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.
