Major Pathogen (major + pathogen)

Distribution by Scientific Domains

Selected Abstracts


Iruru Maetani
Percutaneous endoscopic gastrostomy (PEG) was first described in 1980 as an effective means of enteral nutrition where oral intake is not possible. PEG placement is safe and has now replaced the nasogastric tube in patients who need long-term feeding. Although it is relatively safe with a very low associated mortality, minor complications, especially local and systemic infection, remain a problem. Of these, peristomal wound infections are the most common complication of PEG. In patients indicated for this procedure who are aged and/or frail, this complication may pose a critical problem. In the commonly used pull or push methods for PEG placement, the PEG tube is readily colonized by oropharyngeal bacteria. Infection of the PEG site is considered to be associated with contamination of the PEG catheter. There are important measures that should be taken to prevent peristomal infection. A number of rigorous studies have shown that prophylactic antibiotics are effective in reducing the risk of peristomal infection. As methicillin-resistant Staphylococcus aureus (MRSA) or other resistant organisms are emerging as a major pathogen in peristomal infection, however, currently recommended antibiotic prophylaxis regimens might be inappropriate. Alternative regimens and other approaches to prevent contamination of the PEG tube during the procedure are required. [source]

Identification of quorum-sensing regulated proteins in the opportunistic pathogen Pseudomonas aeruginosa by proteomics

Catalina Arevalo-Ferro
Summary The Gram-negative bacterium Pseudomonas aeruginosa is an opportunistic human pathogen which is responsible for severe nosocomial infections in immunocompromised patients and is the major pathogen in cystic fibrosis. The bacterium utilizes two interrelated quorum-sensing (QS) systems, which rely on N -acyl-homoserine lactone (AHL) signal molecules, to control the expression of virulence factors and biofilm development. In this study, we compared the protein patterns of the intracellular, extracellular and surface protein fractions of the PAO1 parent strain with those of an isogenic lasI rhlI double mutant by means of two-dimensional gel electrophoresis (2-DE). This analysis showed that the intensities of 23.7% of all detected protein spots differed more than 2.5-fold between the two strains. We only considered those protein spots truly QS regulated that were changed in the mutant in the absence of signal molecules but were rescued to the wild-type situation when the medium was supplemented with AHLs. These protein spots were characterized by MALDI-TOF peptide mapping. Twenty-seven proteins were identified that were previously reported to be AHL controlled, among them several well-characterized virulence factors. For one of the identified proteins, the serine protease PrpL, a biochemical assay was established to verify that expression of this factor is indeed QS regulated. Furthermore, it is shown that the quorum-sensing blocker C-30 specifically interferes with the expression of 67% of the AHL-controlled protein spots of the surface fraction, confirming the high specificity of the compound. Importantly, 20 novel QS-regulated proteins were identified, many of which are involved in iron utilization, suggesting a link between quorum sensing and the iron regulatory system. Two of these proteins, PhuR and HasAp, are components of the two distinct haem-uptake systems present in P. aeruginosa. In agreement with the finding that both proteins are positively regulated by the QS cascade, we show that the lasI rhlI double mutant grows poorly with haemoglobin as the only iron source when compared with the wild type. These results add haemoglobin utilization to the list of phenotypes controlled through QS in P. aeruginosa. The surprisingly high number of AHL-regulated proteins relative to the number of regulated genes suggests that quorum-sensing control also operates via post-transcriptional mechanisms. To strengthen this hypothesis we investigated the role of quorum sensing in the post-translational modification of HasAp, an extracellular protein required for the uptake of free and haemoglobin-bound haem. [source]

Studies on the epidemiology and yield losses from rice black-streaked dwarf disease in a recent epidemic in Zhejiang province, China

H.-D. Wang
The spread of rice black-streaked dwarf disease, which has emerged as a major problem on winter wheat and the two summer rice crops (early indica and late japonica) grown in central and southern Zhejiang province, China, is documented from 1995 to 2007. The late japonica crop suffered the most: up to 64 640 ha were affected with estimated losses of c. 120 000 t grain per year. Peak adult numbers of the small brown planthopper vector, Laodelphax striatellus, coincided with the seedling stages of both rice crops and the proportion of the insect population carrying virus increased during 1998,2005. Seedlings with three to four leaves were the most susceptible, whereas plants inoculated after the end of tillering developed few or no symptoms. Disease levels were strongly correlated with numbers of viruliferous vectors. In sowing-date experiments with both rice crops, the earliest sowings had the most disease and suffered the greatest yield losses. With the last sowing date (25 days after the first), there were almost no losses. There were yield losses of 080% for every 1% increase in disease incidence in early indica rice and rather more (092%) in the late japonica crop. There were large differences in susceptibility between cultivars, indicating the possibility, within currently available germplasm, of using more resistant cultivars to help contain the disease. Changes in cropping practice and in recent winter weather conditions have probably contributed to the emergence of the virus as a major pathogen in eastern China. [source]

A large-scale, high-efficiency and low-cost platform for structural genomics studies

Xiao-Dong Su
A large-scale, high-efficiency and low-cost platform based on a Beckman Coulter Biomek FX and custom-made automation systems for structural genomics has been set up at Peking University, Beijing, People's Republic of China. This platform has the capacity to process up to 2000 genes per year for structural and functional analyses. Bacillus subtilis, a model organism for Gram-positive bacteria, and Streptococcus mutans, a major pathogen of dental caries, were selected as the main targets. To date, more than 470 B. subtilis and 1200 S.,mutans proteins and hundreds of proteins from other sources, including human liver proteins, have been selected as targets for this platform. The selected genes are mainly related to important metabolism pathways and/or have potential relevance for drug design. To date, 40 independent structures have been determined; of these 11 are in the category of novel structures by the criterion of having less than 30% sequence identity to known structures. More than 13 structures were determined by SAD/MAD phasing. The macromolecular crystallography beamline at the Beijing Synchrotron Radiation Facility and modern phasing programs have been crucial components of the operation of the platform. The idea and practice of the genomic approach have been successfully adopted in a moderately funded structural biology program and it is believed this adaptation will greatly improve the production of protein structures. The goal is to be able to solve a protein structure of moderate difficulty at a cost about US $10,000. [source]

Crystallization and preliminary crystallographic studies of Helicobacter pylori HugZ, a novel haem oxygenase

Fan Jiang
The haem oxygenase HugZ is part of the iron-acquisition mechanism that is essential for the adaptive colonization of Helicobacter pylori, a major pathogen of gastroenteric diseases. The HugZ,haemin complex has been purified and crystallized and diffraction data sets have been collected to 1.8, resolution. The HugZ,haemin complex crystals belonged to space group P212121, with unit-cell parameters a = 88.40, b = 139.37, c = 152.97,. [source]

Streptococcus pneumoniae: still a major pathogen

E. Varon
No abstract is available for this article. [source]

PCR-based Detection and Differentiation of Anthracnose Pathogens, Colletotrichum gloeosporioides and C. truncatum, from Vegetable Soybean in Taiwan

L. S. Chen
Abstract Anthracnose of vegetable soybean sometimes occurs in summer and causes severe symptoms and yield loss in southern Taiwan. Despite previous reports that Glomerella glycines and Colletotrichum truncatum were causal agents of soybean anthracnose, C. truncatum and C. gloeosporioides (teleomorph G. cingulata), but not G. glycines, were identified as the major pathogens causing anthracnose on the pods and stems of vegetable soybeans from 2003 to 2005. Most strains of C. truncatum and C. gloeosporioides were derived from diseased pods. Morphological formation of fruiting bodies separates the Colletotrichum isolates into two groups. Colletotrichum truncatum forms acervuli only while C. gloeosporioides produces acervuli and/or perithecia. Based on the sequence variation in the ITS1 and ITS2 regions, C. truncatum isolates were highly similar (99,100% nucleotide identity) while C. gloeosporioides isolates diverged into two separate groups that were not associated with morphotype. For early detection of C. truncatum and C. gloeosporioides infection on vegetable soybean plants, two species-specific primer pairs Colg 1/Colg 2 (expected size of 443 bp) and Colg 1/CT 2 (375 bp) were designed that allowed differentiation of C. gloeosporioides and C. truncatum in multiplex polymerase chain reaction. [source]

Incidence of Cotton Seedling Diseases Caused by Rhizoctonia solani and Thielaviopsis basicola in Relation to Previous Crop, Residue Management and Nutrients Availability in Soils in SW Spain

A. Delgado
Abstract Cotton seedling damping-off is considered a disease complex, in which several pathogens can be involved. In SW Spain, postemergence damping-off seems to be mainly associated with Rhizoctonia solani and Thielaviopsis basicola, posing a serious limitation for crop, especially in cold springs. Ninety-seven commercial plots, where postemergence damping-off of cotton seedlings was observed during previous years, were selected in April 2001. In each plot, plants were randomly sampled between cotyledon to three true-leaf stage and soil samples besides the plants were taken. Symptomatic plants were separated according to the main observable seedling disease symptom: black necrosis (black root rot), brown necrosis and other symptoms. Thielaviopsis basicola inoculum was estimated in soil samples. Soil samples were also analysed for nutrient availability (N, P, K, Ca, Mg, Fe, Cu, Mn and Zn). All the sampled plants showed some seedling disease symptom. Macroscopic symptoms can provide a reasonable distinction between these two major pathogens involved in seedling disease symptoms in the studied area: the percentage of T. basicola isolates (18%) from black necrosis symptomatic plants was significantly higher than that of R. solani (4.1%), whereas in brown necrosis symptomatic plants, the situation was reversed (10.7 vs. 12.8%). The percentage of plants with black necrosis symptoms was inversely related to the portion of plants with brown necrosis in each plot. The mean incidence of black necrosis was significantly lower in plots with residue incorporation (sugar beet as the preceding crop) than in plots without residue incorporation. No significant effect of preceding crop or residue management on brown necrosis incidence was observed. Incidence of black necrosis was negatively correlated with available N measured as NO3 -N when corn or sunflower were the preceding crop. The incidence of black necrosis was positively related to Fe availability in soil after cotton as preceding crop, whereas brown necrosis was negatively related to the availability of this micronutrient. [source]

Tapping the nucleotide pool of the host: novel nucleotide carrier proteins of Protochlamydia amoebophila

Ilka Haferkamp
Summary Protochlamydia amoebophila UWE25 is related to the Chlamydiaceae comprising major pathogens of humans, but thrives as obligate intracellular symbiont in the protozoan host Acanthamoeba sp. The genome of P. amoebophila encodes five paralogous carrier proteins belonging to the nucleotide transporter (NTT) family. Here we report on three P. amoebophila NTT isoforms, PamNTT2, PamNTT3 and PamNTT5, which possess several conserved amino acid residues known to be critical for nucleotide transport. We demonstrated that these carrier proteins are able to transport nucleotides, although substrate specificities and mode of transport differ in an unexpected manner and are unique among known NTTs. PamNTT2 is a counter exchange transporter exhibiting submillimolar apparent affinities for all four RNA nucleotides, PamNTT3 catalyses an unidirectional proton-coupled transport confined to UTP, whereas PamNTT5 mediates a proton-energized GTP and ATP import. All NTT genes of P. amoebophila are transcribed during intracellular multiplication in acanthamoebae. The biochemical characterization of all five NTT proteins from P. amoebophila in this and previous studies uncovered that these metabolically impaired bacteria are intimately connected with their host cell's metabolism in a surprisingly complex manner. [source]

Scavenger receptors: role in innate immunity and microbial pathogenesis

Thomas Areschoug
Summary Accumulating evidence shows that many scavenger receptors (SR), including SR-A, MARCO and CD36, represent an important part of the innate immune defence by acting as pattern-recognition receptors, in particular against bacterial pathogens. Several SR are expressed on macrophages and dendritic cells, where they act as phagocytic receptors mediating non-opsonic phagocytosis of pathogenic microbes. Another important function of some SR is to act as co-receptors to Toll-like receptors (TLR), modulating the inflammatory response to TLR agonists. On bacteria, the SR ligands have commonly been reported to be lipopolysaccharide and lipoteichoic acid, but recent advances in the field indicate that bacterial surface proteins play a more important role as target molecules for SR than previously thought. Interestingly, recent data show that major pathogens, including Streptococcus pyogenes and the group B streptococcus, have evolved mechanisms to evade SR-mediated recognition. Moreover, intracellular pathogens, such as hepatitis C virus and Plasmodium falciparum, utilize the SR to gain entry into host cells, focusing interest on the importance of SR also in the molecular pathogenesis of infectious diseases. This review highlights the complex interactions between SR and pathogenic microbes, and discusses the role of these interactions in host defence and microbial pathogenesis. [source]