Antibacterial Effect of Lemongrass (_Cymbopogon citratus_) against the Aetiological Agents of Pitted Keratolyis  
[PERSON]  
1 Department of Medical Microbiology and Immunology, Medical School, University of Pecs, Szigetti ut 12, H-7624 Pecs, Hungary, srcbtabt,[EMAIL_ADDRESS] (B.S.), [EMAIL_ADDRESS] (T.P.)  
[PERSON]  
2 Department of Pharmacogos, University of Pecs, Rokius u.  
protease enzymes of the colonizing bacteria [5]. _Kytococcus_ (formerly _Microoccus_) _sedentarius_ and _Dernatophilus congolensis_ were documented as aetiological agents of PK [6; 7], and in a very recent study the aetiological role of the Gram-positive, spore-forming _Bacillus thuringiensis_ was demonstrated [8].  
Today, the treatment of PK is primarly empiric, and is based on antibiotics, such as erythromycin, tetracycline and clindamycin. However, the spread of antibiotic resistance among the bacterial isolates limits therapeutic success [9].  
Due to their antibacterial features, the use of essential oils (EOs) is a potential way to combat emerging antibiotic resistance [10]. EOs are secondary metabolites of aromatic plants consisting of \(\sim\)20-60 components at different concentrations. There can be major compounds at relatively high concentrations (20-70%) compared to other components present in trace amounts [11].  
_Cymbopogon citratus_ (DC.) Stapf, commonly known as lemongrass, is a coarse grass with a strong lemon taste. It is a perennial herb widely cultivated in the tropics and sub-tropics [12]. Researchers have found that lemongrass holds antidepressant, antioxidant, antiseptic, astringent, nervine and sedative properties [13]. Furthermore, the antibacterial activity of lemongrass oil against a diverse range of species comprising Gram-positive and Gram-negative organisms, along with yeast and fungi, was formerly established [13; 14; 15]. The major component of lemongrass EO is citral, consisting of the two geometric isomers citral A (geranial) and citral B (neral) [16]. Other compounds identified in lemongrass EO include limonene, citronellal, \(\beta\)-myrcene and geraniol [16], along with trace compounds [17]. On the compound level, citral, the major component of lemongrass EO, is known to be antibacterial, but other compounds have not yet been studied in detail from this perspective. Furthermore, an earlier study has also reported about the capacity of thyme EO, cinnamon EO and lemongrass EO to reduce viable spores [18], which could be an important feature of these EOs, as _B. thuringiensis_, one aetiological agent of pitted keratolysis, is a typical spore-forming bacterium species, and spore fomation can influence survival and therefore therapeutic success [19].  
The aim of this study was to screen the antibacterial potential of certain EOs against all the known aetiological agents of pitted keratolysis and try to reveal the most effective EO from an antibacterial point of view, including growth- and spore-formation inhibitions and bactericidal effects. To best of our knowledge, this is the first study where these aspects were investigated in relation to the aetiological agents of PK, by combining antibacterial screenings, such as the drop plate method, minimal inhibitory and minimal bactericidal concentration determinations, spore-formation suppression test and analytic methods such as (TLC-DB) and headspace solid-phase microextraction followed by gas chromatography-mass spectrometry (HS-SPME/GC-MS) and thin-layer chromatography combined with direct bioautography (TLC-DB).