Antimicrobial potency of single and combined mupirocin and monoterpenes, thymol, menthol and 1,8-cineole against Staphylococcus aureus planktonic and biofilm growth

Abstract

Staphylococcus aureus is one of the most commonly isolated microbes in chronic rhinosinusitis (CRS) that can be complicated due to the formation of a staphylococcal biofilm. In this study, we investigated antimicrobial efficacy of single mupirocin and three types of monoterpenes (thymol, menthol and 1,8-cineole) as well as mupirocin-monoterpene combinations against S. aureus ATCC 29213 and 5 methicilin-resistant S. aureus strains (MRSA) grown in planktonic and biofilm form. MIC against planktonic bacteria as well as minimum biofilm-eliminating concentrations (MBECs) and minimum biofilm inhibitory concentrations (MBICs) were determined by TTC and MTT reduction assay, respectively. The MICs of mupirocin (0.125-0.156 μg ml(-1)) were three orders of magnitude lower than the MICs of monoterpenes, which were as follows: thymol (0.250-0.375 mg ml(-1)) > menthol (1 mg ml(-1)) > 1,8-cineole (4-8 mg ml(-1)). Mupirocin-monoterpene combinations showed indifferent effect as compared with MICs of single substances. Mupirocin (0.016-2 mg ml(-1)) failed to destroy the biofilm. The MBECs of thymol and menthol were two- to sixfold higher than their MICs, while 1,8-cineole exerted a weak antibiofilm effect with MBECs 16- to 64-fold higher than MICs. Mixture of mupirocin and 1,8 cineole exerted a potentiated biofilm-eliminating effect, mupirocin-menthol showed antagonism, while effect of thymol-mupirocin mixture was inconclusive. MBICs of antimicrobials were close to their MICs, except 1,8-cineole, MBIC was about three- to fivefold higher. Dominant synergy was observed for mixtures of mupirocin and menthol or thymol, whereas mupirocin-1,8-cineol exerted an indifferent or additive biofilm inhibitory effect. Particular combinations of mupirocin and the monoterpenes could be applied in CRS therapy in order to eliminate or prevent bacterial biofilm growth.

Evaluation of the antimicrobial activity and cytotoxicity of different components of natural origin present in essential oils

“…THY and CRV produced even higher reductions of about 5 and 6 logs, respectively. As expected, the concentrations needed to retard biofilm growth and development were higher than the MIC values retrieved for planktonic bacteria (Table 1) but they are in the same range than those reported in the literature (32).…”

“…The antibacterial effect of several components present in different essential oils reported as bactericidal, such as carvacrol (31), thymol (32), cinnamaldehyde (33), eugenol (EU) (34), β-caryophyllene (35) and rosmarinic acid (36) were studied. Squalene, a well-known natural antioxidant (37) was also included in the study for comparison.…”

Chemical Characterization of Lavandula dentata Essential Oil Cultivated in Chile and Its Antibiofilm Effect against Candida albicans

“…These concentrations were used as a reference for the morphogenesis, adhesion, biofilm formation, and biofilm viability assays. Among the essential oil-derived compounds, 1,8-cineol or eucalyptol and β-pinene are well known for their antimicrobial activity and are related to the antifungal effect of the essential oils from various species [21][22][23]. This is in agreement with the results obtained from the disc diffusion and microdilution susceptibility assays in this study.…”

African peppermint (Mentha piperita) from Morocco: Chemical composition and antimicrobial properties of essential oil

“…Moreover, among the identified compounds, some were previously reported to have antimicrobial activity including menthol and menthone that have been proven effective against human pathogenic[1619] and also 1,8-cineole[20] and menthofuran. [21]…”