Antimicrobial and anti-Quorum Sensing activities of selected medicinal plants of Ethiopia: Implication for development of potent antimicrobial agents

Abstract

BackgroundTraditional medicinal plants have been used as an alternative medicine in many parts of the world, including Ethiopia. There are many documented scientific reports on antimicrobial activities of the same. To our knowledge, however, there is no report on the anti-Quorum Sensing (Quorum Quenching, QQ) potential of traditional Ethiopian medicinal plants. As many of the opportunistic pathogenic bacteria depend on Quorum Sensing (QS) systems to coordinate their virulence expression, interference with QS could be a novel approach to control bacterial infections. Thus, the aim of this study was to evaluate selected medicinal plants from Ethiopia for their antimicrobial activities against bacterial and fungal pathogens; and to assess the interference of these plant extracts with QS of bacteria.MethodsAntimicrobial activities of plant extracts (oil, resins and crude extracts) were evaluated following standard agar diffusion technique. The minimum inhibitory concentrations (MIC) of potent extracts were determined using 96 well micro-titer plates and optical densities were measured using an ELISA Microplate reader. Interference with Quorum Sensing activities of extracts was determined using the recently established E. coli based reporter strain AI1-QQ.1 and signaling molecule N-(ß-ketocaproyl)-L-homoserine lactone (3-oxo-C6-HSL).ResultsPetroleum ether extract of seed of Nigella sativa exhibited the highest activity against both the laboratory isolated Bacillus cereus [inhibition zone (IZ), 44 ± 0.31 mm] and B. cereus ATCC 10987 (IZ, 40 ± 2.33 mm). Similarly, oil extract from mature ripe fruit husk of Aframomum corrorima and mature unripe fruit of A. corrorima revealed promising activities against Candida albicans ATCC 90028 (IZ, 35 ± 1.52 mm) and Staphylococcus aureus DSM 346 (IZ, 25 ± 1.32 mm), respectively. Antimicrobial activities of oil extract from husk of A. corrorima and petroleum ether extract of seed of N. sativa were significantly higher than that of the control antibiotic [Gentamycin sulfate, (IZ, 25–30 mm)]. The lowest MIC value (12.5 mg/mL) was recorded for oil from husk of A. corrorima against Pseudomonas aeruginosa. Of the total eighteen extracts evaluated, two of the extracts [Methanol extract of root of Albiza schimperiana (ASRM) and petroleum ether extract of seed of Justica schimperiana (JSSP)] interfered with cell-cell communication most likely by interacting with the signaling molecules.ConclusionTraditional medicinal plants from Ethiopia are potential source of alternative medicine for the local community and scientific research in search for alternative drugs to halt challenges associated with the emerging antimicrobial resistance. Furthermore, the Quorum Quenching activities observed in two of the plant extracts calls for more comprehensive evaluation of medicinal plants for the control of many bacterial processes and phenotypic behaviors such as pathogenicity, swarming, and biofilm formation. Being the first assessment of its kind on the potential application of Ethiopian traditional medic...

Antibacterial activity of selected medicinal plants used in South-western Ethiopia

“…According to recent review made in Ethiopia (Mogese et al, 2014), some of the antibiotics have become virtually useless, alarming for the urgent need to apply antibiotic restriction policies as well as measures to prevent further spread of resistant clones. Thus, the pressure due to drug resistance necessitates search for novel antimicrobial substances from plants as the development of resistance to bioactive substance from plants is low, if any (Bacha et al, 2016). Although not evaluated against resistance bacterial strains, our extract could have potent activity against resistance strains as it did against the sensitive test strains.…”

“…For several reasons, including low access to modern health care systems, high cost of the available commercial drugs and trust developed over long years of traditional practices, large proportion of a population in rural community prefer using traditional medicinal plants in order to manage infectious diseases of different sorts (Giday et al, 2003;Bacha et al, 2016). The current study area is not exceptional.…”

“…The emergence of multiple drug resistant pathogens, including Multi-Drug Resistant TB (MDR TB), MethicillinResistant Staphylococcus aureus (MRSA), and Vancomycin-Resistant Entero-cocci (VRE), is making the treatment and control of infectious diseases more difficult (Bacha et al, 2016), with over 480 000 new cases of MDR-TB only in 2013 [31]. According to recent review made in Ethiopia (Mogese et al, 2014), some of the antibiotics have become virtually useless, alarming for the urgent need to apply antibiotic restriction policies as well as measures to prevent further spread of resistant clones.…”

“…Furthermore, in the era of high pressure from emergence of microbial drug resistance and limited therapeutic efficacy of many of the available drugs, search for potent antibacterial drugs with new modes of action should be given emphasis. Local medicinal plants are potential source of novel antimicrobial agents and anti-Quorum sensing substances (Bacha et al, 2016).…”

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“…If these medicinal plants possess a quorum sensing inhibitor they can be used for therapeutic purpose in future [41][42][43][44][45][46][47][48] . They can be used to overcome the problem of multidrug resistant organism and thus can be used in combination with conventional antibiotics.…”