13[C]-urea breath test as a novel point-of-care biomarker for tuberculosis treatment and diagnosis

Mycobacteria-derived biomarkers for tuberculosis diagnosis

Tuberculosis (TB) remains an escalating problem worldwide. The current diagnostic methods do not always guarantee reliable diagnosis. TB treatment is a time-consuming process that requires the use of several chemotherapeutics, to which mycobacteria are becoming increasingly resistant. This article focuses on the potential utility of biomarkers of mycobacterial origin with potential implications for TB diagnosis. Properly standardized indicators could become new diagnostic tools, improving and streamlining the identification of Mycobacterium tuberculosis infection and the implementation of appropriate therapy. These markers can also potentially provide a quick confirmation of effectiveness of new anti-mycobacterial drugs and TB vaccines, leading to a possible application in practice.

Stool microbiome reveals diverse bacterial ureases as confounders of oral urea breath testing for Helicobacter pylori and Mycobacterium tuberculosis in Bamako, Mali

Detection of bacterial urease activity has been utilized successfully to diagnose Helicobacter pylori (H. pylori). While Mycobacterium tuberculosis (M. tuberculosis) also possesses an active urease, it is unknown whether detection of mycobacterial urease activity by oral urease breath test (UBT) can be exploited as a rapid point of care biomarker for tuberculosis (TB) in humans. We enrolled 34 individuals newly diagnosed with pulmonary TB and 46 healthy subjects in Bamako, Mali and performed oral UBT, mycobacterial sputum culture and H. pylori testing. Oral UBT had a sensitivity and specificity (95% CI) of 70% (46-88%) and 11% (3-26%), respectively, to diagnose culture-confirmed M. tuberculosis disease among patients without H. pylori, and 100% sensitivity (69-100%) and 11% specificity (3-26%) to diagnose H. pylori among patients without pulmonary TB. Stool microbiome analysis of controls without TB or H. pylori but with positive oral UBT detected high levels of non-H. pylori urease producing organisms, which likely explains the low specificity of oral UBT in this setting and in other reports of oral UBT studies in Africa.

A Proof of Concept Study to Detect Urease Producing Bacteria in Lungs Using Aerosolized 13C-Urea

This is a "proof of concept" study to determine whether inhalation of ¹³C-urea can be safely used to detect the presence of urease producing bacteria in the airways of patients with cystic fibrosis (CF) by detecting ¹³CO₂ in breath. This was a prospective, 2-part, open label, single-center, single-arm, single-administration, dose-escalation investigational device exemption trial. First, the safety of 20 and 50 mg inhaled ¹³C-urea was evaluated in 6 healthy adult participants. Then, 3 adult CF participants colonized with Pseudomonas aeruginosa were enrolled for each dose of inhaled ¹³C-urea. The safety of inhaled ¹³C-urea was assessed by spirometry and physical examination. ¹³C-urea was administered using a jet nebulizer, followed by serial spirometry (10 min and 30 min post inhalation) and collection of exhaled breath at 5, 10, and 15 min post inhalation. There was no clinical significant change in any of the spirometry values compared to baseline in healthy participants and CF patients. Mean of ¹³CO₂/¹²CO₂ delta over baseline (DOB) values in CF participants at 5, 10, and 15 min post inhalation was as follows: 20 mg dose 4‰ (2.2‰-4.9‰), 1‰ (1.0‰-1.4‰), and 1‰ (0.4‰-1.5‰); 50 mg dose: 10‰ (6.2‰-14.5‰), 3‰ (2.1‰-4.3‰), and 1.5‰ (0.6‰-2.3‰). Inhaled ¹³C-urea for detection of urease producing bacteria was safe, and preliminary data suggest that ¹³CO₂/¹²CO₂ DOB values may be higher in CF patients with P. aeruginosa at 5-10 min after inhalation of ¹³C-urea. A future direction is to investigate use of inhaled ¹³C-urea in young children who have difficulty producing sputum for culturing.

Bacterial volatiles and diagnosis of respiratory infections

Breath testing has enormous potential in the medical diagnostic field. The underlying complexity and perceived availability of adequate specimens, combined with a lack of knowledge of the metabolic pathways that give rise to compounds that are sources of analytes detectable in breath, has greatly slowed development. These real obstacles have recently been largely overcome in the use of breath testing to identify patients with cystic fibrosis associated Pseudomonas aeruginosa infection and tuberculosis. This review summarizes progress made in the characterization of microbial volatiles produced by major lower respiratory tract bacterial pathogens, and their potential use as diagnostic markers in patient breath testing.

Detecting virulence and drug-resistance mycobacterial phenotypes in vivo

Bacterial phenotypes are predominantly studied in culture because detection of their specific metabolic pathways in the host is challenging. Development of stable-isotope breath tests, allowing in situ phenotype analyses, may endow diagnostics with new modalities based upon direct monitoring of in vivo microbial metabolism and host-pathogen phenotypic interactions.

Urea

Urea is generated by the urea cycle enzymes, which are mainly in the liver but are also ubiquitously expressed at low levels in other tissues. The metabolic process is altered in several conditions such as by diets, hormones, and diseases. Urea is then eliminated through fluids, especially urine. Blood urea nitrogen (BUN) has been utilized to evaluate renal function for decades. New roles for urea in the urinary system, circulation system, respiratory system, digestive system, nervous system, etc., were reported lately, which suggests clinical significance of urea.

Amperometric immunosensor for rapid detection of Mycobacterium tuberculosis

Tuberculosis (TB) has been a major public health problem, which can be better controlled by using accurate and rapid diagnosis in low-resource settings. A simple, portable, and sensitive detection method is required for point-of-care (POC) settings. This paper studies an amperometric biosensor using a microtip immunoassay for a rapid and low cost detection of Mycobacterium Tuberculosis (MTB) in sputum. MTB in sputum is specifically captured on the functionalized microtip surface and detected by electric current. According to the numerical study, the current signal on microtip surface is linearly changed with increasing immersion depth. Using a reference microtip, the immersion depth is compensated for a sensing microtip. On the microtip surface, target bacteria are concentrated and organized by a coffee ring effect, which amplifies the electric current. To enhance the signal-to-noise ratio, both the sample processing- and rinsing steps are presented with use of deionized water as a medium for the amperometric measurement. When applied to cultured MTB cells spiked into human sputum, the detection limit was 100 CFU/mL, comparable to a more labor-intensive fluorescence detection method reported previously.

Rapid in vivo detection of isoniazid-sensitive Mycobacterium tuberculosis by breath test

There is urgent need for rapid, point of care diagnostic tools for tuberculosis (TB) and drug sensitivity. Current methods based on in vitro growth take weeks, while DNA amplification can neither differentiate live from dead organisms nor determine phenotypic drug resistance. Here we show the development and evaluation of a rapid breath test for isoniazid (INH)-sensitive TB based on detection of labeled N₂ gas formed specifically from labeled INH by mycobacterial KatG enzyme. In vitro data shows the assay is specific, dependent on mycobacterial abundance, and discriminates between INH-sensitive and resistant (S315T mutant KatG) TB. In vivo, the assay is rapid with maximal detection of ¹⁵N₂ in exhaled breath of infected rabbits within five to ten minutes. No increase in ¹⁵N₂ is detected in un-infected animals, and the increases in ¹⁵N₂ are dependent on infection dose. This test may allow rapid detection of INH-sensitive TB.

In vitro and in vivo studies of a rapid and selective breath test for tuberculosis based upon mycobacterial CO dehydrogenase

One of the major hurdles in treating tuberculosis (TB) is the time-consuming and difficult methodology for diagnosis. Stable-isotope breath tests hold great potential for rapidly diagnosing an infectious disease, monitoring therapy, and determining a bacterial phenotype in a rapid, point-of-care manner that does not require invasive sampling. Here we describe the preclinical development of a potentially highly selective TB diagnostic breath test based upon the organism’s CO dehydrogenase activity. After development of the test in vitro, we were able to use the breath test to discriminate between infected and control rabbits, demonstrating that a diagnosis can potentially be made and also that a complex bacterial phenotype can be noninvasively and rapidly studied in the host.

Tuberculosis (TB) remains a major infectious cause of disease and death worldwide, and effective diagnosis and then treatment are the tools with which we fight TB. The more quickly and more specific the diagnosis can be made, the better, and this is also true of diagnosis being as close to the patient (point of care) as possible. Here we report our preclinical development of breath tests based upon specific mycobacterial metabolism that could, with development, allow rapid point-of-care diagnosis through measuring the mycobacterial conversion of labeled CO to labeled CO₂.

Bacterial urease and its role in long-lasting human diseases

Urease is a virulence factor found in various pathogenic bacteria. It is essential in colonization of a host organism and in maintenance of bacterial cells in tissues. Due to its enzymatic activity, urease has a toxic effect on human cells. The presence of ureolytic activity is an important marker of a number of bacterial infections. Urease is also an immunogenic protein and is recognized by antibodies present in human sera. The presence of such antibodies is connected with progress of several long-lasting diseases, like rheumatoid arthritis, atherosclerosis or urinary tract infections. In bacterial ureases, motives with a sequence and/or structure similar to human proteins may occur. This phenomenon, known as molecular mimicry, leads to the appearance of autoantibodies, which take part in host molecules destruction. Detection of antibodies-binding motives (epitopes) in bacterial proteins is a complex process. However, organic chemistry tools, such as synthetic peptide libraries, are helpful in both, epitope mapping as well as in serologic investigations.

In this review, we present a synthetic report on a molecular organization of bacterial ureases - genetic as well as structural. We characterize methods used in detecting urease and ureolytic activity, including techniques applied in disease diagnostic processes and in chemical synthesis of urease epitopes. The review also provides a summary of knowledge about a toxic effect of bacterial ureases on human body and about occurrence of anti-urease antibodies in long-lasting diseases.

Breath tests in respiratory and critical care medicine: from research to practice in current perspectives

Today, exhaled nitric oxide has been studied the most, and most researches have now focused on asthma. More than a thousand different volatile organic compounds have been observed in low concentrations in normal human breath. Alkanes and methylalkanes, the majority of breath volatile organic compounds, have been increasingly used by physicians as a novel method to diagnose many diseases without discomforts of invasive procedures. None of the individual exhaled volatile organic compound alone is specific for disease. Exhaled breath analysis techniques may be available to diagnose and monitor the diseases in home setting when their sensitivity and specificity are improved in the future.

Developments in novel breath tests for bacterial and fungal pulmonary infection

PURPOSE OF REVIEW

Breath testing has developed over the last 20 years. New techniques that can identify fingerprints for specific diseases and specific markers of respiratory pathogens have been applied to breath analysis. This review discusses the recent advances in breath analysis for the diagnosis of bacterial and fungal lower respiratory tract infections.

RECENT FINDINGS

The current techniques continue to develop rapidly, but preconcentration techniques are needed to analyse many target volatile organic compounds for most systems. Breath testing with an electronic nose is promising for the diagnosis of tuberculosis (TB), and specific volatiles identifiable by gas chromatography with mass spectrometry have been identified in breath for Mycobacterium tuberculosis, Pseudomonas aeruginosa and Aspergillus fumigatus, but are found at very low concentrations in breath. Contamination from the environment is an ongoing confounding influence. Exhaled breath condensate (EBC) is disappointing as a diagnostic sample.

SUMMARY

Careful attention needs to be paid to the sensitivity and specificity of a technique and confounding from the environment. The role of technologies such as selected ion flow tube-mass spectrometry is emerging. The electronic nose requires further validation for TB. The identification of specific microbial biomarkers aids the quest for improved accuracy. EBC is currently of limited value.

Promising directions in the diagnosis of childhood tuberculosis

Estimates of the burden of childhood tuberculosis have been hampered by the lack of a reliable diagnostic test. Clinical scoring systems, radiological findings and tuberculin skin testing (the traditional methods used for diagnosis) are unreliable, particularly in the era of HIV. Microbiologic confirmation using induced sputum is feasible and has become increasingly important to define the burden of disease and to enable appropriate treatment. The availability of a rapid molecular diagnostic test (Xpert® MTB/RIF; Cepheid) is an important advance that can improve case detection in children and enable rapid detection of mycobacterial drug resistance. Xpert testing of two induced sputum specimens detected approximately 75% of children with culture-confirmed disease. Urine lipoarabinomannan has shown promise as a rapid diagnostic in a subgroup of HIV-infected severely immunocompromised adults, but there have been no data in children so far. Further research is needed to develop a rapid point-of-care, reliable and affordable diagnostic test for childhood tuberculosis that can be widely used.

Urease activity represents an alternative pathway for Mycobacterium tuberculosis nitrogen metabolism

Urease represents a critical virulence factor for some bacterial species through its alkalizing effect, which helps neutralize the acidic microenvironment of the pathogen. In addition, urease serves as a nitrogen source provider for bacterial growth. Pathogenic mycobacteria express a functional urease, but its role during infection has yet to be characterized. In this study, we constructed a urease-deficient Mycobacterium tuberculosis strain and confirmed the alkalizing effect of the urease activity within the mycobacterium-containing vacuole in resting macrophages but not in the more acidic phagolysosomal compartment of activated macrophages. However, the urease-mediated alkalizing effect did not confer any growth advantage on M. tuberculosis in macrophages, as evidenced by comparable growth profiles for the mutant, wild-type (WT), and complemented strains. In contrast, the urease-deficient mutant exhibited impaired in vitro growth compared to the WT and complemented strains when urea was the sole source of nitrogen. Substantial amounts of ammonia were produced by the WT and complemented strains, but not with the urease-deficient mutant, which represents the actual nitrogen source for mycobacterial growth. However, the urease-deficient mutant displayed parental colonization profiles in the lungs, spleen, and liver in mice. Together, our data demonstrate a role for the urease activity in M. tuberculosis nitrogen metabolism that could be crucial for the pathogen's survival in nutrient-limited microenvironments where urea is the sole nitrogen source. Our work supports the notion that M. tuberculosis virulence correlates with its unique metabolic versatility and ability to utilize virtually any carbon and nitrogen sources available in its environment.

Current tuberculosis diagnostic tools & role of urease breath test

Tuberculosis (TB) remains a significant public health issue worldwide especially in developing countries, where the disease is endemic, and effective TB diagnostic as well as treatment-monitoring tools are serious barriers to defeating the disease. Detection of pathogen-specific metabolic pathways offers a potential alternative to current methods, which focus on bacterial growth, bacterial nucleic acid amplification, or detection of host immune response to the pathogen. Metabolic pathway detection may provide rapid and effective new tools for TB that can improve TB diagnostics for children and HIV infected patients. Metabolic breath tests are attractive because these are safe, and provide an opportunity for rapid point of care diagnostics and tool for drug efficacy evaluation during clinical trials. Our group has developed a rabbit urease breath test model to evaluate the sensitivity and the specificity of urease based detection of Mycobacterium tuberculosis. TB infected rabbits were given stable isotopically labelled urea as the substrate. The urea tracer was metabolized to 13 C-CO 2 and detected in exhaled breaths using portable infrared spectrometers. The signal correlated with bacterial load both for primary diagnostics and treatment monitoring. Clinical trials are currently ongoing to evaluate the value of the test in clinical management settings. Urea breath testing may provide a useful diagnostic and biomarker assay for tuberculosis and treatment response.

Psychological stress and strain in dialysis staff: a systematic review

BACKGROUNG: As the number of dialysis patients increases, the psychological stress and strain suffered by dialysis personnel is of growing importance. For this reason a systematic review of the international literature was performed.

METHODS

A search of relevant databases for original studies or reviews published after 1990 resulted in 20 articles. The quality of these studies was assessed and they were grouped according to their focused central issues.

RESULTS

Stress and burnout were examined in 10 studies and a review. Working conditions and working situation in general were examined in eight studies. The findings were heterogeneous and difficult to compare. The results indicate that employees in the dialysis sector are subject to moderate levels of stress and burnout. Job satisfaction seems to be good. The few studies that allowed for comparison with other professions did not reveal excess stress and strain in dialysis personnel.

CONCLUSION

The results do not indicate that dialysis workers are exposed to above-average levels of stress or strain. Nevertheless, there is room for optimisation and need for action in some facilities.

Reporter phage and breath tests: emerging phenotypic assays for diagnosing active tuberculosis, antibiotic resistance, and treatment efficacy

The rapid and accurate diagnosis of active tuberculosis (TB) and its drug susceptibility remain a challenge. Phenotypic assays allow determination of antibiotic susceptibilities even if sequence data are not available or informative. We review 2 emerging diagnostic approaches, reporter phage and breath tests, both of which assay mycobacterial metabolism. The reporter phage signal, Green fluorescent protein (GFP) or β-galactosidase, indicates transcription and translation inside the recipient bacilli and its attenuation by antibiotics. Different breath tests assay, (1) exhaled antigen 85, (2) mycobacterial urease activity, and (3) detection by trained rats of disease-specific odor in sputum, have also been developed. When compared with culture, reporter phage assays shorten the time for initial diagnosis of drug susceptibility by several days. Both reporter phage and breath tests have promise as early markers to determine the efficacy of treatment. While sputum often remains smear and Mycobacterium tuberculosis DNA positive early in the course of efficacious antituberculous treatment, we predict that both breath and phage tests will rapidly become negative. If this hypothesis proves correct, phage assays and breath tests could become important surrogate markers in early bactericidal activity (EBA) studies of new antibiotics.