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R Das

Publications and source records attributed to R Das.

At least 19 recordsLinked to original sources
PubMed2006

Comparative evaluation of Löwenstein-Jensen proportion method, BacT/ALERT 3D system, and enzymatic pyrazinamidase assay for pyrazinamide susceptibility testing of Mycobacterium tuberculosis.

Pyrazinamide (PZA) is an important first-line antituberculosis drug because of its sterilizing activity against semidormant tubercle bacilli. In spite of its very high in vivo activity, its in vitro activity is not apparent unless an acidic environment is available, which makes PZA susceptibility testing difficult by conventional methods. The present study was, therefore, planned to assess the performance of the colorimetric BacT/ALERT 3D system and compare the results with those from conventional tests, i.e., the Löwenstein-Jensen (LJ) proportion method (pH 4.85) and Wayne's pyrazinamidase (PZase) assay, using 107 clinical isolates. The concordance among all of these tests was 89.71% after the first round of testing and reached 92.52% after resolution of the discordant results by retesting. Prolonged incubation of the PZase tube for up to 10 days was found to increase the specificity of the PZase test. The concordances between LJ proportion and BacT/ALERT 3D, LJ proportion and the PZase assay, and BacT/ALERT 3D and the PZase assay were found to be 99.06%, 93.46%, and 92.52%, respectively. Using the LJ results as the gold standard, the sensitivities of BacT/ALERT 3D and the PZase assay were 100 and 82.85%, respectively, while the specificity was 98.61% for both of the tests. The difference between the sensitivities of BacT/ALERT 3D and the PZase assay was significant (P = 0.025). The mean turnaround times for the detection of resistant and susceptible results by BacT/ALERT 3D were 8.04 and 11.32 days, respectively. While the major limitations associated with the PZase assay and the LJ proportion method are lower sensitivity in previously treated patients and a longer time requirement, respectively, the BacT/ALERT 3D system was found to be rapid, highly sensitive, and specific.

Amidohydrolases↗
PubMed2006

Occurrence, virulence characteristics and antimicrobial resistance of Escherichia coli O157 in slaughtered cattle and diarrhoeic calves in West Bengal, India.

AIMS: (i) To study the occurrence of Escherichia coli serotype O157 in cattle stool in West Bengal, India, and (ii) the virulence properties and antimicrobial resistance of the E. coli isolates. METHODS AND RESULTS: Following enrichment in modified EC broth and plating onto HiCrome MS.O157 agar, a total of 14 strains of E. coli serotype O157 was isolated from faecal samples from two (2.04%) slaughtered cattle and six (7.59%) diarrhoeic calves. By multiplex PCR, Shiga toxin genes were detected in all the isolates. The enterohaemolysin phenotype was found in all, but one strain. Among 14 strains, ten were resistant to at least one of the antimicrobial agents tested. Multiple antibiotic resistance was frequent. CONCLUSIONS: The study showed that occurrence of Shiga toxin-producing and multiple antibiotic-resistant E. coli O157 among cattle population in this region of India is significant. SIGNIFICANCE AND IMPACT OF THE STUDY: Considering routine human contacts with cattle, a large human population in this region may be at risk for exposure to Shiga toxin-producing E. coli O157.

Animals↗
PubMed2005

Interaction of glutathione S-transferase with hypericin: A photophysical study.

The photophysics of hypericin have been studied in its complex with two different isoforms, A1-1 and P1-1, of the protein glutathione S-transferase (GST). One molecule of hypericin binds to each of the two GST subunits. Comparisons are made with our previous results for the hypericin/human serum albumin complex (Photochem. Photobiol. 1999, 69, 633-645). Hypericin binds with high affinity to the GSTs: 0.65 microM for the A1-1 isoform and 0.51 microM for the P1-1 isoform (Biochemistry 2004, 43, 12761-12769). The photophysics and activity of hypericin are strongly modulated by the binding protein. Intramolecular hydrogen-atom transfer is suppressed in both cases. Most importantly, while there is significant singlet oxygen generation from hypericin bound to GST A1-1, binding to GST P1-1 suppresses singlet oxygen generation to almost negligible levels. The data are rationalized in terms of a simple model in which the hypericin photophysics depends entirely upon the decay of the triplet state by two competing processes, quenching by oxygen to yield singlet oxygen and ionization, the latter of these two are proposed to be modulated by A1-1 and P1-1.

Anthracenes↗
PubMed2005

External validation, extension and recalibration of Braunwald's simple risk index in a community-based cohort of patients with both STEMI and NSTEMI.

BACKGROUND: Using the simple risk index (SRI) that is based on age, heart rate and systolic blood pressure, we sought to evaluate the ability to predict outcome in AMI patients in a community-based population. METHODS AND RESULTS: We identified and evaluated 3684 consecutive patients with an admission diagnosis of possible AMI, who attended between 1st September and 30th November 1995. Two thousand one hundred fifty three patients had confirmed evidence of WHO definition AMI, of whom 1656 survived to hospital discharge. We evaluated the ability of the SRI to predict mortality over 30 days using the score generated by the equation (heart ratex[age/10]2)/systolic blood pressure. The SRI was a strong (c-statistic = 0.77 CI 0.74-0.79) predictor of 30-day mortality in both STEMI and all consecutive cases of WHO definition AMI. However, the model showed poor calibration when used on a community-based population with 30-day mortality being underestimated across all risk quintiles. Consequently we sought to recalibrate the quantitative aspects of the model for the total AMI population in the following way (Risk Index; 30-day mortality) (< or = 29.2; 9.2%), (29.3-37.8; 23.9%), (37.9-47.3; 34.6%), (47.4-61.5; 40.3%), (> or = 61.6; 65.5%). CONCLUSION: We have externally validated the SRI in an unselected cohort of consecutive WHO definition AMI patients. However, the original model consistently underestimated the likelihood of death at 30 days regardless of the calculated risk score. We have therefore suggested corrections to the risk estimates, to allow its application in an unselected community cohort.

Age Factors↗
PubMed2005

The British Cardiac Society Working Group definition of myocardial infarction: implications for practice.

OBJECTIVE: To assess the impact on observed mortality of the British Cardiac Society (BCS) definition of myocardial infarction (MI) in 11 UK hospitals. DESIGN: Prospective observational registry. SETTING: 11 adjacent hospitals in the West Yorkshire region. PATIENTS: 2484 patients with the acute coronary syndrome (ACS) were identified during a six month period (28 April to 28 October 2003). Demographic, clinical, and treatment variables were collected on all patients. Deaths were monitored through the Office of National Statistics. Patients were categorised into three groups according to the BCS definition of MI: ACS with unstable angina (UA), ACS with myocyte necrosis, and ACS with clinical MI. RESULTS: 30 day mortality was 4.5%, 10.4%, and 12.9% (p < 0.001) in the ACS with UA, ACS with myocyte necrosis, and ACS with clinical MI groups, respectively. At six months the mortality for patients in the groups ACS with clinical MI and ACS with myocyte necrosis was similar (19.2% v 18.7%), being higher than for ACS with UA (8.6%). Same admission percutaneous coronary intervention was similar in groups with clinical MI and myocyte necrosis (11.1% v 10.7%, respectively) as was coronary artery bypass grafting (2.6% v 2.7%, respectively). However, these two groups differed significantly in the prescribing of secondary prevention (aspirin, 79% v 69%; statins, 80% v 68%; beta blockers, 66% v 53%; and angiotensin converting enzyme inhibitors, 65% v 53%; p < 0.001). CONCLUSIONS: At 30 days the new BCS categories for MI predict three distinct outcomes. However, within a contemporary UK population this was no longer apparent at six months, as mortality for patients with ACS with myocyte necrosis had risen to the same level as those for patients with ACS with clinical MI. One possible explanation for this is the apparent under use of drugs known to improve prognosis after traditionally defined MI.

Aged↗
PubMed2005

Transcriptional response signature of human lymphoid cells to staphylococcal enterotoxin B.

Two shock-inducing toxins that result in similar eventual outcome of disease were studied to determine host gene expression responses, for correlation of both similar and unique gene patterns. We initially used differential display (DD)-PCR and identified 859 cDNA fragments that were differentially expressed after 16 h of in vitro exposure of human peripheral blood mononuclear cells (PBMC) to staphylococcal enterotoxin B (SEB). Upon further examination using custom cDNA microarrays and RT-PCR analysis, we found unique set of genes to each toxin (SEB or lipopolysaccharide (LPS)), especially at early time periods. By 16 h, there was a convergence of some gene expression responses and many of those genes code for proteins such as proteinases, transcription factors, vascular tone regulators, and respiratory distress. In an attempt to replicate the findings in vivo, monkeys were challenged with SEB and the resultant gene expression responses indicated a pattern typical of SEB exposure when compared to LPS, with a similar outcome. We provide evidence that vastly diverse global gene analysis techniques used in unison can not only effectively identify pathogen-specific genomic markers and provide a solid foundation to mechanistic insights but also explain some of the toxin-related symptoms through gene functions.

Animals↗
PubMed2004

Spatial distribution of competing ions around DNA in solution.

The competition of monovalent and divalent cations for proximity to negatively charged DNA is of biological importance and can provide strong constraints for theoretical treatments of polyelectrolytes. Resonant x-ray scattering experiments have allowed us to monitor the number and distribution of each cation in a mixed ion cloud around DNA. These measurements provide experimental evidence to support a general theoretical prediction: the normalized distribution of each ion around polyelectrolytes remains constant when ions are mixed at different ratios. In addition, the amplitudes of the scattering signals throughout the competition provide a measurement of the surface concentration parameter that predicts the competition behavior of these cations. The data suggest that ion size needs to be taken into account in applying Poisson-Boltzmann treatments to polyelectrolytes such as DNA.

Cations↗
PubMed2004

Mycobacterium tuberculosis isolate with a distinct genomic identity overexpresses a tap-like efflux pump.

BACKGROUND: One mechanism proposed for drug resistance in Mycobacterium tuberculosis (MTB) is by efflux of the drugs by membrane located pumps. We report a novel and definite association between drug resistance and transcription levels of a tap-like pump (Rv1258c) in a multi-drug resistant MTB patient isolate (ICC154) which possesses a unique genotypic signature. MATERIALS AND METHODS: The isolate ICC154 was tested for drug sensitivity. Over-expression of Rv1258c as a function of drug pressure was analyzed by RT-PCR and the strain was typed using fluorescent amplified fragment length polymorhism (FAFLP). RESULT: In the presence of rifampicin and ofloxacin, this isolate shows increased transcription of the gene Rv1258c. Genotypic fingerprinting revealed the presence of unique FAFLP markers. CONCLUSION: A clear association between drug resistance and overexpression of an efflux protein is evident from our studies. The presence of specific markers has implications in rapid identification of MDR clinical isolates and consequent disease management.

Anti-Bacterial Agents↗
PubMed2004

An evaluation of the relationship between specialist training in cardiology and implementation of evidence-based care of patients following acute myocardial infarction.

AIMS: Large clinical trials have provided evidence of prognostically beneficial treatment strategies for patients with acute myocardial infarction. However, the implementation of this evidence into routine clinical practice is suboptimal. We hypothesised that the speciality of the attending physician (cardiologist or not) would affect the use of evidence-based strategies. METHODS: Over a 3-month period (1st September to 30th November 1995), 3684 consecutive potential cases of acute myocardial infarction (AMI) in 20 adjacent hospitals in the Yorkshire Region were identified from coronary care registers, clinical coding and biochemistry records of cardiac enzyme assay requests. There were 2153 consecutive cases of AMI identified, of which 1643 patients were alive at discharge. We compared the admission use of aspirin and thrombolysis, and the use of aspirin, beta-blockers, angiotensin-converting enzyme (ACE) inhibitors and statins at discharge between cardiologists and other physicians. RESULTS: AMI patients under the care of cardiologists are more likely to receive aspirin and thrombolysis on the day of their event and to be prescribed aspirin, beta-blockers and statins on discharge. After correction for contraindications to their use, the above findings were broadly confirmed. DISCUSSION: Cardiologists are more likely than general physicians to use evidence-based treatment strategies recognised to improve AMI patient outcome. It is likely that this will translate into a reduction of mortality or other hard endpoints in patient outcomes.

Adrenergic beta-Antagonists↗
PubMed2004

Parvovirus B19-associated transient red cell aplasia in children: the role of bone marrow examination in unusual presentations.

Human parvovirus B19 (PV B19) infection in children commonly presents as fifth disease. Transient red cell crisis, the other manifestation of PV B19 infection, is usually reported in children with chronic hemolytic anemia, with a worsening of the anemia. However, this condition may pass unrecognized in children without an underlying hemolytic disorder, since the anemia may be of a short duration and self-limiting. The authors report 3 cases of PV B19-induced transient aplastic in different clinical settings--pancytopenia in one child, during induction phase for acute lymphoblastic leukemia in the second, and fever with joint pains in the third. Treatment for PV B19-induced transient aplastic crisis is essentially supportive. There may be a dilemma in patients on immunosuppressive therapy, since initially it is difficult to distinguish between chronic pure red cell aplasia (a condition where intravenous immunoglobulin therapy is beneficial) and transient aplastic crisis, where supportive red cell transfusions suffice. The patient with leukemia also recovered spontaneously despite being on steroids. In all the 3 patients, the pure red cell aplasia recovered spontaneously without administration of intravenous gammaglobulins.

Bone Marrow Examination↗
PubMed2004

Correlation of mutations detected by INNO-LiPA with levels of rifampicin resistance in Mycobacterium tuberculosis.

BACKGROUND & OBJECTIVES: Due to emergence of drug resistance in Mycobacterium tuberculosis, there is a need to have accurate and rapid methods for detection of drug resistance to important drugs like rifampicin. The present study was aimed at evaluation of a commercially available INNO-LiPA assay, for the detection of mutation in rpoB gene region of M. tuberculosis and correlate these mutations with levels of rifampicin resistance for assessing their clinical relevance. METHODS: Fifty five well-characterized isolates of M. tuberculosis deposited from various regions of India in Mycobacterial Repository Centre at the CJILOMD, Agra were subjected to susceptibility testing for rifampicin at various concentrations of drug viz., 10, 40, 64, 128 microg/ml on Lowenstein- Jensen (LJ) medium. rpoB gene fragment (260 bp) was amplified using Rif-TB amplification kit and after hybridization, detection was done by using INNO-LiPA Rif TB kit. RESULTS: The rpoB gene could be amplified from DNA extracted from all the 55 culture isolates and showed clear hybridization pattern with M. tuberculosis complex specific probes on LiPA strips. Mutations detected were correlated with degree of rifampicin resistance. All the sensitive isolates (identified by MIC) were identified as rifampicin sensitive (100%) by INNO-LiPA as they exhibit positive for wild type 'S' probes and negative for 'R' probes. Two of the 5 isolates, resistant at 10 microg/ml and 40 microg/ml had either D516V, H526Y mutations or unknown mutations. Thirty (85.71%) isolates resistant at clinically relevant levels (64,128microg/ml) exhibited double, triple or more 'R' type mutations (R(2(D516V)), R(4a(H526Y)), R(4b(H526D)), R(5(S531L))) as well as unknown mutations present at 'S' probes region whereas remaining isolates did not show any mutation by this method. This method could identify with definitiveness 60 per cent ( 21/35) isolates as rifampicin resistant as mutations observed in others were also present in isolates with low levels of resistance. INTERPRETATION & CONCLUSION: The results indicate that INNO-LiPA Rif TB test is a rapid and easy to use method for detection of mutations associated with rifampicin resistance in M. tuberculosis. However, as some of these mutations are also present in isolates with low degree of resistance which are still microbiologically sensitive to rifampicin, there is a need to improve this assay by exclusion of some of the current probes and inclusion of more probes.

Antibiotics, Antitubercular↗
PubMed2003

Counterion distribution around DNA probed by solution X-ray scattering.

Counterion atmospheres condensed onto charged biopolymers strongly affect their physical properties and biological functions, but have been difficult to quantify experimentally. Here, monovalent and divalent counterion atmospheres around DNA double helices in solution are probed using small-angle x-ray scattering techniques. Modulation of the ion scattering factors by anomalous (resonant) x-ray scattering and by interchanging ion identities yields direct measurements of the scattering signal due to the spatial correlation of surrounding ions to the DNA. The quality of the data permit, for the first time, quantitative tests of extended counterion distributions calculated from atomic-scale models of biologically relevant molecules.

Cations↗
PubMed2003

Identifying acute myocardial infarction: effects on treatment and mortality, and implications for National Service Framework audit.

BACKGROUND: The National Service Framework (NSF) for Coronary Heart Disease requires annual clinical audit of the care of patients with myocardial infarction, with little guidance on how to achieve these standards and monitor practice. AIM: To assess which method of identification of acute myocardial infarction (AMI) cases is most suitable for NSF audit, and to determine the effect of the definition of AMI on the assessment of quality of care. DESIGN: Observational study. METHODS: Over a 3-month period, 2153 consecutive patients from 20 hospitals across the Yorkshire region, with confirmed AMI, were identified from coronary care registers, biochemistry records and hospital coding systems. The sensitivity and positive predictive value of AMI patient identification using clinical coding, biochemistry and coronary care registers were compared to a 'gold standard' (the combination of all three methods). RESULTS: Of 3685 possible cases of AMI singled out by one or more methods, 2153 patients were identified as having a final diagnosis of AMI. Hospital coding revealed 1668 (77.5%) cases, with a demographic profile similar to that of the total cohort. Secondary preventative measures required for inclusion in NSF were also of broadly similar distribution. The sensitivities and positive predictive values for patient identification were substantially less in the cohorts identified through biochemistry and coronary care unit register. Patients fulfilling WHO criteria (n=1391) had a 30-day mortality of 15.9%, vs. 24.2% for the total cohort. DISCUSSION: Hospital coding misses a substantial proportion (22.5%) of AMI cases, but without any apparent systematic bias, and thus provides a suitably representative and robust basis for NSF-related audit. Better still would be the routine use of multiple methods of case identification.

Aged↗
PubMed2002

GeneCensus: genome comparisons in terms of metabolic pathway activity and protein family sharing.

We present a prototype of a new database tool, GeneCensus, which focuses on comparing genomes globally, in terms of the collective properties of many genes, rather than in terms of the attributes of a single gene (e.g. sequence similarity for a particular ortholog). The comparisons are presented in a visual fashion over the web at GeneCensus.org. The system concentrates on two types of comparisons: (i) trees based on the sharing of generalized protein families between genomes, and (ii) whole pathway analysis in terms of activity levels. For the trees, we have developed a module (TreeViewer) that clusters genomes in terms of the folds, superfamilies or orthologs--all can be considered as generalized 'families' or 'protein parts'--they share, and compares the resulting trees side-by-side with those built from sequence similarity of individual genes (e.g. a traditional tree built on ribosomal similarity). We also include comparisons to trees built on whole-genome dinucleotide or codon composition. For pathway comparisons, we have implemented a module (PathwayPainter) that graphically depicts, in selected metabolic pathways, the fluxes or expression levels of the associated enzymes (i.e. generalized 'activities'). One can, consequently, compare organisms (and organism states) in terms of representations of these systemic quantities. Develop ment of this module involved compiling, calculating and standardizing flux and expression information from many different sources. We illustrate pathway analysis for enzymes involved in central metabolism. We are able to show that, to some degree, flux and expression fluctuations have characteristic values in different sections of the central metabolism and that control points in this system (e.g. hexokinase, pyruvate kinase, phosphofructokinase, isocitrate dehydrogenase and citric synthase) tend to be especially variable in flux and expression. Both the TreeViewer and PathwayPainter modules connect to other information sources related to individual-gene or organism properties (e.g. a single-gene structural annotation viewer).

Animals↗