Evaluation of the Effect of Outer Membrane Vesicles (EcN) as an Effective and New Postbiotic on Inhibiting the Growth of Staphylococcus Aureus

The use of antibiotics is one of the most important ways to deal with bacterial infections. However, the improper of antibiotics and the emergence of drug resistance have compromised the effectiveness of antibiotics. Staphylococcus aureus causes a wide range of clinical diseases, and infections caused by this pathogen are increasing rapidly in the community and hospitals. Today, the treatment of this pathogen has become a challenging issue due to the emergence of multi-drug resistant strains such as MRSA (Methicillin-resistant Staphylococcus aureus). Since the antibiotic resistance of pathogens has become a global public health problem, the introduction of novel drug candidates against pathogens has become a necessity. Recently, there have been more reports on the use of OMVs as active antibacterial agents or carriers of antibiotics, which indicates the potential of OMVs in antibacterial therapy. The study aims to evaluate the effect of outer membrane vesicles of E. coli Nissle 1917 on the growth ability of Staphylococcus aureus strains.

The present study was conducted on 50 samples of Staphylococcus aureus isolated from wounds, urine, and blood. In this study, to emphasize the beneficial effect of OMVs derived from the probiotics (EcN) as a postbiotic agent, the outer membrane vesicles were extracted using the ultracentrifugation method. After confirming the presence of protein content by the SDS-PAGE method, we confirmed the structure and maintained the integrity of the vesicles during the extraction process using a FE-SEM electron microscope. Finally, to evaluate the effect of these structures on the viability of Staphylococcus aureus, we used the MTT method.

In the analysis of the protein pattern by SDS-PAGE, protein bands in the range of 15 to 100 kDa were observed. Also, the structure and integrity of outer membrane vesicles in the range of 40 to 100 nm were confirmed by an electron microscope. Finally, we saw a significant decrease in growth inhibition of all Staphylococcus aureus strains in the presence of outer membrane vesicles caused by EcN.

Considering the non-proliferative nature of OMV structures and their effects similar to probiotics, as well as, results obtained due to the significant reduction of growth inhibition of Staphylococcus aureus strains in the presence of outer membrane vesicles caused by EcN, it seems that these compounds can be a powerful tool for developing therapeutic approaches for human health and a better lifestyle.