Effects of Cream Containing Rhamnolipid Microbial Surfactants from Pseudomonas aeruginosa MR01 on Growth Inhibition of Staphylococcus aureus

Abstract

Background and purpose: Dramatic increase in antibiotic-resistant bacteria highlights the need for new compounds with more effective antibacterial properties and biotechnology could be useful in producing these metabolites. The present study aimed at investigating the effects of rhamnolipid microbial surfactants in a cream-based formulation on growth inhibition of Staphylococcus aureus using in vitro and animal models. Materials and methods: The inhibitory effects of rhamnolipids produced by Pseudomonas aeruginosa MR01 on the growth of S. aureus were investigated by disk diffusion method. Then, the effects of dirhamnolipid compounds on the survival and morphology of bacteria were studied using estimation of colony forming units (CFUs) and scanning electron microscopy (SEM). The di-rhamnolipid-containing cream was prepared and its effects on inhibition of the bacterial growth was evaluated in in vitro and animal subjects. Results: Disk diffusion tests showed a minimum inhibitory value of 30mg/disk for aqueous solutions of mono- and di-rhamnolipids, and 20mg/disk and 10mg/disk for mono- and di-rhamnolipid solutions in Dimethyl sulfoxide (DMSO), respectively. The aqueous solution of di-rhamnolipids at 20mg/ml resulted in lack of viable cells of S. aureus. SEM images showed changes in spherical shape of S. aureus during rhamnolipid treatments. Di-rhamnolipid-containing cream led to inhibition of bacterial growth in vitro on agar medium. Moreover, findings in rats indicated inhibition of bacterial growth in wound areas after 20 days of treatment with the cream. Conclusion: In current study, Di-rhamnolipids demonstrated inhibitory effects on the growth of S. aureus. These compounds in cream formulation could also have antibacterial effects.

Keywords

• rhamnolipids
• cream
• antibacterial
• staphylococcus aureus
• animal model