A Biosurfactant-Sophorolipid Acts in Synergy with Antibiotics to Enhance Their Efficiency

Abstract

Sophorolipids (SLs), biosurfactants with antimicrobial properties, have been tried to address the problem of antibiotic resistance. The synergistic action of SL and antibiotics was checked using standard microdilution and spread plate methods. With Staphylococcus aureus, SL-tetracycline combination achieved total inhibition before 4 h of exposure while tetracycline alone couldnot achieve total inhibition till the end of 6 h. The inhibition caused by exposure of bacterium to SL-tetracycline mixture was ~25% more as compared to SL alone. In spite of known robustness of gram-negative bacteria, SL-cefaclor mixture proved to be efficient against Escherichia coli which showed ~48% more inhibition within 2 h of exposure as compared to cefaclor alone. Scanning electron microscopy of the cells treated with mixture revealed bacterial cell membrane damage and pore formation. Moreover, SLs being a type of asymmetric bola, they are expected to form self-assemblies with unique functionality. This led to the speculation that SLs being amphiphilic in nature can span through the structurally alike cell membrane and facilitate the entry of drug molecules.

Sophorolipid biosurfactants: Possible uses as antibacterial and antibiofilm agent

“…The biofilm formed was treated with sophorolipid sample S1 (which was selected as no significant differences were observed to S2 sample on planktonic cells). In agreement with previous studies [18,19] were are able to confirm here that Bacillus subtilis BBK006 biofilm cells are sensitive to some extent to sophorolipids (S1) which was seen by the reduction of number of active cells upon exposure and the appearance of some inactive reddish-brown fluorescing cells (Fig 2B). The results of the present study indicate that sophorolipids have the potential to be used for biofilm disruption and removal.…”

“…Bacillus subtilis BBK006 was able to form biofilms like those observed for strains of Pseudomonas aeruginosa and Staphylococcus epidermidis [39]. In agreement with previous studies [40,41] we are able to confirm here that Bacillus subtilis BBK006 biofilm cells are sensitive to some extent to sophorolipids as seen by the reduction of number of active cells upon exposure and the appearance of some inactive reddish-brown fluorescing cells (Fig 2B). These results indicate that sophorolipids have the potential to be used for efficient removal of detrimental biofilms.…”

“…Further studies on the action of different natural sophorolipids, alone or as adjuvants in combination with other compounds such as antibiotics or enzymes is of great importance. Such combination may play an important role on the stability of the EPS during biofilm formation [40,48] which can lead to new approaches to combat the establishment or disrupt biofilms formed by different bacterial species. It is also important to take into account that the combinations treatments may behave differently for some species.…”

Adjuvant Antibiotic Activity of Acidic Sophorolipids with Potential for Facilitating Wound Healing

“…In contrast, biosurfactants are a diverse group of surfactants produced by certain species of yeast or bacteria, which represent a more sustainable and perceived environmentally friendly alternative to traditional surfactants. There is increasing evidence that microbial biosurfactants, as well as possessing industrially valuable properties of detergency, emulsification, and foaming, also have significant bioactivities, including inhibitory or antibacterial adjuvant activities against various microorganisms (6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18) and specific anticancer activity (19).…”

“…The antimicrobial effects of SLs are dependent on the SL structure and class of bacteria examined, yet SLs are predominantly produced and used as mixtures, with very few studies examining the effects of SL samples containing well-defined and purified single congeners. In addition, sophorolipids have virucidal and antibiotic adjuvant characteristics (6,7) and may have potential applications in infection, wound healing, or antiinflammatory contexts (8,19). However, the widely variable methods of production, extraction, and purification, coupled with the diversity of possible SL structures and a lack of sufficient characterization of preparations, make comparison between data from in vitro and in vivo studies difficult to interpret.…”