Gluconeogenic mutations in Pseudomonas aeruginosa: genetic linkage between fructose-bisphosphate aldolase and phosphoglycerate kinase

Mutants of mucoid Pseudomonas aeruginosa defective in fructose-bisphosphate aldolase (FBA), NADP-linked glyceraldehyde-3-phosphate dehydrogenase (GAP) or 3-phosphoglycerate kinase (PGK) were unable to grow on gluconeogenic precursors like glutamate, succinate or lactate. The gap and pgk mutants could grow on glucose, gluconate or glycerol, but fba mutants could not. This suggests that the metabolism of glucose or gluconate does not require either PGK or NADP-linked GAP but does require the operation of the aldolase-catalysed step. For gluconeogenesis, however, all three steps are essential. Recombinant plasmids carrying genes for FBA, PGK, GAP or phospho-2-keto-3-deoxygluconate aldolase (EDA) activities were constructed from a genomic library of mucoid P. aeruginosa selecting for complementation of deficiency mutations. Analysis of their complementation profile indicated that one group of plasmids carried fba and pgk genes, while another group carried eda, 6-phosphogluconate dehydratase (edd) and glucose-6-phosphate dehydrogenase (zwf) genes. The gap gene was not linked to any of these markers. Partial restoration of FBA activity in spontaneous revertants of Fba mutants was accompanied by a concomitant loss of PGK activity. These experiments indicate a linkage between the fba and pgk genes on the P. aeruginosa chromosome

Gastrointestinal bleeding risk with rivaroxaban vs aspirin in atrial fibrillation: a multinational study

Purpose: Comparative gastrointestinal bleeding (GIB) risk between rivaroxaban and low‐dose aspirin is unknown in patients with atrial fibrillation (AF). This study investigated GIB risk with rivaroxaban vs aspirin among two separate AF cohorts in Hong Kong and the United Kingdom, using a common protocol approach. Methods: This was a population‐based cohort study using separate data from the Clinical Data Analysis and Reporting System (CDARS) of the Hong Kong Hospital Authority (2010‐2018) and The Health Improvement Network (THIN) database in the United Kingdom (2011‐2017). Patients with AF newly prescribed aspirin or rivaroxaban were included. Cox proportional hazards regression was used to compare GIB risks for rivaroxaban vs aspirin, accounting for confounders using propensity score fine stratification approach. Results: In CDARS, 29 213 patients were included; n = 1052 (rivaroxaban), n = 28 161 (aspirin). Crude GIB event rates per 100 patient‐years in CDARS were 3.0 (aspirin) and 2.6 (rivaroxaban). No difference in GIB risk was observed between rivaroxaban and aspirin overall (HR = 1.04, 95%CI = 0.76‐1.42), and in dose‐stratified analyses (HR = 1.21, 95%CI = 0.84‐1.74 [20 mg/day]; HR = 0.80, 95%CI = 0.44‐1.45 [≤15 mg/day]). In THIN, 11 549 patients were included, n = 3496 (rivaroxaban) and n = 8053 (aspirin). Crude GIB event rates were 1.3 (aspirin) and 2.4 (rivaroxaban) per 100 patient‐years. No difference in GIB risk was observed between rivaroxaban and aspirin overall (HR = 1.40, 95%CI = 1.00‐1.98) and low‐dose rivaroxaban (≤15 mg/day) (HR = 1.00, 95%CI = 0.56‐1.30), but increased GIB risk was observed for rivaroxaban 20 mg/day vs aspirin (HR = 1.57, 95%CI = 1.08‐2.29). Conclusion: In patients with AF, GIB risk was comparable between aspirin and rivaroxaban ≤15 mg/day. GIB risk for rivaroxaban 20 mg/day vs aspirin remains uncertain and warrants further investigation

Low Dose Aerosol Fitness at the Innate Phase of Murine Infection Better Predicts Virulence amongst Clinical Strains of Mycobacterium tuberculosis

Background: Evaluation of a quick and easy model to determine the intrinsic ability of clinical strains to generate active TB has been set by assuming that this is linked to the fitness of Mycobacterium tuberculosis strain at the innate phase of the infection. Thus, the higher the bacillary load, the greater the possibility of inducting liquefaction, and thus active TB, once the adaptive response is set. Methodology/Principal Findings: The virulence of seven clinical Mycobacterium tuberculosis strains isolated in Spain was tested by determining the bacillary concentration in the spleen and lung of mice at weeks 0, 1 and 2 after intravenous (IV) inoculation of 10 4 CFU, and by determining the growth in vitro until the stationary phase had been reached. Cord distribution automated analysis showed two clear patterns related to the high and low fitness in the lung after IV infection. This pattern was not seen in the in vitro fitness tests, which clearly favored the reference strain (H37Rv). Subsequent determination using a more physiological low-dose aerosol (AER) inoculation with 10 2 CFU showed a third pattern in which the three best values coincided with the highest dissemination capacity according to epidemiological data. Conclusions/Significance: The fitness obtained after low dose aerosol administration in the presence of the innate immune response is the most predictive factor for determining the virulence of clinical strains. This gives support to a mechanism o

Characterization of the alginate biosynthetic gene cluster in Pseudomonas syringae pv. syringae

Alginate, a copolymer of D-mannuronic acid and L-guluronic acid, is produced by a variety of pseudomonads, including Pseudomonas syringae. Alginate biosynthesis has been most extensively studied in P. aeruginosa, and a number of structural and regulatory genes from this species have been cloned and characterized. In the present study, an alginate-defective (Alg2) mutant of P. syringae pv. syringae FF5 was shown to contain a Tn5 insertion in algL, a gene encoding alginate lyase. A cosmid clone designated pSK2 restored alginate production to the algL mutant and was shown to contain homologs of algD, alg8, alg44, algG, algX (alg60), algL, algF, and algA. The order and arrangement of the structural gene cluster were virtually identical to those previously described for P. aeruginosa. Complementation analyses, however, indicated that the structural gene clusters in P. aeruginosa and P. syringae were not functionally interchangeable when expressed from their native promoters. A region upstream of the algD gene in P. syringae pv. syringae was shown to activate the transcription of a promoterless glucuronidase (uidA) gene and indicated that transcription initiated upstream of algD as described for P. aeruginosa. Transcription of the algD promoter from P. syringae FF5 was significantly higher at 32°C than at 18 or 26°C and was stimulated when copper sulfate or sodium chloride was added to the medium. Alginate gene expression was also stimulated by the addition of the nonionic solute sorbitol, indicating that osmolarity is a signal for algD expression in P. syringae FF5.Peer reviewedPlant Patholog

Prevention of age-related macular degeneration

Age-related macular degeneration (AMD) is one of the leading causes of blindness in the developed world. Although effective treatment modalities such as anti-VEGF treatment have been developed for neovascular AMD, there is still no effective treatment for geographical atrophy, and therefore the most cost-effective management of AMD is to start with prevention. This review looks at current evidence on preventive measures targeted at AMD. Modalities reviewed include (1) nutritional supplements such as the Age-Related Eye Disease Study (AREDS) formula, lutein and zeaxanthin, omega-3 fatty acid, and berry extracts, (2) lifestyle modifications, including smoking and body-mass-index, and (3) filtering sunlight, i.e. sunglasses and blue-blocking intraocular lenses. In summary, the only proven effective preventive measures are stopping smoking and the AREDS formula

Copper as a signal for alginate sythesis in Pseudomonas syringae pv. Syringae

Plant-associated pseudomonads are commonly exposed to copper bactericides, which are applied to reduce the disease incidence caused by these bacteria. Consequently, many of these bacteria have acquired resistance or tolerance to copper salts. We recently conducted a survey of 37 copper-resistant (Cu^r) Pseudomonas spp., including P. cepacia, P. fluorescens, P. syringae, and P. viridiflava, and found that a subset of the P. syringae strains showed a dramatic increase in exopolysaccharide (EPS) production on mannitol-glutamate medium containing CuSO4 at 250 mg/ml. A modified carbazole assay indicated that the EPS produced on copperamended media contained high levels of uronic acids, suggesting that the EPS was primarily alginic acid. Uronic acids extracted from selected strains were further confirmed to be alginate by demonstrating their sensitivity to alginate lyase and by descending paper chromatography following acid hydrolysis. Subinhibitory levels of arsenate, cobalt, lithium, rubidium, molybdenum, and mercury did not induce EPS production, indicating that alginate biosynthesis is not induced in P. syringae cells exposed to these heavy metals. A 200-kb plasmid designated pPSR12 conferred a stably mucoid phenotype to several P. syringae recipients and also increased their resistance to cobalt and arsenate. A cosmid clone constructed from pPSR12 which conferred a stably mucoid phenotype to several P. syringae strains but not to Pseudomonas aeruginosa was obtained. Results obtained in this study indicate that some of the signals and regulatory genes for alginate production in P. syringae differ from those described for alginate production in P. aeruginosa.Peer reviewedPlant Patholog