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Background: The aim of this study was to determination of Anti-Quorum Sensing (AQS) and anti-biofilm potential of the methanol extract of ginger (Zingiber officinale) rhizomes against multidrug-resistant clinical isolates of Pseudomonas aeruginosa (P. aeruginosa). Methods: The AQS activity of ginger was determined against Chromobacterium violaceum (C. violaceum) ATCC 12472 (CV12472), a biosensor strain, in qualitative manner using the agar well diffusion method. The violacein pigment inhibition was assessed to confirm AQS activity of ginger. The AQS potential of sub-minimum Inhibitory Concentrations (sub-MICs) of the ginger extract was determined by targeting different QS regulated virulence factors, including swarming motility (using swarm diameter measurement method), pyocyanin pigment (using chloroform extraction method), Exopolysaccharide (EPS) (using phenol-sulphuric acid method), and biofilm formation (using microtiter plate assay), against clinical isolates (CIs 2, 3, and 4) and standard reference strain of P. aeruginosa (PA01). Results: The AQS activity of methanol extract of ginger was confirmed against C. violaceum (CV12472) as inhibition of violacein pigment formation without effecting the growth of CIs and PA01 of P. aeruginosa. The ginger extract exhibited concentration-dependent inhibition of virulence factors and biofilm formation. The maximum reduction was found in swarming motility, pyocyanin, EPS and biofilm formation against PA01 (51.38%), CI3 (57.91%), PA01 (63.29%) and CI2 (64.37%), respectively at 1/2 MIC of ginger extract. Conclusion: The results of present study revealed the effective AQS and anti-biofilm potential of Zingiber officinale rhizome methanol extract at a reduced dose (sub-MICs). The extract may be explored as an agent of antimicrobial compounds having AQS and anti-biofilm activity for controlling microbial infection and also for reducing the chances of emergence of resistance in P. aeruginosa.
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Objectives: The quorum-sensing-inhibitory and anti-biofilm activities of the methanol extract of E. globulus leaves were determined against clinically isolated multidrug-resistant Pseudomonas aeruginosa. Methods: The preliminary anti-quorum-sensing (AQS) activity of eucalyptus was investigated against a biosensor strain Chromobacterium violaceum ATCC 12472 (CV12472) by using the agar well diffusion method. The effect of sub-minimum inhibitory concentrations (sub-MICs) of the methanol extract of eucalyptus on different quorum-sensing-regulated virulence factors, such as swarming motility, pyocyanin pigment, exopolysaccharide (EPS), and biofilm formation, against clinical isolates (CIs 2, 3, and 4) and reference PA01 of Pseudomonas aeruginosa were determined using the swarm diameter (mm)-measurement method, chloroform extraction method, phenol (5%)-sulphuric acid (concentrated) method, and the microtiter plate assay respectively, and the inhibition (%) in formation were calculated. Results: The preliminary AQS activity (violacein pigment inhibition) of eucalyptus was confirmed against Chromobacterium violaceum ATCC 12472 (CV12472). The eucalyptus extract also showed concentration-dependent inhibition (%) of swarming motility, pyocyanin pigment, EPS, and biofilm formation in different CIs and PA01 of P. aeruginosa. Conclusion: Our results revealed the effectiveness of the E. globulus extract for the regulation of quorum-sensing-dependent virulence factors and biofilm formation at a reduced dose (sub-MICs) and suggest that E. globulus may be a therapeutic agent for curing and controlling bacterial infection and thereby reducing the possibility of resistance development in pathogenic strains.
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BACKGROUND: Nosocomial infections caused by multidrug-resistant Pseudomonas aeruginosa are commonly treated with conventional antibiotic which may lead to some serious side effects in the patients. Conventionally, medicinal plants, including clove, eucalyptus, and ginger, are used for the safe and effective treatment of several diseases. AIMS AND OBJECTIVES: The aim and objective of this study is to evaluate the combined antibacterial efficacy of medicinal plants (clove, eucalyptus, and ginger) and selected antibiotic and also combined efficacy of different plants extracts against clinical isolates of P. aeruginosa. MATERIALS AND METHODS: A total of seven clinical isolates and one reference strain (PA01) of P. aeruginosa were included in this study. The antibacterial activity of crude methanol extracts of medicinal plants and selected antibiotics was screened using well-diffusion assay and their minimum inhibitory concentration (MIC) was determined by the microdilution method. Combined efficacy of ceftazidime and plant extracts was tested using standard checkerboard method and different plant extracts were evaluated using broth macrodilution method. RESULTS: All of the seven clinical isolates of P. aeruginosa showed multidrug resistance pattern and were found highly sensitive to ciprofloxacin followed by ceftazidime and gentamicin. Clove exhibited better antibacterial activity as compared to eucalyptus and ginger. Synergistic interaction was found between ceftazidime and plants extracts against reference PA01 and clinical isolate 2. Highest two-fold reduction in MIC was found in the combination of clove-ginger against reference PA01 and clinical isolate 3. CONCLUSION: The selected medicinal plants are highly efficient for enhancing the antibacterial activity of antibiotic.
