Formulation Development of a Topical Probiotic Gel for Antidermatophytosis Effect

Background: Topical drug delivery is a painless route of drug administration. Skin is one of the most easily accessible parts of human body for topical administration and also is a main route of topical drug delivery system. There are different skin diseases and infections caused by fungus. An antifungal compound is a pharmaceutical fungicide used to treat mycoses such as dermatophytes which have the ability to attack keratinized tissues and used keratin cause dermatophytosis, the most common human contagious fungal disease. Because of drug resistance, side effects and cytotoxicity associated with long-term treatment with antifungal drugs, finding new useful drugs to treat fungal infections is necessary. Objectives: The purpose of the present study was to formulate topical gel containing stabilized extract of Lactobacillus as an antidermatophytic preparation and evaluate its physicochemical properties. Materials and Methods: Lactobacillus casei was cultured in MRS anaerobically and then its extract was collected by separating the bacterial cells with centrifugation. Firstly, antifungal activity of the extract against four dermatophyte species (Tricophyton rubrum, Tricophyton verocosum, Microsporum canis, and Microsporum gypseum) was done using the well-plate method. The macrodilution method was used to determine the minimum inhibitory concentration (MIC) of the probiotic extract in the range of 0.0625 mg/mL to 1 mg/mL. To select the best gel formulation, one general formula was considered and then corrected by changing the polymer ratio. Gel formulations were characterized for monotonousness, probiotic extract content, pH determination, viscosity measurement, grittiness and antifungal activity in comparison to topical cream of clotrimazole 1%. Results: The results showed the same effect of the probiotic extract against 4 pathogens; however, the greatest average zone of inhibition was measured 34 mm against T. rubrum. The MIC test showed that stabilized probiotic extract had more antidermatophyte effect compared to supernatant (P < 0.01). Formulation containing 5% probiotic extract (F5) was chosen as the best antidermatophyte topical gel because of its more stability. Also, all formulations were studied for antifungal activity compared to clotrimazole, and F5 was found to be significantly more effective than clotrimazole (P < 0.01). Conclusions: The results of this study show that the beneficial effect of Lactobacillus casei is related to its metabolites. A formulated gel shows a significant antidermatophytosis activity compared to clotrimazole.