**The Antibacterial Activity of Lavender Essential Oil Alone and In Combination with Octenidine Dihydrochloride against MRSA Strains**

**Paweł Kwiatkowski 1,\*, Łukasz Łopusiewicz 2, Mateusz Kostek 1, Emilia Drozłowska 2, Agata Pruss 3, Bartosz Wojciuk 1, Monika Sienkiewicz 4, Hanna Zieli ´nska-Bli ´zniewska <sup>4</sup> and Barbara Doł ˛egowska <sup>3</sup>**


Academic Editor: Igor Jerkovi´c

Received: 23 November 2019; Accepted: 24 December 2019; Published: 26 December 2019

**Abstract:** In the post-antibiotic era the issue of bacterial resistance refers not only to antibiotics themselves but also to common antiseptics like octenidine dihydrochloride (OCT). This appears as an emerging challenge in terms of preventing staphylococcal infections, which are both potentially severe and easy to transfer horizontally. Essential oils have shown synergisms both with antibiotics and antiseptics. Therefore the aim of this study was to investigate the impact of lavender essential oil (LEO) on OCT efficiency towards methicillin-resistant *S. aureus* strains (MRSA). The LEO analyzed in this study increased the OCT's susceptibility against MRSA strains. Subsequent FTIR analysis revealed cellular wall modifications in MRSA strain cultured in media supplemented with OCT or LEO/OCT. In conclusion, LEO appears to be a promising candidate for an efficient enhancer of conventional antiseptics.

**Keywords:** MRSA; lavender essential oil; octenidine dihydrochloride; synergistic activity; FTIR
