PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Rhodococcus”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 685 records · Page 38Linked to original sources
PubMed2005

Rhodococcus equi can survive a phagolysosomal environment in macrophages by suppressing acidification of the phagolysosome.

Rhodococcus equi is one of the most important causes of pneumonia in foals and has emerged as a significant opportunistic pathogen of immunosuppressed hosts such as human immunodeficiency virus-infected patients. Virulent R. equi harbouring an 85 kb plasmid, but not the avirulent form lacking the plasmid, has the ability to survive in macrophages. However, the survival mechanism is not known. In the present study, morphological interactions were observed between virulent or plasmid-cured avirulent R. equi and phagolysosomes in murine macrophage-like J774.1 cells by immunocytological methods. The J774.1 cells phagocytosed virulent and avirulent bacteria to a similar extent, and both bacteria replicated in single membrane vacuoles at similar rates up to 6 h after infection. Thereafter, the virulent bacteria continued to grow, whereas the avirulent bacteria stopped growing. When the infected cells were stained with phagosomal and lysosomal markers and observed with a confocal fluorescence microscope, the majority of phagosomes containing these bacteria were fused with lysosomes. Neither R. equi organism has the ability to hinder phagosome-lysosome fusion. The acidity in phagolysosomes containing R. equi was examined by staining with LysoTracker Red DND-99, an acidotropic probe. The phagolysosomes containing virulent organisms were not acidic as compared with avirulent organisms. Over 90% of the phagolysosomes containing avirulent R. equi were stained with LysoTracker 6 h after infection, whereas less than 50% of those containing virulent R. equi were stained. Furthermore, when the supernatant obtained from a virulent R. equi culture was added to the cell cultures, the acidity of acidic compartments in macrophages was reduced. The authors conclude that some substance(s) produced by virulent R. equi suppress acidification in phagolysosomes, and help R. equi survival and replication in the bactericidal environment.

Amines↗
PubMed2004

A linear megaplasmid, p1CP, carrying the genes for chlorocatechol catabolism of Rhodococcus opacus 1CP.

The Gram-positive actinobacterium Rhodococcus opacus 1CP is able to utilize several (chloro)aromatic compounds as sole carbon sources, and gene clusters for various catabolic enzymes and pathways have previously been identified. Pulsed-field gel electrophoresis indicates the occurrence of a 740 kb megaplasmid, designated p1CP. Linear topology and the presence of covalently bound proteins were shown by the unchanged electrophoretic mobility after S1 nuclease treatment and by the immobility of the native plasmid during non-denaturing agarose gel electrophoresis, respectively. Sequence comparisons of both termini revealed a perfect 13 bp terminal inverted repeat (TIR) as part of an imperfect 583/587 bp TIR, as well as two copies of the highly conserved centre (GCTXCGC) of a palindromic motif. An initial restriction analysis of p1CP was performed. By means of PCR and hybridization techniques, p1CP was screened for several genes encoding enzymes of (chloro)aromatic degradation. A single maleylacetate reductase gene macA, the clc gene cluster for 4-chloro-/3,5-dichlorocatechol degradation, and the clc2 gene cluster for 3-chlorocatechol degradation were found on p1CP whereas the cat and pca gene clusters for the catechol and the protocatechuate pathways, respectively, were not. Prolonged cultivation of the wild-type strain 1CP under non-selective conditions led to the isolation of the clc- and clc2-deficient mutants 1CP.01 and 1CP.02 harbouring the shortened plasmid variants p1CP.01 (500 kb) and p1CP.02 (400 kb).

Catechols↗
PubMed2005

N-Acylhomoserine lactone quorum-sensing molecules are modified and degraded by Rhodococcus erythropolis W2 by both amidolytic and novel oxidoreductase activities.

The Rhodococcus erythropolis strain W2 has been shown previously to degrade the N-acylhomoserine lactone (AHL) quorum-sensing signal molecule N-hexanoyl-L-homoserine lactone, produced by other bacteria. Data presented here indicate that this Gram-positive bacterium is also capable of using various AHLs as the sole carbon and energy source. The enzymic activities responsible for AHL inactivation were investigated in R. erythropolis cell extracts and in whole cells. R. erythropolis cells rapidly degraded AHLs with 3-oxo substituents but exhibited relatively poor activity against the corresponding unsubstituted AHLs. Investigation of the mechanism(s) by which R. erythropolis cells degraded AHLs revealed that 3-oxo compounds with N-acyl side chains ranging from C8 to C14 were initially converted to their corresponding 3-hydroxy derivatives. This oxidoreductase activity was not specific to 3-oxo-AHLs but also allowed the reduction of compounds such as N-(3-oxo-6-phenylhexanoyl)homoserine lactone (which contains an aromatic acyl chain substituent) and 3-oxododecanamide (which lacks the homoserine lactone ring). It also reduced both the D- and L-isomers of n-(3-oxododecanoyl)-L-homoserine lactone. A second AHL-degrading activity was observed when R. erythropolis cell extracts were incubated with N-(3-oxodecanoyl)-L-homoserine lactone (3O,C10-HSL). This activity was both temperature- and pH-dependent and was characterized as an amidolytic activity by HPLC analysis of the reaction mixture treated with dansyl chloride. This revealed the accumulation of dansylated homoserine lactone, indicating that the 3O,C10-HSL amide had been cleaved to yield homoserine lactone. R. erythropolis is therefore capable of modifying and degrading AHL signal molecules through both oxidoreductase and amidolytic activities.

4-Butyrolactone↗
PubMed2006

The Ralstonia eutropha H16 phasin PhaP1 is targeted to intracellular triacylglycerol inclusions in Rhodococcus opacus PD630 and Mycobacterium smegmatis mc2155, and provides an anchor to target other proteins.

In Ralstonia eutropha, the H16 phasin PhaP1 represents the major phasin that binds to the surface of polyhydroxyalkanoate (PHA) inclusions. In this study, C-terminal fusions of PhaP1 with enhanced green fluorescent protein (eGFP) and with Escherichia coli beta-galactosidase (LacZ) were expressed separately in the triacylglycerol (TAG)-accumulating actinomycetes Rhodococcus opacus PD630 and Mycobacterium smegmatis mc(2)155, employing the M. smegmatis acetamidase (ace) promoter of the Escherichia-Mycobacterium/Rhodococcus shuttle plasmid pJAM2. PhaP1 and the PhaP1 fusion proteins were expressed stably in the recombinant strains. Western blot analysis of cell fractions of Rh. opacus revealed that PhaP1 and the PhaP1-eGFP fusion protein were associated with the TAG inclusions, whereas no phasin or phasin fusion protein was detected in the soluble and membrane fractions. Additional electron microscopy/immunocytochemistry studies demonstrated that PhaP1 was mainly located on the surface of intracellular TAG inclusions; in addition, some PhaP1 also occurred at the plasma membrane. Fluorescence microscopic investigations of the subcellular distribution of the PhaP1-eGFP fusion protein in vivo and on isolated TAG inclusions revealed that the fusion protein was bound to TAG inclusions at all stages of their formation, and to some extent at the cytoplasmic membrane. The PhaP1-LacZ fusion protein also bound to the TAG inclusions, and could be separated together with the inclusions from Rh. opacus crude extracts, thus demonstrating the immobilization of beta-galactosidase activity on the inclusions. This is believed to be the first report demonstrating the ability of PhaP1 to bind to lipid inclusions in addition to PHA inclusions. Furthermore, it was demonstrated that this non-specificity of PhaP1 can be utilized to anchor enzymically active fusion proteins to a matrix of bacterial TAG inclusions.

Bacterial Proteins↗
PubMed2002

4-Chlorocatechol 1,2-dioxygenase from the chlorophenol-utilizing Gram-positive Rhodococcus opacus 1CP: crystallization and preliminary crystallographic analysis.

4-Chlorocatechol 1,2-dioxygenase (4-ClC1,2DO) from the Gram-positive bacterium Rhodococcus opacus (erythropolis) 1CP, an enzyme involved in the aerobic biodegradation of chloroaromatic compounds, has been crystallized. 4-ClC1,2DO, which specifically catalyzes the intradiol cleavage of 4-substituted catechols, which are intermediates in the degradation of a variety of aromatic pollutants, to the corresponding maleylacetates, has recently been purified to homogeneity. The enzyme is an homodimer composed of two identical subunits in an alpha(2)-type quaternary structure; it has a molecular weight of about 29 kDa per monomer and contains one Fe(III) and one Mn(II) ion per homodimer. Hexagonal crystals grown in 1.6 M ammonium sulfate, 0.1 M sodium chloride, 100 mM Tris-HCl pH 9.0, 5-15% glycerol were successfully frozen under liquid nitrogen, adding 30% glycerol to the mother-liquor solution as a cryoprotectant. A complete data set was collected at 2.8 A resolution using the EMBL beamline BW7A at the DORIS storage ring, DESY, Hamburg, Germany with a MAR CCD detector and a wavelength of 1.01 A. The crystals belong to the primitive hexagonal space group P6(3)22, with unit-cell parameters a = 90.4, c = 307.5 A. This is the first intradiol dioxygenase which specifically catalyzes the cleavage of chlorocatechols in Gram-positive bacteria to give diffraction-quality crystals.

Chlorophenols↗
PubMed2002

Preliminary crystallographic analysis of 3-chlorocatechol 1,2-dioxygenase of a new modified ortho-pathway from the Gram-positive Rhodococcus opacus 1CP grown on 2-chlorophenol.

3-Chlorocatechol 1,2-dioxygenase (3-ClC1,2DO), a key enzyme of a new modified ortho-pathway, was isolated from a variant of the Gram-positive bacterium Rhodococcus opacus 1CP utilizing 2-chlorophenol as the sole energy and carbon source via a 3-chlorocatechol branch of a modified ortho-pathway. 3-ClC1,2DO catalyzes the intradiol cleavage of 3-chlorocatechol. The enzyme contains Fe(III) ions essential to the catalytic activity; it is a homodimer with a molecular weight of about 58 kDa composed of two identical subunits in an (alphaFe)(2)-type quaternary structure. Its physicochemical properties are intermediate between those of the pyrocatechase from the ordinary pathway and those of the chloro-pyrocatechase from the modified pathway described previously for this strain. 3-ClC1,2DO was crystallized using the sitting-drop vapour-diffusion method. After 2 d, prismatic crystals grew in 15% PEG 8000, 0.3 M magnesium acetate, 100 mM HEPES pH 7.5, 5% glycerol. X-ray diffraction data were collected from a frozen crystal to a maximum resolution of 2.0 A using 25% PEG 400 as cryoprotectant at the Elettra synchrotron source, Trieste, Italy, at a wavelength of 1.01 A using a MAR CCD detector. The crystals belong to space group P1, with unit-cell parameters a = 83.18, b = 86.61, c = 93.44 A. Assuming a reasonable range for V(M), the asymmetric unit could contain from three to five (alphaFe(III))(2) dimers. A peak present in the kappa = 180 degrees and kappa = 90 degrees sections is consistent with a fourfold axis and four dimers in the asymmetric unit. Comparison of the crystal structure of this enzyme with that of the 4-chlorocatechol 1,2-dioxygenase recently crystallized from the same bacterium (Ferraroni et al., 2002) may reveal important details of the influence of the active-site conformation and the amino-acid substitutions involved in substrate selectivity.

Chlorophenols↗
PubMed2006

Crystallization and preliminary X-ray analysis of a bacterial L-amino-acid oxidase from Rhodococcus opacus.

L-Amino-acid oxidases (EC 1.4.3.2) catalyse the stereospecific oxidative deamination of an L-amino-acid substrate to an alpha-keto acid with the production of ammonia and hydrogen peroxide. In this study, the crystallization and preliminary X-ray analysis of a bacterial L-amino-acid oxidase from Rhodococcus opacus (RoLAAO) is described. RoLAAO is a dimeric protein consisting of two identical subunits of 489 amino acids with a calculated molecular weight of 54.2 kDa and a non-covalently bound FAD molecule. RoLAAO was crystallized by the vapour-diffusion method in two different space groups: P2(1)2(1)2(1) (unit-cell parameters a = 65.7, b = 109.7, c = 134.4 A) and C222(1) (unit-cell parameters a = 68.3, b = 88.4, c = 186.6 A). Both crystal forms diffracted X-rays to a resolution of at least 1.6 A.

Crystallization↗
PubMed1988

Differentiation between genera Rhodococcus and Nocardia by susceptibility testing to kanamycin and some other antituberculosis agents.

The test for susceptibility to kanamycin is useful for differentiating between the genera Rhodococcus and Nocardia. All rhodococci except R. equi, R. erythropolis, and R. aurantiacus are susceptible to kanamycin, whereas all nocardiae except N. otitidis-caviarum are resistant to kanamycin. Tests for susceptibility to rifampicin, streptomycin, and minocycline also are useful for differentiating among the species of each genus.

Animals↗
PubMed1990

Granuloma-forming activity and antitumor activity of newly isolated mycoloyl glycolipid from Rhodococcus terrae 70012 (Rt. GM-2).

A newly isolated mycoloyl glycolipid (Rt. GM-2) from Rhodococcus terrae 70012 was identified and the granulomagenic and antitumor activities were studied as compared with trehalose-6,6'-dimycolate (cord factor) also from R. terrae (Rt. TDM). The alkaline hydrolysis products of Rt. GM-2 contained trehalose, methyl-alpha-mycolate and a less-polar ester than the usual methyl-alpha-mycolate, possibly beta-keto mycolate (1:1:1, by mol. ratios). On the other hand, analysis of alditol acetate obtained after the mild permethylation, NaBH4 reduction, and acetylation showed the occurrence of 2,3,4-tri-O-methyl-6-O-acetylglucitol. Therefore, the original glycolipid (Rt. GM-2) was identified tentatively as 6-O-alpha-mycoloyl 6'-O-beta-ketomycoloyl trehalose. Intravenous injection of Rt. GM-2 in the form of water-in-oil-in-water emulsion caused prominent granulomas in lungs and spleen of ICR and BALB/c mice. The granulomagenic effects were as strong as those caused by Rt. TDM. The lung and spleen weights reached peaks one week after an injection of Rt. GM-2 in mice and then gradually decreased. Multiple intravenous injections of Rt. GM-2 and Rt. TDM showed antitumor activity against subcutaneously implanted Sarcoma-180, and caused prominent granulomatous changes and growth suppression of mice.

Adjuvants, Immunologic↗
PubMed1990

Induction of interferons (IFNs) and tumor necrosis factor (TNF) in mice by a novel glycolipid trehalose 2,3,6'-trimycolate from Rhodococcus aurantiacus (Gordona aurantiaca).

The immunomodifying activity of a novel mycoloyl glycolipid, trehalose 2,3,6'-trimycolate (GaGM), from a unique psychrophilic acid-fast bacterium, Rhodococcus aurantiacus, was examined. ICR mice were primed intravenously (i.v.) or intraperitoneally (i.p.) with liposomes containing GaGM (300 micrograms/mouse), and were administered LPS dissolved in saline (25 micrograms/mouse, i.v.) 2 weeks later. Two hours after injection of LPS, interferons (IFNs) and tumor necrosis factor (TNF) were induced significantly in mice sera. The increase in activities of IFNs and TNF was approximately paralleled with granuloma formation in spleen of mice primed with GaGM. However, IFNs and TNF were not induced either in mice primed with GaGM but not elicited with LPS, or in those primed with GaGM and elicited by GaGM. Both activities induced were lower in mice primed with trehalose mono- or dimycolate from R. aurantiacus (GaTMM, GaTDM) or TDM from Nocardia rubra than in GaGM-primed mice. Time course study showed that the maximum activity of each interferon (alpha, beta, or gamma) was observed at different stages after LPS administration; IFN-alpha, IFN-beta, and IFN-gamma appeared 3, 2, and 6 hours most abundantly after LPS administration, respectively.

Animals↗
PubMed1991

Mycolic acid-containing glycolipid as a possible virulence factor of Rhodococcus equi for mice.

By the use of various Rhodococcus equi strains differing in the length of carbon chains of glycolipid, we examined whether the glycolipid, glucose monomycolate, was contributing to the virulence of R. equi for mice. R. equi strains with longer carbon chain mycolic acid showed a higher virulence as determined by lethality and granuloma formation in mice than those with shorter ones. When purified glycolipid was injected into mice, granuloma formation and liver damage were most prominent with the glycolipid having longer carbon chain mycolic acid. Only a representative strain with longer carbon chain mycolic acid persisted in the spleen of mice after intravenous injection, while a strain with shorter carbon chain mycolic acid was readily eliminated. These results suggested that glycolipid was at least one of the virulence factors of R. equi and that the carbon chain length of mycolic acid might be critical in the expression of virulence.

Actinomycetales Infections↗
PubMed1995

Development of a new selective plating medium for Rhodococcus equi.

A new selective plating medium for Rhodococcus equi containing ceftazidime (20 mg/l) and novobiocin (25 mg/l) on a Mueller-Hinton agar basis is described. It proved to be less inhibitory for R. equi than selective plating media devised earlier and grew only very few other nocardioform bacteria.

Actinomycetales Infections↗
PubMed1995

Sequential involvement of NK cells and CD8+ T cells in granuloma formation of Rhodococcus aurantiacus-infected mice.

We investigated the effect of in vivo administration of antibodies against T-cell subsets and natural killer (NK) cells on endogenous gamma interferon (IFN-gamma) production and granuloma formation in Rhodococcus aurantiacus-infected mice. High titers of endogenous IFN-gamma were detected in the extracts of the livers and spleens during 24 hr of the infection, reaching the peak at 8 hr, and the IFN-gamma production was reduced by in vivo administration of anti-NK 1.1 monoclonal antibody (MAb) or antibody against asialo GM1+ cells. Endogenous IFN-gamma declined until 2 days of the infection, then reappeared from 1 week and peaked at 3 weeks. Endogenous IFN-gamma at 1 and 3 weeks was reduced by in vivo administration of anti-CD8 MAb, but not by anti-CD4 MAb or anti-NK 1.1 MAb. Granulomatous lesions in the livers and spleens began to appear from 1 week of the infection and developed in 3 weeks. In vivo administration of rat anti-IFN-gamma MAb reduced the development of granulomas. In addition, granuloma formation was reduced by depletion of NK cells prior to the infection or depletion of CD8+ T cells at 1 week of the infection. Based on these findings, it is presumed that the biphasic production of IFN-gamma is attributable to NK cells in the early phase of the infection and CD8+ T cells in the phase of granuloma formation, and that granuloma formation is regulated by NK cells and CD8+ T cells through the secretion of endogenous IFN-gamma.

Actinomycetales Infections↗
PubMed1996

Expression of virulence-associated antigens of Rhodococcus equi is regulated by temperature and pH.

We recently reported that there are two different virulence-associated antigens correlated with virulence levels in Rhodococcus equi isolates from AIDS patients: virulent R. equi that kills mice with 10(6) cells expresses 15- to 17-kDa antigens and intermediately virulent R. equi that kills mice with 10(7) cells expresses a 20-kDa antigen. Environmental parameters were evaluated for their effects on the expression of these virulence-associated antigens in virulent R. equi strains by immunoblotting using monoclonal antibodies in this study. Expression of these two virulence-associated antigens of R. equi was regulated by pH and temperature; the antigens were produced maximally when the isolates were grown at 38 C and pH 6.5, but were not produced when grown at 38 C and pH 8, nor at temperatures below 30 C. The 20-kDa antigen was found to be located on the cell surface, as were the 15- to 17-kDa antigens, and showed susceptibility to proteolysis by trypsin. These results indicate that expression of the virulence-associated antigens of R. equi is dependent on the environmental conditions.

Antibodies, Bacterial↗
PubMed2005

Immune response to the Rhodococcus equi infection in high and low antibody-producing mice (Selection IV-A).

Rhodococcus equi is a gram-positive, facultative intracellular bacterium which infects macrophages and causes rhodococcal pneumonia and enteritis in foals. Recently, this agent has been recognized as an opportunistic pathogen for immunocompromised humans. Several murine experimental models have been used to study R. equi infection. High (H(IV-A)) and Low (L(IV-A)) antibody (Ab)-producers mice were obtained by bi-directional genetic selections for their ability to produce antibodies against sheep and human erythrocytes (Selection IV-A). These lines maintain their phenotypes of high and low responders also for other antigens than those of selection (multispecific effect). A higher macrophage activity in L(IV-A) mice has been described for several intracellular infectious agents, which could be responsible for their intense macrophage antigens (Ag)-handling and low Ab production. Due to these differences, L(IV-A) mice were found to exhibit a better performance to trigger an effective immune response towards intracellular pathogens. The objective of this work was to characterize the immune response of Selection IV-A against R. equi. H(IV-A) and L(IV-A) mice were infected with 2.0x10(6) CFU of ATCC 33701+R. equi by intravenous route. With regards to bacterial clearance and survival assays, L(IV-A) mice were more resistant than H(IV-A) mice to virulent R. equi. L(IV-A) mice presented a higher hydrogen peroxide (H2O2) and nitric oxide (NO) endogenous production by splenic macrophages than H(IV-A) mice. L(IV-A) expressed the most intense cellular response, available by the Delayed-Type Hypersensitivity (DTH) reaction, which activated macrophages and produced more H2O2 and NO. The three times higher specific antibodies titres in H(IV-A) indicated that Selection IV-A maintained the multispecific effect and the polygenic control of humoral and cellular responses also to R. equi.

Actinomycetales Infections↗
PubMed2003

Up-regulation of granulomatous inflammation in interleukin-6 knockout mice infected with Rhodococcus aurantiacus.

After intravenous injection of Rhodococcus aurantiacus normal mice develop non-necrotic granulomas, the formation of which is dependent on endogenous interferon-gamma (IFN-gamma). In the early phase of R. aurantiacus infection a high level of endogenous interleukin-6 (IL-6) is detected in the spleen extracts, though its importance is unknown. Using IL-6 knockout (IL-6-/-) mice, we studied the role of IL-6 in granulomatous inflammation induced by R. aurantiacus. The size of granulomas generated in IL-6-/- mice was significantly larger than that of wild-type (IL-6+/+) mice at 2 weeks postinjection (p.i). Moreover, central necrosis of the granuloma was observed in IL-6-/- mice but not in IL-6+/+ controls. Titres of endogenous IFN-gamma and tumour necrosis factor-alpha (TNF-alpha) were markedly increased in the spleens and livers of IL-6-/- mice in comparison with IL-6+/+ mice at days 1 through 3 p.i. In vivo administration of either an anti-IFN-gamma monoclonal antibody (mAb) or anti-TNF-alpha mAb to IL-6-/- mice reduced the number and size of granulomas, and prevented formation of necrotic granulomas. In addition, the production of endogenous IFN-gamma and TNF-alpha in the early phase of R. aurantiacus infection by IL-6-/- mice was suppressed by treatment with recombinant IL-6 (rIL-6). This suppression of IFN-gamma and TNF-alpha production was followed by a reduction in the number and size of central necrotic granulomas at 2 weeks p.i. These findings suggest that overproduction of IFN-gamma and TNF-alpha induces central necrotic granuloma formation in IL-6-/- mice, and that IL-6 down-regulates granulomatous inflammation reaction in response to R. aurantiacus infection by modulating production of IFN-gamma and TNF-alpha.

Actinomycetales Infections↗
PubMed1994

Haemolytic and phospholipase C (PLC) activities of Rhodococcus equi.

Rhodococcus equi, an intracellular organism causing pneumonia and lung abscesses in foals, is generally thought to be non-haemolytic. In the present study, however, 13 of 14 representative isolates were found to be haemolytic when tested on agar media containing washed red blood cells rather than whole blood. Red cells of rabbits, dogs, horses and man were more sensitive to lysis than were those of ruminants. Two new enzymatic activities of the species were defined: a lecithinase and a phosphatidylinositol-specific phospholipase C (PI-PLC). As judged from tests for trypsin, temperature and ethanol sensitivity, the haemolytic activity was primarily dependent on PI-PLC though the participation of lecithinase seemed probable. The haemolytic activity of growing strains, but not of cell-free preparations, was partially inhibited by lecithin but enhanced by cholesterol; however, cholesterol oxidase (CO) activity, known to mediate cooperative lysis of RBC sensitized with sphingomyelin-specific phospholipases C or D of some other species, did not contribute to the direct haemolysis caused by R. equi as demonstrated here.

Actinomycetales Infections↗