A Selective Chromogenic Medium for Detecting Meropenem-Resistant Pseudomonas aeruginosa in Respiratory Samples

<b>Background/Objectives</b>: Meropenem is widely used to treat Pseudomonas aeruginosa infections; however, the pathogen's increasing resistance compromises its efficacy. In this study, we aimed to develop a selective culture medium for detecting the presence of meropenem-resistant <i>Pseudomonas aeruginosa</i> in respiratory specimens within 24 h. <b>Methods</b>: The medium's performance was challenged using a collection of 130 clinical <i>Pseudomonas aeruginosa</i> strains (of which 85 were meropenem-susceptible, 14 were meropenem-intermediate, and 21 were meropenem-resistant). Subsequently, clinical validation was carried out using 130 respiratory samples. <b>Results</b>: The selective medium demonstrated excellent sensitivity (average 98.7%) and specificity (average 90%) across bacterial concentrations ranging from 1 × 10⁴ to 1 × 10⁸ CFU/mL, and a high negative predictive value (average 99.2%) compared to the broth microdilution (BMD) method. Clinical validation with bronchoalveolar lavage (BAL) and tracheobronchial aspirate (TBA) clinical specimens (N = 130) revealed a strong performance, with 92,3% categorical agreement. <b>Conclusions</b>: This method accelerates susceptibility testing, is user-friendly, and delivers reliable results, contributing to the optimization of empirical treatment for respiratory tract infections.