• Korean Journal of Microbiology
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• v.44 no.2
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• pp.85-92
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• 2008

Pseudomonas aeruginosa is an opportunistic human pathogen, causing a wide variety of infections including cystic fibrosis, microbial keratitis, and burn wound infections. The cell-to-cell signaling mechanism known as quorum sensing (QS) plays a key role in these infections and the QS systems of P. aeruginosa have been most intensively studied. While many literatures that introduce the QS systems of P. aeruginosa have mostly focused on two major acyl-homo serine lactone (acyl-HSL) QS signals, N-3-oxododecanoyl homoserine lactone (3OC12) and N-butanoyl homoserine lactone (C4), several new signal molecules have been discovered and suggested for their significant roles in signaling and virulence of P. aeruginosa. One of them is PQS (Pseudomonas quinolone signal; 2-heptyl-3-hydroxy-4-quinolone), which is now considered as a well-characterized major signal meolecule of P. aeruginosa. In addition, recent researches have also suggested some more putative signal molecules of P. aeruginosa, which are diketopiperazines (DKPs) and pyocyanin. DKPs are cyclic dipeptides and structurally diverse depending on what amino acids are involved in composition. Some DKPs from the culture supernatant of P. aeruginosa are suggested as new diffusible signal molecules, based on their ability to activate Vibrio fischeri LuxR biosensors that are previously considered specific for acyl-HSLs. Pyocyanin (1-hydroxy-5-methyl-phenazine), one of phenazine derivatives produced by P. aeruginosa is a characteristic blue-green pigment and redox-active compound. This has been recently suggested as a terminal signaling factor to upregulate some QS-controlled genes during stationary phase under the mediation of a transcription factor, SoxR. Here, details about these newly emerging signaling molecules of P. aeruginosa are discussed.

• Microbiology and Biotechnology Letters
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• v.47 no.4
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• pp.651-661
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• 2019

Targeting the pathogen viability using drugs is associated with development of drug resistance due to selective pressure. Hence, there is an increased interest in developing agents that target bacterial virulence. In this study, the inhibitory effect of ciclopirox, an antifungal agent with iron chelation potential, on the microbial virulence factors was evaluated in 26 clinical MDR Pseudomonas aeruginosa isolates collected from Alexandria Main University Hospital, a tertiary hospital in Egypt. Treatment with 9 ㎍/ml ciclopirox inhibited the hemolytic activity in 70% isolates, reduced pyocyanin production, decreased protease secretion in 46% isolates, lowered twitching and swarming motility, and decreased biofilm formation by 1.5- to 4.5-fold. The quantitative real-time PCR analysis revealed that treatment with ciclopirox downregulated the expression levels of alkaline protease (aprA) and pyocyanin (phzA1). Ciclopirox is used to treat hematological malignancies and the systemic administration of ciclopirox is reported to have adequate oral absorption with a satisfactory drug safety profile. It is important to calculate the appropriate clinical dose and therapeutic index to reposition ciclopirox from a topical antifungal agent to a promising virulence-modifying agent agent against P. aeruginosa, a problematic Gram-negative pathogen.

• Journal of Pharmacopuncture
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• v.25 no.1
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• pp.37-45
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• 2022

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.

• Journal of Microbiology and Biotechnology
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• v.30 no.2
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• pp.226-236
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• 2020

Antibiotic resistance by pathogenic bacteria and fungi is one of the most serious global public health problems in the 21^st century, directly affecting human health and lifestyle. Pseudomonas aeruginosa and Staphylococcus aureus with strong resistance to the common antibiotics have been isolated from Intensive Care Unit patients at Zagazig Hospital. Thus, in this study we assessed the biocidal activity of nanoparticles of silver, copper and zinc synthesized by Fusarium solani KJ 623702 against these multidrug resistant-bacteria. The synthesized Metal Nano-particles (MNPs) were characterized by UV-Vis spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and Zeta potential. The Fourier transform infrared spectroscopy (FTIR) result showed the presence of different functional groups such as carboxyl, amino and thiol, ester and peptide bonds in addition to glycosidic bonds that might stabilize the dispersity of MNPs from aggregation. The antimicrobial potential of MNPs by F. solani against the multidrug-resistant (MDR) P. aeruginosa and S. aureus in addition to the mycotoxigenic Aspergillus awamori, A. fumigatus and F. oxysporum was investigated, based on the visual growth by diameter of inhibition zone. Among the synthesized MNPs, the spherical AgNPs (13.70 nm) displayed significant effect against P. aeruginosa (Zone of Inhibition 22.4 mm and Minimum Inhibitory Concentration 21.33 ㎍/ml), while ZINC oxide Nano-Particles were the most effective against F. oxysporum (ZOI, 18.5 mm and MIC 24.7 ㎍/ml). Transmission Electron Microscope micrographs of AgNP-treated P. aeruginosa showed cracks and pits in the cell wall, with internalization of NPs. Production of pyocyanin pigment was significantly inhibited by AgNPs in a concentration-dependent manner, and at 5-20 ㎍ of AgNPs/ml, the pigment production was reduced by about 15-100%, respectively.

• Korean Journal of Microbiology
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• v.36 no.3
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• pp.242-248
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• 2000

Since the official allowance of bottled water at Korean domestic market in 1995, Pseudomo~zas aemginosu has been detected from 2.3% and 1.2% of source and products of bottled water sa~nple tested, respectively. according to the nation-wide dala froin May 1995 to December 1996. Therefore, P aeivginosa was the second most important parameter, next to colifoi~ns, anlong the bacieriological parameters regulated for bonled water. The official standard method initially adopted the Japanese officlal method and Standard Methods of the US, w~hich is using aspai-agiii-acetamid mnedia(A-A method). how eve^; the method showed low specificity regardless of the high sensitivity. The $42^{\circ}C$ growth test was the best biochemical featu1-e differentiating the P uelarginosu 6-om P aei-uginosa-like species such as P puririir and P Jhoi.escens amo1zg the other characierisiics such as fluorescence pigment_ pyocyanin, casein hy&olysis, etc. Thel-efore, addition of the $42^{\circ}C$ growth Lest in advance ofthe biochemical identification test, when sainple is positive by A-A method, should strengthen the spec~IiclQ w~tli ~ninin~um addition of testing load.

• Journal of Pharmacopuncture
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• v.26 no.4
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• pp.307-318
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• 2023

Objectives: Bacterial biofilm is regarded as a significant threat to the production of safe food and the arise of antibiotic-resistant bacteria. The objective of this investigation is to evaluate the quorum sensing inhibitory effect of Nepeta curviflora methanolic extract. Methods: The effectiveness of the leaves at sub-inhibitory concentrations of 2.5, 1.25, and 0.6 mg/mL on the virulence factors and biofilm formation of P. aeruginosa was evaluated. The effect of N. curviflora methanolic extract on the virulence factors of P. aeruginosa, including pyocyanin, rhamnolipid, protease, and chitinase, was evaluated. Other tests including the crystal violet assay, scanning electron microscopy (SEM), swarming motility, aggregation ability, hydrophobicity and exopolysaccharide production were conducted to assess the effect of the extract on the formation of biofilm. Insight into the mode of antiquorum sensing action was evaluated by examining the effect of the extract on the activity of N-Acyl homoserine lactone (AHL) and the expression of pslA and pelA genes. Results: The results showed a significant attenuation in the production of pyocyanin and rhamnolipid and in the activities of protease and chitinase enzymes at 2.5 and 1.25 mg/mL. In addition, N. curviflora methanolic extract significantly inhibited the formation of P. aeruginosa biofilm by decreasing aggregation, hydrophobicity, and swarming motility as well as the production of exopolysaccharide (EPS). A significant reduction in AHL secretion and pslA gene expression was observed, indicating that the extract inhibited quorum sensing by disrupting the quorum-sensing systems. The quorum-sensing inhibitory effect of N. curviflora extract appears to be attributed to the presence of kaempferol, quercetin, salicylic acid, rutin, and rosmarinic acid, as indicated by LCMS analysis. Conclusion: The results of the present study provide insight into the potential of developing anti-quorum sensing agents using the extract and the identified compounds to treat infections resulting from quorum sensing-mediated bacterial pathogenesis.

• Journal of Microbiology and Biotechnology
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• v.29 no.8
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• pp.1299-1309
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• 2019

As an opportunistic bacterial pathogen, Pseudomonas aeruginosa PAO1 contains two phenazine-producing gene operons, phzA1B1C1D1E1F1G1 (phz1) and phzA2B2C2D2E2F2G2 (phz2), each of which is independently capable of encoding all enzymes for biosynthesizing phenazines, including phenazine-1-carboxylic acid and its derivatives. Other previous study reported that the RpoS-deficient mutant SS24 overproduced pyocyanin, a derivative of phenazine-1-carboxylic acid. However, it is not known how RpoS mediates the expression of two phz operons and regulates pyocyanin biosynthesis in detail. In this study, with deletion of the rpoS gene in the $PA{\Delta}phz1$ mutant and the $PA{\Delta}phz2$ mutant respectively, we demonstrated that RpoS exerted opposite regulatory roles on the expression of the phz1and phz2 operons. We also confirmed that the phz1 operon played a critical role and especially biosynthesized much more phenazines than the phz2 operon when the rpoS gene was knocked out in P. aeruginosa. By constructing the translational reporter fusion vector lasR'-'lacZ and the chromosomal fusion mutant $PA{\Delta}lasR::lacZ$, we verified that RpoS deficiency caused increased expression of lasR, a transcription regulator gene in a first quorum sensing system (las) that activates overexpression of the phz1 operon, suggesting that in the absence of RpoS, LasR might act as an intermediate in overproduction of phenazine biosynthesis mediated by the phz1 operon in P. aeruginosa.

• Natural Product Sciences
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• v.25 no.2
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• pp.172-180
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• 2019

Infections with Pseudomonas aeruginosa are difficult to treat not only because it is often associated with multidrug-resistant infections but also it is able to form biofilm. The aim of this study was to evaluate the antibiofilm and anti-Quorum Sensing (QS) activities of Thymbra capitata essential oils (EOs) against Beta Lactamase (BL) producing P. aeruginosa and the reference strain P. aeruginosa 10145. GC/MS analysis showed that thymol (23.25%) is the most dominant compound in T. capitata EOs. The MICs of T. capitata EOs against P. aeruginosa (BL) and P. aeruginosa 10145 were 1.11%. At sub MIC (0.041, 0.014 and 0.0046%), the EOs of T. capitata remarkably inhibited the biofilm formation of both strains tested and complete inhibition of the biofilm formation was reported at 0.041%. The EOs of T. capitata were found to inhibit the swarming motility, aggregation ability and hydrophobic ability of P. aeruginosa (BL) and P. aeruginosa 10145. Interestingly, the EOs of T. capitata reduce the production of three secreted virulence factors that regulated by QS system including pyocyanin, rhamnolipids and LasA protease. The potent antibiofilm and anti-QS activities of T. capitata EOs can propose it as a new antibacterial agent to control pseudomonas infections.

• Preventive Nutrition and Food Science
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• v.7 no.3
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• pp.305-309
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• 2002

Raw soybean sprouts were tested for contamination with the following bacteria which have potential for pathogenesis or food spoilage : Salmonella spp., Escherichia coli O157:H7, Yersinia enterocolitica, Vibrio parahae-molyticus, Aeromonas hydrophila, Plesidomonas shigeloides, Pseudomonas aeruginosa, Staphylococcus aureus, Lis-teria monocytogenes, Bacillus cereus, Clostridium perfringens, Campylobacter jejuni, Erwinia spp., and Fusarium spp. Three of the above strains were isolated from the sprouts, and identified by morphological and biochemical methods including an API kit and ATB automated identification system. The isolate cultured in Cereus selective agar, a selective medium, was a Gram-positive, rod shaped, anaerobic spore former. The biochemical and culture tests revealed the following characteristics: catalase-positive, no growth on Simmon's citrate, NO₂ production and requirement of arginine for growth; the ATB automated identification system gave 99.8 % agreement for the identification of Bacillus cereus to the species level. The isolate cultured in Macconkey agar selective medium was Gram-negative, rod shaped and a gas former; the ATB-system gave 99.9% agreement for the identification of Aeromonas hydrophila to the species level. The isolate found in Pseudomonas isolation agar was Gram-negative, rod shaped, cytochrome oxidase-positive, a reducer of nitrates to nitrogen, and pyocyanin producer; the ATB-system gave 99.9 % agreement for the identification of Pseudomonas aeruginosa to the species level. These results indicate that the three bacteria species present in the soybean sprouts were Bacillus cereus, Aero-monas hydrophila, and Pseudomonas aeruginosa. Salmonella spp., Escherichia coli O157:H7, and Yersinia enter-ocolitica, which are associated with serious disease in humans, were not isolated from soybean sprouts examined in this study.

• ALGAE
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• v.30 no.2
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• pp.147-161
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• 2015

Brown algal extracts have long been used as feed supplements to promote health of farm animals. Here, we show new molecular insights in to the mechanism of action of a fucose containing polymer (FCP) rich fraction from the brown seaweed Ascophyllum nodosum using the Caenorhabditis elegans-Pseudomonas aeruginosa PA14 infection model. FCP enhanced survival of C. elegans against pathogen stress, correlated with up-regulation of key immune response genes such as: lipases, lysozyme (lys-1), saponin-like protein (spp-1), thaumatin-like protein (tlp-1), matridin SK domain protein (msk-1), antibacterial protein (abf-1), and lectin family protein (lfp). Further, FCP caused down regulation of P. aeruginosa quorum sensing genes: (lasI, lasR, rhlI, and rhlR), secreted virulence factors (lipase, proteases, and elastases) and toxic metabolites (pyocyanin, hydrogen cyanide, and siderophore). Biofilm formation and motility of pathogenic bacteria were also greatly attenuated when the culture media were treated with FCP. Interestingly, FCP failed to mitigate the pathogen stress in skn-1, daf-2, and pmk-1 mutants of C. elegans. This indicated that, FCP treatment acted on the regulation of fundamental innate immune pathways, which are conserved across the majority of organisms including humans. This study suggests the possible use of FCP, a seaweed component, as a functional food source for healthy living.