Genome-scale comparison and constraint-based metabolic reconstruction of the facultative anaerobic Fe(III)-reducer Rhodoferax ferrireducens

<p>Abstract</p> <p>Background</p> <p><it>Rhodoferax ferrireducens </it>is a metabolically versatile, Fe(III)-reducing, subsurface microorganism that is likely to play an important role in the carbon and metal cycles in the subsurface. It also has the unique ability to convert sugars to electricity, oxidizing the sugars to carbon dioxide with quantitative electron transfer to graphite electrodes in microbial fuel cells. In order to expand our limited knowledge about <it>R. ferrireducens</it>, the complete genome sequence of this organism was further annotated and then the physiology of <it>R. ferrireducens </it>was investigated with a constraint-based, genome-scale <it>in silico </it>metabolic model and laboratory studies.</p> <p>Results</p> <p>The iterative modeling and experimental approach unveiled exciting, previously unknown physiological features, including an expanded range of substrates that support growth, such as cellobiose and citrate, and provided additional insights into important features such as the stoichiometry of the electron transport chain and the ability to grow via fumarate dismutation. Further analysis explained why <it>R. ferrireducens </it>is unable to grow via photosynthesis or fermentation of sugars like other members of this genus and uncovered novel genes for benzoate metabolism. The genome also revealed that <it>R. ferrireducens </it>is well-adapted for growth in the subsurface because it appears to be capable of dealing with a number of environmental insults, including heavy metals, aromatic compounds, nutrient limitation and oxidative stress.</p> <p>Conclusion</p> <p>This study demonstrates that combining genome-scale modeling with the annotation of a new genome sequence can guide experimental studies and accelerate the understanding of the physiology of under-studied yet environmentally relevant microorganisms.</p

Complete Genome Sequence of the N2-Fixing Broad Host Range Endophyte Klebsiella pneumoniae 342 and Virulence Predictions Verified in Mice

We report here the sequencing and analysis of the genome of the nitrogen-fixing endophyte, Klebsiella pneumoniae 342. Although K. pneumoniae 342 is a member of the enteric bacteria, it serves as a model for studies of endophytic, plant-bacterial associations due to its efficient colonization of plant tissues (including maize and wheat, two of the most important crops in the world), while maintaining a mutualistic relationship that encompasses supplying organic nitrogen to the host plant. Genomic analysis examined K. pneumoniae 342 for the presence of previously identified genes from other bacteria involved in colonization of, or growth in, plants. From this set, approximately one-third were identified in K. pneumoniae 342, suggesting additional factors most likely contribute to its endophytic lifestyle. Comparative genome analyses were used to provide new insights into this question. Results included the identification of metabolic pathways and other features devoted to processing plant-derived cellulosic and aromatic compounds, and a robust complement of transport genes (15.4%), one of the highest percentages in bacterial genomes sequenced. Although virulence and antibiotic resistance genes were predicted, experiments conducted using mouse models showed pathogenicity to be attenuated in this strain. Comparative genomic analyses with the presumed human pathogen K. pneumoniae MGH78578 revealed that MGH78578 apparently cannot fix nitrogen, and the distribution of genes essential to surface attachment, secretion, transport, and regulation and signaling varied between each genome, which may indicate critical divergences between the strains that influence their preferred host ranges and lifestyles (endophytic plant associations for K. pneumoniae 342 and presumably human pathogenesis for MGH78578). Little genome information is available concerning endophytic bacteria. The K. pneumoniae 342 genome will drive new research into this less-understood, but important category of bacterial-plant host relationships, which could ultimately enhance growth and nutrition of important agricultural crops and development of plant-derived products and biofuels

Osteomas of the craniofacial region: A case series and review of literature

Objective: 0 To discuss the clinical presentation, diagnosis and management of osteomas involving the craniomaxillofacial region. Materials and Methods: This study was conducted from June 2004 to March 2012 at our institute. A total of 12 cases between the ages of 10 and 50 years were managed with surgical excision and reconstruction. The criteria used to diagnose osteoma included radiographic and clinical features and histological confirmation of the specimen. The total follow-up period ranged from 6 to 24 months. Results: Out of 12 osteomas, 10 were peripheral and 2 were centrally located. Mandible involvement was seen in six patients, four involved the orbit, one the frontal bone and one the frontal bone with the skull base. All patients undergoing excision and reconstruction had a favourable aesthetic and functional outcome. There were no recurrences and no post-operative complications. Conclusion: Osteomas affect all age groups with no sex predilection and are usually clinically asymptomatic till they become large in size. Surgical excision and appropriate reconstruction is the mainstay of management. Surgery is indicated when lesion is symptomatic or actively growing and the surgical approach for exposure of the lesion should be case specific

Microbiological and Clinical Outcomes of Methicillin-Susceptible Isolated in Lung Transplant Perioperative Donor and Recipient Respiratory Cultures

Staphylococcus aureus is one of the most common organisms isolated from respiratory secretions in lung transplant donors and recipients perioperatively. Within the first 90 days after lung transplantation, methicillin-susceptible Staphylococcus aureus (MSSA) infections have been associated with increased mortality and acute and chronic rejection. However, it is unclear whether respiratory cultures positive for MSSA at the time of transplantation can lead to clinically significant infection. The aim of this study was to assess the microbiological and clinical outcomes for lung transplant recipients (LTRs) with positive perioperative donor or/and recipient respiratory cultures for MSSA. A retrospective study was conducted evaluating MSSA-positive respiratory cultures at the time of lung transplantation from donors and/or recipients from January 1, 2008, to December 30, 2019. Patients who did not have a bronchoalveolar lavage at 2 weeks after the lung transplant or died within 2 weeks of lung transplant were excluded. The main outcome was MSSA eradication at 2-week bronchoscopy. Recipients were evaluated for MSSA infections at the 12-week period after the transplant. Of the 1,678 individuals who underwent lung transplantation, 218 LTRs had S. aureus isolated in perioperative donor or recipient respiratory cultures, and 29 were subsequently excluded. Of the remaining 189 LTRs, MSSA eradication at the 2-week bronchoscopy was achieved in 186 (98.4%) recipients. During the 12-week follow-up, 15 (7.9%) recipients were diagnosed with MSSA pneumonia; concurrent MSSA bacteremia was noted in one recipient. No anastomotic infection, empyema, or lung abscess related to MSSA was diagnosed during the follow-up period. In LTRs, the rate of MSSA eradication at 2-week post-transplant recipients is high, and it is associated with a low rate of infectious complication within the first 12 weeks after transplant. Most of the recipients received a combination therapy with at least one agent active against MSSA. More studies to evaluate the optimal antimicrobial stewardship policies regarding the regimen and duration of antibiotic therapy for these patients are needed

Spontaneous Renal Artery Dissection in COVID-19 Pneumonia: Potential Danger of Cytokine Storm

The coronavirus disease (COVID-19) pandemic has rapidly spread across the globe since its first detection in March 2020. Its widespread manifestations and vascular complications are increasingly being reported even in young and middle-aged patients. Hyperinflammation is a continuum of host’s exaggerated inflammatory response representing cytokine dysregulation/storm which produces coagulopathy and vascular endothelial dysfunction, apart from a prothrombotic state. Cytokine storm or direct viral invasion of the vascular endothelial cells through surface angiotensin-converting enzyme 2 receptors may result in endothelial dysfunction which can potentially result in dissection. Only a few case reports have been published in the literature describing vascular dissection without any inciting factors in COVID-19 patients. Herein, we present the first case report of bilateral renal artery dissection in a 41-year-old male patient who recently recovered from COVID-19 and was managed successfully in stages after many medical hurdles

Implementation of a Routine Screening Program for Latent Tuberculosis Infection among Patients with Acute Leukemia at a Canadian Cancer Center

Background: Screening for latent tuberculosis infection (LTBI) in patients with hematological malignancy is recommended because of their increased risk of tuberculosis (TB). We assessed the utility of tuberculin skin test (TST) screening in patients with acute leukemia and subsequent outcomes of LTBI treatment. Methods: We retrospectively evaluated patients &ge;16 years of age with acute leukemia from 2013&ndash;2014 with a TST planted and read prior to the initiation of antineoplastic chemotherapy treatment. Demographics, clinical information and treatment outcomes of LTBI therapy were compared between patients with positive TST (&ge;10 mm induration) and negative TST. Results: A total of 389 patients with acute leukemia were included in the cohort. Of them, 37/389 (9.5%) had a positive TST. Only 3.4% (8/235) of individuals originating from North and South America as well as the Caribbean were TST positive, while 21% (20/95) of individuals from Asia were TST positive. Diagnostic imaging findings consistent with prior tuberculosis infection were higher in TST positive patients compared to TST negative ones (29.7% versus 9.4%, p &lt; 0.0001). Furthermore, 31/38 patients (81.6%) who were TST positive received LTBI therapy, which was well tolerated. There was no significant difference in overall survival among those who received LTBI therapy compared to those who did not. No patients developed active TB. Conclusions: Universal screening with TST may be of low yield in individuals with acute leukemia unless patients originate from a TB endemic country. When therapy for LTBI is prescribed, patients with acute leukemia do not experience drug-induced liver toxicity and are likely to complete the intended duration of therapy, thus preventing the development of active tuberculosis