Abstract: OBJECTIVE To investigate the impact of 5% sodium sulfate-induced demucoidization of mucoid Pseudomonas aeruginosa (mPA) on its growth status and drug susceptibility test results, aiming to optimize the drug susceptibility test method and provide a basis for rational clinical drug use. METHODS Clinically isolated mPA was treated with 5% sodium sulfate to observe phenotypic changes. The alginate content was determined by bacterial growth curve and enzyme-linked immunosorbent assay (ELISA), and the mucA and algT genes were sequenced and analyzed for expression levels. The Kirby-Bauer (KB) method and minimum inhibitory concentration (MIC) method were used to compare the drug susceptibility test results of the strain before and after demucoidization. RESULTS Sodium sulfate induction significantly reduced the alginate content of the strain (P<0.05), but did not cause mutations in the mucA and algT gene sequences. After demucoidization, the expression of algT and algD genes decreased, and the phenotype of the strain changed. After demucoidization, the result consistency between the KB method and MIC method improved (Kappa=0.631, P<0.001), and the concentration changes in inhibition zone and MIC were biologically significant (P<0.05), but there was no statistically significant difference in overall drug susceptibility judgment. CONCLUSIONS 5% sodium sulfate can effectively induce demucoidization of mPA without causing mutations in key regulatory genes. Demucoidization improves the growth status of the strain, enhances the consistency between the KB method and the MIC method, and results in more stable and accurate drug susceptibility test, which is more aligned with the CLSI-M100 standards.