Abstract
BackgroundThe emergence of multidrug-resistant bacteria is a worldwide concern and in order to find an alternative to this problem, the occurrence of antimicrobial compounds in Plectranthus amboinicus essential oil was investigated. Thus, this study aims to determine susceptibility of Staphylococcus aureus isolated from food to antibiotics, P. amboinicus essential oil (PAEO) and carvacrol.MethodsLeaves and stem of P. amboinicus were used for extraction of essential oil (PAEO) by hydrodistillation technique and EO chemical analysis was performed by gas chromatography coupled to a mass spectrometer. S. aureus strains (n = 35) isolated from food and S. aureus ATCC 6538 were used to evaluate the antimicrobial and antibiofilm activity of PAEO and carvacrol. All strains (n = 35) were submitted to antimicrobial susceptibility profile by disk diffusion method. Determination of MIC and MBC was performed by microdilution technique and antibiofilm activity was determined by microtiter-plate technique with crystal violet assay and counting viable cells in Colony Forming Units (CFU).ResultsCarvacrol (88.17%) was the major component in the PAEO. Antibiotic resistance was detected in 28 S. aureus strains (80%) and 12 strains (34.3%) were oxacillin and vancomycin-resistant (OVRSA). From the 28 resistant strains, 7 (25%) showed resistance plasmid of 12,000 bp. All strains (n = 35) were sensitive to PAEO and carvacrol, with inhibition zones ranging from 16 to 38 mm and 23 to 42 mm, respectively. The lowest MIC (0.25 mg mL−1) and MBC (0.5 mg mL−1) values were observed when carvacrol was used against OVRSA. When a 0.5 mg mL−1 concentration of PAEO and carvacrol was used, no viable cells were found on S. aureus biofilm.ConclusionThe antibacterial effect of carvacrol and PAEO proves to be a possible alternative against planktonic forms and staphylococcal biofilm.
Highlights
The emergence of multidrug-resistant bacteria is a worldwide concern and in order to find an alternative to this problem, the occurrence of antimicrobial compounds in Plectranthus amboinicus essential oil was investigated
Antibiotic resistance was observed in 28 S. aureus strains (80%) and ten resistance profiles were observed: three profiles of monoresistance (n = 5, 17.8%), three cross-resistance to beta-lactams (n = 8; 28.6%) and four multidrug resistant (n = 15; 53.6%) (Table 1)
All strains (n = 35) of S. aureus were sensitive to P. amboinicus essential oil (PAEO) and carvacrol with inhibition zones ranging from 16 to 38 mm and 23 to 42 mm, respectively (Table 3)
Summary
The emergence of multidrug-resistant bacteria is a worldwide concern and in order to find an alternative to this problem, the occurrence of antimicrobial compounds in Plectranthus amboinicus essential oil was investigated. As an alternative to mitigate the occurrence of multidrug-resistant bacteria, the study of antimicrobial compounds in phanerogams has been proposed [9]. In this context, the plants of genus Plectranthus - 3000 recognized species, spread along countries in Africa, South America, Asia and Australia – are widely recognized in folk and popular medicine, being employed in digestive treatments as well as in infectious, inflammatory and respiratory problems [10, 11]. Species of Plectrantus [12, 13], including P. amboinicus [14], has been studied due to its pharmacological properties in order to validate its popular use
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