Rationale:Multiple infections with different strains of Mycobacterium tuberculosis may occur in settings where the infection pressure is high. The relevance of mixed infections for the patient, clinician, and control program remains unclear. Objectives: This study aimed to describe reinfection and mixed infection as underlying mechanisms of changing drug-susceptibility patterns in serial sputum cultures. Methods: Serial M. tuberculosis sputum cultures from patients diagnosed with multi-drug-resistant (MDR) tuberculosis were evaluated by phenotypic drug-susceptibility testing and mutation detection methods. Genotypic analysis was done by IS6110 DNA fingerprinting and a novel strain-specific polymerase chain reaction amplification method. Measurements and Main Results: DNA fingerprinting analysis of serial sputum cultures from 48 patients with MDR tuberculosis attributed 10 cases to reinfection and 1 case to mixed infection. In contrast, strain-specific polymerase chain reaction amplification analysis in 9 of the 11 cases demonstrated mixed infection in 5 cases, reinfection in 3 cases, and laboratory contamination in 1 case. Analysis of clinical data suggests that firstline therapy can select for a resistant subpopulation, whereas poor adherence or second-line therapy resulted in the reemergence of the drug-susceptible subpopulations. Conclusions: We have shown that, in some patients with MDR tuberculosis, mixed infection may be responsible for observations attributed to reinfection by DNA fingerprinting. We conclude that treatment and adherence determines which strain is dominant. We hypothesize that treatment with second-line drugs may lead to reemergence of the drug-susceptible strain in patients with mixed infection.
Keywords: drug resistance; mixed infections; Mycobacterium tuberculosis; reinfectionTraditionally, infection by Mycobacterium tuberculosis was assumed to be caused by a single strain, and recurrences were believed to be due to reactivation of the strain that caused the (Received in original form March 22, 2005; accepted in final form May 19, 2005) Supported by GlaxoSmithKline Action TB Program for funding the collection of clinical and demographic data, sputum culturing, and DNA fingerprinting; the Harry Crossley Foundation and the National Research Foundation (project 2054201 and the DST/NRF Centre of Excellence for Biomedical TB Research) for funding the development of the polymerase chain reaction-based strain-typing method; and the National Institutes of Health (R21 A155800-01) and the Wellcome Trust (DDS PC3145) for funding the identification of genotypic mechanisms conferring drug resistance.Correspondence and requests for reprints should be addressed to Robin M. Warren, Ph.D.,
Our study provides evidence that ASP increases glucose oxidation and modulates fatty acid utilization producing a favorable substrate shift in H9c2 cardiomyocytes exposed to high glucose. Such a favorable shift will be of importance in the protection of cardiomyocytes in the diabetic heart.
Parents caring for infants with AD have clearly defined, unmet information needs, forcing them into more active roles in the treatment decision-making process than they desire. The study-findings may inform the development of written information specifically for these parents and improve partnership during consultations.
T70N human lysozyme is the only known naturally occurring destabilised lysozyme variant that has not been detected in amyloid deposits in human patients. Its study and a comparison of its properties with those of the amyloidogenic variants of lysozyme is therefore important for understanding the determinants of amyloid disease. We report here the X-ray crystal structure and the solution dynamics of T70N lysozyme, as monitored by hydrogen/deuterium exchange and NMR relaxation experiments. The X-ray crystal structure shows that a substantial structural rearrangement results from the amino acid substitution, involving residues 45-51 and 68-75 in particular, and gives rise to a concomitant separation of these two loops of up to 6.5 Å . A marked decrease in the magnitudes of the generalised order parameter (S 2 ) values of the amide nitrogen atom, for residues 70-74, shows that the T70N substitution increases the flexibility of the peptide backbone around the site of mutation. Hydrogen/deuterium exchange protection factors measured by NMR spectroscopy were calculated for the T70N variant and the wild-type protein. The protection factors for many of backbone amide groups in the b-domain of the T70N variant are decreased relative to those in the wild-type protein, whereas those in the a-domain display wild-type-like values. In pulse-labelled hydrogen/deuterium exchange experiments monitored by mass spectrometry, transient but locally cooperative unfolding of the b-domain of the T70N variant and the wild-type protein was observed, but at higher temperatures than for the amyloidogenic variants I56T and D67H. These findings reveal that such partial unfolding is an intrinsic property of the human lysozyme structure, and suggest that the readiness with which it occurs is a critical feature determining whether or not amyloid deposition occurs in vivo.
Diabetic patients are at an increased risk of developing heart failure when compared to their non-diabetic counter parts. Accumulative evidence suggests chronic hyperglycemia to be central in the development of myocardial infarction in these patients. At present, there are limited therapies aimed at specifically protecting the diabetic heart at risk from hyperglycemia-induced injury. Oxidative stress, through over production of free radical species, has been hypothesized to alter mitochondrial function and abnormally augment the activity of the NADPH oxidase enzyme system resulting in accelerated myocardial injury within a diabetic state. This has led to a dramatic increase in the exploration of plant-derived materials known to possess antioxidative properties. Several edible plants contain various natural constituents, including polyphenols that may counteract oxidative-induced tissue damage through their modulatory effects of intracellular signaling pathways. Rooibos, an indigenous South African plant, well-known for its use as herbal tea, is increasingly studied for its metabolic benefits. Prospective studies linking diet rich in polyphenols from rooibos to reduced diabetes associated cardiovascular complications have not been extensively assessed. Aspalathin, a flavonoid, and phenylpyruvic acid-2-O-β-D-glucoside, a phenolic precursor, are some of the major compounds found in rooibos that can ameliorate hyperglycemia-induced cardiomyocyte damage in vitro. While the latter has demonstrated potential to protect against cell apoptosis, the proposed mechanism of action of aspalathin is linked to its capacity to enhance the expression of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) expression, an intracellular antioxidant response element. Thus, here we review literature on the potential cardioprotective properties of flavonoids and a phenylpropenoic acid found in rooibos against diabetes-induced oxidative injury.
HighlightsDepending on the concentration, dimethyl sulfoxide (DMSO) can be toxic to cells.3T3-L1 adipocytes are a well-established model to study anti-obesity properties.DMSO doses ≥1% reduced cell viability and promoted cell damage in 3T3-L1 adipocytes.
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