Microbially influenced corrosion of galvanized steel pipes in aerobic water systems.

AIMS: To investigate the role of heterotrophic bacteria in the corrosion of galvanized steel in the presence of water. METHODS AND RESULTS: Samples were taken from corroding galvanized steel pipes conveying water for specialist applications, and heterotrophic bacteria were isolated and cultured. The majority of bacteria were Gram-negative aerobes and included Pseudomonas sp., Bacillus pumilus, Afipia spp. and Blastobacter denitrificans/Bradyrhizobium japonicum. Zinc tolerance was assessed through growth and zinc disc diffusion experiments. In general, zinc negatively influenced growth rates. An unidentified yeast also isolated from the system demonstrated a high tolerance to zinc at concentrations up to 4 g l(-1) . Coupon experiments were performed to assess corrosion by the bacteria on galvanized steel and steel coupons. The majority of isolates as pure culture biofilms (69%) accelerated corrosion of galvanized coupons, assessed as zinc release, relative to sterile control coupons (P < 0·05). Pure culture biofilms did not increase the corrosion of steel, with four isolates demonstrating protective effects. CONCLUSIONS: Pure culture biofilms of heterotrophic bacteria isolated from a corroding galvanized pipe system were found to accelerate the corrosion of galvanized steel coupons. SIGNIFICANCE AND IMPACT OF THE STUDY: Microbially influenced corrosion is a potential contributor to sporadically occurring failures in galvanized steel systems containing water. Management strategies should consider microbial control as a means for corrosion prevention in these systems.

The efficacy of biocides and other chemical additives in cooling water systems in the control of amoebae.

AIMS: In vitro experiments were undertaken to evaluate biocide formulations commonly used in cooling water systems against protozoa previously isolated from cooling towers. The investigations evaluated the efficacy of these formulations against amoebic cysts and trophozoites. METHODS AND RESULTS: Laboratory challenges against protozoa isolated from cooling towers using chlorine, bromine and isothiazolinone biocides showed that all were effective after 4 h. The presence of molybdate and organic phosphates resulted in longer kill times for bromine and isothiazolinones. All treatments resulted in no detectable viable protozoa after 4 h of exposure. CONCLUSIONS: The chemical disinfection of planktonic protozoa in cooling water systems is strongly influenced by the residence time of the formulation and less so by its active constituent. Bromine and isothiazolinone formulations may require higher dosage of concentrations than currently practiced if used in conjunction with molybdate- and phosphate-based scale/corrosion inhibitors. SIGNIFICANCE AND IMPACT OF THE STUDY: Cooling water systems are complex microbial ecosystems in which predator-prey relationships play a key role in the dissemination of Legionella. This study demonstrated that at recommended dosing concentrations, biocides had species-specific effects on environmental isolates of amoebae that may act as reservoirs for Legionella multiplication in cooling water systems.

Microbiological influences in 'blue water' copper corrosion.

AIMS: To investigate the influence of micro-organisms associated with copper corrosion on 'blue water' corrosion in drinking water. METHODS AND RESULTS: Laboratory rigs comprising of polycarbonate containers attached to annealed copper plumbing tubes were filled with Melbourne drinking water and sterilized by autoclaving. The copper tubes were inoculated with sterile or nonsterile extracts obtained from corroding copper and allowed to stand for 7 days. The extracts were drained and the tubes flushed and filled with sterile water from the rig. The water within the tubes was removed weekly for analysis and the tubes were refilled with freshly aerated water. The tube water sampled was analysed for pH, total copper and the presence of micro-organisms. Sterile rigs and rigs containing nonsterile water, both without tube inoculums, were used as controls. The results demonstrated that tubes inoculated with nonsterile corrosion extracts showed statistically higher copper release compared with the other rigs. Copper release as blue water was only observed after a lag period of 9 weeks. The internal surfaces of tubes releasing copper showed significant amounts of corrosion products and the presence of biofilm. Bacteria isolated from the corroding tubes included Acidovorax spp. and Sphingomonas sp. CONCLUSIONS: The results demonstrate a microbial role in blue water, as corrosion was induced in new copper tubes by exposure to nonsterile copper corrosion products. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential for micro-organisms present in corrosion products to initiate blue water corrosion presents significant implications for the management of corrosion in distribution systems.

The influence of the chemical composition of drinking water on cuprosolvency by biofilm bacteria.

AIMS: This study investigated the influence of water chemistry on copper solvation (cuprosolvency) by pure culture biofilms of heterotrophic bacteria isolated from copper plumbing. METHODS AND RESULTS: Heterotrophic bacteria isolated from copper plumbing biofilms including Acidovorax delafieldii, Flavobacterium sp., Corynebacterium sp., Pseudomonas sp. and Stenotrophomonas maltophilia were used in laboratory coupon experiments to assess their potential for cuprosolvency. Sterile copper coupons were exposed to pure cultures of bacteria to allow biofilm formation and suspended in drinking waters with different chemical compositions. Sterile coupons not exposed to bacteria were used as controls. After 5 days of incubation, copper release and biofilm accumulation was quantified. The results demonstrated that cuprosolvency in the control experiments was influenced by water pH, total organic carbon (TOC) and conductivity. Cuprosolvency in the presence of biofilms correlated with the chemical composition of the water supplies particularly pH, Langeliers Index, chloride, alkalinity, TOC and soluble phosphate concentrations. CONCLUSIONS: The results suggest water quality may influence cuprosolvency by biofilms present within copper plumbing pipes. SIGNIFICANCE AND IMPACT OF THE STUDY: The potential for water chemistry to influence cuprosolvency by biofilms may contribute to the sporadic nature of copper corrosion problems in distribution systems.

Biofilms and microbially influenced cuprosolvency in domestic copper plumbing systems.

AIMS: To survey biofilm accumulation within domestic copper plumbing pipes in South Australian drinking water distribution systems and examine its role in copper solvation (cuprosolvency). METHODS AND RESULTS: Cold water copper pipes were sampled from two different plumbing systems receiving filtered and unfiltered potable water respectively. Biomass was quantified by total organic carbon measurements and viable cell counts and microbial activity by respirometry. Biofilm accumulation was related to water chemistry within the systems, particularly nutrients, alkalinity and conductivity, as well as water turbulence. Laboratory coupon experiments were used to determine the effect of extracted biofilm on copper solvation. Biofilms were shown to be capable of both increasing and decreasing aqueous copper concentrations in comparison to sterile controls. CONCLUSIONS: The results suggest that water quality may influence the accumulation of biofilms in copper plumbing systems, as well as potential cuprosolvency activity. SIGNIFICANCE AND IMPACT OF THE STUDY: The presence of biofilms in copper plumbing systems and their ability to influence aqueous copper concentrations has implications for both public health and the management of distribution systems.

Is the dyspnea during adenosine cardiac stress test caused by bronchospasm?

BACKGROUND: Adenosine cardiac stress is widely used as an alternative to exercise testing during myocardial perfusion imaging (MPI). Dyspnea often accompanies the adenosine stress test. Although known asthmatic patients are excluded from this test because of the danger of bronchospasm, there is incomplete information regarding the role of factors such as chronic obstructive pulmonary disease (COPD) and tobacco smoking in adenosine-induced dyspnea. PATIENTS AND METHODS: A total of 122 consecutive patients (75 male, 47 female; mean age 59 years, SD 10 years) undergoing pharmacologic stress testing with an intravenous infusion of adenosine also had volume-flow spirometry (Vitalograph Compact, Vitalograph Ltd) before, during, and after the test. The indices assessed were forced expiratory volume in one second, its ratio to the forced vital capacity, and peak expiratory flow rate. RESULTS: Mild to severe symptoms were experienced by 81% of patients during adenosine infusion. More than half the patients had dyspnea, but there was no associated bronchospasm. Although the patients with COPD showed parameters indicative of bronchial resistance compared with those without this problem, there was no further deterioration after adenosine infusion. Similarly, patients with a history of tobacco abuse, despite showing a tendency toward increasing airways resistance, had no bronchospasm during the administration of adenosine. CONCLUSIONS: (1) Although dyspnea is a common problem during adenosine stress MPI, it is not associated with any appreciable bronchospasm. (2) COPD and tobacco abuse do not appear to be contraindications to adenosine stress MPI studies. However, it is probably safe to exclude patients with severe COPD from adenosine stress MPI until after further evaluation with larger numbers of patients.

The adsorption of cyanobacterial hepatotoxins from water onto soil during batch experiments.

Public health concerns associated with cyanobacteria, both chronic and acute, arise from their ability to produce toxins. Rural communities within Australia and those in developing countries require an inexpensive and low-cost method for removing toxins from drinking water. A candidate technology is bank filtration. Adsorption of cyanobacterial hepatotoxins was measured in batch studies to determine the applicability of bank filtration as an efficient removal strategy. Five soils with different physicochemical properties were collected from regions around South Australia. The soils were mixed with either nodularin or microcystin-LR in distilled water and buffered solutions (pH 4.8, 6.9 and 9.1). Additionally, nodularin was mixed in unbuffered solutions (pH 4.8 and 8.9). The three soils with the high clay and/or organic carbon contents (Paringa A, McLaren Flat and Lakes Plains) had the higher nodularin adsorption coefficients, ranging from 0.2 to 16.59 L kg-1. Soil suspensions in acetate buffer (pH 4.8) generally produced significantly higher nodularin adsorption coefficients, when compared to the other buffer systems. The background interference from the ionic strength of the buffers, however, made interpretation of the effect of pH on toxin sorption difficult. Increases in solution ionic strength, from freshwater to seawater, resulted in corresponding increases in the nodularin adsorption coefficients for all sites, except the sandy Hallett Cove site. The implications for bank filtration are that higher water pH values and lower salinities will enhance the in situ mobility of the toxins, resulting in an increased distance of filtration through the river bank before toxin free water could be abstracted for human consumption.

Do alterations in the rate of gastric emptying after injection sclerotherapy for oesophageal varices play any role in the development of portal hypertensive gastropathy?

Bleeding from portal hypertensive gastropathy (PHG) has been estimated to account for up to 30% of all upper gastrointestinal haemorrhage in patients with cirrhosis and portal hypertension. Although portal hypertension seems to be an essential prerequisite, the precise mechanisms responsible for the development of PHG are unknown. The aim of this study was to examine the role of injection sclerotherapy of oesophageal varices in the development of PHG. Gastric emptying was studied using a radionuclide test meal with the emptying characteristics of a slow liquid in 57 patients with cirrhosis and/or portal hypertension (median age 53 yrs), of whom 34 had received injection sclerotherapy for their oesophageal varices and 20 normal healthy volunteers (median age 42 yrs). As vagal damage is associated with more rapid emptying of liquids, despite hold up of solids, this technique might be expected to demonstrate such damage if gastric emptying was accelerated. The results indicated that there was no difference in the rate of gastric emptying between normal healthy volunteers and portal hypertensive patients. However, patients who had received injection sclerotherapy emptied their stomachs faster than those who had not (p < 0.05). Furthermore, the speed of gastric emptying correlated directly with the number of injections (r = 0.41; p = 0.02) and the volume of sclerosant injected (r = 0.39; p = 0.03). These observations suggest that injection sclerotherapy for oesophageal varices results in disturbances of gastric emptying that may contribute to the pathogenesis of portal hypertensive gastropathy.

Gastroesophageal reflux in patients fed by percutaneous endoscopic gastrostomy (PEG): detection by a simple scintigraphic method.

OBJECTIVES: Gastroesophageal scintigraphy has been described as a sensitive and accurate way to detect and quantitate gastroesophageal reflux (GER). Our objectives here were to evaluate the usefulness of a modified scintigraphic technique in the detection of GER and lung aspiration in patients fed by percutaneous endoscopic gastrostomy (PEG), and to assess the incidence of GER after insertion of PEG. Further, we sought to examine whether or not the underlying cause of dysphagia plays any significant part in the causation of GER. METHODS: Twenty-two patients, 13 with neurological dysphagia and nine with mechanical dysphagia, were studied. Each patient received 25 MBq of Tc-99m-tin colloid in orange juice followed by 300 ml of normal saline through the PEG tube. Dynamic and static images were taken immediately and at 4 h over esophagus, stomach, and lungs. RESULTS: Twelve patients (10 with neurological dysphagia) had GER and one had aspiration into the lungs. In all but one patient GER occurred in the immediate postprandial period. CONCLUSIONS: Scintigraphy is useful in assessing GER in PEG-fed patients. We also note that GER is a major problem in patients with PEG, especially in those with neurological dysphagia.

Tubular peptide hypermetabolism and urinary ammonia in chronic renal failure in man: a maladaptive response?

Excessive renal tubular peptide uptake and degradation reflecting hypercatabolism may be a maladaptive response in chronic renal failure (CRF). It may also offer an explanation for the increased ammoniagenesis, per surviving nephron, observed in CRF but as yet unexplained. Neither has been explored in man. We have shown in patients with normal renal function and heavy (>5.0 g/24 h) proteinuria that tubular catabolism of a technetium-labelled peptide marker, aprotinin, and urinary ammonia were increased compared to others with less proteinuria. We now measure tubular kinetics of aprotinin and urinary ammonia in 16 CRF patients with variable proteinuria. Metabolism and turnover of aprotinin and ammonia excretion were increased, corrected for glomerular filtration rate, to levels found in patients with normal function and heavy proteinuria.

Proximal renal tubular peptide catabolism, ammonia excretion and tubular injury in patients with proteinuria: before and after lisinopril.

1. Progression to renal failure may be linked to the degree of proteinuria through tubulo-interstitial mechanisms. However, there are no data in man on the kinetics of proximal renal tubular protein catabolism or markers of tubular injury before and after lisinopril. We developed a method to allow such studies, and found increased tubular catabolism of 99mTc-labelled aprotinin (Trasylol) in patients with nephrotic range proteinuria which was associated with increased ammonia excretion. 2. In this study, 10 patients with mild renal impairment (51Cr-EDTA clearance 63.7 +/- 8.3 ml.min-1.1.73 m-2) and heavy proteinuria (8.2 +/- 2.3 g/ 24 h) were given lisinopril (10-20 mg) for 6 weeks. Renal tubular catabolism of intravenous aprotinin was measured before and after lisinopril by renal imaging and urinary excretion of the free radiolabel over 26 h. Fractional degradation was calculated from these data. Fresh timed urine collections were also analysed for ammonia excretion every fortnight from 6 weeks before treatment. Total urinary N-acetyl-beta-D-glucosaminidase and the more tubulo-specific N-acetyl-beta-D-glucosaminidase 'A2' isoenzyme were also measured. 3. After lisinopril proteinuria fell significantly as expected (from 9.5 +/- 1.6 to 4.5 +/- 1.0 g/24 h, P < 0.01). This was associated with a reduction in metabolism over 26 h (from 1.7 +/- 0.1 to 1.2 +/- 0.1% dose/h, P < 0.01) and in fractional degradation of aprotinin (from 0.08 +/- 0.02 to 0.04 +/- 0.007/h, P < 0.04). Ammonia excretion also fell significantly (from 1.2 +/- 0.1 to 0.6 +/- 0.1 mmol/h, P < 0.0001), as did both total urinary N-acetyl-beta-D-glucosaminidase (P < 0.0001) and the N-acetyl-beta-D-glucosaminidase 'A2' isoenzyme (P < 0.015). These observations after lisinopril treatment have not been described previously. There was no significant change in blood pressure nor in glomerular haemodynamics.

Oral sodium bicarbonate reduces proximal renal tubular peptide catabolism, ammoniogenesis, and tubular damage in renal patients.

Oral sodium bicarbonate (NaHCO3) is widely used to treat acidosis in patients with renal failure. However, no data are available in man on the effects on proximal renal tubular protein catabolism or markers of tubular injury. We have developed methods to allow such studies, and both increased tubular catabolism of 99mTc-labelled aprotinin (Apr*), as well as tubular damage were found in association with increased ammonia (NH3) excretion in patients with nephrotic range proteinuria. We now examine the effects of reducing renal ammoniogenesis, without altering proteinuria, using oral NaHCO3 in 11 patients with mild/moderate renal impairment and proteinuria. Renal tubular catabolism of Apr* was measured before and after NaHCO3 by renal imaging (Kidney uptake, K% of dose) and urinary excretion of free 99mTcO4- (metabolism, Met% of dose/h) over 26 h. Fractional degradation (Frac) was calculated from Met/K (/h). Fresh urine was also analyzed for NH3 excretion every fortnight from 6/52 before treatment. Total urinary N-acetyl-beta-D-glucose-aminidase (NAG) and the more tubulo-specific NAG "A2" were measured. 51CrEDTA clearance and 99mTc-MAG 3 TER were also assessed. After NaHCO3 Met over 26 h was significantly reduced (from 1.3 +/- 0.2% of dose/h to 0.9 +/- 0.1% dose/hr, p < 0.005), as was Frac of Apr* (from 0.06 +/- .006/h to 0.04 +/- 0.005/hr, p < 0.003). NH3 excretion also fell significantly (from 0.9 +/- 0.2 mmol/h to 0.2 +/- 0.05 mmol/h, p < 0.007), as did both total urinary NAG (from 169 mumol/24 h, 74-642 mumol/24 h to 79 mumol/ 24 h, 37-393 mumol/24 h, p < 0.01), and the NAG 'A2' isoenzyme (from 81.5 mumol/24 h, 20-472 mumol/24 h to 35.0 mumol/24 h, 6-388 mumol/24 h, p < 0.001). Proteinuria remained unaltered, and there was no change in blood pressure nor in glomerular haemodynamics. Oral NaHCO3 may thus pro-tect the proximal renal tubule and help delay renal disease progression.

Randomised trial of octreotide for long term management of cirrhosis after variceal haemorrhage.

OBJECTIVE: To assess the efficacy of long term octreotide as adjuvant treatment to programmed endoscopic sclerotherapy after acute variceal haemorrhage in cirrhotic portal hypertension. DESIGN: Randomised clinical trial. SETTING: University hospital. SUBJECTS: 32 patients with cirrhotic portal hypertension. INTERVENTIONS: Programmed injection sclerotherapy with subcutaneous octreotide 50 micrograms twice daily for 6 months, or programmed injection sclerotherapy alone. MAIN OUTCOME MEASURES: Episodes of recurrent variceal bleeding and survival. RESULTS: Significantly fewer patients receiving combined octreotide and sclerotherapy had episodes of recurrent variceal bleeding compared with patients given sclerotherapy alone (1/16 v 7/16; P = 0.037, Fisher's exact test), and their survival was significantly improved (P < 0.02, log rank test); this improvement was maintained for 12 months after the end of the study. Combined treatment also resulted in a sustained decrease in portal pressure (median decrease -6.0 mm Hg, interquartile range -10 to -4.75 mm Hg, P = 0.0002) compared with sclerotherapy alone (median increase 1.5 mm Hg, interquartile range 0.25 to 3.25 mm Hg), as well as a significant improvement in liver function as assessed by plasma concentrations of bilirubin, albumin, and alanine aminotransferase and by hepatocyte metabolism of aminopyrine labelled with carbon-14. CONCLUSION: Long term octreotide may be a valuable adjuvant to endoscopic sclerotherapy for acute variceal haemorrhage in cirrhotic portal hypertension.

Octreotide scanning for carcinoid tumours.

The somatostatin analogue octreotide may be used in the diagnosis of carcinoid and other neuroendocrine tumours. Radionuclide scanning following intravenous injection of 111Indium-labelled octreotide (111In-DTPA-pentetreotide) provides a sensitive, non-invasive method of localising somatostatin-positive tumours. The technique may also be used to identify patients who may respond to 'cold' octreotide therapy and to monitor therapeutic efficacy.

The value of ventilation-perfusion imaging in pregnancy.

Pulmonary embolism (PE) is a major cause of maternal death during pregnancy. The aims of this retrospective study were to review 5 years experience of ventilation-perfusion (V/Q) imaging in pregnancy, to evaluate the effect of the V/Q scan report on the referring clinician's use of anticoagulants and to monitor the course and outcome of pregnancy. 82 patients (aged 17-44 years, gestation 6-40 weeks) underwent V/Q imaging for suspected PE, over a 5 year period. Modified PIOPED criteria were used to assess the probability of PE. 31 patients were shown to have normal scans (38%); 19 (23%) had low probability (LP) scans; 14 (17%) had intermediate probability (IP) scans and 18 (22%) had high probability (HP) scans for PE. Referring clinicians saw the reports and took action within 12 h. Anticoagulation was continued or started in 31 patients (all HP, 12 IP and 1 LP). Anticoagulation was considered unnecessary in 52 patients (all normal, 19 LP and 2 IP). None of the patients with normal or LP scans had documented PE during the follow-up period (median 25 months, range 3-60 months). No complications of anticoagulation were observed and no adverse outcome of pregnancy were reported. V/Q imaging is a valuable technique in the management of pregnant women suspected of having PE.

Radionuclide imaging of abomasal emptying in sheep.

A liquid radionuclide tracer was administered to nine sheep in order to visualise the abomasum with a gamma camera computer system. The aim was to develop a method of studying gastric emptying, with minimal surgical intervention. Oral administration of the tracer gave good images of the whole complex stomach, but quantifying abomasal emptying was not possible because of the superimposition of the stomach compartments. When the reticular groove reflex was stimulated with oral copper sulphate the radionuclide bypassed the reticulorumen, allowing quantitative analysis of abomasal activity. However, the repeatability of the reflex activation was low. Radionuclide administered directly into the abomasum produced good images of abomasal outflow and provided digital data which were analysed quantitatively. A wide range of emptying rates was observed, generally with a stepped pattern.

Uptake of 99mTc-MDP after uncemented hip arthroplasty: a quantitative analysis of findings around the femoral component in asymptomatic patients.

We studied the pattern of 99mTc-methylene diphosphonate uptake around uncemented femoral components in 44 asymptomatic hip arthroplasties, performing isotope scans at intervals from 4 to 48 months after operation. We used phase-II images obtained with a high-resolution gamma camera and measured the activity in various zones using a specially designed computer program. The components studied at 4, 6, 9 and 12 months were coated with hydroxyapatite (HA) and those studied at 18, 24, 36 and 48 months were not coated. We found a statistically significant fall in activity between four and six months around HA-coated prostheses in all five femoral periprosthetic zones. After six months activity was relatively uniform, but remained higher than that in normal femoral bone at 48 months in non-coated prostheses. We discuss the application of these patterns in the evaluation of painful cementless hip arthroplasties.

Outcome of 259 patients with primary proliferative polycythaemia (PPP) and idiopathic thrombocythaemia (IT) treated in a regional nuclear medicine department with phosphorus-32--a 15 year review.

259 patients with primary proliferative polycythaemia (PPP) and idiopathic thrombocythaemia (IT) have been treated with 32P over the last 15 years. Complete follow-up data were obtained in 238 patients. PPP was the diagnosis in 183 patients and 76 patients had IT. The sex ratio in PPP was male/female 1.1:1 and in IT 1:1.4. Patients' ages ranged from 28 to 95 years (median 72 years). The number of 32P administrations per patient ranged from 1 to 13 (median 2) and the total administered activity per patient ranged from 81.4 to 4162 MBq (median 496 MBq). The outcome showed a normalization of the full blood count in 50% of patients after a single administration of 32P and in 73% after two treatments. 13 patients (5.5%) developed myelofibrosis; 18 (7.6%) developed leukaemia while other cancers arose in 19 patients (8%). 32P therapy proved to be of particular value in the elderly. 32P is easy to administer and is cost effective, compared with the alternative of chemotherapy where good compliance and frequent hospital visits are required.