Urease-producing Bacteria Research Articles

The effect of plum juice on the prevention of struvite calculus formationin vitro

To evaluate the effect of plum juice on struvite calculus formation in vitro and to explore the effect of plum juice on urease-producing bacteria and urease activity. The compliance of available drugs is low for struvite calculus after surgical treatment and functional food may represent a good choice as an alternative therapy. Antibacterial activity was assessed using a microdilution antimicrobial susceptibility test. Urease activity was determined by measuring ammonia production. Struvite crystals were induced by Proteus mirabilis in artificial urine with natural and pH-adjusted plum juice. The optical density (OD)(600) and pH of artificial urine were examined, as well the shape and weights of crystals. Natural plum juice showed an antibacterial effect on urease-producing bacteria, whereas the pH-adjusted juice did not. A concentration-dependent inhibition on urease activity was found for both natural and pH-adjusted juice. Natural plum juice at a high concentration of 0.5% showed an obvious inhibition on the increase of OD(600) and pH of the artificial urine, and crystal formation was prevented by up to or more than 8 h, depending on the concentration of juice. Crystal weight in the natural plum juice groups was decreased in a concentration-dependent manner. The pH-adjusted plum juice did not show any effect on OD(600) and pH, although the presence of juice changed the crystal habit, indicating that the juice slowed the growth rate of crystals. Natural plum juice at high and moderate concentrations prevented the formation of P. mirabilis-induced crystals for up to 8 h in artificial urine. Although pH-adjusted and low-concentration natural juice did not prevent the occurrence of crystals, both types of juice slowed their growth rate.

The construction and application of a molecular wire piezoelectric urease-producing bacteria sensor

The series piezoelectric quartz crystal (SPQC) sensor is widely used for detecting microorganisms. However, because of the slight corrosion of metal electrodes in ammonia-containing media, the SPQC is unsuitable for the detection of urease-producing bacteria. In this paper, a molecular wire piezoelectric urease-producing bacteria (MWPUB) sensor was proposed for rapid identification and quantification of urease-producing bacteria. A polyimide–polypyrrole composite film was used as an electrode in place of the original metal electrode in SPQC and connected to a piezoelectric quartz crystal in series in a self-made oscillator. The composite film could react with NH3, which caused a decrease of conductance and resulted in a change in oscillating frequency of the piezoelectric quartz crystal. When the MWPUB sensor was used to quantitatively determine urease-producing bacteria, the frequency detection time (FDT) obtained from the frequency shift curve had a linear relationship with the logarithm values of the initial concentration of urease-producing bacteria in the range of 8 to 3.2 × 108 colony forming units (cfu) per millilitre (mL). Compared with SPQC, the new method was sensitive, rapid and stable in culture media.

Development of an “early warning” sensor for encrustation of urinary catheters following Proteus infection

Biofilm formation in long-term urinary catheterized patients can lead to encrustation and blockage of urinary catheters with serious clinical complication. Catheter encrustation stems from infection with urease-producing bacteria, particularly Proteus mirabilis. Urease generates ammonia from urea, and the elevated pH of the urine results in crystallization of calcium and magnesium phosphates, which block the flow of urine. The aim of this research is to develop an "early warning" silicone sensor for catheter encrustation following bacterial infection of an in vitro bladder model system. The in vitro bladder model was infected with a range of urease positive and negative bacterial strains. Developed sensors enabled catheter blockage to be predicted ~17-24 h in advance of its occurrence. Signaling only occurred following infection with urease positive bacteria and only when catheter blockage followed. In summary, sensors were developed that could predict urinary catheter blockage in in vitro infection models. Translation of these sensors to a clinical environment will allow the timely and appropriate management of catheter blockage in long-term catheterized patients.

Acidic environments induce differentiation of Proteus mirabilis into swarmer morphotypes

Although swarmer morphotypes of Proteus mirabilis have long been considered to result from surfaced-induced differentiation, the present findings show that, in broth medium containing urea, acidic conditions transform some swimmer cells into elongated swarmer cells. This study has also demonstrates that P. mirabilis cells grown in acidic broth medium containing urea enhance virulence factors such as flagella production and cytotoxicity to human bladder carcinoma cell line T24, though no significant difference in urease activity under different pH conditions was found. Since there is little published data on the behavior of P. mirabilis at various hydrogen-ion concentrations, the present study may clarify aspects of cellular differentiation of P. mirabilis in patients at risk of struvite formation due to infection with urease-producing bacteria, as well as in some animals with acidic or alkaline urine.

HYPERAMMONEMIC ENCEPHALOPATHY DUE TO A URINARY DIVERSION: AN UNCOMMON CAUSE OF REVERSIBLE DEMENTIA

To the Editor: Patients with cognitive impairment may have potentially reversible conditions. Metabolic diseases constitute an important group of these nondegenerative etiologies. Urinary diversion has been reported to cause hyperammonemic encephalopathy (HE), even without liver disease. This letter presents the case of a patient with hyperammonemia and history of a Bricker diversion after radical cystectomy for bladder cancer previously misdiagnosed with early-onset dementia. After specific treatment for hyperammonemia, the patient's cognition improved greatly. A 74-year-old man was admitted to the acute geriatric unit of our hospital because of a 3-week history of drowsiness and general stiffness. He had a prior medical history of a Bricker uretero-ileostomy after radical cystectomy for bladder cancer performed 1 year before admission and cognitive impairment, labelled as Alzheimer's disease, detected 3 months before by his general physician, although no specific tests had been performed to evaluate it. Omeprazole and lorazepam were his regular medications. On examination, he was unaware of time and place, and he presented with signs of dehydration. Neurological findings included slurred speech, drowsiness, clumsiness, stiffness, postural instability, and bradykinesia. Symptoms were present and stable all day. Blood tests showed mildly high C-reactive protein (3.5 mg/dL), hypernatremia (156 mEq/L), and leucocytosis (18 × 109/L). Glucose, calcium, magnesium, Vitamin B12, thyroid hormone, and renal and liver function tests were normal. Urine sediment evidenced mild leukocyturia with bacteriuria. Chest radiography was normal. Initial diagnosis was hypernatremia secondary to dehydration and urinary infection, and fluid therapy and antibiotic with ceftriaxone were started. Urinary culture was negative. Natremia normalized progressively, but the patient's symptoms did not improve at all. A cranial computed tomography (CT) scan showed mild diffuse cerebral atrophy, and an electroencephalogram revealed diffuse nonspecific encephalopathy. Despite normal liver function, given the urinary diversion, blood ammonia levels were tested revealing marked hyperammonemia (122 μmol/L). An abdominal–pelvic CT scan did not evidence signs of obstruction or dilatation of the uretero-ileal anastomosis. Specific treatment with dietary protein restriction and lactulose therapy was initiated. In a few days, ammonemia became normal, and the patient quickly showed great improvement in his mental state (Mini-Mental State Examination score 29/30 at 1 month after discharge). The global prevalence of dementia in the elderly population is approximately 5%.1 Alzheimer's disease is the most common disorder, accounting for 60% to 80% of cases, followed by vascular dementia (10–20%).2 The prevalence of a potentially reversible cause (Table 1) ranges from less than 1% to 9%, being higher in younger (<60) than older adults and significantly more common in patients with only subjective symptoms than in patients with established dementia.2–4 The most common reversible causes are depression, drugs, hydrocephalus, and metabolic diseases; thyroid disease and vitamin B12 deficiency are the most frequently detected causes from metabolic diseases.2,3 HE is an uncommon reversible etiology of cognitive impairment. Liver diseases, some drugs, portosystemic shunting, congenital defects of enzymes of the urea cycle, parenteral nutrition, hematological dyscrasia, and urinary diversion have been reported as causes of hyperammonemia.5–7 Nonhepatic hyperammonemia in patients undergoing urinary diversion is due to the prolonged contact of urine and the intestinal epithelium that results in high intestinal uptake of urine-excreted products, which can overload the detoxifying capacity of the liver, leading to the download of ammonia into the blood flow.8 Furthermore, urinary tract infections with urease-producing bacteria may cause urine ammonia concentration to rise. Proteus mirabilis and Pseudomonas aeruginosa are the best-known urea-splitting bacteria.9 There are no standardized guidelines for treating acute nonhepatic hyperammonemia. The reduction of intestinal ammonia levels by limiting protein ingestion to 20 g/d and using nonabsorbable disaccharides such as lactulose and lactitol to increase intestinal ammonia elimination is encouraged. If urinary tract infection is suspected, an antibiotic should also be started.10 In conclusion, unexplained neurological or neuropsychiatric symptoms in a patient with a urinary diversion should include hyperammonemia in the differential diagnosis. Conflict of Interest: The editor in chief has reviewed the conflict of interest checklist provided by the authors and has determined that the authors have no financial or any other kind of personal conflicts with this paper. Author Contributions: All authors: diagnosis and care of patients and preparation of manuscript. Sponsor's Role: None.

Molecular analysis and characterization of a urease gene operon from Campylobacter sputorum biovar paraureolyticus

When recombinant plasmid DNA from a genomic DNA library and inverse PCR products of Campylobacter sputorum biovar paraureolyticus LMG17591 strain were analyzed, an approximate 6.5-kb pair region, encoding a urease gene operon, was identified. Within the operon, seven closely spaced and putative open reading frames for ureG, ureH(D), ureA, ureB, ureC, ureE, and ureF were detected in order. A possible overlap was detected between ureG and ureH(D), ureH(D) and ureA, and ureE and ureF. In addition, two putative promoter structures, probable ribosome-binding sites and a putative ρ-independent transcriptional terminator structure were identified. The urease gene operon transcription in the cells was confirmed by the reverse transcription-PCR analysis. A neighbor-joining tree constructed based on the nucleotide sequence information of urease genes showed that C. sputorum biovar paraureolyticus formed a cluster with Arcobacter butzleri, urease-positive thermophilic Campylobacter and some Helicobacter spp., separating those from the other urease-producing bacteria, suggesting a commonly shared ancestry among these organisms.

T1922 The Eqqq-Rich C-Terminus of Human Apolipoprotein a-IV Inhibits Basolateral Chylomicron Triacylglycerol Secretion

Background: The colonic microbiome is remarkable in that it is amongst the most densely populated microbial habitats on Earth. The study of gut microbial ecology and its interplay with the host metabolome has emerged as a critical frontier in contemporary nutritional and metabolic research. Classic studies in physiology have shown that the gut microbiome plays an important role in nitrogen balance of the host. Urea, produced by the host, is hydrolyzed in the colon by urease-producing gut bacteria and the resultant ammonia is absorbed by the host and utilized for protein metabolism. In this study, we determined the effect of the gut microbiome on the metabolic alterations induced by a low protein diet (LPD). Methods and Results: Female C57B/6J mice were fed either a normal chow (20% kcal protein) or low protein diet (3% kcal protein) for 1 month. Metabolic phenotyping revealed that mice fed a low protein diet failed to gain weight despite a 40% increase in food intake. Compared to mice fed a normal chow diet, mice fed a LPD also showed significant alterations in body composition, as assessed by MRI, with a decrease in lean mass and a proportional increase in fat mass as well as a significant increase in energy expenditure, as determined by indirect calorimetry. In addition, LPD fed mice suffered a profound defect of water conservation manifested as severe polydypsia and polyuria. Remarkably, except for growth retardation, the administration of oral antibiotics to mice fed a LPD dramatically prevented all of these adverse metabolic sequelae. GC-MS of urinary samples revealed that oral antibiotics did not lead to profound alterations in urinary amino acid excretion suggesting that gut bacteria were not competing with the host for dietary nitrogen sources in a significant way. This notion is supported by the failure of LPD mice to increase serum IGF-1 levels and normalize body weight when placed on oral antibiotics. Preliminary determination of gut microbiome composition, by 16S rDNA sequencing using the 454/Roche method and taxonomic group assignment at the genus level using RDPclassifier, revealed modest alterations induced by a LPD. Conclusions: These results suggest that the gut microbiome evokes deleterious metabolic consequences in the host in the setting of a low protein diet that are independent of competition for dietary nitrogen. The gut microbiome may, therefore, play an important role in the regulation of host metabolic physiology in settings where the consumption of dietary protein is severely limited.

T1920 Oral Antibiotics Reverse Maladaptive Metabolic Responses to a Low Protein Diet

Background: The colonic microbiome is remarkable in that it is amongst the most densely populated microbial habitats on Earth. The study of gut microbial ecology and its interplay with the host metabolome has emerged as a critical frontier in contemporary nutritional and metabolic research. Classic studies in physiology have shown that the gut microbiome plays an important role in nitrogen balance of the host. Urea, produced by the host, is hydrolyzed in the colon by urease-producing gut bacteria and the resultant ammonia is absorbed by the host and utilized for protein metabolism. In this study, we determined the effect of the gut microbiome on the metabolic alterations induced by a low protein diet (LPD). Methods and Results: Female C57B/6J mice were fed either a normal chow (20% kcal protein) or low protein diet (3% kcal protein) for 1 month. Metabolic phenotyping revealed that mice fed a low protein diet failed to gain weight despite a 40% increase in food intake. Compared to mice fed a normal chow diet, mice fed a LPD also showed significant alterations in body composition, as assessed by MRI, with a decrease in lean mass and a proportional increase in fat mass as well as a significant increase in energy expenditure, as determined by indirect calorimetry. In addition, LPD fed mice suffered a profound defect of water conservation manifested as severe polydypsia and polyuria. Remarkably, except for growth retardation, the administration of oral antibiotics to mice fed a LPD dramatically prevented all of these adverse metabolic sequelae. GC-MS of urinary samples revealed that oral antibiotics did not lead to profound alterations in urinary amino acid excretion suggesting that gut bacteria were not competing with the host for dietary nitrogen sources in a significant way. This notion is supported by the failure of LPD mice to increase serum IGF-1 levels and normalize body weight when placed on oral antibiotics. Preliminary determination of gut microbiome composition, by 16S rDNA sequencing using the 454/Roche method and taxonomic group assignment at the genus level using RDPclassifier, revealed modest alterations induced by a LPD. Conclusions: These results suggest that the gut microbiome evokes deleterious metabolic consequences in the host in the setting of a low protein diet that are independent of competition for dietary nitrogen. The gut microbiome may, therefore, play an important role in the regulation of host metabolic physiology in settings where the consumption of dietary protein is severely limited.

Crystalline bacterial biofilm formation on urinary catheters by urease-producing urinary tract pathogens: a simple method of control

The problem of catheter encrustation stems from infection by urease-producing bacteria. These organisms generate ammonia from urea, elevate the pH of urine and cause crystals of calcium and magnesium phosphates to form in the urine and the biofilm that develops on the catheter. In this study, a laboratory model was used to compare the ability of 12 urease-positive species of urinary tract pathogens to encrust and block catheters. Proteus mirabilis, Proteus vulgaris and Providencia rettgeri were able to raise the urinary pH above 8.3 and produce catheter-blocking crystalline biofilms within 40 h. Morganella morganii and Staphylococcus aureus elevated the pH of urine to 7.4 and 6.9, respectively, and caused some crystal deposition in the biofilms but did not block catheters in the 96 h experimental period. Isolates of Klebsiella pneumoniae, Klebsiella oxytoca, Enterobacter cloacae, Serratia marcescens, Pseudomonas aeruginosa and Providencia stuartii were only capable of raising the pH of urine to a maximum of 6.4 and failed to cause crystal deposition in the biofilm. The most effective way to prevent catheter encrustation was shown to be diluting urine and increasing its citrate concentration. This strategy raises the nucleation pH (pH(n)) at which calcium and magnesium phosphates crystallize from urine. Increasing the fluid intake of a healthy volunteer with citrated drinks resulted in urine with a pH(n) of >8.0 in which catheter encrustation was inhibited. It is suggested that this dietary strategy will be an effective means of controlling catheter encrustation, whichever bacterial species is causing the problem.

Bacterial biofilms in patients with indwelling urinary catheters

Bacteria have a basic survival strategy: to colonize surfaces and grow as biofilm communities embedded in a gel-like polysaccharide matrix. The catheterized urinary tract provides ideal conditions for the development of enormous biofilm populations. Many bacterial species colonize indwelling catheters as biofilms, inducing complications in patients' care. The most troublesome complications are the crystalline biofilms that can occlude the catheter lumen and trigger episodes of pyelonephritis and septicemia. The crystalline biofilms result from infection by urease-producing bacteria, particularly Proteus mirabilis. Urease raises the urinary pH and drives the formation of calcium phosphate and magnesium phosphate crystals in the biofilm. All types of catheter are vulnerable to encrustation by these biofilms, and clinical prevention strategies are clearly needed, as bacteria growing in the biofilm mode are resistant to antibiotics. Evidence indicates that treatment of symptomatic, catheter-associated urinary tract infection is more effective if biofilm-laden catheters are changed before antibiotic treatment is initiated. Infection with P. mirabilis exposes the many faults of currently available catheters, and plenty of scope exists for improvement in both their design and production; manufacturers should take up the challenge to improve patient outcomes.

Urease-positive bacteria in the stomach induce a false-positive reaction in a urea breath test for diagnosis of Helicobacter pylori infection

This study investigated the influence of urease-positive non-Helicobacter pylori bacteria on the results of a urea breath test (UBT) to evaluate the diagnostic utility of a UBT using film-coated [(13)C]urea tablets. The UBT was performed in 102 patients treated with a proton pump inhibitor and antibiotics for the eradication of H. pylori. Urease-producing bacteria other than H. pylori were isolated and identified from the oral cavity and stomach. In 4/102 patients, the UBT gave false-positive results. These false-positive results were found to be caused by the presence of urease-positive bacteria in the oral cavity and stomach. Five bacterial species with urease activity (Proteus mirabilis, Citrobacter freundii, Klebsiella pneumoniae, Enterobacter cloacae and Staphylococcus aureus) were subsequently isolated from the oral cavity and/or stomach. As there was no correlation between the in vitro urease activity of urease-positive non-H. pylori bacteria and the UBT value, and all of the patients with a false-positive UBT result were suffering from atrophic gastritis, it is possible that the false-positive results in the UBT were a result of colonization of urease-positive bacteria and gastric hypochlorhydric conditions. Thus, for the diagnosis of H. pylori infection using a UBT, the influence of stomach bacteria must be considered when interpreting the results.

Observations on the development of the crystalline bacterial biofilms that encrust and block Foley catheters

The care of many patients undergoing long-term bladder catheterisation is complicated when the flow of urine through the catheter is blocked by encrustation. The problem results from infection by urease-producing bacteria, especially Proteus mirabilis, and the subsequent formation of crystalline biofilms on the catheter. The aim of this study was to discover how P. mirabilis initiates the development of these crystalline biofilms. The early stages in the formation of the biofilms were observed on a range of Foley catheters in a laboratory model of the catheterised bladder. Scanning electron micrographs revealed that when all-silicone, silicone-coated latex, hydrogel-coated latex, hydrogel/silver-coated latex and nitrofurazone silicone catheters were inserted into bladder models containing P. mirabilis and alkaline urine, their surfaces were rapidly coated with a microcrystalline foundation layer. X-ray microanalysis showed that this material was composed of calcium phosphate. Bacterial colonisation of the foundation layer followed and by 18h the catheters were encrusted by densely populated crystalline P. mirabilis biofilms. These observations have important implications for the development of encrustation-resistant catheters. In the case of silver catheters for example, bacterial cells can attach to the crystalline foundation layer and continue to grow, protected from contact with the underlying silver. If antimicrobials are to be incorporated into catheters to prevent encrustation, it is important that they diffuse into the urine and prevent the rise in pH that triggers crystal formation.

Cloning, sequencing and characterization of a urease gene operon from urease-positive thermophilic Campylobacter (UPTC)

To clone, sequence and characterize the genetic organization of urease genes within urease-positive thermophilic Campylobacter (UPTC). An approx. 5.1-kbp region encoding a urease gene operon was identified, when recombinant plasmid DNAs from a genomic DNA library of a Japanese isolate (CF89-12) of UPTC were analysed. Six closely spaced and putative open reading frames (ORFs) for ureA, ureB, ureE, ureF, ureG and ureH were detected. ATG codons initiated each ORF of the UPTC urease operon except for ureB and ureH, which commenced with the most probable TTG codon. Overlaps were detected between ureA and ureB and also between ureB and ureE. Probable ribosome-binding sites and a putative rho-independent transcriptional termination region were identified. Two putative promoter structures, consisting of consensus sequences at the -35 like and -10 regions were also identified. Construction of a neighbour-joining tree based on the nucleotide sequence data of urease genes indicated that UPTC formed a cluster with some Helicobacter organisms separate from the other urease-producing bacteria, suggesting a commonly shared ancestry between UPTC and Helicobacter urease genes.

Urinary-catheter-associated infections in the elderly

The indwelling urinary catheter is the leading cause of complicated urinary tract infections and Gram-negative bacteraemia in this age group. It accounts for about 40% of life-threatening septicaemia. There is a progressive increase in mortality independently associated with the duration of catheterization. Polymicrobial bacteriuria is common. Urease-producing bacteria lead to encrusted and blocked catheters. The current challenges are to develop effective methods to sensitize healthcare workers to avoid the routine use of indwelling catheters, remove them when no longer needed, develop alternative methods for care of incontinence, employ non-invasive methods to measure urine output, and improve urine drainage systems. The research paradigm needs to focus on prevention of catheter-associated infections rather than on futile attempts to treat irreversible sepsis.

Ureases display biological effects independent of enzymatic activity: Is there a connection to diseases caused by urease-producing bacteria?

Ureases are enzymes from plants, fungi and bacteria that catalyze the hydrolysis of urea to form ammonia and carbon dioxide. While fungal and plant ureases are homo-oligomers of 90-kDa subunits, bacterial ureases are multimers of two or three subunit complexes. We showed that some isoforms of jack bean urease, canatoxin and the classical urease, bind to glycoconjugates and induce platelet aggregation. Canatoxin also promotes release of histamine from mast cells, insulin from pancreatic cells and neurotransmitters from brain synaptosomes. In vivo it induces rat paw edema and neutrophil chemotaxis. These effects are independent of ureolytic activity and require activation of eicosanoid metabolism and calcium channels. Helicobacter pylori, a Gram-negative bacterium that colonizes the human stomach mucosa, causes gastric ulcers and cancer by a mechanism that is not understood. H. pylori produces factors that damage gastric epithelial cells, such as the vacuolating cytotoxin VacA, the cytotoxin-associated protein CagA, and a urease (up to 10% of bacterial protein) that neutralizes the acidic medium permitting its survival in the stomach. H. pylori whole cells or extracts of its water-soluble proteins promote inflammation, activate neutrophils and induce the release of cytokines. In this paper we review data from the literature suggesting that H. pylori urease displays many of the biological activities observed for jack bean ureases and show that bacterial ureases have a secretagogue effect modulated by eicosanoid metabolites through lipoxygenase pathways. These findings could be relevant to the elucidation of the role of urease in the pathogenesis of the gastrointestinal disease caused by H. pylori.

Genetic heterogeneity of urease gene loci in urease-positive thermophilic Campylobacter (UPTC)

Degenerate PCR primers in silico based on the two urease structural genes, ureA and ureB, were designed for urease-positive thermophilic Campylobacter (UPTC). Resultant PCR amplification employing these primers generated an amplicon of approximately 2 kb, which was cloned and sequenced in UPTC ( n = 12 ) isolated from various parts of Europe and Japan. Overall, sequence similarities were shown to be 96.7 to 99.9%. Following sequence alignment analysis, the approximate 1.96 kb regions were deduced to consist of parts of ureA (about 570 bps) and ureB (about 1390 bps) with an overlapping region between the ureA and ureB gene loci. Although a total of 144 heterogeneous sites of all substitutions were located throughout this region, the substitution ratio was higher in the ureA region ( 1 / Ω ̲ 10 bases ) than in the ureB region ( 1 / Ω ̲ 15 bases ). A resulting dendrogram was constructed, which was based on the nucleotide sequence data of 12 UPTC isolates and demonstrated that the UPTC were genetically variable. They formed a major cluster with Helicobacter, separate from the other urease-producing bacteria examined, suggesting a shared ancestry between UPTC and Helicobacter.

Effects of Commercial Diazinon and Imidacloprid on Microbial Urease Activity in Soil and Sod

Diazinon [O,O-diethyl O-2-isopropyl-6-methyl(pyrimidine-4-yl) phosphorothioate] and imidacloprid [1-(1-[6-chloro-3-pyridinyl]methyl)-N-nitro-2-imidazolidinimine] are applied to lawns for insect control simultaneously with nitrogenous fertilizers such as urea, but their potential effect on urease activity and nitrogen availability in turfgrass management has not been evaluated. Urease activity in enzyme assays, washed cell assays, and soil slurries was examined as a function of insecticide concentration. Intact cores from field sites were used to assess the effect of insecticide application on urease activity in creeping bentgrass (Agrostis palustris Huds.) and bluegrass (Poa pratensis L.) sod. Bacterial urease from Bacillus pasteurii and plant urease from jack bean [Canavalia ensiformis (L.) DC.] were unaffected by the insecticides. Both insecticides inhibited the growth of Proteus vulgaris, a urease-producing bacterium, but only diazinon significantly reduced urease activity in washed cells; neither insecticide inhibited urease activity in sonicated cells. Neither diazinon nor imidacloprid inhibited urease activity in Woolper soil (fine, mixed, mesic Typic Argiudoll) slurries, but diazinon slightly inhibited urease activity in Maury soil (fine, mixed, semiactive, mesic Typic Paleudalf) slurries. Imidacloprid had no effect on urease activity in creeping bentgrass or bluegrass sod at up to 10 times the commercial application rate. Diazinon briefly, but significantly, reduced urease activity in bluegrass sod. Co-application of imidacloprid and urea appears to be benign with respect to urease activity in soil and sod. Diazinon, in contrast, appears to have a significant, short-term, inhibitory effect on the microbial urease-producing community, but that effect depends on soil type.

Lithiase urinaire de l’enfant

Urolithiasis is not uncommon in children and must be looked for with ultrasonography in any case of pyuria, hematuria or abdominal pain. By means of precise analysis of stone composition or, failing stone, of urines, an etiology can be found in approximately 80 % of child lithiases. In younger children, the two main causes are infection due to urease-producing bacteria, associated or not with urinary tract malformations, and metabolic disorders induced by prematurity and treatment of its complications (furosemide, steroids). In older children, metabolic disorders, particularly those due to inherited diseases, account for the majority of stones : hypercalciurias, secondary, iatrogenic or idiopathic, hyperoxalurias, primary (inherited), secondary, or “mild idiopathic”, cystinuria, hyperuricosurias, inherited or secondary, and other purine excretion disorders. Prevention of stone recurrence, essential in case of underlying metabolic disorder, always requires an abundant water intake (1.5-2 l/m2/day) associated with specific treatment of the causal disease if possible. If a surgical treatment is necessary, extra corporeal shock-wave lithotripsy is the first option like in adults.

Swarming of Proteus mirabilis over ureteral stents: a comparative assessment.

Encrustation on indwelling ureteral stents is commonly related to the presence of urease-producing bacteria that elevate the pH of the urine through the hydrolysis of urea, resulting in the precipitation of calcium and magnesium salts. Using a model previously shown to measure accurately the ability of Proteus mirabilis to swarm over catheter surfaces (Eur J Clin Microbiol Infect Dis 1999;18:206), we investigated the ability of this organism to swarm over three ureteral stents with potential encrustation-resistance properties. Three commercially available ureteral stents were selected for evaluation: a low surface-energy stent, a hydrogel-coated stent, and a silicone stent. Ten-microliter aliquots of a 4-hour culture of P. mirabilis 296 in Trypticase soya (TSA) broth was inoculated 5 mm from a 1-cm channel cut out from TSA plates. Ten-millimeter stent sections were placed as bridges across the central channel adjacent to the inocula. Time to pathogen crossing was measured. The mean time (+/- SD) to pathogen migration across the three test materials was 15.9 +/- 6.1, 19.8 +/- 9.5, and 29.7 +/- 14.3 hours for the low surface-energy, hydrogel-coated, and silicone stents, respectively. Statistical analysis revealed significant differences between the crossing times of the low surface-energy (P = 0.001) and hydrogel-coated (P = 0.034) stents compared with silicone but not between the low surface-energy and hydrogel-coated stents (P = 0.387). Migration of P. mirabilis 296 across silicone stents was significantly reduced compared with low surface-energy and hydrogel-coated stents. These findings suggest that P. mirabilis may have a lower affinity for silicone stents, which may translate into a reduced risk of infection with P. mirabilis and associated stent encrustation.

Care of Patients with Long-Term Indwelling Urinary Catheters

The complications and management of long-term indwelling catheters used for urinary retention and incontinence were reviewed. Research evidence from 1992 – 2002 was located through searches of CINAHL (38 articles), and Medline (89 articles). Fifty studies were critiqued for this review. The most common complications of long-term indwelling catheters are bacteriuria, encrustation, and blockage. Less common is the prevalence of bacteremia and renal disease. Risk factors for bacteriuria include female gender, older age, and long-term indwelling catheter use. Urinary white blood cells are the best indicator of urinary tract infection. For drainable catheter systems used by community dwelling adults, daily bag cleaning with a diluted bleach solution (1:10) is effective in reducing bacterial counts to negligible numbers. Application of topical antibiotic cream to the meatus around the catheter does not reduce bacteriuria. Silicone catheters and larger lumen size catheters are more resistant to encrustation than other catheter types and smaller lumen size catheters. Acidifying the urine without removing the urease-producing bacteria does not reduce encrustation. Removal of catheter blockage is preventive for renal disease. Because of the complications of long-term indwelling catheter usage, periodic assessment and voiding trials should be used to determine the continued need for a catheter. Evidence-based recommendations for managing indwelling urinary catheters include screening for risk factors and evaluating urinary white blood cell count for infection, and assessment of the continued need for a catheter. Interventions include consideration of closed versus open drainage systems, type of catheter, and size of catheter lumen.