Selective Chromogenic Medium for Detection of Meropenem-Resistant Pseudomonas aeruginosa in Respiratory Samples

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