. The tested antibiotics included ceftazidim (CAZ), ceftazidime + clavulanate (CZA), cefotaxime (CTX), cefotaxime +clavulanate (CTC).
Results: A color change was observed for ESBL producing bacteria within 5 to 6 hours by the colorimetric medium. These results were in line with the results of overnight incubation on Mueller Hinton agar.
Conclusion: This new colorimetric medium can be used for rapid and reliable detection of ESBL producing Klebsiella pneumoniae within 5 to 6 hours.