21 research outputs found
Genomic variations define divergence of water/wildlife-associated Campylobacter jejuni niche specialists from common clonal complexes
No full textAlthough the major food-borne pathogen Campylobacter jejuni has been isolated from diverse animal, human and environmental sources, our knowledge of genomic diversity in C. jejuni is based exclusively on human or human food-chain-associated isolates. Studies employing multilocus sequence typing have indicated that some clonal complexes are more commonly associated with particular sources. Using comparative genomic hybridization on a collection of 80 isolates representing diverse sources and clonal complexes, we identified a separate clade comprising a group of water/wildlife isolates of C. jejuni with multilocus sequence types uncharacteristic of human food-chain-associated isolates. By genome sequencing one representative of this diverse group (C. jejuni 1336), and a representative of the bank-vole niche specialist ST-3704 (C. jejuni 414), we identified deletions of genomic regions normally carried by human food-chain-associated C. jejuni. Several of the deleted regions included genes implicated in chicken colonization or in virulence. Novel genomic insertions contributing to the accessory genomes of strains 1336 and 414 were identified. Comparative analysis using PCR assays indicated that novel regions were common but not ubiquitous among the water/wildlife group of isolates, indicating further genomic diversity among this group, whereas all ST-3704 isolates carried the same novel accessory regions. While strain 1336 was able to colonize chicks, strain 414 was not, suggesting that regions specifically absent from the genome of strain 414 may play an important role in this common route of Campylobacter infection of humans. We suggest that the genomic divergence observed constitutes evidence of adaptation leading to niche specialization
Reassessment of Acarbose as a Transition State Analogue Inhibitor of Cyclodextrin Glycosyltransferase
No full textThe binding of several different active site mutants of Bacillus circulans cyclodextrin glycosyltransferase to the inhibitor acarbose has been investigated through measurement of Ki values. The mutations represent several key amino acid positions, most of which are believed to play important roles in governing the product specificity of cyclodextrin glycosyltransferase. Michaelis-Menten parameters for the substrates α-maltotriosyl fluoride (αG3F) and α-glucosyl fluoride (αGF) with each mutant have been determined by following the enzyme-catalyzed release of fluoride with an ion-selective fluoride electrode. In both cases, reasonable correlations are observed in logarithmic plots relating the Ki value for acarbose with each mutant and both kcat/Km and Km for the hydrolysis of either substrate by the corresponding mutants. This indicates that acarbose, as an inhibitor, is mimicking aspects of both the ground state and the transition state. A better correlation is observed for αGF (r = 0.98) than αG3F (r = 0.90), which can be explained in terms of the modes of binding of these substrates and acarbose. Re-refinement of the previously determined crystal structure of wild-type CGTase complexed with acarbose reveals a binding mode consistent with the transition state analogue character of this inhibitor.
Use of suppression subtractive hybridisation to extend our knowledge of genome diversity in <it>Campylobacter jejuni</it>
No full textAbstract Background Previous studies have sought to identify a link between the distribution of variable genes amongst isolates of Campylobacter jejuni and particular host preferences. The genomic sequence data available currently was obtained using only isolates from human or chicken hosts. In order to identify variable genes present in isolates from alternative host species, five subtractions between C. jejuni isolates from different sources (rabbit, cattle, wild bird) were carried out, designed to assess genomic variability within and between common multilocus sequence type (MLST) clonal complexes (ST-21, ST-42, ST-45 and ST-61). Results The vast majority (97%) of the 195 subtracted sequences identified had a best BLASTX match with a Campylobacter protein. However, there was considerable variation within and between the four clonal complexes included in the subtractions. The distributions of eight variable sequences, including four with putative roles in the use of alternative terminal electron acceptors, amongst a panel of C. jejuni isolates representing diverse sources and STs, were determined. Conclusion There was a clear correlation between clonal complex and the distribution of the metabolic genes. In contrast, there was no evidence to support the hypothesis that the distribution of such genes may be related to host preference. The other variable genes studied were also generally distributed according to MLST type. Thus, we found little evidence for widespread horizontal gene transfer between clonal complexes involving these genes.</p
Adenovirus infections within a family cohort in Iran
No full textBackground: Adenovirus is one of the most frequent viruses associated with acute respiratory infections (ARI). There is limited information of its transmission within the community. Methods: Cohorts of 50 families with >= two children were visited weekly for 2 months to ascertain the presence ARI in Rasht, Iran. Nasopharyngeal swabs were obtained from symptomatic participants and at 3-4-day intervals to assess the duration of adenovirus shedding. Adenoviruses were identified by PCR and adenovirus positive amplicons were subjected to DNA sequencing. Results: Thirty-three (35%) of 94 ARI episodes in children and 8 (27%) of 30 episodes in adults were due to adenovirus (not significant, NS). 25/50 (50%) families had adenovirus infections. Children had more infections than adults, were more likely to develop symptoms if there was a symptomatic case within the household and episodes had a longer duration (P < 0.05). Adenoviruses were recovered for a median of 11 (interquartile range 5-26) days of follow up in children and 7 (2-20) days in adults (NS). Adenovirus-7 was the most frequent serotype (12 families), followed by adenovirus-6 (5 families), adenovirus-1 and 2 (4 families each), and adenovirus-5 (3 families). Both adenovirus-5 and 7 amplicons fell into two clusters. No mutations were observed during transmission within a family. Conclusion A substantial proportion of ARI in the community are due to adenovirus with further transmission within the family Children >= 2 years experienced a higher proportion of infections than younger children and adults. Viral shedding was more prolonged in children and adenovirus-7 and 5 predominated with several clusters co-circulating in the same season. Pediatr Pulmonol. 2009; 44:749-753. (C) 2009 Wiley-Liss, Inc.</p
Of good use or serious pleasure : Vitruvius Britannicus and early eighteenth century architectural discourse
No full textThe central thesis of this work is that Colen Campbell's
three volume Vitruvius Britannicus (1715-25) is not, as it has been frequently seen, a Palladian manifesto designed to change architectural practice in England (and in the process Campbell's own fortunes as an architect), but rather a publication celebrating architectural achievements, consumed by polite society.
The twentieth century view of Vitruvius Britannicus, stems from John Surnmerson's seminal work, Architecture in Britain 1530-1830. It posits Vitruvius Britannicus as a stylistic manifesto that served the particular interests of Colen Campbell and his associates as advocates of and builders in the Palladian style, and foregrounds the idea of the author. This view has been incorporated almost unquestioningly into subsequent interpretations not least
because it conforms to a powerful 'Whig' interpretation of history emphasising periodisation, style, revolution, development, and the search for origins. In contrast I argue that Vitruvius Britannicus met the demands of a market interested in architecture as a topic of polite
conversation. The subscription lists for Vitruvius Britannicus show that it was neither priced to be, nor received as, a builder's manual, nor was it a stylistic manifesto. Rather, it was a celebration of contemporary British architecture that gave pleasure and some instruction to polite society. Drawing on disciplines outside of art and architectural history, I consider
Vitruvius Britannicus as an object of consumption offering an alternative reading of the publication that highlights a number of important avenues for further research.
Chapter 1 positions the thesis within critiques of stylistic history. Chapter 2 briefly introduces
some historiographic issues, and then considers the contents and style of the publication, and
the nature of its subscribers. This highlights issues neglected in histories of Vilruvius Britannicus and challenges many of the commonly held conceptions of the publication. These conceptions are then examined in Chapter 3 in the light of evidence and issues raised in the
previous chapter. Chapter 4 considers other architectural and illustrated books and positions Campbell's work within wider publishing paradigms such as cartography and a literature of tourism. Chapter 5 outlines some of the intellectual ideas that influenced the way in which
publications such as Vitruvius Britannicus were understood. This is developed in Chapter 6 which considers the way in which Vitruvius Britannicus functioned within a contemporary
architectural discourse that codified the group identity of a polite elite
Major variations in Aspergillus fumigatus arising within aspergillomas in chronic pulmonary aspergillosis
No full textAspergillomas develop from progressive layers of mycelial growth on the walls of pulmonary cavities over months. Aspergillomas are characteristic of chronic pulmonary aspergillosis and are a risk factor for azole resistance. We investigated genotypic and phenotypic alterations in Aspergillus fumigatus recovered from aspergillomas. Aspergillomas were removed from three patients (two at surgery, one at autopsy) and dissected. Overall 92 colonies of A. fumigatus were isolated. Microsatellite typing was conducted to determine genetic type. Itraconazole, voriconazole and posaconazole susceptibilities were performed. The cyp51A gene was sequenced in 22 isolates. Isolates from Patient 1 (n=25) were azole susceptible and resistant, although all cyp51A sequences were wild type, the isolates split into two distinct clades. In Patient 2, isolates were less variable (n=10), all were azole susceptible. In Patient 3 only azole-resistant strains (n=57) were isolated, with M220K or M220T Cyp51A alterations, and microevolution was indicated. Marked diversity was observed in isolates from these patients; revealing differences in azole susceptibility, mechanism of resistance and genetic type. Importantly, routine sampling from respiratory specimens proved suboptimal in all cases; azole resistance was missed (Patient 1), cultures were negative (Patient 2) and high-level posaconazole resistance was not detected (Patient 3). © 2013 Blackwell Verlag GmbH
Aspergillus species and other molds in respiratory samples from patients with cystic fibrosis: A laboratory-based study with focus on Aspergillus fumigatus azole resistance
No full textRespiratory tract colonization by molds in patients with cystic fibrosis (CF) were analyzed, with particular focus on the frequency, genotype, and underlying mechanism of azole resistance among Aspergillus fumigatus isolates. Clinical and demographic data were also analyzed. A total of 3,336 respiratory samples from 287 CF patients were collected during two 6-month periods in 2007 and 2009. Azole resistance was detected using an itraconazole screening agar (4 mg/liter) and the EUCAST method. cyp51A gene sequencing and microsatellite genotyping were performed for isolates from patients harboring azole-resistant A. fumigatus. Aspergillus spp. were present in 145 patients (51%), of whom 63 (22%) were persistently colonized. Twelve patients (4%) harbored other molds. Persistently colonized patients were older, provided more samples, and more often had a chronic bacterial infection. Six of 133 patients (4.5%) harbored azole-nonsusceptible or -resistant A. fumigatus isolates, and five of those six patients had isolates with Cyp51A alterations (M220K, tandem repeat [TR]/L98H, TR/L98H-S297T-F495I, M220I-V101F, and Y431C). All six patients were previously exposed to azoles. Genotyping revealed (i) microevolution for A. fumigatus isolates received consecutively over the 2-year period, (ii) susceptible and resistant isolates (not involving TR/L98H isolates) with identical or very closely related genotypes (two patients), and (iii) two related susceptible isolates and a third unrelated resistant isolate with a unique genotype and the TR/L98H resistance combination (one patient). Aspergilli were frequently found in Danish CF patients, with 4.5% of the A. fumigatus isolates being azole nonsusceptible or resistant. Genotyping suggested selection of resistance in the patient as well as resistance being achieved in the environment. Copyright © 2011, American Society for Microbiology. All Rights Reserved
Characterisation of <it>Salmonella enterica </it>serotype Typhimurium isolates from wild birds in northern England from 2005 – 2006
No full textAbstract Background Several studies have shown that a number of serovars of Salmonella enterica may be isolated from wild birds, and it has been suggested that wild birds may play a role in the epidemiology of human and livestock salmonellosis. However, little is known about the relationship between wild bird S. enterica strains and human- and livestock- associated strains in the United Kingdom. Given the zoonotic potential of salmonellosis, the main aim of this study was to investigate the molecular epidemiology of S. enterica infections in wild birds in the north of England and, in particular, to determine if wild bird isolates were similar to those associated with disease in livestock or humans. Results Thirty two Salmonella enterica isolates were collected from wild birds in northern England between February 2005 and October 2006, of which 29 were S. enterica serovar Typhimurium (S. Typhimurium); one S. Newport, one S. Senftenberg, and one isolate could not be classified by serotyping. Further analysis through phage typing and macro-restriction pulsed-field gel electrophoresis indicated that wild passerine deaths associated with salmonellosis were caused by closely-related S. Typhimurium isolates, some of which were clonal. These isolates were susceptible to all antimicrobials tested, capable of invading and persisting within avian macrophage-like HD11 cells in vitro, and contained a range of virulence factors associated with both systemic and enteric infections of birds and mammals. However, all the isolates lacked the sopE gene associated with some human and livestock disease outbreaks caused by S. Typhimurium. Conclusion The wild bird isolates of S. enterica characterised in this investigation may not represent a large zoonotic risk. Molecular characterisation of isolates suggested that S. Typhimurium infection in wild passerines is maintained within wild bird populations and the causative strains may be host-adapted.</p
Molecular epidemiology of Campylobacter jejuni populations in dairy cattle, wildlife, and the environment in a farmland area
No full textWe describe a cross-sectional study of the molecular epidemiology of Campylobacter jejuni in a dairy farmland environment, with the aim of elucidating the dynamics of horizontal transmission of C. jejuni genotypes among sources in the area. A collection of 327 C. jejuni isolates from cattle, wildlife, and environmental sources in a 100-km2 area of farmland in northwest England was characterized by multilocus sequence typing. A total of 91 sequence types and 18 clonal complexes were identified. Clonal complexes ST-21, ST-45, and ST-61, which have been frequently associated with human disease, were the most commonly recovered genotypes in this study. In addition, widely distributed genotypes as well as potentially host-associated genotypes have been identified, which suggests that both restricted and interconnecting pathways of transmission may be operating in the dairy farmland environment. In particular, the ST-61 complex and the ST-21 complex were significantly associated with cattle. In contrast, complex strains ST-45, ST-952, and ST-677 were isolated predominantly from wild birds, wild rabbits, and environmental water. A considerable number of novel sequence types have also been identified, which were unassigned to existing clonal complexes and were frequently isolated from wildlife and environmental sources. The segregated distribution of genotypes among samples from different sources suggests that their transmission to humans is perhaps via independent routes. Insight into the dynamics and interactions of C. jejuni populations between important animal reservoirs and their surrounding environment would improve the identification of sources of Campylobacter infection and the design of control strategies. Copyright © 2008, American Society for Microbiology. All Rights Reserved
