pheA (Rv3838c) of Mycobacterium tuberculosis encodes an allosterically regulated monofunctional prephenate dehydratase that requires both catalytic and regulatory domains for optimum activity

Prephenate dehydratase (PDT) is a key regulatory enzyme in l-phenylalanine biosynthesis. In Mycobacterium tuberculosis, expression of pheA, the gene encoding PDT, has been earlier reported to be iron-dependent (1, 2). We report that M. tuberculosis pheA is also regulated at the protein level by aromatic amino acids. All of the three aromatic amino acids (phenylalanine, tyrosine, and tryptophan) are potent allosteric activators of M. tuberculosis PDT. We also provide in vitro evidence that M. tuberculosis PDT does not possess any chorismate mutase activity, which suggests that, unlike many other enteric bacteria (where PDT exists as a fusion protein with chorismate mutase), M. tuberculosis PDT is a monofunctional and a non-fusion protein. Finally, the biochemical and biophysical properties of the catalytic and regulatory domains (ACT domain) of M. tuberculosis PDT were studied to observe that, in the absence of the ACT domain, the enzyme not only loses its regulatory activity but also its catalytic activity. These novel results provide evidence for a monofunctional prephenate dehydratase enzyme from a pathogenic bacterium that exhibits extensive allosteric activation by aromatic amino acids and is absolutely dependent upon the presence of catalytic as well as the regulatory domains for optimum enzyme activity

Consensus statement on the management of invasive candidiasis in Indian scenario

Invasive fungal infections in critically ill patients are associated with increased morbidity and mortality. Candida species are among the most common causes of nosocomial bloodstream infections and of invasive infections in intensive care units (ICUs). The high mortality mandates early identification of invasive candidiasis which is vital to initiate appropriate and timely treatment and improve outcomes. Delaying the initiation of treatment could result in an increase in mortality which can be avoided by usage of more rapid diagnostic techniques. There are multiple diagnostic tests including culture and non-culture tests like 1,3-β-D-glucan and newer techniques like MALDI-TOF which are available to diagnose candidemia but each with their drawbacks. Additionally, there are various guidelines like IDSA and ESCMID on treatment which aim to minimize death, late complications from deep-seated candidiasis and rise of drug- resistant Candida strains. Through this consensus statement prepared by a panel of experts, all of whom are senior intensivists, infectious disease specialists and microbiologists, we aim to address the major aspects of management of invasive candidiasis in the Indian population as per the authors opinions, backed by published evidence and supported by the latest clinical guidelines

Case Report Mucormycosis of Mandible with Unfavorable Outcome

Mucormycosis is a fulminant fungal infection that occurs most often in diabetic and immunocompromised individuals. Our patient, with uncontrolled diabetes mellitus and multiple systemic disorders, developed postextraction mucormycosis of mandible, an extremely rare complication. An initial clinical and radiographic diagnosis of mandibular osteomyelitis was made and the lesion was treated medically and surgically with curettage and saucerisation. The specimen was sent for histopathological evaluation, which showed necrotic area containing broad aseptate fungal hyphae with right angle branching consistent with mucormycosis. The patient succumbed to multipleorgan failure secondary to septicemia. The disease is usually fatal with a poor survival rate; there is still paucity of literature on the definitive management of this disease involving the mandible. This paper emphasizes the need for correction of underlying immunodeficiency and early diagnosis with aggressive multimodality treatment approach to offer the best chance of survival

Mucormycosis of Mandible with Unfavorable Outcome

Mucormycosis is a fulminant fungal infection that occurs most often in diabetic and immunocompromised individuals. Our patient, with uncontrolled diabetes mellitus and multiple systemic disorders, developed postextraction mucormycosis of mandible, an extremely rare complication. An initial clinical and radiographic diagnosis of mandibular osteomyelitis was made and the lesion was treated medically and surgically with curettage and saucerisation. The specimen was sent for histopathological evaluation, which showed necrotic area containing broad aseptate fungal hyphae with right angle branching consistent with mucormycosis. The patient succumbed to multipleorgan failure secondary to septicemia. The disease is usually fatal with a poor survival rate; there is still paucity of literature on the definitive management of this disease involving the mandible. This paper emphasizes the need for correction of underlying immunodeficiency and early diagnosis with aggressive multimodality treatment approach to offer the best chance of survival

Crystallization and preliminary X-ray crystallographic studies of Mycobacterium tuberculosis chorismate mutase

Chorismate mutase from M. tuberculosis has been crystallized. Preliminary X-ray crystallographic studies reveal the occurrence of a dimeric molecule in the crystal asymmetric unit

The 2.15 Å crystal structure of Mycobacterium tuberculosis chorismate mutase reveals an unexpected gene duplication and suggests a role in host-pathogen interactions

Chorismate mutase catalyzes the first committed step toward the biosynthesis of the aromatic amino acids, phenylalanine and tyrosine. While this biosynthetic pathway exists exclusively in the cell cytoplasm, the Mycobacterium tuberculosis enzyme has been shown to be secreted into the extracellular medium. The secretory nature of the enzyme and its existence in M. tuberculosis as a duplicated gene are suggestive of its role in host-pathogen interactions. We report here the crystal structure of homodimeric chorismate mutase (Rv1885c) from M. tuberculosis determined at 2.15 Å resolution. The structure suggests possible gene duplication within each subunit of the dimer (residues 35-119 and 130-199) and reveals an interesting proline-rich region on the protein surface (residues 119-130), which might act as a recognition site for protein-protein interactions. The structure also offers an explanation for its regulation by small ligands, such as tryptophan, a feature previously unknown in the prototypical Escherichia coli chorismate mutase. The tryptophan ligand is found to be sandwiched between the two monomers in a dimer contacting residues 66-68. The active site in the "gene-duplicated" monomer is occupied by a sulfate ion and is located in the first half of the polypeptide, unlike in the Saccharomyces cerevisiae (yeast) enzyme, where it is located in the later half. We hypothesize that the M. tuberculosis chorismate mutase might have a role to play in host-pathogen interactions, making it an important target for designing inhibitor molecules against the deadly pathogen

Ticagrelor in patients with diabetes and stable coronary artery disease with a history of previous percutaneous coronary intervention (THEMIS-PCI) : a phase 3, placebo-controlled, randomised trial

Background: Patients with stable coronary artery disease and diabetes with previous percutaneous coronary intervention (PCI), particularly those with previous stenting, are at high risk of ischaemic events. These patients are generally treated with aspirin. In this trial, we aimed to investigate if these patients would benefit from treatment with aspirin plus ticagrelor. Methods: The Effect of Ticagrelor on Health Outcomes in diabEtes Mellitus patients Intervention Study (THEMIS) was a phase 3 randomised, double-blinded, placebo-controlled trial, done in 1315 sites in 42 countries. Patients were eligible if 50 years or older, with type 2 diabetes, receiving anti-hyperglycaemic drugs for at least 6 months, with stable coronary artery disease, and one of three other mutually non-exclusive criteria: a history of previous PCI or of coronary artery bypass grafting, or documentation of angiographic stenosis of 50% or more in at least one coronary artery. Eligible patients were randomly assigned (1:1) to either ticagrelor or placebo, by use of an interactive voice-response or web-response system. The THEMIS-PCI trial comprised a prespecified subgroup of patients with previous PCI. The primary efficacy outcome was a composite of cardiovascular death, myocardial infarction, or stroke (measured in the intention-to-treat population). Findings: Between Feb 17, 2014, and May 24, 2016, 11 154 patients (58% of the overall THEMIS trial) with a history of previous PCI were enrolled in the THEMIS-PCI trial. Median follow-up was 3·3 years (IQR 2·8–3·8). In the previous PCI group, fewer patients receiving ticagrelor had a primary efficacy outcome event than in the placebo group (404 [7·3%] of 5558 vs 480 [8·6%] of 5596; HR 0·85 [95% CI 0·74–0·97], p=0·013). The same effect was not observed in patients without PCI (p=0·76, p interaction=0·16). The proportion of patients with cardiovascular death was similar in both treatment groups (174 [3·1%] with ticagrelor vs 183 (3·3%) with placebo; HR 0·96 [95% CI 0·78–1·18], p=0·68), as well as all-cause death (282 [5·1%] vs 323 [5·8%]; 0·88 [0·75–1·03], p=0·11). TIMI major bleeding occurred in 111 (2·0%) of 5536 patients receiving ticagrelor and 62 (1·1%) of 5564 patients receiving placebo (HR 2·03 [95% CI 1·48–2·76], p<0·0001), and fatal bleeding in 6 (0·1%) of 5536 patients with ticagrelor and 6 (0·1%) of 5564 with placebo (1·13 [0·36–3·50], p=0·83). Intracranial haemorrhage occurred in 33 (0·6%) and 31 (0·6%) patients (1·21 [0·74–1·97], p=0·45). Ticagrelor improved net clinical benefit: 519/5558 (9·3%) versus 617/5596 (11·0%), HR=0·85, 95% CI 0·75–0·95, p=0·005, in contrast to patients without PCI where it did not, p interaction=0·012. Benefit was present irrespective of time from most recent PCI. Interpretation: In patients with diabetes, stable coronary artery disease, and previous PCI, ticagrelor added to aspirin reduced cardiovascular death, myocardial infarction, and stroke, although with increased major bleeding. In that large, easily identified population, ticagrelor provided a favourable net clinical benefit (more than in patients without history of PCI). This effect shows that long-term therapy with ticagrelor in addition to aspirin should be considered in patients with diabetes and a history of PCI who have tolerated antiplatelet therapy, have high ischaemic risk, and low bleeding risk