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At least 991 records · Page 55Linked to original sources
PubMedDate not supplied

[The urease test for the diagnosis of Campylobacter pylori infection].

To evaluate the usefulness of urea media routinely applied in the diagnosis of Campylobacter pylori infection, 50 patients with gastroduodenal pathology were studied. Two biopsies of antral mucosa were taken; one of them was placed on Urea Agar Base (Difco) prepared without agar, and the other in saline for Gram staining and culture in selective and enriched media. In 39 patients Campylobacter pylori was found by Gram staining and/or culture. 38 of them were urease test positive, 24 (61.5%) during the first hour, 8 (20.5%) between the first and fourth hours and 6 (15.3%) between 4 and 24 hours. The sensitivity of the test increased from 61.5% at the first hour to 82.0% and 97.3% at 4 and 24 hours, respectively. The specificity was 100% for all the readings. We believe that the urease test with medium of Urea Agar Base is useful for the diagnosis of Campylobacter pylori infection. However, we recommend the selection of two or three combined methods for better confirmation of the infection.

Culture Media↗
PubMedDate not supplied

[Comparison of urease test (CLOtest) and histology in the diagnosis of Campylobacter pylori].

Campylobacter pylori has been implicated in the pathogenesis of peptic ulcer, non-ulcer dyspepsia and chronic gastritis. C. pylori produces large amounts of urease which has been used as a biochemical support to identify the microorganism. In this study, we described the use of a rapid urease test (CLOtest) to detect C. pylori. In 46 consecutive patients, biopsy of fundus and antrum were obtained for histology and CLOtest. All specimens showed chronic gastritis. In 22 patients (48%) C. pylori was identified either by histology or CLOtest. In 18 patients (39%) CLOtest was positive and in 16 patients (35%) histology was positive. In 12 patients (26%) C. pylori was identified by both tests. There was no difference in relation to the presence of C. pylori in fundus and antrum. However, in 2 patients (4%) C. pylori was positive in fundus and negative in antrum. In 9 patients (20%) C. pylori was positive in antrum and negative in fundus. CLOtest is a simple, sensitive and rapid test that enables the endoscopist to diagnose C. pylori infection in the endoscopy room.

Adult↗
PubMedDate not supplied

[Immobilization of urease from Staphylococcal saprophyticus L-1 on activated silica].

The paper deals with immobilization of urease obtained from Staphylococcus saprophyticus L-1 on the organic silica surfaces. The process completion time (4-5 h) and the optimal pH of binding (7-8) are practically independent of the chemical nature of the carrier surface. The value of the specific activity of urease grafted to silica depends not only on the type of the enzyme-carrier bond, but also on the macromolecule protein-to-silica distance. The extent of the retained enzyme activity is shown to be 26% after sorption on the initial silica. It grows to 100% with an increase of the organic radical length which separates the biocatalyst and the carrier.

Chemical Phenomena↗
PubMed1989

Usefulness of culture, histology, and urease testing in the detection of Campylobacter pylori.

Several tests have been described which detect the presence of Campylobacter pylori (CP) in the human upper gastrointestinal tract. Antral biopsies from 160 endoscopies were evaluated for the presence of CP; four tests readily available to the practicing endoscopist were used: two urease tests [CLOtest and microtiter biopsy urease test (MBUT)], hematoxylin and eosin staining, and culture. Sensitivity and specificity of each was evaluated and found to be near 90%, except for culture, which was less sensitive. The presence of peptic disease on endoscopy, and age greater than 50 yr, did play a small role in the sensitivity and specificity of the tests. With the advantage of lower cost, ease, and rapidity of performance, either the CLOtest or MBUT is recommended for the standard endoscopic evaluation for CP.

Age Factors↗
PubMed1987

Infection (urease) stones.

Infection-induced stones in man probably form solely as a consequence of urealysis which is catalyzed by the bacterial protein urease. Urease stones composed of struvite and carbonate-apatite may form primarily, or as secondary stones or pre-existent metabolic stones. Struvite stones form and grow rapidly owing to (a) supersaturation of urine with stone forming salts, (b) 'salting out' of poorly soluble organic substances normally dissolved in urine and (c) ammonia-induced destruction of the normally protective urothelial glycosaminoglycan layer. Immature (predominantly organic) matrix stones mature into densely mineralized stones. Curative treatment is possible only by eliminating all of the stone and by eradicating all urinary and parenchymal infection. A variety of operative and pharmaceutical approaches are available. Patient treatment must be individualized inasmuch as some patients are better candidates for one type of treatment than another.

Humans↗
PubMed1987

[Effects of some physiologic factors on Bacillus sp. urease activity].

In this study, culture supernatant of Bacillus sp. has been used as crude enzyme source. It has been determined that 1% urea is the optimal substrate concentration for maximal urease activity. On the other hand, Bacillus sp. urease showed its maximal activity at pH:7.0-8.0, 30 degrees C. 50 minutes of incubation has been found to be the most suitable incubation period. The activity of the enzyme showed a 36% decrease when stored at +4 degrees C for a month.

Bacillus↗
PubMed1987

Rapid urease test in the management of Campylobacter pyloridis-associated gastritis.

Campylobacter pyloridis colonization of the stomach may be an etiological factor in gastritis and peptic ulceration. Campylobacter pyloridis produces large amounts of urease, and the presence of this enzyme in gastric mucosa usually indicates infection with the organism. In this paper we describe the use of a rapid urease test (CLOtest) to detect C. pyloridis infection in gastric mucosal biopsies. In 141 consecutive endoscopy cases, antral biopsies were taken for culture and histology, and an extra biopsy was inserted into the CLOtest gel. There were 79 patients infected with C. pyloridis, 78 of whom were detected by CLOtest: 75% were positive at 20 min, 92% at 3 h, and 98% at 24 h. There were no false positive results. Eighteen infected patients were rebiopsied after a course of amoxycillin and bismuth subcitrate. Active chronic gastritis resolved in eight of nine who were cleared of the organism, but histological gastritis was unchanged in nine patients who were still infected. CLOtest is a simple, sensitive, and highly specific test that enables the endoscopist to diagnose C. pyloridis infection in the endoscopy room. A negative test after antibiotic therapy correlates with clearance of the bacteria and healing of active gastritis.

Amoxicillin↗
PubMed1987

Orally ingested microencapsulated urease and an adsorbent, zirconium phosphate, to remove urea in kidney failure.

Dialysis is the conventional treatment for chronic renal failure. It is cumbersome, expensive and time-consuming and thus alternate treatments have long been sought. A compact system consisting of haemoperfusion in series with ultrafiltration can nearly replace dialysis. A urea removal system is the only step required to complete this approach. The potential of combining a microencapsulated enzyme, urease, with an ammonium ion adsorbent, zirconium phosphate, to remove urea was examined in vitro. Urease converts urea to ammonium ions which are then adsorbed onto zirconium phosphate. This combination would be most effective in the intestinal tract. The capacity of zirconium phosphate is probably not enough to effect the removal of enough urea to completely replace dialysis in patients with no renal function. However, this system could potentially 1) delay the onset of dialysis therapy in patients who still have some renal function, either alone or in combination with haemoperfusion-ultrafiltration, or 2) reduce dialysis treatment times.

Adsorption↗
PubMedDate not supplied

[Urease immobilization on macroporous silicas].

Urease was immobilized on macroporous silicas using gamma-aminopropyl triethoxysilane and glutaraldehyde. The amount of protein on the surface, the structure of pores of the support and the purity of the initial enzyme were varied, the enzymic activity of the immobilized preparations being controlled. After the immobilization of sufficiently large quantities of the enzyme (about 3 mg protein per m2 support) about 35% of the specific activity was retained. The maximum activity per unit weight of the support was observed for silicagels and silochromes with the mean diameter of pores 70-90 nm and the specific surface area about 70 m2/g. The use of purified urease produced highly active preparations of the immobilized enzyme (17,000 U per g dry support). Freeze-drying of the immobilized enzyme in the presence of sorbitol yielded dry preparations retaining their activity.

Enzymes, Immobilized↗
PubMedDate not supplied

[Properties of urease immobilized on silochrome by means of disulfide bonds].

Grafting of SH-groups to the silica surface through the hydrolytically stable Si-C-bond is conducted by gamma-mercaptopropyltrimethoxysilane. After 2,2'-dithiobis-p-nitrobenzoic acid (Ellman's reagent) activation of sulphydryl groups urease of microbial origin was immobilized by these carriers. Certain properties of the preparations obtained were studied. The Km of the enzyme during nonporous silicon aerosil immobilization is shown to remain without considerable changes. The found variations in properties of silochrome-immobilized urease are caused by the diffusion inhibition for the substrate and product of the reaction observed even when the substrate concentration is two orders higher than Km.

Catalysis↗
PubMed1982

Inhibitors of bacterial urease: microbiological considerations on hydroxyurea influenza virus.

Hydroxyurea is a well known enzyme urease inhibitor. Bacteria strains producers of enzyme urease can be the cause of struvite calculosis. Clinical studies have shown that treatment with hydroxyurea can produce acid urine in patients suffering from struvite calculosis. In this work antiurease and antibacterial activity of hydroxyurea was valued in vitro against Proteus mirabilis strains. Our results seem not to agree with the ones obtained in vivo.

Escherichia coli↗
PubMed1980

Prevention of infected urinary stones in rats by urease inhibitor: a new hydroxamic acid derivative.

We tested the inhibitory power and urinary excretion of several derivatives of hippurohydroxamic acid, including some newly synthesized compounds. m-Methoxyhippurohydroxamic acid (UCD II) strongly inhibited urease activity and high urinary excretion after oral administration to rats. UCD II inhibited the alkalinization of infected urine in vitro and in vivo and prevented bladder stone formation when it was orally administered to rats with urinary tract infection caused by Proteus mirabilis. The clinical application of UCD II to the prevention of pathologic sequelae of urinary infection with urease-producing bacteria awaits evaluation of the safety of the compound.

Animals↗
PubMed1982

A rapid, simple and reliable test for the routine identification of urease producing gram-negative bacteria.

The present investigation was prompted by the need to find a simple, rapid, reliable and low-cost method for the routine identification of urease producing bacteria. This method uses Nessler's reagent as an indicator of the presence of volatile ammonia produced by organisms which possess urease. The proposed method is comparable to the conventional Christensen's agar method, but is simpler and more rapid to perform.

Bacteriological Techniques↗
PubMed1980

[Equilibrium of the reactions of synthesis and hydrolysis of carbamide in the presence of urease].

The values of Km and V, pH optimum and thermal stability of urease were determined. It was shown that urease can be effectively used for the study of equilibrium of synthesis and hydrolysis of carbamide under conditions of carbamide in the ammonium carbonate--carbamide--water system at 20 degrees and 37 degrees were determined. The equilibrium constants for carbamide synthesis at the given temperatures were calculated.

Hydrolysis↗
PubMed1995

[Amplifying Helicobacter pylori's urease gene by nested polymerase chain reaction].

By using nested polymerase chain reaction (PCR) composed of three primers that derived from Helicobacter pylori's (Hp) urease gene region, we have not only successfully amplified control Hp and 214 clinic samples but also studied deeply preparation of the sample, composition of PCR reaction liquid and circulatory mental conditions of the PCR. So this method shortens the operation time, simplifies processes and reduces costs. Compared with urease test (54%) and Warthin-Starry silver stained test (50%), ever used the positive rate of PCR is the highest (61%), so our method is more specific, sensitive, simple, rapid and accurate, and could be applied to the routine clinical detection.

Adolescent↗
PubMed1995

Competitive inhibitors of free and chitosan-immobilized urease.

The influence of four inhibitors: boric acid, thioglycolic acid, sodium fluoride and acetohydroxamic acid on the activity of urease, both in the native form and immobilized covalently on glutaraldehyde-pretreated chitosan membrane, was studied. Urea hydrolysis was carried out in phosphate buffer, pH 7, at 25 degrees C at urea concentration of 50 mM. The immobilized urease was more resistant than the native one to the action of all the investigated inhibitors, except boric acid. This property of the enzyme offers a possibility of its practical application.

Binding Sites↗
PubMed1993

Serum 13C-bicarbonate in the assessment of gastric Helicobacter pylori urease activity.

Noninvasive detection of Helicobacter pylori (HP) requires serum or salivary antibody testing or the CO2 breath test. Since gastric HP produces a potent urease, a meal rich in 13C-labeled urea should lead to a measurable quantity of isotopic CO2 in the serum. This study investigates the feasibility, sensitivity, specificity, and potential of the measurement of serum 13C-bicarbonate (13CHCO3) in determining the presence of gastric HP. Nineteen patients with upper gastrointestinal symptoms assessed by intensity-duration questionnaire underwent endoscopy and biopsies for histology, Giemsa stain, and urease activity testing by CLOtest. Patients also consumed a 13C-urea-rich meal (5 mg/kg body weight, 99% 13C, MSD Isotopes, Montreal Canada). Serum was collected every 30 min for 3 h for quantitative determination of 13C by mass spectrometry. Fractional elevation of 13C after the enriched meal was then correlated with endoscopy, histology, and CLOtest. Fourteen of the 19 patients studied had histologic evidence of gastritis; 11 of 19 had positive CLOtest and had HP by histology and Giemsa stain. All HP-positive patients had significant elevation of 13CHCO3, compared with HP-negative patients. The mean maximum absolute change from baseline was 15.3 delta 13CHCO3 (range, 6.7-29.9) and occurred from 15 to 90 min; 13CHCO3 in HP-negative patients was significantly less (p < 0.05) than HP-positive patients with a mean value of 2.3 delta 13CHCO3 (range, 0-5.3). We conclude that serum 13CHCO3 analysis accurately reflects HP gastritis. This novel method is noninvasive, less labor intensive, less time consuming, and may have a value as a diagnostic screening tool for humans or in the assessment of the results of therapy in patients with HP infection.

Bicarbonates↗
PubMed1994

The rapid urease test in the diagnosis of Helicobacter pylori infection.

With the increasing recognition of the importance of H. pylori in gastrointestinal disease, there is a need for a reliable, efficient and yet inexpensive diagnostic test. The performance of the rapid urease test (RUT) as an endoscopy suite diagnostic test was compared to the established methods of culture, histology and Gram stain of tissue smear, in 274 gastric biopsy samples. Histology had the highest sensitivity of 99.3% followed by the RUT (96.6%). Culture and Gram stain of tissue smear had 100% specificity, while the rapid urease test had 99.2% specificity. The RUT had a positive predictive value of 99.3% and a negative predictive value of 96.2%. The RUT is an inexpensive, rapid and reliable diagnostic test of H. pylori infection.

Biopsy↗