Evaluation of a New Colorimetric Medium for Detection of Extended Spectrum β-lactamases (ESBLs) Producing Isolates of Entrobacteriaceae family

Due to the increased growth of bacteria producing ESBL, among the members of the Enterobacteriaceae family, monitoring and treatment of nosocomial infections are important, especially caused by ESBL-producing clinical isolates belonging to this family. The aim of this study is to evaluate a rapid method, using new colorimetric culture was made at the University of Al-Zahra (Tehran, Iran).The used method to detect ESBLs, according to disk diffusion method based on CLSI on colorimetric culture and the results of it, compared with the Müller-Hinton agar for disk diffusion method.
In this study, the clinically isolated samples belonged to the Enterobacteriaceae family which was evaluated in both Müller-Hinton agar medium and colorimetric culture using ceftazidime (CAZ), ceftazidime clavulanate (CZA), cefotaxime clavulanate (CTC) and Cefotaxime (CTX) discs.
Results & Because of the metabolic activity of bacteria, a color change occurred from red to yellow in colorimetric culture after 5-6 hours and red inhibitory zone created around the disc. The obtained results from the colorimetric method are same with the results of Müller-Hinton agar method for disk diffusion after a day.