- 1
- Depatment of Biology, College of Natural Sciences, Jimma University, Jimma, Ethiopia. ketemabacha2002@yahoo.com.
- 2
- Department of Chemistry, College of Natural Sciences, Jimma University, Jimma, Ethiopia.
- 3
- Department of Horticulture, College of Agriculture, Adigrat University, Adigrat, Ethiopia.
- 4
- Department
of Horticulture and Plant Science, College of Agriculture and Natural
Resources Management, Gambella University, Gambella, Ethiopia.
- 5
- Departemnt of Postharvest Management, College of Agriculture and Veterinary Medicine, Jimma University, Jimma, Ethiopia.
- 6
- Institut für Allgemeine Mikrobiologie, Christian-Albrechts-Universität zu Kiel, Kiel, Germany.
- 7
- Depatment of Biology, College of Natural Sciences, Jimma University, Jimma, Ethiopia.
- 8
- Derpartment of Biology, College of Natural and Computational Sciences, Wollo University, Dessie, Ethiopia.
Abstract
BACKGROUND:
Traditional 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.
METHODS:
Antimicrobial
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).
RESULTS:
Petroleum
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.
CONCLUSION:
Traditional 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 medicinal plants
for interference in microbial cell-cell communication (anti-Quorum
Sensing activities), the detailed chemistry of the active compounds and
possible mechanism(s) of actions of the bio-molecules responsible for
the observed interference were not addressed in the current study. Thus,
further evaluation for the nature of those active compounds
(bio-molecules) and detailed mechanism(s) of their interaction with
microbial processes are recommended.
KEYWORDS:
Alternative medicine; Drug resistance; Ethiopia; MIC; Medicinal plants; Quorum Quenching; Quorum Sensing
