Introduction: Pseudomonas aeruginosa (PA) is an opportunistic mucosal human pathogen responsible for a wide range of acute and chronic infections. PA releases outer membrane vesicles (OMVs) in all situations and environments. OMVs are bilayered proteolipids ranging in diameter from 50 to 250 nm. Recent studies have demonstrated that OMVs are related to PA pathogenesis. According to strain-dependent components of OMV, in this study, we aimed at identifying significant physicochemical differences among OMVs from lab strain ATCC 17933, an antibiotic-susceptible and an antibiotic-resistant PA clinical strains. Methods: OMVs of the three strains were purified using differential centrifugation with deoxycholate and EDTA. Chemical analyses were assessed using nano-drop, SDS-PAGE and the limulus amebocyte lysate (LAL) test. Moreover, electron microscopy was performed to verify the stability and totality of the extracted OMVs. Results: The nanodrop method and the LAL test showed that total protein and endotoxin concentrations were significantly different among all the 3 mentioned strains. In addition, the quality control of OMVs illustrated that the lab and the antibiotic-susceptible strains were approximately similar in terms of the vesicle yield and size; however they differed in protein contents. Moreover, OMVs generated from the resistant strain had a higher density, smaller size and sharper protein bands as observed by electron microscopy and SDS-PAGE, respectively. Endotoxins measurement were 2.8, 2.9 and 3 EU/ml for OMVs from the lab, the antibiotic-susceptible and the resistant strains, respectively. Conclusion: The results of the current study demonstrated that OMVs of the resistant PA strain may produce vesicles with a particular composition. This characterization profile provides a basis for future studies to elucidate immune responses to OMVs from PA and developing vaccines against Pseudomonal infections as a common nosocomial infection with extremely high resistance to antibiotics.

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