Rubropunctatin-silver composite nanoliposomes for eradicating Helicobacter pylori in vitro and in vivo.

Helicobacter pylori (H. pylori) is a major factor in peptic ulcer disease and gastric cancer, and its infection rate is rising globally. The efficacy of traditional antibiotic treatment is less effective, mainly due to bacterial biofilms and the formation of antibiotic resistance. In addition, H. pylori colonizes the gastrointestinal epithelium covered by mucus layers, the drug must penetrate the double barrier of mucus layer and biofilm to reach the infection site and kill H. pylori. The ethanol injection method was used to synthesize nanoliposomes (EPI/R-AgNPs@RHL/PC) with a mixed lipid layer containing rhamnolipids (RHL) and phosphatidylcholine (PC) as a carrier, loaded with the urease inhibitor epiberberine (EPI) and the antimicrobial agent rubropunctatin silver nanoparticles (R-AgNPs). EPI/R-AgNPs@RHL/PC had the appropriate size, negative charge, and acid sensitivity to penetrate mucin-rich mucus layers and achieve acid-responsive drug release. In vitro experiments demonstrated that EPI/R-AgNPs@RHL/PC exhibited good antibacterial activity, effectively inhibited urease activity, removed the mature H. pylori biofilm, and inhibited biofilm regeneration. In vivo antibacterial tests showed that EPI/R-AgNPs@RHL/PC exhibited excellent activity in eradicating H. pylori and protecting the mucosa compared to the traditional clinical triple therapy, providing a new idea for the treatment of H. pylori infection.

Primary Antibiotic Resistance And Effectiveness Of Clarithromycin Vs Metronidazole Based Therapy For Helicobacter Pylori Infection In Children.

BACKGROUND: NASPGHAN guidelines recommend regional antibiotic susceptibility profiling for H. pylori eradication treatment. Profiling local antibiotic resistance patterns is mandatory for successful H. pylori eradication in children. The aim of our study was to determine primary resistance to Clarithromycin and Metronidazole, most commonly used in the eradication regimens in children presenting with symptomatic H. pylori infection. This study was conducted at Children Hospital PIMS Islamabad from June 2020 to August 2021. METHODS: The children of either gender age 2-14 years having symptomatic H. pylori infection (hematemesis, chronic abdominal pain) underwent stool for H. pylori Antigen. Children requiring urgent diagnostic endoscopy underwent rapid urease tests. Biopsies were taken from children having positive stool H. pylori Ag and rapid urease test for histological examination. The biopsy specimens were cultured and subsequently tested for antibiotic sensitivity. RESULTS: Out of 54 children having H. pylori infection 40/54 (74.074%) children had strains susceptible to antimicrobials and 14/54 (25.92%) were having resistance to antimicrobials. According to the pattern of antimicrobial sensitivity, they were further grouped into three (a) Clarithromycin and Metronidazole sensitive group (18/40, 45%) (b) Clarithromycin sensitive and Metronidazole resistant group (12/40, 30%) (c) Metronidazole sensitive group (10/40 25%). CONCLUSIONS: Clarithromycin and Metronidazole cannot be used as1stline treatment for H. pylori eradication in children and can only be used with known antimicrobial susceptibility.

Antibiotics-free nanoparticles eradicate Helicobacter pylori biofilms and intracellular bacteria.

Biofilms and intracellular survival tremendously help Helicobacter pylori (H. pylori) escape from antibacterial agents attacking, therefore issuing extreme challenges to clinical therapies. Herein, we constructed fucoidan (FU)-coated nanoparticles (FU/ML-LA/EB NPs) via simple self-assembly of biguanide derivative (metformin-linoleic acid, ML) and linoleic acid (LA), encapsulating urease inhibitor ebselen (EB) instead of antibiotics to take antibacterial effect. Negatively charged FU/ML-LA/EB NPs easily penetrated through the gastric mucus layer to arrive at infection sites, then eradicated extracellular polymeric substances (EPS) to destroy H. pylori biofilms structure. After strengthening bacterial membrane permeability, the nanoparticles could enter H. pylori and kill bacteria by inhibiting the activity of urease. FU/ML-LA/EB NPs also entered H. pylori-infected host cells through receptor-mediated internalization, in which they activated AMPK to recover lysosomal acidification for killing intracellular H. pylori. Additionally, FU/ML-LA/EB NPs alleviated oxidative stress, hence reducing gastric mucosal damage and cutting off the pathways of carcinogenesis. Notably, H. pylori burden after FU/ML-LA/EB NPs treatment was reduced to a great extent in vivo, which was significantly lower than that after treatment with clinical therapy. Antibiotics-free FU/ML-LA/EB NPs improving bacterial eradication and alleviating oxidation stress made it a powerful approach against H. pylori.

Helicobacter pylori eradication in renal transplant candidates.

INTRODUCTION: Treatment for Helicobacter pylori (H. pylori) infection is recommended in transplant candidates due to the association between this infection and gastrointestinal disorders, which could significantly increase morbidity after renal transplantation with the use of immunosuppression. The objective of this study was to analyze the rate of eradication of H. pylori after antimicrobial treatment in chronic kidney disease patients who are candidates for kidney transplantation. METHODS: A multicenter prospective cohort study was conducted. All adult chronic kidney disease patients seen at our institution were included. In the pre-transplantation evaluation, 83 patients underwent an upper gastrointestinal endoscopy with 2 diagnostic methods to detect H. pylori: histology and the rapid urease test. In total, 33 patients with H. pylori infection received treatment with 20 mg omeprazole, 500 mg amoxicillin, and 500 mg clarithromycin once daily for 14 days. Another upper gastrointestinal endoscopy was performed 8 to 12 weeks after the end of treatment to check for healing. RESULTS: The study showed a prevalence of H. pylori in 51 (61.4%) patients. Histology was positive in 50 (98%) patients and the rapid urease test was positive in 31 (60.8%). The infection eradication rate was 48.5% (16 patients). CONCLUSIONS: There was a high prevalence rate of H. pylori and a low eradication rate after the long-term antimicrobial triple scheme used. The association of the rapid urease test with gastric mucosa histology did not increase the detection rate of H. pylori.

[A prospective randomized comparative study of the efficacy and safety of a two-week bismuth-based quadrotherapy of Helicobacter pylori infection with the inclusion of the probiotic containing Bifidobacterium longum BB-46 and Enterococcus faecium ENCfa-68 ].

AIM: To study the efficacy and safety of a two-week bismuth-based quadruple of Helicobacter pylori (Hp) infection with the inclusion of a probiotic Bifiform. MATERIALS AND METHODS: An open prospective comparative randomized study included 68 Hp-positive patients: 22 with a confirmed diagnosis of peptic ulcer disease, 46 with chronic gastritis, gastroduodenitis and erosions in the pylorobulbar zone. The diagnosis and Hp infection were verified by the results of endoscopic and morphological studies, as well as using the 13C-urease breath test and determination of the Hp antigen in the feces. Depending on the therapy, the patients were randomized into 2 groups: the main group was taken 2 times a day for 14 days omeprazole 20 mg + amoxicillin 1000 mg + clarithromycin 500 mg + bismuth tripotassium dicitrate 240 mg + Bifiform 2 capsules 2 times a day; control similar therapy was carried out, but without the inclusion of Bifiform. Repeated testing for Нр was carried out one month after the termination of the course of treatment. RESULTS: When using bismuth-containing quadruple, a high frequency of Hp eradication was noted, which in the ITT analysis was 86.1 and 68.8% (p0.05) and in the PP analysis it was 93.9 and 95.7% (p0.05) in patients of the main and control groups, respectively. Side effects of drug therapy were detected in 16.7 and 43.8% (p0.05), which was the reason for the early termination of therapy as a result of their development in 5.6 and 28% (p0.05) in patients of the main and control groups, respectively. The inclusion of the probiotic Bifiform in the eradication triple therapy of Hp infection reduced the frequency of detection of colonic dysbiosis from 27.8 to 3.6% and had a positive effect on the indices of local immunity (increased content of plasma cells in the inflammatory infiltrate and a stable level of secretory immunoglobulin A in coprofiltrate). CONCLUSION: A prospective, comparative, randomized study has shown that when using a two-week bismuth-based quadruple the eradication rate exceeds 90%. The inclusion of Bifiform in the eradication scheme dramatically reduces the frequency of adverse events and increases patient compliance, and also maintains the protective factors of the gastrointestinal mucosa at a higher level.

Bacterial biofilm formation on indwelling urethral catheters.

Urethral catheters are the most commonly deployed medical devices and used to manage a wide range of conditions in both hospital and community care settings. The use of long-term catheterization, where the catheter remains in place for a period >28 days remains common, and the care of these patients is often undermined by the acquisition of infections and formation of biofilms on catheter surfaces. Particular problems arise from colonization with urease-producing species such as Proteus mirabilis, which form unusual crystalline biofilms that encrust catheter surfaces and block urine flow. Encrustation and blockage often lead to a range of serious clinical complications and emergency hospital referrals in long-term catheterized patients. Here we review current understanding of bacterial biofilm formation on urethral catheters, with a focus on crystalline biofilm formation by P. mirabilis, as well as approaches that may be used to control biofilm formation on these devices. SIGNIFICANCE AND IMPACT OF THE STUDY: Urinary catheters are the most commonly used medical devices in many healthcare systems, but their use predisposes to infection and provide ideal conditions for bacterial biofilm formation. Patients managed by long-term urethral catheterization are particularly vulnerable to biofilm-related infections, with crystalline biofilm formation by urease producing species frequently leading to catheter blockage and other serious clinical complications. This review considers current knowledge regarding biofilm formation on urethral catheters, and possible strategies for their control.

Novel tool in rheumatoid arthritis diagnosis-The usage of urease flap region peptidomimetics.

Rheumatoid arthritis (RA) is an autoimmune inflammatory disease. Early diagnosis can prevent joint erosion. However, available biomarkers do not always allow for clear distinction between RA and non-RA individuals. It has become known that bacteria/viruses are among the environmental triggers that initiate RA via multiple molecular mechanisms. Thus, to better understand the role of bacteria in RA, we synthetized 6 peptidomimetics of bacterial ureases' flap region. These peptides were then used to distinguish RA patients from healthy people sera by immunoblotting. Most patients' sera were bound to peptidomimetic characteristic for Enterobacter sp. and Klebsiella sp. flap urease. We also found similarities between peptidomimetic sequence and human proteins connected with RA. This pilot study suggests that bacteria may trigger RA via mechanism of molecular mimicry of urease to host proteins and ureases flap peptidomimetics may be potential candidate as a new additional diagnostic test.

Intraperitoneal immunization with Urease loaded N-trimethyl Chitosan nanoparticles elicits high protection against Brucella melitensis and Brucella abortus infections.

Brucella (B) species are brucellosis causative agents, a worldwide zoonotic illness causing Malta fever in humans and abortion in domestic animals. In this work, we evaluated the vaccine potential of Trimethyl chitosan (TMC) nanoparticles formulation of Urease (TMC/Urease) against brucellosis. TMC/Urease nanoparticles and urease without any adjuvant were separately administered both orally and intraperitoneally. Intraperitoneal (i.p.) administration of urease alone as well as oral administration of both TMC/Urease nanoparticles and urease alone, elicited low titers of specific immunoglobulin G (IgG), while i.p. immunization with TMC/Urease nanoparticles induced high specific IgG production levels. As it was indicated by the cytokine assay and the antibody isotypes, i.p. immunization by urease alone, and TMC/Urease nanoparticles induced a mixed Th1-Th2 immune response, whereas oral administration of both urease alone and TMC/Urease nanoparticles induced a mixed Th1-Th17 immune response. In lymphocyte proliferation assay, spleen cells from i.p.-vaccinated mice with TMC/Urease nanoparticles showed a strong recall proliferative response. Vaccinated animals were challenged with virulent strains of B. melitensis and B. abortus. I.p. vaccination with TMC/Urease nanoparticles resulted in a high degree of protection. Altogether, our results indicated that TMC nanoparticles are a potent delivery system for i.p.-administered Brucella antigens.

Production and characterization of a camelid single domain antibody-urease enzyme conjugate for the treatment of cancer.

A novel immunoconjugate (L-DOS47) was developed and characterized as a therapeutic agent for tumors expressing CEACAM6. The single domain antibody AFAIKL2, which targets CEACAM6, was expressed in the Escherichia coli BL21 (DE3) pT7-7 system. High purity urease (HPU) was extracted and purified from Jack bean meal. AFAIKL2 was activated using N-succinimidyl [4-iodoacetyl] aminobenzoate (SIAB) as the cross-linker and then conjugated to urease. The activation and conjugation reactions were controlled by altering pH. Under these conditions, the material ratio achieved conjugation ratios of 8-11 antibodies per urease molecule, the residual free urease content was practically negligible (<2%), and high purity (>95%) L-DOS47 conjugate was produced using only ultradiafiltration to remove unreacted antibody and hydrolyzed cross-linker. L-DOS47 was characterized by a panel of analytical techniques including SEC, IEC, Western blot, ELISA, and LC-MS(E) peptide mapping. As the antibody-urease conjugate ratio increased, a higher binding signal was observed. The specificity and cytotoxicity of L-DOS47 was confirmed by screening in four cell lines (BxPC-3, A549, MCF7, and CEACAM6-transfected H23). BxPC-3, a CEACAM6-expressing cell line was found to be most susceptible to L-DOS47. L-DOS47 is being investigated as a potential therapeutic agent in human phase I clinical studies for nonsmall cell lung cancer.

Development of a recombinant ureolytic Lactococcus lactis for urea removal.

Kidney failure is a common disease with high frequency. Food-grade recombinant bacteria that can effectively remove urea has great potential for treatment of renal failure. A nonpathogenic strain, L. lactis MG1363, was transformed with plasmid pMG36eure, which carries urease gene. The expression of transgene urease in genetically modified L. lactis MG1363 and the urease activity in removal of urea were investigated. It was found that the removal of urea by recombinant L. lactis MG1363 was pH- and nickel-dependent. At pH 6.5 and in the presence of 250 microM of NiSO4, 50 approximately 60% of urea could be removed in 24 hours. The urea removal activity was also evaluated in imitative gastroenteric environment. After being exposed to acidic solution (pH2.5-4.0) for 2 hours, the cells were then grown in a medium containing 0.1 cfu/ml bile acid salt, 30 mg/dl urea, and 250 microM NiSO4 at pH 6.8. The concentration of urea decreased over time, and the removal was about 30% at 10 hours and 65% at 24 hours, respectively. The safety tests were performed by feeding normal rats with either L. lactis MG1363 or recombinant L. lactis MG1363. The two materials did not cause any changes in blood cells and blood biochemical indexes. There were no differences in terms of body weight and water/food consumption between the two materials. These results indicate the safety, feasibility, and capacity of urease gene modified Lactococcus Lactis in removal of urea under the gastroenteric circumstances. Further investigation may generate a food-grade strain for treatment of chronic renal failure.

Urease loaded alginate microspheres for blood purification.

In this paper a device, based on urease-loaded microspheres, is presented. The first task of this work was the optimization of a procedure for the alginate microspheres realization, having a radius as close as possible to the optimal one necessary to achieve the maximum enzyme exploitation. This optimal radius was calculated theoretically through a mathematical model which describes the concentration of substrate (urea) inside the microspheres on the assumption of a diffusion-reaction mechanism. The enzyme-loaded microspheres were successfully tested in a prototypal device aimed at the depletion of urea from a circulating fluid simulating blood flow: the results showed that urea concentration in the circulating fluid drops down to less than 25% of the initial value after 5 h.

[The preparation and application of cross-linked urease aggregates].

Urease was immobilized in a simple and effective way by physical aggregation using a precipitant-ammonium sulfate, followed by chemical cross-linking using a bifunctional reagent-glutaraldehyde to form insoluble Cross-linked urease aggregates (CLUAs). The optimum pH, optimum temperature and Km of CLUAs were 8.0, 70 degrees C and 0.021 mol/L respectively. Compared with that of free urease, the thermal stability, storage stability and resistance of cross-linked urease aggregates to the exogenous proteolysis were enhanced. The efficacy of CLUAs for the treatment of rats with chronic renal failure was also studies. The rats with chronic renal failure caused by adenine were divided into 3 groups randomly:the control group (fed with 10 mL water /kg per day), Coated Aldehyde Oxystarch (CAO) group (fed with 20 g CAO /kg and 10 mL water /kg per day) and CLUAs + CAO group (fed with 20 g CAO /kg and 10 mL CLUAs /kg per day) in which CAO was used to absorb the ammonia produced from urea. The contents of BUN and Scr in serum before and after 2 weeks treatment were determined. In three groups, the level of Scr decreased slightly (P = 0.922, 0.972 and 0.225 > 0.05 respectively) after treatment. The level of BUN was not changed (P = 0.211 > 0.05) in the control group, but decreased greatly BUN in both CAO group and CLUAs + CAO group (P = 0.004 < 0.05 and P < 0.001 respectively). Furthermore, the decrease of the BUN level after treatment in the CLUAs + CAO group was more remarkable than that in the CAO group (P = 0.016 < 0.05), which showed that the CLUAs + CAD system was more efficient than the CAO system for the removal of urea in serum.

Comparison between targeted and untargeted systemic immunizations with adjuvanted urease to cure Helicobacter pylori infection in mice.

Outbred OF1 mice infected in a first step with a mouse-adapted Helicobacter pylori strain were immunized in a second step by systemic or mucosal routes: systemic immunizations were performed subcutaneously with adjuvanted urease either in the infra or supra-diaphragmatic region of the body, while mucosal immunization was done with urease in the presence of E. coli heat Labile toxin. Mucosal and subcutaneous immunizations induced in infected mice a significant reduction in bacterial density whatever the site of injection but complete eradication was preferentially observed in mice immunized subcutaneously in the back. Systemic immunization with appropriate schedules and formulations could constitute a valuable approach to cure Helicobacter pylori infection.

Therapeutic immunization against Helicobacter mustelae in naturally infected ferrets.

BACKGROUND & AIMS: Helicobacter infection of the gastric antrum is responsible for a number of gastric disorders. Antibiotic therapy is lengthy and is not always effective. It has been shown previously that oral immunization against Helicobacter felis in mice can prevent colonization after challenge. The aim of this study was to investigate the efficacy of therapeutic immunization in eradicating an established Helicobacter infection and in reducing gastritis. METHODS: Domestic ferrets, confirmed to be infected with Helicobacter mustelae by gastric endoscopy, were orally immunized with varying doses of purified Helicobacter pylori urease in combination with the mucosal adjuvant cholera toxin. Ferrets were assessed 1 week and 6 weeks after treatment for infection and pathology. RESULTS: Therapeutic immunization eradicated Helicobacter colonization in 30% of all immunized ferrets, although there was no difference in efficacy between the varying doses of antigen tested. The difference was statistically significant when compared with animals administered cholera toxin alone or buffer (P = 0.04). The intensity of inflammation was also significantly reduced in immunized animals (P = 0.0003). CONCLUSIONS: Oral immunization with purified H. pylori urease and cholera toxin can eradicate H. mustelae in a natural host pathogen model. Oral immunization of chronically infected animals markedly reduced gastric inflammation.

Oral immunization with Helicobacter pylori urease B subunit as a treatment against Helicobacter infection in mice.

BACKGROUND & AIMS: Eradication of Helicobacter pylori infections in humans results in the healing of gastritis and gastric ulcers. This study used a mouse model to test whether oral vaccination can cure Helicobacter infection and gastritis. METHODS: Mice were infected with Helicobacter felis. Three weeks after infection, the mice were orally immunized with H. pylori urease B subunit. Control mice were simultaneously infected but sham immunized. RESULTS: Three to 8 weeks after oral immunization of H. felis-infected mice with recombinant H. pylori urease B subunit, the infection cleared and there was no evidence of gastritis. Vaccinated mice remained protected against two consecutive H. felis challenges. CONCLUSIONS: These results show that the lack of natural immunity against Helicobacter can be overcome by oral immunization and that vaccination offers a novel therapeutic approach to Helicobacter-induced gastritis.

Utilización del clotest y pyloriset en la determinación del helicobacter pylori en adultos sanos asintomáticos / Utilization of the clotes and pyloriset in the determination of the helicobacter pylori in asymptomatic healthy adults

El Helicobacter Pylori (Hp) ha sido relacionado con la patogénesis de la gastritis crónica, úlcera péptica, dispepsia no ulcerosa y en los últimos estudios ha sido encontrado en alta prevalencia en poblaciones con riesgo de cáncer gástrico. El propósito del presente estudio es determinar la presencia del Hp, en un grupo de adultos asintomáticos, voluntarios, aparentemente sanos, mediante la utilización de dos pruebas diagnósticas, una prueba serológica para la determinación de anticuerpos IgG anti Hp (Pyloriset) y la prueba de Ureasa (Clotest) relacionándola con el desarrollo de lesiones. Se estudiaron 20 sujetos, a quienes se les tomó muestra de sangre periférica para la determinación del Hp mediante el test de aglutinacion de látex (Pyloriset) y se les realizó endoscopia digestiva superior (EDS) con toma de biopsia gástrica para prueba de Ureasa (Clotest). En 15 adultos (75 por ciento) el clotest fue positivo y en 13 sujetos (65 por ciento) el Pyloriset fue positivo. En 9 personas (47 por ciento) El Hp se evidenció por ambos métodos. En 13 personas (65 por ciento) la EDS fue concluida patológica y todos fueron positivos para el Hp y en los 7 (35 por ciento) que la EDS resultó normal, solo uno resultó negativo para el Hp. En 7 sujetos (35 por ciento) la EDS resulto normal. La presencia del anticuerpo contra el Hp predice alteraciones de la mucosa gástrica como el desarrollo de gastritis crónica, úlcera peptica, y otras patologías. El Clotest es una prueba sencilla, rápida y sensible que nos permite aplicar tratamiento de inmediato. Estos resultados sugieren una alta incidencia de esta bacteria en nuestros trabajadores, lo que justifica estudios endoscópicos altos prospectivos para determinarla

Irritant and protective action of urea-urease ammonia in rat gastric mucosa. Different effects of ammonia and ammonium ion.

The effects of urea-urease-ammonia on the rat gastric mucosa were examined and compared with those of NH4OH and NH4Cl. The mucosal application of urea with urease produced a reduction in potential difference (PD) in a dose-related manner for urea, and a significant drop was observed by > 0.1% urea in the presence of 100 units urease. Such PD reduction was also observed when the mucosa was exposed to either NH4OH (> 0.03%) or NH4Cl (> 1%); delta PD (20 mV) caused by 0.3% NH4OH and 3% NH4Cl was equivalent to that induced by 0.5% urea+urease (100 units). The combined oral administration of urea (approximately 6%) and urease (100 units) did not induce any macroscopic damage in the gastric mucosa. NH4Cl given orally had no or little effect on the mucosa at any dose levels even at 10%, while NH4OH given orally caused hemorrhagic lesions in the mucosa at the dose of > 0.3%. In contrast, both urea+urease and NH4Cl given prior to HCl/ethanol protected the gastric mucosa against damage in a dose-related manner, and a significant effect was obtained by urea at > 0.5% and by NH4Cl at > 1%. NH4OH was also effective in reducing the severity of HCl/ethanol-induced gastric lesions at lower dose (0.3%). The protective effect of urea+urease was attenuated significantly by prior administration of indomethacin or coadministration of hydroxyurea, while that of NH4Cl or NH4OH was mitigated by indomethacin.(ABSTRACT TRUNCATED AT 250 WORDS)

Fragmentación de las biopsias como factor fundamental el las investigaciones relacionadas con Campylobacter pylori / Biopsy segmentation as a key element in research work related with campylobacter

Campylobacter pylori coloniza la mucosa de tipo antral con una distribución no homogénea que depende del grado de infección. Para conocer el efecto de esa distribución "casual" sobre la sensibilidad de una prueba diagnóstica, se estudiaron 86 pacientes con enfermedad péptica ulcerosa, a los cuales se les realizó la prueba de la ureasa con una y dos biopsias (o sus fragmentos) para conocer la posibilidad de que ocurrieran falsos negativos por el empleo de una sola. Las pruebas de la ureasa hechas con dos biopsias resultaron positivas, mientras el 16,3 % de falsos negativos (14 pacientes) correspondió a las pruebas inoculadas con una biopsia. Este resultado señala que las pruebas deben hacerse a partir del mayor número de biopsias posibles. El investigador está obligado a realizar cada prueba con fragmentos de una misma biopsias (o biopsias) si desean comparar las sensibilidades de las pruebas entre si o asociar el diagnóstico de la bacteria con una imagen histológica

Fragmentación de las biopsias como factor fundamental el las investigaciones relacionadas con Campylobacter pylori / Biopsy segentation as a key element in research work related with campylobacter

Campylobacter pylori coloniza la mucosa de tipo antral con una distribución no homogénea que depende del grado de infección. Para conocer el efecto de esa distribución "casual" sobre la sensibilidad de una prueba diagnóstica, se estudiaron 86 pacientes con enfermedad péptica ulcerosa, a los cuales se les realizó la prueba de la ureasa con una y dos biopsias (o sus fragmentos) para conocer la posibilidad de que ocurrieran falsos negativos por el empleo de una sola. Las pruebas de la ureasa hechas con dos biopsias resultaron positivas, mientras el 16,3

de falsos negativos (14 pacientes) correspondió a las pruebas inoculadas con una biopsia. Este resultado señala que las pruebas deben hacerse a partir del mayor número de biopsias posibles. El investigador está obligado a realizar cada prueba con fragmentos de una misma biopsias (o biopsias) si desean comparar las sensibilidades de las pruebas entre si o asociar el diagnóstico de la bacteria con una imagen histológica

Development of urease-chitosan membrane.

Urease was covalently immobilized on glutaraldehyde-pretreated chitosan membrane. The optimum immobilization conditions were determined with respect to glutaraldehyde pretreatment of membranes (concentration and pH of glutaraldehyde solution, time of membrane-glutaral-dehyde reaction) and to reaction of glutaraldehyde-pretreated membranes with urease (concentration and pH of urease solution). The obtained membrane has high enzymatic activity, and can be applied for enzymatic removal of urea e.g. in the treatment of chronic or acute uraemia.