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PubMed2003

The complete genome sequence of Chromobacterium violaceum reveals remarkable and exploitable bacterial adaptability.

Chromobacterium violaceum is one of millions of species of free-living microorganisms that populate the soil and water in the extant areas of tropical biodiversity around the world. Its complete genome sequence reveals (i) extensive alternative pathways for energy generation, (ii) approximately 500 ORFs for transport-related proteins, (iii) complex and extensive systems for stress adaptation and motility, and (iv) widespread utilization of quorum sensing for control of inducible systems, all of which underpin the versatility and adaptability of the organism. The genome also contains extensive but incomplete arrays of ORFs coding for proteins associated with mammalian pathogenicity, possibly involved in the occasional but often fatal cases of human C. violaceum infection. There is, in addition, a series of previously unknown but important enzymes and secondary metabolites including paraquat-inducible proteins, drug and heavy-metal-resistance proteins, multiple chitinases, and proteins for the detoxification of xenobiotics that may have biotechnological applications.

Adaptation, Physiological↗
PubMed2004

Chromobacterium violaceum genome: molecular mechanisms associated with pathogenicity.

Chromobacterium violaceum is a versatile, Gram-negative beta-protebacterium that grows in a variety of ecosystems in tropical and subtropical areas, such as the water and borders of the Negro River, in the Amazon region of Brazil. Although it is a saprophyte and is generally considered non-pathogenic, sporadic cases of human infection have been described, mainly in young children and in immunodeficient individuals. Although rare, infections with C. violaceum are characterized by rapid dissemination and high mortality. With the complete genome sequence of C. violaceum now available, a detailed description of the molecular arsenal required for this bacterium's remarkable versatility has been revealed. Most importantly, a more detailed picture of its biotechnological properties, including the characteristic violacein pigment, has emerged. The complete genome sequence also enabled us to make a thorough examination of the repertoire of genes encoding probable virulence factors, which determine the potential for pathogenesis. We described a number of genes involved in infectious processes, such as host cell adhesion, "contact-dependent secretion" of factors that promote cell invasion, as well as other virulence factors, such as cytolytic proteins. We also described genes involved with the synthesis of lipopolysaccharides and proteoglycan, known to elicit the synthesis of pro-inflammatory cytokines and involved in the detoxification process, which may contribute to the evasion of the bacteria from the host immune response.

Bacterial Adhesion↗
PubMed2006

Anti-quorum sensing activity of medicinal plants in southern Florida.

Bacterial intercellular communication, or quorum sensing (QS), controls the pathogenesis of many medically important organisms. Anti-QS compounds are known to exist in marine algae and have the ability to attenuate bacterial pathogenicity. We hypothesized that terrestrial plants traditionally used as medicines may also produce anti-QS compounds. To test this hypothesis, 50 medicinal plants from southern Florida were screened for anti-QS activity using two biomonitor strains, Chromobacterium violaceum and Agrobacterium tumefaciens. Of these plants, six showed QS inhibition: Conocarpus erectus L. (Combretaceae), Chamaecyce hypericifolia (L.) Millsp. (Euphorbiaceae), Callistemon viminalis (Sol. ex Gaertn.) G. Don (Myrtaceae), Bucida burceras L. (Combretaceae), Tetrazygia bicolor (Mill.) Cogn. (Melastomataceae), and Quercus virginiana Mill. (Fagaceae). This study introduces not only a new mode of action and possible validation for traditional plant use, but also a potentially new therapeutic direction for the treatment of bacterial infections.

Anti-Bacterial Agents↗
PubMed1999

Regulation of expression of the nonhemolytic phospholipase C of Burkholderia cepacia.

Burkholderia cepacia is an opportunistic pathogen that causes serious pulmonary infections in cystic fibrosis patients. We have purified and partially characterized one potential virulence factor for the organism-a nonhemolytic phospholipase C-and we studied the effect of iron restriction and choline and phosphate concentrations on the expression of phospholipase C. Iron limitation did not affect expression, the effect of choline was variable, and high phosphate concentrations repressed expression. Experiments with heat-treated spent culture supernatants suggested that autoinducers affected the expression of the phospholipase and two other potential virulence factors, a protease and a lipase. We screened 26 B. cepacia isolates for autoinducer activity: 11 induced violacein production in the autoinducer-deficient mutant Chromobacterium violaceum CV026. Spent supernatants from two strains, one that was positive in the C. violaceum assay and one that was negative, were tested for inducing early expression of phospholipase C, protease, and lipase in homologous and heterologous cultures. Expression of all three enzymes was increased or induced at an earlier stage in the growth curve in every case, suggesting not only that autoinducers were involved in the regulation of the expression of these enzymes, but also that the autoinducers were of two different classes.

Burkholderia cepacia↗
PubMed1997

Quorum sensing in Vibrio anguillarum: characterization of the vanI/vanR locus and identification of the autoinducer N-(3-oxodecanoyl)-L-homoserine lactone.

Certain gram-negative pathogens are known to control virulence gene expression through cell-cell communication via small diffusible signal molecules termed autoinducers. This intercellular signal transduction mechanism termed quorum sensing depends on the interaction of an N-acylhomoserine lactone (AHL) auto-inducer molecule with a receptor protein belonging to the LuxR family of positive transcriptional activators. Vibrio anguillarum is a gram-negative pathogen capable of causing a terminal hemorrhagic septicemia known as vibriosis in fish such as rainbow trout. In this study, we sought to determine whether V. anguillarum employs AHLs to regulate virulence gene expression. Spent V. anguillarum culture supernatants stimulated bioluminescence in a recombinant lux-based Escherichia coli AHL biosensor strain, whereas they both stimulated and inhibited AHL-mediated violacein pigment production in Chromobacterium violaceum. This finding suggested that V. anguillarum may produce multiple AHL signal molecules. Using high-performance liquid chromatography and high-resolution tandem mass spectrometry, we identified the major V. anguillarum AHL as N-(3-oxodecanoyl)-L-homoserine lactone (ODHL), a structure which was unequivocally confirmed by chemical synthesis. The gene (vanI) responsible for ODHL synthesis was cloned and sequenced and shown to belong to the LuxI family of putative AHL synthases. Further sequencing downstream of vanI revealed a second gene (vanR) related to the LuxR family of transcriptional activators. Although deletion of vanI abolished ODHL synthesis, no reduction of either metalloprotease production or virulence in a fish infection model was observed. However, the vanI mutant remained capable of weakly activating both bioluminescence and violacein in the E. coli and C. violaceum biosensors, respectively, indicating the existence of additional layers of AHL-mediated regulatory complexity.

Amino Acid Sequence↗
PubMed2005

Quorum sensing signal molecules (acylated homoserine lactones) in gram-negative fish pathogenic bacteria.

The aim of the present study was to investigate the production of quorum sensing signals (specifically acylated homoserine lactones, AHLs) among a selection of strains of Gram-negative fish bacterial pathogens. These signals are involved in the regulation of virulence factors in some human and plant-pathogenic bacteria. A total of 59 strains, representing 9 different fish pathogenic species, were tested against 2 AHL monitor bacteria (Agrobacterium tumefaciens NT1 [pZLR4] and Chromobacterium violaceum CV026) in a well diffusion assay and by thin-layer chromatography (TLC). Representative samples were further characterized by high performance liquid chromatography-high resolution mass spectrometry (HPLC-HR-MS). AHLs were produced by all strains of Aeromonas salmonicida, Aeromonas hydrophila, Yersinia ruckeri, Vibrio salmonicida, and Vibrio vulnificus. Some strains of atypical Aeromonas salmonicida and Vibrio splendidus were also positive. Aeromonas species produced N-butanoyl homoserine lactone (BHL) and N-hexanoyl homoserine lactone (HHL) and 1 additional product, whereas N-3-oxo-hexanoyl homoserine lactone (OHHL) and HHL were detected in Vibrio salmonicida. N-3-oxo-octanoyl homoserine lactone (OOHL) and N-3-octanoyl homoserine lactone (OHL) were detected in Y. ruckeri. AHLs were not detected from strains of Photobacterium damselae, Flavobacterium psychrophilum or Moritella viscosa. AHLs were extracted from fish infected with Y. ruckeri but not from fish infected with A. salmonicida. In conclusion, the production of quorum sensing signals, AHLs, is common among the strains that we examined. If the AHL molecules regulate the expression of the virulence phenotype in these bacteria, as shown to occur in some bacterial pathogens, novel disease control measures may be developed by blocking AHL-mediated communication and suppressing virulence.

4-Butyrolactone↗
PubMed1998

Airways microbial flora in COPD patients in stable clinical conditions and during exacerbations: a bronchoscopic investigation.

Patients affected with chronic obstructive pulmonary disease (COPD) undergo frequent exacerbations of their illness characterized by increased cough and expectoration. The precise aetiology of these episodes often remains unknown. In the absence of clinical or radiographic signs of pneumonia, bacterial or viral cultures of sputum usually provide little useful information. Thus, we performed fibreoptic bronchoscopy using a protected specimen brush (PSB) to obtain uncontaminated secretions for culture from 56 patients with COPD, 16 with stable clinical conditions and 40 affected with exacerbations of the disease. The aim of our study was to evaluate bronchial microbial flora by quantitative aerobic and anaerobic culture of each specimen. Twenty five subjects (45%), 4 (16%) in stable state and 21 (84%) with COPD exacerbations, had specimens which gave rise to significant bacterial growth (> 10(3) colony forming units.mL-1). The predominant bacteria were Streptococcus pneumoniae (in 10 cases) and alpha-haemolytic streptococci (in 6 cases); other bacteria found were coagulase-negative staphylococci and Branhamella catarralis in (2 cases each), and Proteus mirabilis, Haemophilus influenzae, Pseudomonas aeruginosa, Aerococcus viridans and Chromobacterium violaceum (each in a single case only). Although significant bacterial growth was more frequently found in patients with chronic obstructive pulmonary disease exacerbations and in those with a higher degree of bronchial inflammation, the differences between the two groups of patients were not statistically significant. Nevertheless, the results obtained in our study confirm the validity of and the need for reliable sampling methods (like the protected specimen brush) to demonstrate significant bacterial colonization of the airways in chronic obstructive pulmonary disease patients.

Aged↗
PubMed1994

Molecular structures that influence the immunomodulatory properties of the lipid A and inner core region oligosaccharides of bacterial lipopolysaccharides.

The relationship between chain length as well as the position of fatty acyl groups to the ability of lipid A to abolish the expression of suppressor T-cell (Ts) activity was examined. Fatty acyl chain lengths of C12 to C14, as in the lipid A of Escherichia coli and Salmonella minnesota, appear to be optimal for this bioactivity, since lipid A preparations with fatty acyl groups of relatively short chain length (C10 to C12 for Pseudomonas aeruginosa and Chromobacterium violaceum) or predominantly long chain length (C18 for Helicobacter pylori) are without effect. The presence of an acyloxyacyl group of appropriate chain length at the 3' position of the glucosamine disaccharide backbone of lipid A also plays a decisive role. By contrast, the lipid A proximal inner core region oligosaccharides of some bacterial lipopolysaccharides increase the expression of Ts activity; this is due mainly to the capacity of such oligosaccharides, which are relatively conserved in structure among gram-negative bacteria, to enlarge or expand upon the population of CD8+ Ts generated during the course of a normal antibody response to unrelated microbial antigens. The minimal structure required for the expression of the added immunosuppression observed appears to be a hexasaccharide containing one 2-keto-3-deoxyoctonate residue, two glucose residues, and three heptose residues to which are attached two pyrophosphorylethanolamine groups. The relevance of these findings to virulence and to the pathogenesis of gram-negative infections is discussed.

Animals↗
PubMed2001

Production of N-acyl homoserine lactones by gram-negative bacteria isolated from contact lens wearers.

The purpose of this study was to investigate the production of N-acyl-homoserine lactone (AHL) signal molecules in ocular gram-negative bacteria. A total of 91 ocular strains isolated from contact lens adverse response patients and asymptomatic subjects were used in the study. These included Acinetobacter, Aeromonas hydrophila, Escherichia coli, Haemophilus influenzae, Klebsiella oxytoca, Pseudomonas aeruginosa, Serratia liquefaciens, Serratia marcescens, and Stenotrophomonas maltophilia. The biosensor strains Chromobacterium violaceum mutant CV026 and Agrobacterium tumefaciens A136 were used for detection of AHL signal molecules. The majority of A. hydrophila, P. aeruginosa, and S. liquefaciens strains produced more than one AHL molecule. Serratia marcescens strains were AHL positive only under detection of A136. The rest of the test species did not show any AHL production under the current detection system. These findings indicate that AHL-mediated quorum-sensing systems are present in some of the ocular bacteria, and the different signal molecules may be involved with the quorum-sensing pathway in the other bacterial species.

4-Butyrolactone↗
PubMed2001

Laribacter hongkongensis gen. nov., sp. nov., a novel gram-negative bacterium isolated from a cirrhotic patient with bacteremia and empyema.

A bacterium was isolated from the blood and empyema of a cirrhotic patient. The cells were facultatively anaerobic, nonsporulating, gram-negative, seagull shaped or spiral rods. The bacterium grows on sheep blood agar as nonhemolytic, gray colonies 1 mm in diameter after 24 h of incubation at 37 degrees C in ambient air. Growth also occurs on MacConkey agar and at 25 and 42 degrees C but not at 4, 44, and 50 degrees C. The bacterium can grow in 1 or 2% but not 3, 4, or 5% NaCl. No enhancement of growth is observed with 5% CO(2). The organism is aflagellated and nonmotile at both 25 and 37 degrees C. It is oxidase, catalase, urease, and arginine dihydrolase positive, and it reduces nitrate. It does not ferment, oxidize, or assimilate any sugar tested. 16S rRNA gene sequencing showed that there are 91 base differences (6.2%), 112 base differences (7.7%), and 116 base differences (8.2%) between the bacterium and Microvirgula aerodenitrificans, Vogesella indigofera, and Chromobacterium species, respectively. The G+C content (mean and standard deviation) is 68.0% +/- 2.43%, and the genomic size is about 3 Mb. Based on phylogenetic affiliation, the bacterium belongs to the Neisseriaceae family of the beta-subclass of Proteobacteria. For these reasons, a new genus and species, Laribacter hongkongensis gen. nov., sp. nov., is proposed, for which HKU1 is the type strain. Further studies should be performed to ascertain the potential of this bacterium to become an emerging pathogen.

Bacteremia↗
PubMed1983

Isolation and identification of ropy bacteria in raw milk.

Approximately 4.2% of 4,000 Maryland-Virginia raw milk tanker samples developed ropiness when incubated at 10 degrees C. Of the 56 bacterial isolates 30 were identified by species. Klebsiella oxytoca and Pseudomonas aeruginosa were isolated most frequently. Other ropy isolates were identified as Pseudomonas spp., Chromobacterium, Flavobacterium multivorum, presumptive Yersinia pestis, Enterobacter agglomerans, Klebsiella pneumoniae, and Pasteurella-Actinobacter spp. Six of the Klebsiella oxytoca isolates were mesophilic (optimum temperatures of 32.0 to 37.8 degrees C) with two isolates having psychrotrophic tendencies (optimum temperature of 26.8 degrees C). All Pseudomonas aeruginosa isolates appeared to be psychrotropic in their temperature requirements (optimum temperature of 23.0 to 31.0 degrees C). Klebsiella oxytoca was significant in preliminary development of the ropy condition. All Klebsiella oxytoca isolates developed ropiness within 24 h. The Pseudomonas spp. and Klebsiella pneumoniae isolates required at long as 7 days to develop detectable ropiness at 10 degrees C. A recommended Klebsiella oxytoca differentiation agar is presented as a rapid screening method during outbreaks where Klebsiella oxytoca is the organism of significance.

Animals↗
PubMed1979

[Combination of 5-fluorocytosine and amphotericin B in the treatment of chromomycosis].

The authors discuss the problem of resistance of chromomycosis to 5-fluorocytosine (5-FC), observed in a previous study in 7 patients initially treated with the drug and subsequently treated with 5-FC associated with other medicaments. All the associations, including that with amphotericin B, failed to overcome resistance. Experiments in mice and "in vitro" show a synergism between 5-FC and amphotericin B against "C. albicans", "C. neoformans" and "Fonsecaeae pedrosoi" already confirmed in human subjects infected with the above mentioned fungi. Resistance to 5-FC seems to be irreversible, as shown in previous experiments. The mechanism of action of the drugs on the fungi is discussed, as well as the fact that amphothericin B prevents the development of resistance to 5-FC. Results obtained with the use of the above association in 5 cases of chromomycosis are presented; all the patients had old and well established lesions, and in three cases these lesions were large and disseminated, conditions probably associated with the development of resistance to 5-FC used alone. The drugs were given in small doses, inferior to those usually recommended. The good therapeutic results seem to confirm the synergism observed in laboratory trials. Four cases were discharged as cured and one abandoned treatment for personal reasons. The association seems to act more rapidly than 5-FC alone. Tolerance was excellent in all cases.

Adult↗