Investigation of the synergistic effect of glycolipid biosurfactant produced by Shewanella algae with some antibiotics against planktonic and biofilm forms of MRSA and antibiotic resistant Acinetobacter baumannii.

To tackling antibiotic resistance and the appearance of multidrug-resistant (MDR) strains, one current approach is the combined use of biosurfactants with antibiotics to increase their efficacy. The antimicrobial ability of biosurfactant produced by Shewanella algae strain B12 was examined using the agar well diffusion method versus some resistant Gram-negative and Gram-positive bacteria. The Minimum Inhibitory Concentration (MIC) of Glycolipid-Biosurfactant of B12 (GBB12) was performed by the broth dilution technique. The inhibition of biofilm formation, disruption of biofilm, and reducing the population of viable cells in biofilm were evaluated by the microtiter plate method. Finally, Scanning Electron Microscopy (SEM) analysis was used to confirm the disruption of the cell membrane by GBB12. In all experiments, when GBB12 was added to antibiotics (except Amikacin), the antimicrobial activity was increased. The synergistic effects of GBB12 and antibiotics (Ciprofloxacin and Gentamycin) against Methicillin-Resistant Staphylococcus aureus (MRSA) and Acinetobacter baumannii were confirmed by the Fractional Inhibitory Concentration Index (FICI). GBB12-Gentamycin mixture almost completely inhibits the formation of A. baumannii biofilm, reaching 99.8% inhibition. Also, the rate of MRSA biofilm inhibition treated with GBB12-Ciprofloxacin mixture was found to be 99.4%. biosurfactant-antibiotic mixture could be adequate replacements for traditional antibiotics in the near future. This study shows the potential of GBB12 as antimicrobial and antibiofilm agent.