In vivo healing of low temperature deproteinized bovine bone xenograft in a rabbit cranial model.

The physicochemical properties of grafting materials affect the quality of the osteointegration, resorption rate, and the new bone (NB) formation. This study assessed the physicochemical properties and integration of a low temperature deproteinized bovine bone xenograft (BBX), referred to as optimized MoaBone® (OMB). This novel BBX was physiochemically characterized both pre and post chemical bleaching and sterilization by gamma irradiation. OMB was compared to two commercial BBX; Bio-Oss® (BO) and MoaBone® (MB) using a rabbit cranial model. Residual graft and NB were quantified using histology and micro-computed tomography. Results showed that chemical treatment and gamma irradiation had limited effect on the surface texture. A significant decrease in the collagen content was detected post chemical treatment and in the carbonate content post gamma irradiation. There was no evidence of inflammatory infiltrate, necrosis, or connective tissue encapsulation, and a significant increase of NB in all grafted sites as compared to untreated defects could be observed. However, there was no statistically significant difference between the grafted sites. We conclude that chemical treatment and terminal sterilization strongly impact the final graft's properties. OMB graft showed equivalence with BO for in vivo bone formation and potentially results in lower levels of graft retention.

The Effect of Low-Processing Temperature on the Physicochemical and Mechanical Properties of Bovine Hydroxyapatite Bone Substitutes.

Bovine bone grafts (BBX) require protein removal as part of the manufacturing process to reduce antigenicity and, in consequence, to be safely used in humans. Deproteinisation may have direct effects on the characteristics of the bone material and on in vivo material performance. This research aimed to comprehensively study the physicochemical and mechanical properties of BBX processed at low deproteinisation processing temperatures. Cubes of bovine bone (8 mm3) were treated with temperatures between 100 °C and 220 °C at 30 °C intervals and with pressures ranging from 1.01 to 24.58 Bar. The samples were characterised topographically and mechanically using scanning electron microscopy (SEM), atomic force microscopy (AFM), and uniaxial bending tests. The organic content and the chemical composition were determined using thermogravimetric analysis (TGA) and Fourier-transform infrared spectroscopy (FTIR). X-ray diffraction (XRD) and FTIR were also used to quantitatively determine the specimen crystallinity. Increasing temperature/pressure was associated with decreasing protein levels and compressive strength and increasing surface irregularities and crystallinity. The findings suggest that low-temperature processed bone is likely to exhibit a rapid in vivo degradation rate. The deproteinisation temperature can be adjusted to tailor the graft properties for specific applications.

The Effect of Low-Temperature Thermal Processing on Bovine Hydroxyapatite Bone Substitutes, toward Bone Cell Interaction and Differentiation.

Ideal bone grafting scaffolds are osteoinductive, osteoconductive, and encourage osteogenesis through the remodeling processes of bone resorption, new bone formation, and successful integration or replacement; however, achieving this trifecta remains challenging. Production methods of bone grafts, such as thermal processing, can have significant effects on the degree of cell-surface interactions via wide-scale changes in the material properties. Here, we investigated the effects of small incremental changes at low thermal processing temperatures on the degree of osteoclast and osteoblast attachment, proliferation, and differentiation. Bovine bone scaffolds were prepared at 100, 130, 160, 190, and 220 °C and compared with a commercial control, Bio-Oss®. Osteoclast attachment and activity were significantly higher on lower temperature processed bone and were not present ≥190 °C. The highest osteoblast proliferation and differentiation were obtained from treatments at 130 and 160 °C. Similarly, qRT2-PCR assays highlighted osteoblasts attached to bone processed at 130 and 160 °C as demonstrating the highest osteogenic gene expression. This study demonstrated the significant effects of small-scale processing changes on bone graft materials in vitro, which may translate to a tailored approach of cellular response in vivo.

Risk Factors for Tuberculosis (TB) Among Household Contacts of Patients With Smear-Positive TB in 8 Provinces of Vietnam: A Nested Case-Control Study.

BACKGROUND: Tuberculosis (TB) continues to account for significant morbidity and mortality annually. Household contacts (HHCs) of persons with TB are a key population for targeting prevention and control interventions. We aimed to identify risk factors associated with developing TB among HHCs. METHODS: We conducted a nested case-control study among HHCs in 8 provinces in Vietnam enrolled in a randomized controlled trial of active case finding for TB. Cases were any HHCs diagnosed and registered with TB within the Vietnam National TB Program during 2 years of follow-up. Controls were selected by simple random sampling from the remaining HHCs. Risk factor data were collected at enrollment and during follow-up. A logistic regression model was developed to determine predictors of TB among HHCs. RESULTS: We selected 1254 HHCs for the analysis: 214 cases and 1040 controls. Underlying characteristics varied between both groups; cases were older, more likely to be male, with a higher proportion of reported previous TB and diabetes. Risk factors associated with a TB diagnosis included being male (adjusted odds ratio [aOR], 1.4; 95% confidence interval [CI], 1.03-2.0), residing in an urban setting (aOR, 1.8; 1.3-2.5), prior TB (aOR, 4.6; 2.5-8.7), history of diabetes (aOR, 3.1; 1.7-5.8), current smoking (aOR, 3.1; 2.2-4.4), and prolonged history of coughing in the index case at enrollment (OR , 1.6; 1.1-2.3). CONCLUSIONS: Household contacts remain an important key population for TB prevention and control. TB programs should ensure effective contact investigations are implemented for household contacts, particularly those with additional risk factors for developing TB.

Preoperative Risk Factors for Nonhome Discharge of Home-Dwelling Geriatric Patients Following Elective Surgery.

To identify patient risk factors for nonhome discharge (NHD) for home-dwelling older patients undergoing surgery, we performed a retrospective cohort study of patients aged ≥65 years undergoing elective surgery between 2014 and 2016 using the geriatric research file from the National Surgical Quality Improvement Program (NSQIP). Multivariable logistic regression examined the association between preoperative demographics, comorbidities, and functional status and NHD to determine which factors are most strongly predictive of NHD. Risk of NHD was higher among those of age >85 years, age 75 to 85 years, Black race, with body mass index (BMI) >30, dyspnea with exertion or at rest, partially or totally dependent in activities of daily living (ADLs), preoperative steroid use, preoperative wound infection, use of a mobility aid, fall within 3 months, or living alone at home without support. NHDs were statistically more likely among orthopedic, neurosurgery, or cardiac surgery interventions. Understanding individual patient's risks and setting expectations for likely postoperative course is integral to appropriate preoperative counseling and preoperative optimization.

Household contact investigation for the detection of tuberculosis in Vietnam: economic evaluation of a cluster-randomised trial.

BACKGROUND: Active case finding is recommended as an important strategy to control tuberculosis, particularly in low-income and middle-income countries with a high prevalence of the disease. However, the costs and cost-effectiveness of active case finding are unclear due to the absence of evidence from randomised trials. We assessed the costs and cost-effectiveness of an active case finding strategy in Vietnam, where there is a high prevalence of tuberculosis. METHODS: We conducted an economic evaluation alongside the Active Case Finding in Tuberculosis (ACT2) trial-a pragmatic cluster-randomised controlled trial in 70 districts across eight provinces of Vietnam. Patients aged 15 years and older with smear-positive pulmonary tuberculosis were recruited to the trial if they lived with one or more other household members. Household contacts were verbally invited to the clinic by the index patient with tuberculosis. ACT2 compared a combination of active and passive case finding with usual care (passive case finding) of household contacts of patients with tuberculosis from a health system perspective. Clustering occurred at the district and household level. Districts were the unit of randomisation, and we used minimisation to ensure balance of intervention and control districts within each province. In the intervention group, participants were invited to attend screening at baseline, 6 months, 12 months, and 24 months. We determined health-care costs with a standardised national costing survey and reported results in 2017 $US. The primary outcome of our study was disability-adjusted life years (DALYs) averted over a 24-month period. ACT2 was registered prospectively with the Australian and New Zealand Clinical Trials Registry, number ACTRN126.100.00600044. FINDINGS: Between Aug 11, 2010, and Aug 11, 2015, 10 964 index patients and 25 707 household contacts completed the ACT2 study. There were 10 069 household contacts in the intervention group and 15 638 household contacts in the control group. The incremental cost-effectiveness ratio per DALY averted was $544 (330-1375). INTERPRETATION: Active case finding was shown to be highly cost-effective in a setting with a high prevalence of tuberculosis. Investment in the wide-scale implementation of this programme in Vietnam should be strongly supported. FUNDING: Australian National Health and Medical Research Council.

Recurrence of tuberculosis among patients following treatment completion in eight provinces of Vietnam: A nested case-control study.

BACKGROUND: Patients completing treatment for tuberculosis (TB) in high-prevalence settings face a risk of developing recurrent disease. This has important consequences for public health, given its association with drug resistance and a poor prognosis. Previous research has implicated individual factors such as smoking, alcohol use, HIV, poor treatment adherence, and drug resistant disease as risk factors for recurrence. However, little is known about how these factors co-act to produce recurrent disease. Furthermore, perhaps factors related to the index disease means higher burden/low resource settings may be more prone to recurrent disease that could be preventable. METHODS: We conducted a case-control study nested within a cohort of consecutively enrolled adults who were being treated for smear positive pulmonary TB in 70 randomly selected district clinics in Vietnam. Cases were patients with recurrent TB, identified by follow-up from the parent cohort study. Controls were selected from the cohort by random sampling. Information on demographic, clinical and disease-related characteristics was obtained by interview. Treatment information was extracted from clinic registries. Logistic regression, with stepwise selection, was used to develop a fully adjusted model for the odds of recurrence of TB. RESULTS: We recruited 10,964 patients between October 2010 and July 2013. Median follow-up was 988 days. At the end of follow-up, 505 patients (4.7%) with recurrence were identified as cases and 630 other patients were randomly selected as controls. Predictors of recurrence included multidrug-resistant (MDR)-TB (adjusted odds ratio 79.6; 95% CI: 25.1-252.0), self-reported prior TB therapy (aOR=2.5; 95% CI: 1.7-3.5), and incomplete adherence (aOR=1.9; 95% CI 1.1-3.1). CONCLUSIONS: Index disease treatment history is a leading determinant of relapse among patients with TB in Vietnam. Further research is required to identify interventions that will reduce the risk of recurrent disease and enhance its early detection within high-risk populations.

Effect of Titanium Surfaces on the Osteogenic Differentiation of Human Adipose-Derived Stem Cells.

PURPOSE: To investigate whether human adipose-derived stem cells will form a functional bone-like matrix on titanium substrates. The behavior of human adipose-derived stem cells was examined when grown in either serum-free, xeno-free stem cell growth medium or osteogenic differentiation medium and cultured on either machined titanium (MTi) or on roughened alumina-blasted titanium (ABTi) discs. MATERIALS AND METHODS: Cellular proliferation, extracellular mineralized matrix production, osteogenic-related protein production (RUNX2 and osteocalcin), and gene expression for pluripotency and self-renewal (TERT and OCT4) and osteogenic-related (MSX2, RUNX2, and BGLAP) genes were performed. RESULTS: Human adipose-derived stem cells in serum-free medium (hADSC) proliferated at a higher rate compared with osteogenically differentiated cells (hOS-ADSC); however, the osteogenically committed cells produced more mineralized matrix on the titanium surfaces compared with either tissue culture plastic or the undifferentiated cells. The immunofluorescence analysis showed that human adipose-derived stem cells cultured in serum-free medium and osteogenic differentiation medium produced RUNX2 on both the machined titanium surface and on the alumina-blasted titanium surface after 7 days in culture. Only osteogenically differentiated cells produced osteocalcin after 21 days. Relative gene expression showed stable expression of MSX2, RUNX2, and BGLAP over time on all surfaces. Only osteogenically differentiated cells displayed osteogenic characteristics over time. CONCLUSION: This study confirmed that human adipose-derived stem cells could be successfully grown in serum-free, xeno-free culture medium suitable for clinical use. Adipose-derived stem cells thus show potential utility for bone regeneration in association with titanium surfaces.

In vivo bone regeneration on titanium devices using serum-free grown adipose-derived stem cells, in a sheep femur model.

AIM: The aim of this study was to investigate the capacity of adipose-derived stem cells (ADSC), grown in serum-free conditions, to regenerate bone around titanium discs with different titanium surfaces. MATERIAL AND METHODS: Ovine ADSC (oADSC) were isolated from seven sheep and cultured using serum-free and osteogenic conditions. Prior to in vivo testing, the growth and osteogenic behaviour of these cells were analysed in vitro using cell proliferation and extracellular matrix mineralisation assays. The bone regenerative capacity of autologous oADSC was evaluated in vivo on titanium discs in a sheep femur epicondyle model. Machined (MTi) and alumina-blasted (ABTi) titanium discs were used. Bone regeneration within the defects was evaluated after 1 month using histology and histomorphometry. PKH26 cell-tracking dye was used to verify the persistence of oADSC in the surgical wound. RESULTS: oADSC sourced from five of seven sheep differentiated into osteoblast-like cells. Cellular proliferation was reduced only for osteogenically induced oADSC (oOS-ADSC) grown on ABTi, compared to non-induced oADSC grown on ABTi and tissue culture polystyrene (P = 0.03 and 0.02 respectively). There was no significant difference for in vitro mineralisation assays comparing oADSC with oOS-ADSC, regardless of implant surface type. oADSC labelled with PKH26 were detected 1 month after surgery within the defect. There was no difference in bone regeneration between the bone defects treated with oADSC vs. just blood clot. CONCLUSION: After 1-month healing, the use of autologous oADSC did not improve bone regeneration in defects containing titanium devices with different surfaces.

Dry powder inhalable formulations for anti-tubercular therapy.

Tuberculosis (TB) is an intracellular infectious disease caused by the airborne bacterium, Mycobacterium tuberculosis. Despite considerable research efforts, the treatment of TB continues to be a great challenge in part due to the requirement of prolonged therapy with multiple high-dose drugs and associated side effects. The delivery of pharmacological agents directly to the respiratory system, following the natural route of infection, represents a logical therapeutic approach for treatment or vaccination against TB. Pulmonary delivery is non-invasive, avoids first-pass metabolism in the liver and enables targeting of therapeutic agents to the infection site. Inhaled delivery also potentially reduces the dose requirement and the accompanying side effects. Dry powder is a stable formulation of drug that can be stored without refrigeration compared to liquids and suspensions. The dry powder inhalers are easy to use and suitable for high-dose formulations. This review focuses on the current innovations of inhalable dry powder formulations of drug and vaccine delivery for TB, including the powder production method, preclinical and clinical evaluations of inhaled dry powder over the last decade. Finally, the risks associated with pulmonary therapy are addressed. A novel dry powder formulation with high percentages of respirable particles coupled with a cost effective inhaler device is an appealing platform for TB drug delivery.

MALDI-MSI for the analysis of a 3D tissue-engineered psoriatic skin model.

MALDI-MS Imaging is a novel label-free technique that can be used to visualize the changes in multiple mass responses following treatment. Following treatment with proinflammatory cytokine interleukin-22 (IL-22), the epidermal differentiation of Labskin, a living skin equivalent (LSE), successfully modeled psoriasis in vitro. Masson's trichrome staining enabled visualization and quantification of epidermal differentiation between the untreated and IL-22 treated psoriatic LSEs. Matrix-assisted laser desorption ionization mass spectrometry imaging was used to observe the spatial location of the psoriatic therapy drug acetretin following 48 h treatments within both psoriatic and normal LSEs. After 24 h, the drug was primarily located in the epidermal regions of both the psoriatic and nonpsoriatic LSE models whereas after 48 h it was detectible in the dermis.

Histomorphometric and histologic evaluation of titanium-zirconium (aTiZr) implants with anodized surfaces.

The choice of implant surface has a significant influence on osseointegration. Modification of TiZr surface by anodization is reported to have the potential to modulate the osteoblast cell behaviour favouring more rapid bone formation. The aim of this study is to investigate the effect of anodizing the surface of TiZr discs with respect to osseointegration after four weeks implantation in sheep femurs. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing DL-α-glycerophosphate and calcium acetate at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, atomic force microscopy and goniometry. Forty implant discs with thickness of 1.5 and 10 mm diameter (10 of each-titanium, titanium-zirconium, anodized titanium and anodized titanium-zirconium) were placed in the femoral condyles of 10 sheep. Histomorphometric and histologic analysis were performed 4 weeks after implantation. The anodized implants displayed hydrophilic, porous, nano-to-micrometer scale roughened surfaces. Energy dispersive spectroscopy analysis revealed calcium and phosphorous incorporation into the surface of both titanium and titanium-zirconium after anodization. Histologically there was new bone apposition on all implanted discs, slightly more pronounced on anodised discs. The percentage bone-to-implant contact measurements of anodized implants were higher than machined/unmodified implants but there was no significant difference between the two groups with anodized surfaces (P > 0.05, n = 10). The present histomorphometric and histological findings confirm that surface modification of titanium-zirconium by anodization is similar to anodised titanium enhances early osseointegration compared to machined implant surfaces.

Spark anodization of titanium-zirconium alloy: surface characterization and bioactivity assessment.

Titanium (Ti) and its alloys have been popularly used as implant biomaterial for decades. Recently, titanium-zirconium (TiZr) alloy has been developed as an alternative implant material with improved strength in load bearing areas. Surface modification is one of the key factors to alter the surface properties to hasten osseointegration. Spark anodic oxidation (anodization) is one such method that is reported to enhance the bone formation around implants. This study aims to anodize TiZr and study its surface characteristics and cytocompatibility by cell culture experiments using osteoblast-like cells. Titanium (Ti) and TiZr discs were anodized in an electrolyte containing DL-α-glycerophosphate and calcium acetate (CA) at 300 V. The surface characteristics were analyzed by scanning electron microscopy, electron dispersive spectroscopy, X-ray diffraction (XRD), atomic force microscopy and goniometry. Using osteoblast-like cells viability, proliferation, differentiation and mineralization was assessed. The anodized surfaces demonstrated increased oxygen, entrapped calcium and phosphorous from the electrolyte used. XRD analysis confirmed the presence of anatase in the oxide layer. Average roughness increased and there was a significant decrease in contact angle (P < 0.01) following anodization. The anodized TiZr (aTiZr) surfaces were more nano-porous compared to anodized Ti (aTi). No significant difference was found in the viability of cells, but after 24 h the total number of cells was significantly higher (P < 0.01). Proliferation, alkaline phosphatase activity and calcium deposits were significantly higher on anodized surfaces compared to machined surfaces (P < 0.05, ANOVA). Anodization of TiZr resulted in a more nanoporous and hydrophilic surface than aTi, and osteoblast biocompatibility appeared comparable to aTi.

Barriers to adherence with tuberculosis contact investigation in six provinces of Vietnam: a nested case-control study.

BACKGROUND: Close contacts of patients with tuberculosis (TB) have a substantial risk of developing the disease, particularly during the first year after exposure. Household contact investigation has recently been recommended as a strategy to enhance case detection in high-burden countries. However the barriers to its implementation in these settings remain poorly understood. METHODS: A nested case-control study was conducted in Vietnam within the context of a large cluster randomised controlled trial of active screening for TB in household contacts of patients with pulmonary TB. The study population comprised contacts (and their index patients) from 12 Districts in six provinces throughout the country. Cases were contacts (and their index patients) that did not attend the scheduled screening appointment. Controls were those who did attend. We assessed relevant knowledge, attitudes and practices in cases and controls. RESULTS: The acceptability of contact investigation was high among both cases (n = 109) and controls (n = 194). Both cases (47%) and controls (36%) commonly reported discrimination against people with TB. Cases were less likely than controls to understand that sharing sleeping quarters with a TB patient increased their risk of disease (OR 0.46, 0.27 - 0.78) or recognise TB as an infectious disease (OR 0.65, 0.39 - 1.08). A higher proportion of cases than controls held the mistaken traditional belief that a non-infectious form of TB caused the disease (OR 1.69, 1.02 - 2.78). CONCLUSIONS: The knowledge, attitudes and practices of contacts and TB patients influence their ongoing participation in contact investigation. TB case detection policies in high-prevalence settings can be strengthened by systematically evaluating and addressing locally important barriers to attendance. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry, ACTRN12610000600044 .

Soft and Hard Tissue Response to Zirconia versus Titanium One-Piece Implants Placed in Alveolar and Palatal Sites: A Randomized Control Trial.

BACKGROUND: Titanium (Ti) implants have been used in the last four decades to replace missing teeth. Alternatives to Ti such as zirconia (Zr) may offer aesthetic advantages and be more acceptable to patients and clinicians concerned about Ti allergy but must show equivalent biological acceptability to Ti. PURPOSE: The research aimed to investigate soft and hard tissue response to Ti and Zr implants in edentulous patients. MATERIALS AND METHODS: The research included 24 participants (Ti = 12, Zr = 12) restored with one-piece ball-abutment implants to support overdentures. Participants received four maxillary implants (two in the premolar alveolus, one off center in the alveolar midline, and one wide-diameter implant in the anterior median palate) and three mandibular implants (one in the midline and bilateral posterior implants). RESULTS: Success rates for both Ti and Zr implants were low, 67.9% for all alveolar implants and a survival rate of 50.0% for the palatal implants. Only 11 (52.4%) of 21 palatal implants survived the follow-up period. Peri-implant health was equivalent for Ti and Zr implants and showed no statistically significant changes from loading to the 1-year follow-up. Statistically significant differences were noted in radiographic bone level between Ti and Zr implants (p = .02), with Zr showing greater bone loss. CONCLUSIONS: Although the failure rates with the one-piece Zr implants were higher than with the Ti ones, suggesting that the former's clinical usage as in this study cannot be recommended, it should be borne in mind that the fault may also lie with the novel prosthodontic design which was used.

Allergen-specific IL-5 responses in early childhood predict asthma at age eight.

BACKGROUND: The pattern of development of allergen-specific T cell cytokine responses in early childhood and their relation to later disease is poorly understood. Here we describe longitudinal changes in allergen-stimulated T cell cytokine responses and their relation to asthma and allergic disease during the first 8 years of life. METHODS: Subjects with a family history of asthma, who were enrolled antenatally in the Childhood Asthma Prevention Study (public trials registration number ACTRN12605000042640), had skin prick tests, clinical evaluation for asthma and eczema, and in vitro assessment of T cell cytokine responses to HDM extract performed at ages 18 months (n = 281), 3 years (n = 349), 5 years (n = 370) and 8 years (n = 275). We measured interleukin (IL-) 13 at 3, 5 and 8 years, and IL-5, IL-10, and interferon-γ (IFN-γ), at 18 months, 3, 5 and 8 years by ELISA. A cohort analysis was undertaken. Independent effects of cytokine responses at each age on the risk of asthma and allergic outcomes at age 8 years were estimated by multivariable logistic regression. RESULTS: HDM-specific IL-5 responses increased with age. HDM-specific IL-13 and IL-10 responses peaked at age 5 years. HDM-specific IL-5 responses at 3 years, 5 years and 8 years were significantly associated with the presence of asthma and atopy at 8 years. IL-13 responses at 3 years, 5 years and 8 years were significantly associated with atopy at 8 years, but this association was not independent of the effect of IL-5. Other HDM-specific cytokine responses were not independently related to asthma or eczema at 8 years. CONCLUSION: HDM-specific IL-5 responses at age 3 years or later are the best measure of T cell function for predicting asthma at age 8 years.

Contact investigation in households of patients with tuberculosis in Hanoi, Vietnam: a prospective cohort study.

SETTING: Existing tuberculosis control strategies in Vietnam are based on symptomatic patients attending health services for investigation. This approach has not resulted in substantial reductions in the prevalence of tuberculosis disease, despite the National Tuberculosis Program achieving high treatment completion rates. Alternative approaches are being considered. OBJECTIVE: To determine the feasibility and yield of contact investigation in households of patients with smear positive pulmonary tuberculosis among household members of tuberculosis patients in Hanoi, Vietnam. METHODS: Household contacts of patients with smear positive pulmonary tuberculosis were recruited at four urban and rural District Tuberculosis Units in Hanoi. Clinical and radiological screening was conducted at baseline, six months and 12 months. Sputum microscopy and culture was performed in contacts suspected of having tuberculosis. MIRU-VNTR molecular testing was used to compare the strains of patients and their contacts with disease. RESULTS: Among 545 household contacts of 212 patients, four were diagnosed with tuberculosis at baseline (prevalence 734 cases per 100,000 persons, 95% CI 17-1451) and one was diagnosed with tuberculosis during the subsequent 12 months after initial screening (incidence 180 cases per 100,000 person-years, 95% CI 44-131). Two of these cases were culture positive for M. tuberculosis and both had identical or near-identical MIRU-VNTR strain types. CONCLUSION: Household contacts of patients with potentially infectious forms of tuberculosis have a high prevalence of disease. Household contact investigation is feasible in Vietnam. Further research is required to investigate its effectiveness.

Modelling of mercury transport and transformation processes in the Idrijca and Soca river system.

In the town of Idrija, Slovenia, the world's second largest mercury mine was active for 500 years and about 37,000 tons of mercury has been lost in the environment. Mercury is still drained from soil, riverbed and floodplains and transported with the Idrijca and Soca Rivers to the Gulf of Trieste. A part of inorganic mercury is methylated either in the river system, or later in the coastal area, and, due to its bioaccumulation and biomagnification represents potential danger to human health. A 1-D aquatic model MeRiMod was used to simulate hydrodynamics and sediment transport in the river system from Idrija to the Soca River mouth. Transport of particle bound and dissolved mercury as well as potential net methylation of mercury in the river system was simulated. The simulation of an observed flood wave with 20-year recurrence period was performed in order to validate the model. Methylation was simulated at lower discharges, as higher methylation rates occur in such conditions. The measurement data and the MeRiMod model were also used to establish a historical mercury mass balance of the Idrijca and Soca Rivers catchment. Sediment core data from the Gulf of Trieste and the measured concentrations from floodplains were used to verify and calibrate the model. Simulations of different high discharges were performed as most of the transport of particulate mercury occurs within flood wave conditions. Compared to the measurements, the results of the model showed an agreement within an order of magnitude, for the transport of total mercury mostly within a factor of 4, and for the methylation within a factor of 5. However, proper trends of the phenomena were obtained by simulations. The combination of modelling and measurements has resulted in some interesting conclusions about the phenomenon of the transport and transformations of mercury in the observed river system.