The Therapeutic Potential of West Indian Lemongrass (Cymbopogon citratus) Essential Oil-Based Ointment in the Treatment of Pitted Keratolysis.

Background: Due to their antibacterial activities, essential oils can be potential alternatives to antibiotics in certain cases. West Indian lemongrass (Cymbopogon citratus) essential oil (LEO) is effective against a broad range of bacteria by inhibiting spore formation, and is considered safe. In this study, we demonstrated its therapeutical potential in the treatment of pitted keratolysis (PK), a superficial skin infection affecting the pressure-bearing areas of plantar surfaces. Methods: For in vitro antibacterial efficacy testing, LEO was mixed into different ointment bases, including Hydrogelum methylcellulose FoNo VIII., Ungentum oleosum FoNo VIII. (Ung. oleoso), Unguentum stearini FoNo VIII. (Ung. stearin), and Vaselinum cholesterinatum FoNo VIII. (Vasel. cholest.), at different concentrations of 1, 3, and 5%. These formulations were tested on representatives of three bacterial species associated with PK: Kytococcus sedentarius, Dermatophilus congolensis, and Bacillus thuringiensis. Results: In the in vitro tests, Hydrogelum methylcellulose (HM) gel best supported the antibacterial effects of LEO, reducing the number of living bacteria on agar plates by 4-5 orders of magnitude in a concentration-dependent manner during the 30 min exposure times. This was also confirmed by the Franz diffusion cell drug release test; after 30 min, several active compounds could be detected in the HM samples, in contrast to the other bases. Shelf-life experiments showed that the HM base supported the antibacterial features of 3% LEO for at least 2 years without significant loss of efficacy. Conclusions: Our study highlights that ointments containing essential oils potentially have a place in the treatment of PK. Therefore, antibiotics may potentially be replaced for the treatment of PK, thereby reducing environmental antibiotic pressure, which is one of the driving forces behind the spread of antibiotic resistance.