In vitro activity of carvacrol against staphylococcal preformed biofilm by liquid and vapour contact

Abstract

Carvacrol is an important component of essential oils and recently has attracted much attention as a result of its biological properties, such as a wide spectrum of antimicrobial activity. The aim of this study was to evaluate the effect of carvacrol in liquid and vapour phase on preformed biofilms of Staphylococcus aureus and Staphylococcus epidermidis by determining biofilm biomass and cultivable cell numbers, and by using epifluorescence and scanning electron microscopy. Carvacrol was able to reduce biofilm biomass and cell viability more effectively when used with liquid contact rather than with vapour phase. The efficacy of treatment with carvacrol vapour was found to be dependent on exposure time. The predominance of red fluorescence using a LIVE/ DEAD BacLight Viability kit (Molecular Probes) and the partially destroyed biofilm architecture as determined by microscopy in treated samples provided evidence for the efficacy of carvacrol. The findings of this investigation suggest a potential application for carvacrol in the inactivation of staphylococcal biofilms. INTRODUCTIONIn recent decades, an increase in the number of staphylococcal infections has been observed worldwide. This has become a clinical and therapeutic problem, as these micro-organisms are resistant to many antimicrobial agents and are a common cause of biofilm-related infections associated with the widespread use of implanted medical devices (O'Gara & Humphreys, 2001;Vuong & Otto, 2002). Poor antimicrobial penetration, nutrient limitation, adaptive stress responses, phenotypic variability and persister-cell formation all contribute towards making biofilm eradication difficult (Hoyle & Costerton, 1991;Mah & O'Toole, 2001).Carvacrol (5-isopropyl-2-methylphenol) is one of the most common components of essential oils. Approved as a safe food additive in the USA and Europe (Center for Food Safety and Applied Nutrition, 2006; Commission of the European Communities, 1999), carvacrol has attracted considerable attention as a result of its wide-spectrum antimicrobial activity, which has been the subject of several investigations (Ben Arfa et al., 2006;Chami et al., 2005;Helander et al., 1998;Lambert et al., 2001;Ultee et al., 1998; Veldhuizen et al., 2006). Carvacrol is effective against bacteria, yeasts, fungi, insects and mites (Ben Arfa et al., It has recently been reported that carvacrol is able to inhibit the growth of preformed biofilm and to interfere with biofilm formation (Knowles & Roller, 2001;Knowles et al., 2005;Nostro et al., 2004). Moreover, a higher antimicrobial activity of carvacrol has been shown using the vapour form compared with solution contact (Burt et al., 2007a;Inouye et al., 2000Inouye et al., , 2001a Inouye et al., , b, 2003Ló pez et al., 2007).The antibacterial activity of carvacrol has been attributed to its hydrophobic nature, the presence of a free hydroxyl group and a delocalized electron system. Carvacrol acts on the cytoplasmic membrane, with considerable effects on the structural and functional properties of the...

Potential of Herbal Drug and Antibiotic Combination Therapy: A New Approach to Treat Multidrug Resistant Bacteria

“…Carvacrol [2-methyl-5-(methylethyl) phenol] is one of the major components of oregano oil which is known for a wide spectrum of antimicrobial activity in vitro or in vivo [110,111]. Carvacrol is a wellknown constituent of some medicinal plants, like black cumin (Nigella sativa), oregano (Origanum compactum), Monarda didyma, Origanum dictamnus, Origanum microphyllum, Origanum onites, Origanum scabrum, Origanum vulgare, thyme (Thymus glandulosus), savory (Satureja hortensis) [112].…”

“…Botelho et al, [119] reported its antifungal activity against Candida albicans. Nostro et al [110], proved it effective even against meticillin-resistant strains of Staphylococcus aureus and Staphylococcus epidermidis.…”

A review on recent research results (2008–2010) on essential oils as antimicrobials and antifungals. A review.

“…It can be assumed that carvacrol is capable of destroying biofilms formed by Staphylococcus strains. [170] M. alternifolia EO exerted remarkable activity against S. aureus biofilms used in concentrations lower than 1% (v/v). These concentrations were twice as high as the measured MBC values.…”

Resistance of Staphylococcus aureus to the cationic antimicrobial agent poly(2-(dimethylamino ethyl)methacrylate) (pDMAEMA) is influenced by cell-surface charge and hydrophobicity

“…The hydrophobic portions may be important in permeabilization of bacterial membranes (Nostro et al, 2009;Rawlinson et al, 2010b). The hydrophilic portions of amphiphilic molecules are implicated in enabling diffusion of antimicrobial agents through the polysaccharide matrix of biofilms (Nostro et al, 2009) and in initial attraction of cationic agents. pDMAEMA is effective at inhibiting growth of S. epidermidis when presented in a more protonated and hydrophilic state (Rawlinson et al, 2010b).…”