Antimicrobial and antibiofilm potential of biosurfactants as novel combination therapy against bacterium that cause skin infections

Biosurfactants (BS) are amphiphilic molecules produced as a secondary metabolite by various bacteria and yeast species and are secreted extracellularly. BS have shown to work in synergy with antibiotics and also demonstrate strong antimicrobial and anti-adhesive characteristics. This coupled with their low toxicity makes them suitable candidates as combination therapies to combat skin infections. In this study, the aim was to investigate the in-vitro antimicrobial and anti-biofilm properties of mannosylerythritol lipids (MELs) produced by Moesziomyces aphidis against Staphylococcus aureus DSM-20231, Streptococcus pyogenes ATCC-19615, Staphylococcus epidermidis DSM – 28319, Pseudomonas aeruginosa DSM-3227, Escherichia coli ATCC – 25 922 and Propionibacerium acnes DSM- 1897. MELs are most predominantly used in skin creams, thus, a rationale was developed to investigate antibiotics used to treat bacterial skin infections, namely, Polymyxin B Sulphate, Neomycin, Mupirocin and Bacitracin. Minimum inhibitory concentration (MIC) values where determined for each antibiotic and BS per bacterium using the broth dilution technique based on CLSI guidelines. BS where extracted by solvent extraction and characterised using Mass Spectrometry – High Performance Liquid Chromatography, standards were quality assured using MALDI-TOF. Flow cytometry determined percentage dead versus alive for each antibiotic, BS and combination of antibiotic and BS. Scanning Electron Microscopy determined the effect of the BS on the bacterial cell walls. This study proves that BS work synergistically with antibiotics to increase the MIC of the antibiotics resulting in a substantial decrease in antibiotic use and at lower concentration. The use of BS combination therapy has the potential to reduce resistant rates and also lengthen the time taken for resistance to develop.