The Zinc Transporter ZnuABC Is Critical for the Virulence of Chromobacterium violaceum and Contributes to Diverse Zinc-Dependent Physiological Processes.

Chromobacterium violaceum is a ubiquitous environmental bacterium that causes sporadic life-threatening infections in humans. How C. violaceum acquires zinc to colonize environmental and host niches is unknown. In this work, we demonstrated that C. violaceum employs the zinc uptake system ZnuABC to overcome zinc limitation in the host, ensuring the zinc supply for several physiological demands. Our data indicated that the C. violaceum ZnuABC transporter is encoded in a zur-CV_RS15045-CV_RS15040-znuCBA operon. This operon was repressed by the zinc uptake regulator Zur and derepressed in the presence of the host protein calprotectin (CP) and the synthetic metal chelator EDTA. A ΔznuCBA mutant strain showed impaired growth under these zinc-chelated conditions. Moreover, the deletion of znuCBA provoked reductions in violacein production, swimming motility, biofilm formation, and bacterial competition. Remarkably, the ΔznuCBA mutant strain was highly attenuated for virulence in an in vivo mouse infection model and showed low capacities to colonize the liver, grow in the presence of CP, and resist neutrophil killing. Overall, our findings demonstrate that ZnuABC is essential for C. violaceum virulence, contributing to subversion of zinc-based host nutritional immunity.

Screening of antibiofilm and anti-quorum sensing activty of Actinomycetes isolates extracts against aquaculture pathogenic bacteria.

BACKGROUND: Indonesia is the third largest producer of fish and other aquaculture products in the world, making this industry a major contributor in the economy of Indonesia. However, this industry continually overcome challenges, one of them are bacterial outbreaks. In addition, the emergence of these bacterial outbreaks were worsen due to the biofilm produced by many significant pathogenic bacteria and the impact of increased antibiotic resistance. These issues have become a global concern, because antibiotics are currently one of the main treatments available to overcome this problems. Therefore, studies aimed at finding and characterizing bioactive compounds to combat these issues. In this study actinomycetes isolates were screened and characterized for their bioactive compounds produced which have inhibitory and destructive activity and also QS inhibitors against biofilm structure of aquatic pathogenic bacteria, such as Vibrio harveyi, A. hydrophila, and S. agalactiae. RESULT: Extracts (20 mg/mL) produced by sixteen Actinomycetes isolates showed anti-quorum sensing activity towards reporter stain Chromobacterium violaceum wild-type. Most of these extracts showed better inhibitory activity on all of the pathogenic bacteria biofilm structure tested than the destructive activity on the preformed of those biofilm structure. Subsequently, we also performed characterization of bioactive compound and found that in this study, polysaccharide is the most common antibiofilm agents, which were responsible to their antibiofilm activity. Finally, we found that the value of LC50 of all extracts tested were more than 1 mg/mL, thereby all of extracts tested did not show cyto-toxic effect against Artemia salina. CONCLUSION: All of the extracts of Actinomycetes isolates showed promising inhibitory activity towards biofilm structure of pathogenic bacteria tested. So far, all of the extracts are potential to be QS inhibitors and antibiofilm agents of all pathogenic bacteria tested.

Ferric Uptake Regulator Fur Coordinates Siderophore Production and Defense against Iron Toxicity and Oxidative Stress and Contributes to Virulence in Chromobacterium violaceum.

Iron is a highly reactive metal that participates in several processes in prokaryotic and eukaryotic cells. Hosts and pathogens compete for iron in the context of infection. Chromobacterium violaceum, an environmental Gram-negative bacterial pathogen, relies on siderophores to overcome iron limitation in the host. In this work, we studied the role of the ferric uptake regulator Fur in the physiology and virulence of C. violaceum A Δfur mutant strain showed decreased growth and fitness under regular in vitro growth conditions and presented high sensitivity to iron and oxidative stresses. Furthermore, the absence of fur caused derepression of siderophore production and reduction in swimming motility and biofilm formation. Consistent with these results, the C. violaceum Δfur mutant was highly attenuated for virulence and liver colonization in mice. In contrast, a manganese-selected spontaneous fur mutant showed only siderophore overproduction and sensitivity to oxidative stress, indicating that Fur remained partially functional in this strain. We found that mutations in genes related to siderophore biosynthesis and a putative CRISPR-Cas locus rescued the Δfur mutant growth defects, indicating that multiple Fur-regulated processes contribute to maintaining bacterial cell fitness. Overall, our data indicated that Fur is conditionally essential in C. violaceum mainly by protecting cells from iron overload and oxidative damage. The requirement of Fur for virulence highlights the importance of iron in the pathogenesis of C. violaceumIMPORTANCE Maintenance of iron homeostasis, i.e., avoiding both deficiency and toxicity of this metal, is vital to bacteria and their hosts. Iron sequestration by host proteins is a crucial strategy to combat bacterial infections. In bacteria, the ferric uptake regulator Fur coordinates the expression of several iron-related genes. Sometimes, Fur can also regulate several other processes. In this work, we performed an in-depth phenotypic characterization of fur mutants in the human opportunistic pathogen Chromobacterium violaceum We determined that fur is a conditionally essential gene necessary for proper growth under regular conditions and is fully required for survival under iron and oxidative stresses. Fur also controlled several virulence-associated traits, such as swimming motility, biofilm formation, and siderophore production. Consistent with these results, a C. violaceumfur null mutant showed attenuation of virulence. Therefore, our data established Fur as a major player required for C. violaceum to manage iron, including during infection in the host.

Agricultural Injury-Associated Chromobacterium violaceum Infection in a Bangladeshi Farmer.

Chromobacterium violaceum is an emerging environmental pathogen that causes life-threatening infection in humans and animals. In October 2017, a Bangladeshi farmer was hospitalized with high-grade fever due to an agricultural injury-related wound infection. Bacteriological and 16S rRNA gene investigation detected C. violaceum in the wound discharge. The patient recovered successfully after a combination treatment with meropenem and ciprofloxacin, followed by prolonged medication to avoid recurrence. We strongly propose to incorporate C. violaceum in the differential diagnosis of wound and skin infections occurring in tropical and subtropical regions, especially when the injury was exposed to soil or sluggish water.

A Chemical Counterpunch: Chromobacterium violaceum ATCC 31532 Produces Violacein in Response to Translation-Inhibiting Antibiotics.

Antibiotics produced by bacteria play important roles in microbial interactions and competition Antibiosis can induce resistance mechanisms in target organisms, and at sublethal doses, antibiotics have been shown to globally alter gene expression patterns. Here, we show that hygromycin A from Streptomyces sp. strain 2AW. induces Chromobacterium violaceum ATCC 31532 to produce the purple antibiotic violacein. Sublethal doses of other antibiotics that similarly target the polypeptide elongation step of translation likewise induced violacein production, unlike antibiotics with different targets. C. violaceum biofilm formation and virulence against Drosophila melanogaster were also induced by translation-inhibiting antibiotics, and we identified an antibiotic-induced response (air) two-component regulatory system that is required for these responses. Genetic analyses indicated a connection between the Air system, quorum-dependent signaling, and the negative regulator VioS, leading us to propose a model for induction of violacein production. This work suggests a novel mechanism of interspecies interaction in which a bacterium produces an antibiotic in response to inhibition by another bacterium and supports the role of antibiotics as signal molecules.IMPORTANCE Secondary metabolites play important roles in microbial communities, but their natural functions are often unknown and may be more complex than appreciated. While compounds with antibiotic activity are often assumed to underlie microbial competition, they may alternatively act as signal molecules. In either scenario, microorganisms might evolve responses to sublethal concentrations of these metabolites, either to protect themselves from inhibition or to change certain behaviors in response to the local abundance of another species. Here, we report that violacein production by C. violaceum ATCC 31532 is induced in response to hygromycin A from Streptomyces sp. 2AW, and we show that this response is dependent on inhibition of translational polypeptide elongation and a previously uncharacterized two-component regulatory system. The breadth of the transcriptional response beyond violacein induction suggests a surprisingly complex metabolite-mediated microbe-microbe interaction and supports the hypothesis that antibiotics evolved as signal molecules. These novel insights will inform predictive models of soil community dynamics and the unintended effects of clinical antibiotic administration.

Calpurnia aurea (Aiton) Benth Extracts Reduce Quorum Sensing Controlled Virulence Factors in Pseudomonas aeruginosa.

Pseudomonas aeruginosa is the causative agent of several life-threatening human infections. Like many other pathogens, P. aeruginosa exhibits quorum sensing (QS) controlled virulence factors such as biofilm during disease progression, complicating treatment with conventional antibiotics. Thus, impeding the pathogen's QS circuit appears as a promising alternative strategy to overcome pseudomonas infections. In the present study, Calpurnia aurea were evaluated for their antibacterial (minimum inhibitory concentrations (MIC)), anti-quorum sensing/antivirulence (AQS), and antibiofilm potential against P. aeruginosa. AQS and antivirulence (biofilm formation, swimming, and swarming motility) activities of plant extracts were evaluated against Chromobacterium violaceum and P. aeruginosa, respectively. The in vitro AQS potential of the individual compounds were validated using in silico molecular docking. Acetone and ethanolic extracts of C. aurea showed MIC at 1.56 mg/mL. The quantitative violacein inhibition (AQS) assay showed ethyl acetate extracts as the most potent at a concentration of 1 mg/mL. GCMS analysis of C. aurea revealed 17 compounds; four (pentadecanol, dimethyl terephthalate, terephthalic acid, and methyl mannose) showed potential AQS through molecular docking against the CviR protein of C. violaceum. Biofilm of P. aeruginosa was significantly inhibited by ≥60% using 1-mg/mL extract of C. aurea. Confocal laser scanning microscopy correlated the findings of crystal violet assay with the extracts significantly altering the swimming motility. C. aurea extracts reduced the virulence of pseudomonas, albeit in a strain- and extract-specific manner, showing their suitability for the identification of lead compounds with QS inhibitory potential for the control of P. aeruginosa infections.

Genomic analysis of Chromobacterium haemolyticum: insights into the species resistome, virulence determinants and genome plasticity.

The increasing number of Chromobacterium haemolyticum human infection reports, especially in tropical regions and connected with environmental sources, resulted in an urge to better describe this species. This study aimed to characterize the C. haemolyticum resistome, virulence determinants and genetic platforms related with genome plasticity. A comparative genomic analysis was conducted between clinical C. haemolyticum genomes publicly available and the genome of an environmental isolate obtained in this study. The pangenome of C. haemolyticum was calculated and a total of 3378 core genes were predicted in its core genome, corresponding to 51.7% of the pangenome. Genetic determinants putatively encoding resistance to beta-lactams, fosfomycin, aminoglycosides and trimethoprim were predicted in all genomes, possibly constituting the intrinsic resistome of this species. In terms of resistance to beta-lactams, 4 genes were predicted encoding beta-lactamases of classes A, C and D. Moreover, the analysis of Chromobacterium genomes and C. haemolyticum environmental isolates reinforced the role of this genus as progenitor of the blaKPC gene. Putative virulence factors (VFs) were predicted in all genomes, related to adherence, toxins production, colonization and cell invasion. Secretion systems, including type III, were detected. A significant number of transposases and genomic islands were predicted in C. haemolyticum, in some cases above the average reported for Gram-negative bacterial genomes. We conclude that C. haemolyticum strains, including those of environmental origin, present a noteworthy collection of antibiotic resistance genes and VFs. Furthermore, sequences related to gene mobility and genome plasticity suggest high adaptability potential and a possible role as disseminator of antibiotic resistance.

Production and Uptake of Distinct Endogenous Catecholate-Type Siderophores Are Required for Iron Acquisition and Virulence in Chromobacterium violaceum.

Bacteria use siderophores to scavenge iron from environmental or host sources. The iron acquisition systems of Chromobacterium violaceum, a ubiquitous environmental bacterium that can cause infections in humans, are still unknown. In this work, we demonstrated that C. violaceum produces putative distinct endogenous siderophores, here named chromobactin and viobactin, and showed that they are each required for iron uptake and virulence. An in silico analysis in the genome of C. violaceum revealed that genes related to synthesis and uptake of chromobactin (cba) and viobactin (vba) are located within two secondary-metabolite biosynthetic gene clusters. Using a combination of gene deletions and siderophore detection assays, we revealed that chromobactin and viobactin are catecholate siderophores synthesized from the common precursor 2,3-dihydroxybenzoate (2,3-DHB) on two nonribosomal peptide synthetase (NRPS) enzymes (CbaF and VbaF) and taken up by two TonB-dependent receptors (CbuA and VbuA). Infection assays in mice revealed that both the synthesis and the uptake of chromobactin or viobactin are required for the virulence of C. violaceum, since only the mutant strains that do not produce any siderophores or are unable to take up both of them were attenuated for virulence. In addition, the mutant strain unable to take up both siderophores showed a pronounced attenuation of virulence in vivo and reduced neutrophil extracellular trap (NET) formation in in vitro assays, suggesting that extracellularly accumulated siderophores modulate the host immune response. Overall, our results revealed that C. violaceum uses distinct endogenous siderophores for iron uptake and its establishment in the host.

Serious imported infections: A focus on Chromobacterium violaceum.

The authors report on the main threats in the Czech Republic connected with travel and migration. The spectrum of diseases differs in the group of Czech citizens departing abroad, especially in the tropics and subtropics, from infections detected in foreigners, in particular from developing countries.A case report of sepsis caused by the exotic bacteria Chromobacterium violaceum is added to illustrate the potential severity of imported infection. A 54-year-old man acquired the infection during a diving holiday in Thailand. The disease began as a local ear infection, and progressed to septic shock with multiple organ failure and ischemic necrosis of all extremities. The original infection was cured but the patient eventually died due to subsequent complications. In order to properly diagnose and treat such rare diseases, we feel useful to study their pathogenesis (Tab. 2, Ref. 16). Keywords: imported infections, Chromobacterium violaceum, sepsis.

Quorum sensing inhibitors from marine bacteria Oceanobacillus sp. XC22919.

In this study, three active compounds isolated from Oceanobacillus sp. XC22919 were identified as 2-methyl-N-(2'-phenylethyl) butyramide (1), 3-methyl-N-(2'-phenylethyl)-butyramide (2) and benzyl benzoate (3), and were first reported to exhibit the apparent quorum sensing inhibitory activities against C. violaceum 026 and P. aeruginosa. Compounds 1-3 inhibited violacein production of C. violaceum 026 by 10.5-55.7, 11.2-55.7, and 27.2%-95.7%, respectively, and inhibited pyocyanin production of P. aeruginosa by 1.7-50.8, 39.1-90.7, and 57.2%-98.7%, respectively. The azocasein-degrading proteolytic rates of P. aeruginosa were observed by 13.4-31.5, 13.4-28.8, and 11.3%-21.1%, respectively. With respect to elastase, the range of inhibition of activity of compounds 1-3 was 2.1-30.3, 4.2-18.2, and 8.9%-15.7%, respectively. Compounds 1 and 3 also showed a concentration-dependent attenuation in biofilm formation, with the maximum of 50.6% inhibition, and 37.7% inhibition at 100 µg/mL, respectively.

Chromobacterium violaceum and Pseudomonas aeruginosa PAO1: Models for Evaluating Anti-Quorum Sensing Activity of Melaleuca alternifolia Essential Oil and Its Main Component Terpinen-4-ol.

The problem of antibiotic resistance among pathogens encourages searching for novel active molecules. The aim of the research was to assay the anti-quorum sensing (anti-QS) and antibiofilm potential of Melaleuca alternifolia essential oil and its main constituent, terpinen-4-ol, to prevent the infections due to methicillin-resistant Staphylococcus aureus strains as an alternate to antibiotics. The tea tree oil (TTO) was evaluated for its potential in inhibiting QS-dependent phenomena such as violacein production in Chromobacterium violaceum, swarming motility of Pseudomonas aeruginosa PAO1, and biofilm formation in MRSA strains on glass. The results showed that terpinen-4-ol was able to inhibit MRSA strain biofilm formation on the glass strips by 73.70%. TTO inhibited the violacein production at a mean inhibitory concentration (MIC) value of 0.048 mg/mL by 69.3%. At 100 µg/mL TTO and terpinen-4-ol exhibited inhibition in swarming motility of PAO1 by 33.33% and 25%, respectively. TTO revealed anti-QS and anti-biofilm activities at very low concentrations, but it could be further investigated for new molecules useful for the treatment of MRSA infections.

Necrotizing Pneumonia Caused by Chromobacterium violaceum: Report of a Rare Human Pathogen Causing Disease in an Immunodeficient Child.

Chromobacterium violaceum is a rare, potentially serious pathogen. Most clinicians have no experience with its clinical appearance or treatment. We describe a case of a child presenting with necrotizing pneumonia caused by C. violaceum. We describe case complexities, including the need for a multidisciplinary approach to diagnosis and treatment.

Inhibition of quorum sensing-mediated virulence in Serratia marcescens by Bacillus subtilis R-18.

Serratia marcescens is an opportunistic human pathogen causing various nosocomial infections, most importantly urinary tract infections (UTIs). It exhibits increased resistance towards the conventional antibiotics. This study was aimed to evaluate the anti-virulence effect of a rhizosphere soil bacterium Bacillus subtilis strain R-18 against the uropathogen S. marcescens. First, the bacterial cell-free culture supernatant (CFCS) of B. subtilis strain R-18 was evaluated for its quorum sensing inhibitory (QSI) potential against biomarker strain Chromobacterium violaceum and the test pathogen S. marcescens. The B. subtilis R-18 CFCS effectively inhibited the quorum sensing (QS)-mediated violacein pigment production in C. violaceum and prodigiosin pigment production in S. marcescens. Furthermore, B. subtilis R-18 CFCS was successively extracted with different solvent systems. Of these solvents, B. subtilis R-18 petroleum ether (PE) extract showed inhibition in biofilm formation, protease, lipase, and hemolysin productions in S. marcescens. Fourier transform infrared spectroscopic (FT-IR) analysis revealed the alterations in the cellular components of bacterial cell pellets obtained from B. subtilis R-18 PE extract treated and untreated S. marcescens. The differential gene expression study further validated the downregulation of virulence-associated genes. Characterization of the active principle in B. subtilis R-18 PE extract by gas chromatography-mass spectrometry (GC-MS) analysis showed the presence of multiple compounds with therapeutic values, which could possibly reduce the QS-dependent phenotypes in S. marcescens.

Antiquorum Sensing Activity of Seed Oils from Oleaginous Plants and Protective Effect During Challenge with Chromobacterium violaceum.

Seed oils from oleaginous plants are rich in fatty acids (FAs) that play important roles in the health of the consumers. Recent studies indicate that FA also can play an important role in communication and regulation of virulence in bacteria. Nevertheless, evidence demonstrating protection against bacterial infections mediated by their quorum sensing inhibition (QSI) activity is scarce. In this study, sunflower, chia, and amaranth oils, were assayed for their QSI capacity by inhibiting violacein production and alkaline exoprotease activity of Chromobacterium violaceum. In vitro assays revealed that the oils exhibited QSI activities, whereas in vivo they delayed death of mice inoculated intraperitoneally with the bacterium. Gas chromatography coupled with mass spectrometry analysis of the oils indicated the presence of saturated FA (SAFA) and unsaturated FA as main components. Through a structure-activity relationship study of free FAs, bactericidal effect was identified mainly for polyunsaturated FAs, whereas QSI activity was restricted to SAFA of chains 12-18 carbon atoms in length. These data correlate with a possible interaction suggested by molecular docking analysis of lauric, myristic, and stearic acids with the CviR protein. Our study highlights the antiquorum sensing potential of SAFA, which may be future antivirulence therapeutic agents for the treatment of bacterial infections.

Identification of Chromobacterium violaceum by MALDI-TOF mass spectrometry in blood culture

Report of Chromobacterium violaceum isolation from blood culture. Identification by MALDI-TOF mass spectrometry. Relevant report due to the site affected, infection severity, and importance of correct and rapid identification for a successful treatment and lower risk of morbidity and mortality. (AU)

Global Transcriptional Response to Organic Hydroperoxide and the Role of OhrR in the Control of Virulence Traits in Chromobacterium violaceum.

A major pathway for the detoxification of organic hydroperoxides, such as cumene hydroperoxide (CHP), involves the MarR family transcriptional regulator OhrR and the peroxidase OhrA. However, the effect of these peroxides on the global transcriptome and the contribution of the OhrA/OhrR system to bacterial virulence remain poorly explored. Here, we analyzed the transcriptome profiles of Chromobacterium violaceum exposed to CHP and after the deletion of ohrR, and we show that OhrR controls the virulence of this human opportunistic pathogen. DNA microarray and Northern blot analyses of CHP-treated cells revealed the upregulation of genes related to the detoxification of peroxides (antioxidant enzymes and thiol-reducing systems), the degradation of the aromatic moiety of CHP (oxygenases), and protection against other secondary stresses (DNA repair, heat shock, iron limitation, and nitrogen starvation responses). Furthermore, we identified two upregulated genes (ohrA and a putative diguanylate cyclase with a GGDEF domain for cyclic di-GMP [c-di-GMP] synthesis) and three downregulated genes (hemolysin, chitinase, and collagenase) in the ohrR mutant by transcriptome analysis. Importantly, we show that OhrR directly repressed the expression of the putative diguanylate cyclase. Using a mouse infection model, we demonstrate that the ohrR mutant was attenuated for virulence and showed a decreased bacterial burden in the liver. Moreover, an ohrR-diguanylate cyclase double mutant displayed the same virulence as the wild-type strain. In conclusion, we have defined the transcriptional response to CHP, identified potential virulence factors such as diguanylate cyclase as members of the OhrR regulon, and shown that C. violaceum uses the transcriptional regulator OhrR to modulate its virulence.

Novel RAG1 mutation and the occurrence of mycobacterial and Chromobacterium violaceum infections in a case of leaky SCID.

Severe combined immunodeficiency (SCID) is a potentially fatal primary immunodeficiency (PID) that is caused by mutations in genes such as IL2RG, JAK3, IL7RA, RAG1, RAG2, and ADA. The products of these genes are involved in the development of several immune cells such as T, B and natural killer (NK) cells. Most of the SCID forms are autosomal recessive with the exception of IL2RG defects that cause an X-linked SCID. Among the different SCID types, there is a rare SCID form called leaky SCID, which is less severe when compared to the other classical SCID phenotypes. Leaky SCID can be caused by hypomorphic mutations in RAG1 and RAG2 that result in only partial loss of enzymatic function of the proteins respectively encoded by these genes. Here we report a novel missense mutation (c. 307C > T/p.H103Y) in the RAG1 gene in a patient with leaky SCID. In addition, we characterize the clinical and immunological features of this patient that developed along with other severe and recurrent infections such as mycobacterial diseases (BCGitis and pulmonary tuberculosis), the first occurrence of Chromobacterium violaceum in a patient with SCID. Understanding the increased susceptibility to mycobacteria presented by the patient, in which a functional investigation of IL-12/IFN-γ axis was performed, which demonstrated reduced production of IFN-γ in the supernatans of peripheral blood mononuclear cell cultures from the patient compared with those from healthy subjects. In conclusion, our data expands the molecular and clinical spectrum associated with the leaky SCID phenotype.

Action and function of Chromobacterium violaceum in health and disease: Violacein as a promising metabolite to counteract gastroenterological diseases.

Chromobacterium violaceum is a Gram negative, ß-proteobacterium found in the microbiota of tropical and subtropical environments. Although considered an opportunistic pathogen, infection rapidly progress to fatal sepsis, with metastatic abscesses. It is noteworthy the multidrug resistant phenotype of C. violaceum and the possibility of relapse. Recently, an influence of global climate in the incidence of cases beyond the previous areas has been observed. Furthermore, chronic granulomatous disease has been considered a risk factor to infection. Despite the increase in C. violaceum infection incidence and high mortality, most clinicians are not familiar with it. This review pointed out important features of this life threatening microorganism, including its pathogenicity, mechanistic aspects, genetic and drug resistance associated factors, and the clinical association with chronic granulomatous disease. In addition, its main metabolite violacein may be a promising agent to counteract gastroenterological diseases, such as colorectal cancer and inflammatory gastric lesions.

Genetic variability in isolates of Chromobacterium violaceum from pulmonary secretion, water, and soil.

Chromobacterium violaceum is a free-living Gram-negative bacillus usually found in the water and soil in tropical regions, which causes infections in humans. Chromobacteriosis is characterized by rapid dissemination and high mortality. The aim of this study was to detect the genetic variability among C. violaceum type strain ATCC 12472, and seven isolates from the environment and one from a pulmonary secretion from a chromobacteriosis patient from Ilhéus, Bahia. The molecular characterization of all samples was performed by polymerase chain reaction (PCR) sequencing and 16S rDNA analysis. Primers specific for two ATCC 12472 pathogenicity genes, hilA and yscD, as well as random amplified polymorphic DNA (RAPD), were used for PCR amplification and comparative sequencing of the products. For a more specific approach, the PCR products of 16S rDNA were digested with restriction enzymes. Seven of the samples, including type-strain ATCC 12472, were amplified by the hilA primers; these were subsequently sequenced. Gene yscD was amplified only in type-strain ATCC 12472. MspI and AluI digestion revealed 16S rDNA polymorphisms. This data allowed the generation of a dendogram for each analysis. The isolates of C. violaceum have variability in random genomic regions demonstrated by RAPD. Also, these isolates have variability in pathogenicity genes, as demonstrated by sequencing and restriction enzyme digestion.

ANTI-QUORUM SENSING ACTIVITY OF SOME MEDICINAL PLANTS.

BACKGROUND: Quorum sensing is the key regulator of virulence factors of Pseudomonas aeruginosa such as biofilm formation, motility, productions of proteases, hemolysin, pyocyanin, and toxins. The aim of this study was to explore the effect of the extracts from some medicinal plants on quorum sensing and related virulence factors of P. aeruginosa. MATERIAL AND METHODS: Quorum sensing inhibitory (OSI) effect of the alcohol extracts of 20 medicinal plants was evaluated by Chromobacterium violaceum reporter using agar cup diffusion method. The efficient QSI extracts were tested for their activity against biofilm synthesis, motility, and synthesis of pyocyanin from P. aeruginosa PA14. RESULTS: The extracts of Citrus sinensis, Laurus nobilis, Elettaria cardamomum, Allium cepa, and Coriandrum sativum exhibited potent quorum quenching effect. On the other hand, Psidium guajava and Mentha longifolia extracts showed lower QSI activity. These extracts exhibited significant elimination of pyocyanin formation and biofilm development of Pseudomonas aeruginosa PA14. In addition, they significantly inhibited twitching and swimming motilities of P. aeruginosa PA14. CONCLUSION: This study illustrated, for the first time, the importance of C. sinensis, L. nobilis, E. cardamomum, A. cepa, and C. sativum as quorum sensing inhibitors and virulence suppressors of P. aeruginosa. Thus, these plants could provide a natural source for the elimination of Pseudomonas pathogenesis.