Evaluation of FASTinov for rapid antimicrobial susceptibility testing in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is a critical priority pathogen due to its high resistance rates and limited treatment options. Rapid antimicrobial susceptibility testing (rAST) is essential to optimize therapy, particularly because resistance mechanisms in P. aeruginosa often arise from adaptive genetic expression rather than specific resistance genes. FASTinov, a flow cytometry-based rAST system, was developed to address this challenge by providing phenotypic susceptibility results within hours. In this study, we assessed FASTinov's performance for rapid antimicrobial susceptibility testing (rAST) in 100 P. aeruginosa strains, using broth microdilution as the reference method. For clinical relevance, we also included the MicroScan WalkAway system as a comparator. FASTinov demonstrated a categorical agreement of 99% across the tested antibiotics, with particularly strong agreement for cephalosporins. Notably, FASTinov significantly reduced the time to results, delivering susceptibility data in an average of 3.15 h (CI 95% 3.13-3.17), compared to 28.88 h (CI 95% 20.71-37.04) for standard methods. Additionally, the system exhibited lower rates of major and very major errors compared to MicroScan, further reinforcing its reliability. These findings highlight FASTinov as a promising rAST system capable of providing rapid and accurate susceptibility profiles directly from bacterial colonies. Further research is warranted to evaluate its clinical impact on patient outcomes and cost-effectiveness.