Antimicrobial efficacy of Mutellina purpurea essential oil and α-pinene against Staphylococcus epidermidis grown in planktonic and biofilm cultures

Abstract

The staphylococcal biofilms are the most frequent causes of nosocomial infections and infections on indwelling medical devices. Staphylococcus epidermidis biofilms exhibit typically up to 1000 times greater resistance to antibiotics than the planktonic cells. Because the essential oils are described as antimicrobial agents, the aim of this study was to investigate the antimicrobial efficacy of Mutellina purpurea essential oil (EO) and α-pinene against planktonic and biofilm cultures of S. epidermidis ATCC 35984 and the clinical strain S. epidermidis 37IINL. The obtained values of MIC (minimal inhibitory concentration) were: 0.625mg/mL of α-pinene for both strains, 0.312 and 0.625mg/mL of EO, while 1.5 and 2.5mg/mL of thymol as a reference substance for S. epidermidis ATCC 35984 and S. epidermidis 37IINL planktonic cells respectively. The lowest EO concentration completely inhibiting the biofilm formation (MBIC – minimal biofilm inhibitory concentration) for both strains was 0.625mg/mL; α-pinene caused the same result at a slightly higher concentration with MBIC=1.25mg/mL.