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At least 19 recordsLinked to original sources

PubMed1975

Comparison of Sirius red and Congo red as stains for amyloid in animal tissues.

Sirius red and Congo red were compared for specificity and sensitivity of amyloid staining in animal and human material. Previously described advantages of Sirius red as an amyloid dye were confirmed, as well as its disadvantage of lack of ultraviolet fluorescence. Two further disadvantages of Sirius red were discovered, both relating to animal material: (a) its unexpectedly weak staining of early experimentally induced amyloid deposits and (b) frequent uncontrollable nonspecific staining of fibrous tissues. It is therefore concluded that, overall, Congo red used by the improved alkaline technique of Puchtler, Sweat and Levine (1962) remains the best single method for demonstration of amyloid in both human and animal tissues.

Amyloid↗

PubMed1976

Clinical significance of Congo red test.

Clinical significance of Congo red test was studied, especially on its relation to the liver function and amyloidosis. No significant relationship was observed between Congo red test and Indocyanin green test in cases of various liver diseases except liver cirrhosis. Histological studies also revealed that there were no pathologic features specifically affecting Congo red index (CRI), even though CRI in cases of various liver diseases tended to be increased as compared with other diseases. As a cause of increased CRI which was seen most remarkably in cases of liver cirrhosis, obstructive change of the liver blood flow followed by the hepatic tissue damage is suspected. The concept that Congo red test is a kind of the hepatic excretory function test does not have, from our data, enough evidence. The present study confirmed our previous data on the fate of Congo red injected intravenously, which indicated that this test is one of the best tests available for RES function and this test is related mainly to Kupffer's cell rather than to the so-called hepatic excretory function. There were no cases which showed notable decrease of CRI in experimental amyloidosis and in clinical amyloidosis, and it can be said that Congo red test is not the best test for the diagnosis of amyloidosis.

Acute Disease↗

PubMedDate not supplied

The congo red stain revisited.

The Congo red stain has undergone several modifications since it was first used by Bennhold in 1922 in order to increase the specificity for staining amyloid. Most of the laboratories in the United States use the method of Puchtler which uses alkaline Congo red solution. Some of the variables associated with the procedure were investigated by us. Our results showed the following: (1) amyloid showed green birefringence at all levels between 4 to 12 mu thick sections with better visualization of small deposits with increased thickness. Best results were obtained with 8 mu thick sections; (2) omission of the pretreatment with alkaline alcoholic solution of sodium chloride (NaCl) did not affect the sensitivity of the method; (3) the use of polar mounting media had no effect on amyloid and collagen birefringence; (4) 50 percent saturation of the Congo red staining solution with NaCl caused strong staining of collagen, elastic fibers and eosinophilic granules. In addition, collagen showed green birefringence and dichroism and its differentiation from amyloid became difficult; and (5) using the staining solution fully saturated with NaCl, no positive staining was seen with tissues other than amyloid. Collagen and elastic fibers showed red fluorescence which was of less intensity than amyloid. It is our conclusion that the method of Puchtler for detecting amyloid gives better results if the staining solution is fully saturated with NaCl. The pretreatment step may be deleted without compromising the quality of staining. Improved staining of amyloid enhances the specificity of green birefringence, dichroism, and red fluorescence.

Amyloid↗

PubMed1988

Differentiation of phase I and variant strains of Bordetella pertussis on Congo red media.

The addition of Congo red, Trypan blue or haemin to the growth medium allowed the differentiation of phase-I and variant strains of Bordetella pertussis. Phase-I strains produced red (CR+), blue or dark brown colonies on a modified cyclodextrin solid medium containing Congo red, Trypan blue or haemin, respectively, whereas variant (Vir- and phase IV) strains grew as pale (CR-) colonies. Spontaneous CR- variants were isolated and characterised and had a phenotype like that of Vir- or phenotypically modulated, C-mode strains in that they did not produce the haemolysin, haemagglutinin(s), histamine-sensitising factor (pertussis toxin), heat-labile toxin and two major envelope polypeptides associated with phase-I strains. Two such variants had reduced virulence for mice. CR+ strains, when grown on a high nicotinic acid medium to induce modulation, gave CR- colonies. Thus the CR+ phenotype is a characteristic of phase-I B. pertussis and its expression appears to be controlled in a manner similar to that of other phase I-related factors. CR- variants of B. parapertussis and B. bronchiseptica were also deficient in these factors. Four isolates of B. avium were CR-.

Bordetella pertussis↗

PubMed1977

Detection and differentiation of iron-responsive avirulent mutants on Congo red agar.

Agar medium containing Congo red dye differentiates virulent and avirulent colonies of Shigella, Vibrio cholerae, Escherichia coli, and Neisseria meningitidis. Like virulent plague bacilli, wild-type cells of these species absorb the dye and produce red colonies. Mutants or colonial variants have been isolated that fail to absorb the dye and produce colorless colonies. These mutants exhibit reduced virulence in the chicken embryo model, but their virulence is enhanced by supplementation with iron. Of those species tested, only Neisseria gonorrhoeae isolates failed to grow in the presence of this dye. Inhibition of growth by Congo red may thus provide a simple means for differentiating gonococci from other Neisseria.

Bacteria↗

PubMed1988

Inhibition of cell-cell interactions in Myxococcus xanthus by congo red.

The function of molecules associated with the cell surface may be determined by examining the phenotype of cells treated with inhibitors specific to these cell surface molecules. This strategy was used to examine the function of the major Congo red receptor of the myxobacterium Myxococcus xanthus, which has a developmental cycle that involves social interactions among cells. A class of social motility mutations (A+ S-), known as dsp, may inhibit the same subcellular component as Congo red because the phenotype of wild-type cells which had been treated with Congo red resembled in several ways the phenotype of the Dsp mutants. First, Congo red inhibited agglutination of wild-type cells, whereas Dsp cells were incapable of agglutinating, even in the absence of Congo red. Second, Congo red inhibited fruiting body formation by wild-type cells and reduced the yield of myxospores. Untreated Dsp cells were unable to form fruiting bodies and produced few myxospores. Third, Congo red reduced the rate of wild-type gliding motility to a level comparable to that of untreated Dsp cells, but did not inhibit the A motility of Dsp cells. Finally, binding studies showed that Dsp cells lacked the major Congo red receptor. Wild-type cells bound Congo red with an apparent association constant of 2.4 X 10(5) M-1, while Dsp cells bound it with an apparent association constant of 8.5 X 10(3) M-1. Binding of Congo red to wild-type cells was saturated in less than 10 min and was reversible when excess Congo red was removed. These results suggest that the Congo red receptors are controlled by the S motility system and that these receptors are involved in cell cohesion, social motility, and fruiting body formation.

Agglutination↗

PubMed1989

Quantitative evaluation of congo red binding to amyloid-like proteins with a beta-pleated sheet conformation.

The binding of Congo red to several purified amyloid-like peptides having a beta-pleated sheet conformation was quantitatively examined. Congo red binds preferentially to the beta-pleated sheet conformation of both insulin fibrils and poly-L-lysine. Congo red does not bind nearly so well to poly-L-serine or polyglycine, despite the fact that these peptides also have a beta-pleated sheet conformation. Binding to insulin fibrils was saturable with an apparent Bmax of 2 moles of Congo red per mole of insulin fibrils and an apparent KD of 1.75 x 10(-7) M. Binding to beta-poly-L-lysine was similar but had a much higher apparent Bmax of 43. Binding of Congo red to beta-poly-L-lysine was pH dependent and appeared to be determined by the number of protonated lysine residues in the 250 amino acid peptide. We present a new hypothesis in which Congo red binds to amyloid-like proteins via bonds between the two negatively charged sulfonic acid groups of Congo red and two positively charged amino acid residues of two separate protein molecules which are properly oriented by virtue of the beta-pleated sheet conformation of the peptide backbone.

Amyloid↗

PubMedDate not supplied

Congo red binding of Escherichia coli isolated from the cloacae of psittacine birds.

Binding of Congo red dye by Escherichia coli is associated with the pathogenicity of the organism. The purpose of the present study was to determine the incidence of Congo red binding exhibited by E. coli isolated from the cloacae of psittacine birds, to examine the association between the Congo red status of the E. coli isolates and the health status of birds, and to assess the potential value of Congo red binding as a screening test for identifying pathogenic strains of E. coli isolated form the cloacae of psittacine birds. Escherichia coli was isolated from the cloacae of 120/435 (28%) psittacine birds; 17/120 (14%) of the E. coli isolates bound the dye (Congo red-positive) and 103/120 (86%) did not bind the dye (Congo red-negative). All of the Congo red-positive isolates were recovered from subjectively abnormal birds, whereas Congo red-negative isolates were recovered from both subjectively normal (71/120 [59%]) and abnormal (32/120 [27%]) birds.

Animals↗

PubMed1987

Congo red uptake by motile Aeromonas species.

Virulence of several species of enteropathogenic bacteria has been correlated with the ability of isolates to take up the dye Congo red. To determine whether Congo red uptake might be a useful marker for virulence of motile Aeromonas species, we examined 50 strains of diverse clinical origin on a medium containing 50 micrograms of Congo red per ml. All of the strains took up the dye to various degrees. For most strains, uptake was greatest at 37 degrees C and least at 22 degrees C. Production of acetyl methyl carbinol (Voges-Proskauer test) or lysine decarboxylase has been reported by some investigators to be a virulence marker for Aeromonas species. Congo red uptake did not correlate with either acetyl methyl carbinol or lysine decarboxylase production in our study. These data suggest that Congo red uptake may not be a useful marker for virulence of motile Aeromonas species.

Aeromonas↗

PubMed1988

Congo red binding of elastin in aortic smooth muscle cell cultures.

These studies demonstrate that the strong binding capacity of elastin for Congo red can be used to advantage in aortic smooth muscle cell cultures. A fibrous elastin network fluoresces when Congo red is added. Congo red does not alter accumulation of elastin or of total protein, even when the cells are grown in the presence of the dye for long periods of time, indicating that it is not toxic. Porcine pancreatic elastase was used to solubilize elastin in these cultures, to determine the molar ratio of Congo red to elastin, thus making it possible to estimate the amount of elastin solubilized when the cultures are injured. Congo red binding to elastin will be useful in studying elastin accumulation and/or degradation in vitro and in vivo.

Animals↗

PubMed1986

Characterization of Shigella flexneri sequences encoding congo red binding (crb): conservation of multiple crb sequences and role of IS1 in loss of the Crb+ phenotype.

The ability to bind Congo red (Crb+) is associated with virulence of Shigella flexneri and is encoded by a large, 220-kilobase plasmid. We cloned fragments of this plasmid to isolate the sequences encoding Congo red binding, to determine the degree of conservation of these sequences among S. flexneri strains, and to study the molecular basis for loss of the Crb+ phenotype. At least two separate BamHI fragments cloned into plasmid vectors encode Congo red binding in E. coli or S. flexneri. One Crb+ clone, pTKS2, contains a copy of IS1 adjacent to the crb sequences. IS1 appears to be responsible for deletions leading to loss of Congo red binding in this clone. In addition, this clone was found to integrate into the chromosome at relatively high frequency. Integration resulted in loss of the Crb+ phenotype. A second clone, pTKS15, which has only limited homology to pTKS2, also encodes Congo red binding. The Crb+ phenotype of transformants carrying pTKS15 was detected at 37 degrees C but not at 30 degrees C, and thus it resembles Congo red binding in wild-type S. flexneri. HindIII digests of plasmid DNA from 10 different S. flexneri strains were hybridized to both of these Crb+ clones and to an IS1 probe. More than one fragment hybridized to pTKS2 or pTKS15. In general, the sizes of these fragments were the same in S. flexneri strains of different serotypes, indicating conservation of these sequences. Three of five copies of IS1 were also found on the large S. flexneri plasmids. Two of the copies were on fragments of the same size in each strain. Analysis of Crb- derivatives of the 10 strains indicated that, although IS1 may be closely linked to crb sequences on the 220-kilobase plasmid, it is not responsible for the majority of deletions of this plasmid associated with loss of Congo red binding.

Base Sequence↗

PubMed1978

Demonstration of amyloid with Mesitol WLS-Congo Red: application of a textile auxiliary to histochemistry.

Previous histochemical investigations demonstrated similarities in the binding of Congo Red and other direct cotton dyes by amyloid and cellulose. It seemed therefore of interest to determine whether or not the cellulose-like reactivity of amyloid extends also to dye solutions containing an anionic reserving agent. These reagents are used in the dyeing of wool-cellulose (Halbwolle) fabrics to prevent binding of direct cotton dyes by proteins. Mesitol WLS-Congo Red solutions stained amyloid selectively; other tissue structures, except some hyaline deposits in arterioles, remained unstained. The cause of this non-specific reaction could not be determined with certainty. Therefore, the alkaline Congo Red method is recommended for histochemical identification of amyloid. However, the Mesitol WLS-Congo Red technic was very useful for demonstration of amyloid after prolonged storage of tissues in formalin; amyloid in such material showed little or no reactivity with the alkaline Congo Red or the Sirius dye methods. This pilot study indicates that anionic reserving agents can be effectively employed under conditions of histochemical technics.

Amyloid↗

PubMedDate not supplied

Congo red binding by Escherichia coli isolates from chickens.

An attempt was made to use a recently reported special Congo red medium to determine the pathogenicity of Escherichia coli isolates obtained from chickens. The inclusion of bile salts in the Congo red medium as described in previous reports by others was found in the current experiments to cause the production of red colonies from almost all E. coli cultures tested, including known Congo red-negative control cultures. Cultures of E. coli, regardless of their pathogenic history, rarely produced red colonies on the Congo red medium without added bile salts. Numerous isolates of other bacterial genera were examined and found to produce red colonies on the Congo red medium with or without added bile salts.

Animals↗

PubMedDate not supplied

Congo red binding test in enteroinvasive and nonpathogenic Escherichia coli strains.

Out of 6 variants the appropriate media to perform Congo red binding test for enteroinvasive E. coli strains were established (trypto-soy agar Eiken, T.S.A.--Cantacuzino Institute and B.T.S.D.). 12 E. coli strains belonging to enteroinvasive O-serogroups formed on Congo red agar red-coloured, non-coloured colonies or both; cultures from 59 red colonies and 61 white colonies were inoculated in guinea pig eyes. The correlation between positive Congo red binding test and positive Sereny test was 91% (out of 59 red colonies, 47 evoked keratoconjunctivitis in both infected eyes and 7 in only one eye). The negative Congo red binding test corresponds (98.4%) to the failure to induce illness in the guinea pigs' eye (only one out of 61 Crb = colonies was Sereny positive, evoking keratoconjunctivitis in only one of the two infected eyes of a guinea pig). Comparing in vivo lack of pathogenicity in 44 E. coli strains isolated from human normal intestinal flora and negative Congo red binding test, a correlation of 72.73% on B.T.S.D. and 65.91% on T.S.A. medium was found. Developing an appropriate method based on Crb test about 70% of the nonpathogenic E. coli colonies could be eliminated from the laborious agglutination with enteroinvasive O-serogroups E. coli antisera.

Animals↗

PubMed1976

Congo red vital staining of cornea and conjunctiva.

Vital staining with an aqueous solution of 1% Congo red has been studied in the slit lamp. In 98 cases the dye was mixed with 1% lissamine green, in 120 eyes subsequent staining was performed with 0.125% fluorescein, and in 80 cases the mucous thread from the inferior conjunctival fornix was microscoped. Congo red stains dead cells, degenerate cells, and mucus. The dye discloses keratitis, corneal erosion, contact lens damages, corrosions, etc. It stains like lissamine green and rose bengal, though less frequently and less intensely than these. Congo red is a pH indicator. Acid reaction beyond its pH-range (3.0-5.2) has not been demonstrated. Amyloid-specific colour reaction (red-green dichromatic polarisation) has been noticed in mucous fibrils, most often in relation to infectious conjunctivitis and corrosion, never in normal eyes. The phenomenon is believed to indicate degeneration of the mucous fibrils (on the analogy of toluidine-blue-stained mucus), whereas not presence of genuine amyloid. It is, in other words, an important phenomenon in the differential diagnosis. Congo red is hardly indicated in ordinary clinical practice for vital staining of cornea and conjunctiva. Fluorescein, combined with rose bengal or lissamin green should be preferred.

Congo Red↗

PubMed1988

Congo red binding and salt aggregation as indicators of virulence in Shigella species.

Smooth strains of Shigella dysenteriae type 1, Shigella flexneri, Shigella boydii, and Shigella sonnei which form pigmented colonies (Pcr+) on Congo red agar were virulent in the Sereny test. Smooth variants unable to bind Congo red (Pcr-) were avirulent. Measurements of dye uptake from solution showed that S. dysenteriae type 1 bound the most dye, followed in order of uptake by S. flexneri, S. boydii, and S. sonnei. Using the salt aggregation test (SAT) to determine cell surface hydrophobicity, we found the same order of species. The SAT could not, however, detect differences in surface properties between Pcr+ and Pcr- pairs of isogenic smooth strains. Enteroinvasive Escherichia coli strains used in the study showed SAT and Congo red-binding properties which were similar to those of the S. flexneri strains. A direct correlation was found between pigment-binding ability and the presence of the large 140-megadalton plasmid in S. flexneri, enteroinvasive E. coli, and S. boydii but not in S. dysenteriae type 1 or S. sonnei strains. Congo red interacted with outer membranes and outer membrane proteins of S. dysenteriae type 1 but not with lipopolysaccharides. However, rough mutants of Shigella species deficient in lipopolysaccharides bound Congo red and formed pigmented colonies, showing that dye binding as a virulence assay may be misinterpreted in such cases. There was complete correlation of the Pcr+ phenotype with virulence in the smooth strains in this study, suggesting that Congo red binding can be utilized as a quick and reliable alternative to the Sereny test.

Bacterial Adhesion↗

PubMedDate not supplied

Correlation between Congo red binding as virulence marker in Shigella species and Sereny test.

Six variants of nutrient agar were tested in order to chose the suitable media for Congo red binding test. Trypto-soy Eiken, T.S.A - Cantacuzino Institute and B.T.S.D. (a medium prepared with Difco ingredients) are appropriate to distinguish between virulent Crb+ and avirulent Crb- strains. Congo red binding was compared with Sereny test using 25 Shigella strains. The strains were inoculated onto trypto-soy agar Eiken plates with 0.01% Congo red, incubated 24 hours at 37 degrees C. A number of each kind (Crb+ and Crb-) of colonies developed by every strain was subcultured on nutrient agar and Sereny test was performed with these cultures. As expected, all 84 Crb+ colonies in vivo tested, produced keratoconjunctivitis. In the case of Crb- colonies a proper correlation with Sereny negative test was observed in 57 out of 73 colonies (78.2%) to which 10.9% (8 out of 73) less virulent (evoking illness in only one of the two inoculated eyes) colonies may be added. As our results confirmed that loss of pigmentation was consistently accompanied by loss or diminishing of virulence, we consider that Congo red binding may be used as an alternative of in vivo test for establishing the virulence of Shigellae in the routine practice of microbiology laboratories which usually are not provided with cell cultures or animals. Its reduced cost is an important advantage, too.

Animals↗

PubMed1987

Congo red binding phenotype is associated with hemin binding and increased infectivity of Shigella flexneri in the HeLa cell model.

Wild-type isolates of Shigella flexneri bind the dye Congo red from solid media, thus producing red (Crb+) colonies. Mutants which fail to bind the dye produce white colonies (Crb-) and are avirulent in a variety of systems. In S. flexneri the ability to bind Congo red correlates with the ability to bind hemin and protoporphyrin IX. Binding of hemin by Crb+ S. flexneri was observed both in solid media and in liquid assays. Results of competition experiments suggest that Congo red and hemin bind to the same site on the bacterial cell and are retained on the cell surface. Binding of hemin by Crb+ S. flexneri is independent of hemin transport since both Crb+ and Crb- cells can utilize hemin as a sole source of iron. Both Crb- and Crb- organisms were able to grow in HeLa cell lysates, indicating that the gene(s) that is responsible for Congo red binding does not play a role in the acquisition of intracellular heme iron. By using the HeLa cell invasion system, the effect of hemin prebinding on the invasiveness of Crb+ S. flexneri was determined. Crb+ cells which had prebound hemin exhibited increased invasiveness, indicating a possible role for the crb gene product in the initial stages of invasion by S. flexneri.

Congo Red↗