Abstract
The emergence of multidrug resistant microorganisms represents a global challenge due to the lack of new effective antimicrobial agents. In this sense, essential oils (EOs) are an alternative to be considered because of their anti-inflammatory, antiviral, antibacterial, and antibiofilm biological activities. Therefore, multiple efforts have been made to consider the potential use of EOs in the treatment of infections which are caused by resistant microorganisms. In this study, 15 EOs of both Colombian and introduced aromatic plants were evaluated against pathogenic strains of E. coli O157:H7 and methicillin resistant Staphylococcus aureus (MRSA) in planktonic and sessile states in order to identify relevant and promising alternatives for the treatment of microbial infections. Forty different compounds were identified in the 15 EO with nine of them constituted mainly by oxygenated monoterpenes (OM). EOs from Lippia origanoides, chemotypes thymol, and carvacrol, displayed the highest antibacterial activity against E. coli O157:H7 (MIC50 = 0.9 and 0.3 mg/mL, respectively) and MRSA (MIC50 = 1.2 and 0.6 mg/mL, respectively). These compounds from EOs had also the highest antibiofilm activity (inhibition percentage > 70.3%). Using scanning electron microscopy (SEM), changes in the size and morphology of both bacteria were observed when they were exposed to sub-inhibitory concentrations of L. origanoides EO carvacrol chemotype. EOs from L. origanoides, thymol, and carvacrol chemotypes represented a viable alternative for the treatment of microbial infections; however, the Selectivity Index (SI ≤ 3) indicated that it was necessary to study alternatives to reduce its in vitro cytotoxicity.
Highlights
Antibiotics are one of the main defense weapons in our fight against pathogenic microorganisms; the abuse of these drugs in both medical and industrial fields [1,2] have led to the emergence of multidrug resistant pathogenic bacteria which is one of the most serious public health problems of this century [3,4]
Due to the vital importance of identifying relevant and promising alternatives for the treatment of microbial infections, in this work, we evaluated 15 essential oils (EOs) corresponding to 12 species of Colombian and foreign aromatic plants against the pathogenic strains methicillin resistant Staphylococcus aureus (MRSA) and E. coli O157:H7 in both planktonic and sessile states
When examining the relative amount of individual compounds, it was found that oxygenated monoterpenes (OM) were major compounds in nine of the 15 oils, which represented 49% of the total identified compounds, followed by the oxygenated compounds (OC, 20%), Monoterpenic hydrocarbons (MH, 15%), sesquiterpene hydrocarbons (SH, 13%), and oxygenated sesquiterpenes (OS, 3%)
Summary
Antibiotics are one of the main defense weapons in our fight against pathogenic microorganisms; the abuse of these drugs in both medical and industrial fields [1,2] have led to the emergence of multidrug resistant pathogenic bacteria which is one of the most serious public health problems of this century [3,4]. E. coli O157:H7 but MRSA are responsible of the majority of nosocomial and community-associated infections [7,8], occupying the first and second place among the most common pathogens with 15 and 12% of total cases, respectively [9]. They are commonly associated with outbreaks of foodborne diseases, which can cause a wide range of illnesses, such as endocarditis, osteomyelitis, pneumonia, septicemia, skin infections, food poisoning, and hemolytic uremic syndrome, among others [10,11,12]. Recent investigations point out that at least 65% of all bacterial infectious diseases and 70% of chronic infections in humans could involve biofilms [19,20]
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