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Search Results: 1 - 10 of 5153 matches for " Mohammed Sebaihia "
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Ankyrin repeat domain-encoding genes in the wPip strain of Wolbachia from the Culex pipiens group
Thomas Walker, Lisa Klasson, Mohammed Sebaihia, Mandy J Sanders, Nicholas R Thomson, Julian Parkhill, Steven P Sinkins
BMC Biology , 2007, DOI: 10.1186/1741-7007-5-39
Abstract: The sequencing of the wPip strain of Wolbachia revealed the presence of 60 ankyrin repeat domain (ANK) encoding genes and expression studies of these genes were carried out in adult mosquitoes. One of these ANK genes, pk2, is shown to be part of an operon of three prophage-associated genes with sex-specific expression, and is present in two identical copies in the genome. Another homolog of pk2 is also present that is differentially expressed in different Cx. pipiens group strains. A further two ANK genes showed sex-specific regulation in wPip-infected Cx. pipiens group adults.The high number, variability and differential expression of ANK genes in wPip suggest an important role in Wolbachia biology, and the gene family provides both markers and promising candidates for the study of reproductive manipulation.Wolbachia are obligate endosymbiotic bacteria that are maternally transmitted through the egg cytoplasm and are responsible for several reproductive disorders in arthropods, such as cytoplasmic incompatibility (CI) in infected Culex mosquitoes [1,2] and many other insects. Although Wolbachia are not found in mature sperm, they can modify developing sperm, possibly via chromatin binding proteins [3], such that when they fertilise an uninfected egg embryonic development is arrested. The reciprocal cross between infected females and uninfected males is, however, compatible; Wolbachia-infected females therefore produce a higher mean number of offspring than uninfected females. This unidirectional CI enables Wolbachia to rapidly invade uninfected populations [4], and provides a mechanism for driving anti-pathogen transgenes or a lifespan-shortening phenotype into mosquito populations [5,6]. Bidirectional CI can also occur between insect populations, usually when they are infected with different strains of Wolbachia.The genome sequence of the wMel strain [7], a CI-inducing Wolbachia strain found in Drosophila melanogaster, revealed an unusually high number of ankyrin
Array comparative hybridisation reveals a high degree of similarity between UK and European clinical isolates of hypervirulent Clostridium difficile
Gemma L Marsden, Ian J Davis, Victoria J Wright, Mohammed Sebaihia, Ed J Kuijper, Nigel P Minton
BMC Genomics , 2010, DOI: 10.1186/1471-2164-11-389
Abstract: In this study, we examined 94 clinical strains of the most common PCR-ribotypes isolated in mainland Europe and the UK by array comparative genomic hybridisation. Our array was comprehensive with 40,097 oligonucleotides covering the C. difficile 630 genome and revealed a core genome for all the strains of 32%. The array also covered genes unique to two PCR-ribotype 027 strains, relative to C. difficile 630 which were represented by 681 probes. All of these genes were also found in the commonly occuring PCR-ribotypes 001 and 106, and the emerging hypervirulent PCR-ribotype 078 strains, indicating that these are markers for all highly virulent strains.We have fulfilled the aims of this study by identifying markers for CD630 and markers associated with hypervirulence, albeit genes that are not just indicative of PCR-ribotype 027 strains. We have also extended this study and have defined a more stringent core gene set compared to those previously published due to the comprehensive array coverage. Further to this we have defined a list of genes absent from non-toxinogenic strains and defined the nature of the specific toxin deletion in the strain CD37.Clostridium difficile (C. difficile) is a Gram-positive, spore-forming, anaerobic bacterium currently responsible for virtually all cases of pseudomembranous colitis (PMC) and for 10-25% of cases of antibiotic-associated diarrhoea [1]. The organism is resistant to various antibiotics and capitalizes on the ensuing disruption of the normal intestinal flora to colonization and cause disease. The spectrum of disease ranges from asymptomatic carriage to a fulminant, relapsing, and increasingly fatal colitis [2]. The effects of C. difficile infection (CDI) are devastating, both in terms of morbidity and mortality and the high costs of disease management [3,4]. Once regarded as relatively uncommon, there has been an upward trend in the incidence of CDI in both North America [1,5,6] and Europe [7,8] culminating in 2007 in over 5 t
Comparative genome and phenotypic analysis of Clostridium difficile 027 strains provides insight into the evolution of a hypervirulent bacterium
Richard A Stabler, Miao He, Lisa Dawson, Melissa Martin, Esmeralda Valiente, Craig Corton, Trevor D Lawley, Mohammed Sebaihia, Michael A Quail, Graham Rose, Dale N Gerding, Maryse Gibert, Michel R Popoff, Julian Parkhill, Gordon Dougan, Brendan W Wren
Genome Biology , 2009, DOI: 10.1186/gb-2009-10-9-r102
Abstract: Although the genomes are highly conserved, the 027 genomes have 234 additional genes compared to 630, which may contribute to the distinct phenotypic differences we observe between these strains relating to motility, antibiotic resistance and toxicity. The epidemic 027 strain has five unique genetic regions, absent from both the non-epidemic 027 and strain 630, which include a novel phage island, a two component regulatory system and transcriptional regulators.A comparison of a series of 027 isolates showed that some of these genes appeared to have been gained by 027 strains over the past two decades. This study provides genetic markers for the identification of 027 strains and offers a unique opportunity to explain the recent emergence of a hypervirulent bacterium.Clostridium difficile, a spore-forming anaerobic bacillus that often resides in the gut of mammals, is the causative agent of C. difficile infection (CDI) (reviewed in [1]). The hospital environment and patients undergoing antibiotic treatment provide a discrete ecosystem where C. difficile persists and selected virulent clones thrive. Consequently, C. difficile is the most frequent cause of nosocomial diarrhea worldwide, where patients exhibit a range of symptoms from mild diarrhea to life threatening pseudomembranous colitis (PMC) [2,3]. In most cases of CDI antibiotic therapies disrupt the protective gut microbiota, whereupon ingested or existent C. difficile spores germinate, colonize the gastrointestinal tract and produce toxins. Another feature of CDI is the high relapse rate due to re-infection or reactivation of infection [2,3]. The population at risk for CDI includes not only patients on antimicrobial and other therapies that can alter the balance of the gut microbiota (for example, antacid/proton pump inhibitors and non-steroidal anti-inflammatory drugs), but also the immunocompromised and the elderly. Given the continued use of broad-spectrum antibiotics and the rising numbers of immunocompromi
Complete Genome Sequence and Comparative Metabolic Profiling of the Prototypical Enteroaggregative Escherichia coli Strain 042
Roy R. Chaudhuri,Mohammed Sebaihia,Jon L. Hobman,Mark A. Webber,Denisse L. Leyton,Martin D. Goldberg,Adam F. Cunningham,Anthony Scott-Tucker,Paul R. Ferguson,Christopher M. Thomas,Gad Frankel,Christoph M. Tang,Edward G. Dudley,Ian S. Roberts,David A. Rasko,Mark J. Pallen,Julian Parkhill,James P. Nataro,Nicholas R. Thomson,Ian R. Henderson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008801
Abstract: Escherichia coli can experience a multifaceted life, in some cases acting as a commensal while in other cases causing intestinal and/or extraintestinal disease. Several studies suggest enteroaggregative E. coli are the predominant cause of E. coli-mediated diarrhea in the developed world and are second only to Campylobacter sp. as a cause of bacterial-mediated diarrhea. Furthermore, enteroaggregative E. coli are a predominant cause of persistent diarrhea in the developing world where infection has been associated with malnourishment and growth retardation.
The complete genome, comparative and functional analysis of Stenotrophomonas maltophilia reveals an organism heavily shielded by drug resistance determinants
Lisa C Crossman, Virginia C Gould, J Maxwell Dow, Georgios S Vernikos, Aki Okazaki, Mohammed Sebaihia, David Saunders, Claire Arrowsmith, Tim Carver, Nicholas Peters, Ellen Adlem, Arnaud Kerhornou, Angela Lord, Lee Murphy, Katharine Seeger, Robert Squares, Simon Rutter, Michael A Quail, Mari-Adele Rajandream, David Harris, Carol Churcher, Stephen D Bentley, Julian Parkhill, Nicholas R Thomson, Matthew B Avison
Genome Biology , 2008, DOI: 10.1186/gb-2008-9-4-r74
Abstract: The genome of the bacteremia-associated isolate S. maltophilia K279a is 4,851,126 bp and of high G+C content. The sequence reveals an organism with a remarkable capacity for drug and heavy metal resistance. In addition to a number of genes conferring resistance to antimicrobial drugs of different classes via alternative mechanisms, nine resistance-nodulation-division (RND)-type putative antimicrobial efflux systems are present. Functional genomic analysis confirms a role in drug resistance for several of the novel RND efflux pumps. S. maltophilia possesses potentially mobile regions of DNA and encodes a number of pili and fimbriae likely to be involved in adhesion and biofilm formation that may also contribute to increased antimicrobial drug resistance.The panoply of antimicrobial drug resistance genes and mobile genetic elements found suggests that the organism can act as a reservoir of antimicrobial drug resistance determinants in a clinical environment, which is an issue of considerable concern.The rise of antimicrobial drug resistance in bacteria is one of the biggest threats to healthcare provision in the developed world. Few new antimicrobial drugs are undergoing clinical trials, and almost none are effective against Gram-negative multi-drug resistant (MDR) pathogens [1]. A return to the pre-antibiotic era is a possibility, and for some infections is the current reality [2].Antimicrobial resistance in historically common pathogens is usually either acquired on a mobile genetic element or results from a mutation [3]. However, some opportunistic pathogens are intrinsically resistant to the actions of a number of antimicrobial classes. These tend to be of environmental origin, and their intrinsic drug resistance determinants either provide resistance to antibiotics produced by competitors, or represent broad-spectrum methods for removing toxic compounds or waste products that, by chance, protect against antimicrobials [3,4]. It is known that established opportuni
Correlation of Endoscopic Findings with Various Helicobacter pylori Tests among Dyspeptic Patients  [PDF]
Mohammed O. Mohammed
International Journal of Clinical Medicine (IJCM) , 2014, DOI: 10.4236/ijcm.2014.519151
Abstract: Background: Helicobacter pylori is the most common chronic bacterial infection, and a significant etiological factor in acid peptic diseases and gastric cancer. Dyspepsia is a common gastrointestinal disorder, and the most common indication for gastroscopy. Detection of H. pylori during endoscopy has become standard clinical practice. Elevated levels of inflammatory markers such as C-reactive protein (CRP), are associated with pathological changes, and hence give useful information for exact diagnosis and therapy. Objectives: To determine the relationship between endoscopic findings, highly sensitive C-reactive protein level (hs-CRP) and H. pylori infection among dyspeptic patients using serological tests, stool antigen for H. pylori and antral histology. Methods: This was a prospective study; patients with dyspepsia, who referred to Kurdistan Teaching Center of Gastroenterology & Hepatology in Sulaimani City were assessed, during the period of December 2012 to March 2014. They underwent gastroscopy, and biopsies were taken from the corpus and antral portions of antral portion for histopathological exam. Patients’ serum samples were tested for H. pylori infection using ELISA method to detect (IgG & IgA) anti-bodies and stool samples were examined using rapid immunoassay method to detect H. pylori antigens. hs-CRP was assessed using ELISA. Results: One hundred dyspeptic patients were included in the study. The mean age was 34.2 years and male comprised 54% of the study samples. The common findings in oesophagogastroduodenoscopy (OGD) examination were antral gastropathy (59%) and duodenal ulcer (21%). A statistically significant (P < 0.01) correlation was found between hs-CRP and H. pylori IgG and IgA levels (titer). There was a highly significant (P < 0.01) correlation between the level of H. pylori IgG and the endoscopic findings. The highest serum level of H. pylori IgG was found in duodenal ulcer and antral gastritis, (88.86 ± 42.0) and (70.05 ± 35.2) Au/ml, respectively. There was a highly significant correlation (P < 0.01) between endoscopic findings and H. pylori positive antral biopsy, in duodenal ulcer, antral gastritis and duodenitis was 100%, 94.9% and 75% respectively. Also duodenal ulcer and antral gastritis showed high mean and percentage but no significant differences in both H. pylori IgA and stool Antigen.
The missing link: Bordetella petrii is endowed with both the metabolic versatility of environmental bacteria and virulence traits of pathogenic Bordetellae
Roy Gross, Carlos A Guzman, Mohammed Sebaihia, Vítor AP Martins dos Santos, Dietmar H Pieper, Ralf Koebnik, Melanie Lechner, Daniela Bartels, Jens Buhrmester, Jomuna V Choudhuri, Thomas Ebensen, Lars Gaigalat, Stefanie Herrmann, Amit N Khachane, Christof Larisch, Stefanie Link, Burkhard Linke, Folker Meyer, Sascha Mormann, Diana Nakunst, Christian Rückert, Susanne Schneiker-Bekel, Kai Schulze, Frank-J?rg Vorh?lter, Tetyana Yevsa, Jacquelyn T Engle, William E Goldman, Alfred Pühler, Ulf B G?bel, Alexander Goesmann
BMC Genomics , 2008, DOI: 10.1186/1471-2164-9-449
Abstract: In this manuscript we present the results of the analysis of the completely annotated genome sequence of the B. petrii strain DSMZ12804. B. petrii has a mosaic genome of 5,287,950 bp harboring numerous mobile genetic elements, including seven large genomic islands. Four of them are highly related to the clc element of Pseudomonas knackmussii B13, which encodes genes involved in the degradation of aromatics. Though being an environmental isolate, the sequenced B. petrii strain also encodes proteins related to virulence factors of the pathogenic Bordetellae, including the filamentous hemagglutinin, which is a major colonization factor of B. pertussis, and the master virulence regulator BvgAS. However, it lacks all known toxins of the pathogenic Bordetellae.The genomic analysis suggests that B. petrii represents an evolutionary link between free-living environmental bacteria and the host-restricted obligate pathogenic Bordetellae. Its remarkable metabolic versatility may enable B. petrii to thrive in very different ecological niches.The genus Bordetella comprises several human and animal pathogens and nine species are currently described [see Additional file 1]. Human-restricted B. pertussis and B. parapertussis cause whooping cough, whereas B. bronchiseptica and B. avium are responsible for respiratory infections in many mammals and birds, respectively [1-3]. Despite the availability of vaccines, there are still 300,000 deaths/year caused by B. pertussis and significant economic losses associated with infections in poultry and cattle. The genomes of these Bordetellae were recently sequenced and analyzed [4,5]. The genome sequence of B. avium revealed that it is quite divergent from the mammalian pathogens. In contrast, the genomes of the human pathogens B. pertussis and B. parapertussis showed that they are independent derivatives of B. bronchiseptica-like ancestors. They both underwent significant gene loss, probably mediated by insertion sequence (IS) elements, duri
General Periodic Boundary Value Problem for Systems  [PDF]
Mohammed Elnagi
Applied Mathematics (AM) , 2012, DOI: 10.4236/am.2012.38130
Abstract: The paper deals with the existence of nonzero periodic solution of systems, where k∈(0, π/T), α, β are n×n real nonsingular matrices, μ=(μ1…μn), f(t, u)=(f1(t, u),…,fn(t, u))∈C([0, T]×□n+,□+) is periodic of period T in the t variable are continuous and nonnegative functions. We determine the Green’s function and prove that the existence of nonzero periodic positive solutions if one of . In addition, if all i=(1…n)where λ1 is the principle eigenvalues of the corresponding linear systems. The proof based on the fixed point index theorem in cones. Application of our result is given to such systems with specific nonlinearities.
Pseudocercospora leaf and fruit spot disease of citrus: Achievements and challenges in the citrus industry: A review  [PDF]
Mohammed Yesuf
Agricultural Sciences (AS) , 2013, DOI: 10.4236/as.2013.47046

Citruses are the worlds’ second fruit crops by volume next to banana. It is one of the most important commodity in tropical Africa as source of foreign currency, raw material for agro-industries and source of employment. The production and productivity of citrus in tropical Africa including Ethiopia are critically threatened by a number of diseases. Among others, pseudocercospora leaf and fruit spot of citrus caused by a fungus Pseudocercospora angolensis is the most destructive disease of citrus. Literature reviews have been made by searching the available information on leaf and fruit spot of citrus. Journal articles, research papers, workshop proceedings, Thesis research, manuals, and quarantine regulations were among the information sources of the review. The disease is widespread in 22 African countries including Ethiopia with a single report around Yemen in the Arabian Peninsula. Scattered research efforts have been made by different researchers in Africa mainly dealing with its geographic distribution, biology, and management practices. Fungicides, plant extracts/essential oils, and host resistance are among the research efforts made for the control of P. angolensis. Even though the disease is not yet reported to the rest of the world, it becomes a serious concern as an important quarantine pest thereby critically affecting the world trade and germplasm exchange of the citrus industry. Therefore, the purpose of this paper is to compile the scattered information on various aspects of leaf and fruit spot of citrus mainly to avail the information for researchers, development workers and policy people. Moreover, this review will suggest future research and development direction towards better understanding and sustainable management practices of the disease.

Variation of the Spectrum of Operators in Infinite Dimensional Spaces  [PDF]
Mohammed Yahdi
Advances in Pure Mathematics (APM) , 2013, DOI: 10.4236/apm.2013.37080

The paper investigates the variation of the spectrum of operators in infinite dimensional Banach spaces. Consider the space of bounded operators on a separable Banach space when equipped with the strong operator topology, and the Polish space of compact subsets of the closed unit disc of the complex plane when equipped with the Hausdorff topology. Then, it is shown that the unit spectrum function is Borel from the space of bounded operators into the Polish space of compact subsets of the closed unit disc. Alternative results are given when other topologies are used.

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