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排序方式: 共有181条查询结果,搜索用时 31 毫秒
51.
Claudia Duran Faridabano Nato Sylvie Dartevelle Lan Nguyen Thi Phuong Neelam Taneja Marie No?lle Ungeheuer Guillermo Soza Leslie Anderson Dona Benadof Agustín Zamorano Tai The Diep Truong Quang Nguyen Vu Hoang Nguyen Catherine Ottone Evelyne Bégaud Sapna Pahil Valeria Prado Philippe Sansonetti Yves Germani 《PloS one》2013,8(11)
Background
We evaluated a dipstick test for rapid detection of Shigella sonnei on bacterial colonies, directly on stools and from rectal swabs because in actual field situations, most pathologic specimens for diagnosis correspond to stool samples or rectal swabs.Methodology/Principal Findings
The test is based on the detection of S. sonnei lipopolysaccharide (LPS) O-side chains using phase I-specific monoclonal antibodies coupled to gold particles, and displayed on a one-step immunochromatographic dipstick. A concentration as low as 5 ng/ml of LPS was detected in distilled water and in reconstituted stools in 6 minutes. This is the optimal time for lecture to avoid errors of interpretation. In distilled water and in reconstituted stools, an unequivocal positive reaction was obtained with 4 x 106 CFU/ml of S. sonnei. The specificity was 100% when tested with a battery of Shigella and different unrelated strains. When tested on 342 rectal swabs in Chile, specificity (281/295) was 95.3% (95% CI: 92.9% - 97.7%) and sensitivity (47/47) was 100%. Stool cultures and the immunochromatographic test showed concordant results in 95.5 % of cases (328/342) in comparative studies. Positive and negative predictive values were 77% (95% CI: 65% - 86.5%) and 100% respectively. When tested on 219 stools in Chile, Vietnam, India and France, specificity (190/198) was 96% (95% CI 92%–98%) and sensitivity (21/21) was 100%. Stool cultures and the immunochromatographic test showed concordant results in 96.3 % of cases (211/219) in comparative studies. Positive and negative predictive values were 72.4% (95% CI 56.1%–88.6%) and 100 %, respectively.Conclusion
This one-step dipstick test performed well for diagnosis of S. sonnei both on stools and on rectal swabs. These data confirm a preliminary study done in Chile. 相似文献52.
T4 lysozyme has two easily distinguishable but energetically coupled domains: the N and C-terminal domains. In earlier studies, an amide hydrogen/deuterium exchange pulse-labeling experiment detected a stable submillisecond intermediate that accumulates before the rate-limiting transition state. It involves the formation of structures in both the N and C-terminal regions. However, a native-state hydrogen exchange experiment subsequently detected an equilibrium intermediate that only involves the formation of the C-terminal domain. Here, using stopped-flow circular dichroism and fluorescence, amide hydrogen exchange-folding competition, and protein engineering methods, we re-examined the folding pathway of T4-lysozyme. We found no evidence for the existence of a stable folding intermediate before the rate-limiting transition state at neutral pH. In addition, using native-state hydrogen exchange-directed protein engineering, we created a mimic of the equilibrium intermediate. We found that the intermediate mimic folds with the same rate as the wild-type protein, suggesting that the equilibrium intermediate is an on-pathway intermediate that exists after the rate-limiting transition state. 相似文献
53.
Garibyan L Huang T Kim M Wolff E Nguyen A Nguyen T Diep A Hu K Iverson A Yang H Miller JH 《DNA Repair》2003,2(5):593-608
Mutations in the rpoB gene of Escherichia coli result in resistance to the antibiotic rifampicin (Rif(r)) by altering the beta subunit of RNA polymerase. Previous studies have identified 39 single base substitutions in the rpoB gene that lead to Rif(r) at 37 degrees C and an additional two mutations that result in temperature sensitive cells. We have extended this work and identified an additional 30 single base substitutions that result in the Rif(r) phenotype. With these mutations the rpoB/Rif(r) system now allows the monitoring of 69 base substitutions at 37 degrees at 37 sites (base pairs) distributed among 24 coding positions. Each of the six possible base substitutions is represented by 8-17 mutations. More than 90% of the mutations are within a small enough region of the rpoB gene to allow PCR amplification with a single pair of oligonucleotide primers, followed by sequencing with a single primer, leading to rapid analysis of numerous mutations. The remaining mutations can be monitored using an additional primer pair. To calibrate this system we sequenced over 500 mutations in rpoB occurring spontaneously or generated by different mutagens and mutators with known specificity. These results show that rpoB/Rif(r) is an accurate and easy to employ detection system, and offers the advantage of allowing analysis of mutations occurring on the chromosome rather than on an extrachromosomal element. The mutS, mutT, mutY, M mutators, as well as the mutagenic agents ethyl methanesulfonate (EMS), ultraviolet (UV) irradiation, 2-aminopurine (2AP), 5-azacytidine (5AZ), and cisplatin (CPT) gave results predicted by their characterized specificities. The number of different sequence contexts is sufficient to reveal significant hotspots among the spontaneous mutS, 2-aminopurine, ultraviolet light, 5-azacytidine, and cisplatin mutational spectra. The cisplatin distribution is particularly striking, with 68% of the mutations resulting from an A:T-->T:A transversion at a single site. Because of the conservation of key regions of RNA polymerase among many microorganisms, using the Rif(r)/rpoB system may be a general method for studying mutational processes in microorganisms without well developed genetic systems. 相似文献
54.
The honey bee (Apis mellifera) is highly valued as a commercial crop pollinator and a model animal in research. Over the past several years, governments, beekeepers, and the general public in the United States and Europe have become concerned by increased losses of honey bee colonies, calling for more research on how to keep colonies healthy while still employing them extensively in agriculture. The honey bee, like virtually all multicellular organisms, has a mutually beneficial relationship with specific microbes. The microbiota of the gut can contribute essential nutrients and vitamins and prevent colonization by non-indigenous and potentially harmful species. The gut microbiota is also of interest as a resource for paratransgenesis; a Trojan horse strategy based on genetically modified symbiotic microbes that express effector molecules antagonizing development or transmission of pathogens. Paratransgenesis was originally engineered to combat human diseases and agricultural pests that are vectored by insects. We suggest an alternative use, as a method to promote health of honey bees and to expand the molecular toolbox for research on this beneficial social insect. The honey bees' gut microbiota contains lactic acid bacteria including the genus Lactobacillus that has paratransgenic potential. We present a strategy for transforming one Lactobacillus species, L. kunkeei, for use as a vector to promote health of honey bees and functional genetic research. 相似文献
55.
Natural antimicrobial peptides from bacteria: characteristics and potential applications to fight against antibiotic resistance 总被引:1,自引:0,他引:1
Because of the emergence of antibiotic‐resistant pathogens worldwide, a number of infectious diseases have become difficult to treat. This threatening situation is worsened by the fact that very limited progress has been made in developing new and potent antibiotics in recent years. However, a group of antimicrobials, the so‐called bacteriocins, have been much studied lately because they hold a great potential in controlling antibiotic‐resistant pathogens. Bacteriocins are small antimicrobial peptides (AMPs) produced by numerous bacteria. They often act toward species related to the producer with a very high potency (at pico‐ to nanomolar concentration) and specificity. The common mechanisms of killing by bacteriocins are destruction of target cells by pore formation and/or inhibition of cell wall synthesis. Several studies have revealed that bacteriocins display great potential in the medical sector as bacteriocinogenic probiotics and in the clinic as therapeutic agents. In this review, we discuss the emerging antibiotic resistance and strategies to control its dissemination, before we highlight the potential of AMPs from bacteria as a new genre of antimicrobial agents. 相似文献
56.
Li M Du X Villaruz AE Diep BA Wang D Song Y Tian Y Hu J Yu F Lu Y Otto M 《Nature medicine》2012,18(5):816-819
The molecular processes underlying epidemic waves of methicillin-resistant Staphylococcus aureus (MRSA) infection are poorly understood(1). Although a major role has been attributed to the acquisition of virulence determinants by horizontal gene transfer(2), there are insufficient epidemiological and functional data supporting that concept. We here report the spread of clones containing a previously extremely rare(3,4) mobile genetic element–encoded gene, sasX. We demonstrate that sasX has a key role in MRSA colonization and pathogenesis, substantially enhancing nasal colonization, lung disease and abscess formation and promoting mechanisms of immune evasion. Moreover, we observed the recent spread of sasX from sequence type 239 (ST239) to invasive clones belonging to other sequence types. Our study identifies sasX as a quickly spreading crucial determinant of MRSA pathogenic success and a promising target for therapeutic interference. Our results provide proof of principle that horizontal gene transfer of key virulence determinants drives MRSA epidemic waves. 相似文献
57.
Fox A Le NM Horby P van Doorn HR Nguyen VT Nguyen HH Nguyen TC Vu DP Nguyen MH Diep NT Bich VT Huong HT Taylor WR Farrar J Wertheim H Nguyen VK 《PloS one》2012,7(2):e31535
Background
It is unclear why the severity of influenza varies in healthy adults or why the burden of severe influenza shifts to young adults when pandemic strains emerge. One possibility is that cross-protective T cell responses wane in this age group in the absence of recent infection. We therefore compared the acute cellular immune response in previously healthy adults with severe versus mild pandemic H1N1 infection.Methods and Principal Findings
49 previously healthy adults admitted to the National Hospital of Tropical Diseases, Viet Nam with RT-PCR-confirmed 2009 H1N1 infection were prospectively enrolled. 39 recovered quickly whereas 10 developed severe symptoms requiring supplemental oxygen and prolonged hospitalization. Peripheral blood lymphocyte subset counts and activation (HLADR, CD38) and differentiation (CD27, CD28) marker expression were determined on days 0, 2, 5, 10, 14 and 28 by flow cytometry. NK, CD4 and CD8 lymphopenia developed in 100%, 90% and 60% of severe cases versus 13% (p<0.001), 28%, (p = 0.001) and 18% (p = 0.014) of mild cases. CD4 and NK counts normalized following recovery. B cell counts were not significantly associated with severity. CD8 activation peaked 6–8 days after mild influenza onset, when 13% (6–22%) were HLADR+CD38+, and was accompanied by a significant loss of resting/CD27+CD28+ cells without accumulation of CD27+CD28− or CD27−CD28− cells. In severe influenza CD8 activation peaked more than 9 days post-onset, and/or was excessive (30–90% HLADR+CD38+) in association with accumulation of CD27+CD28− cells and maintenance of CD8 counts.Conclusion
Severe influenza is associated with transient T and NK cell deficiency. CD8 phenotype changes during mild influenza are consistent with a rapidly resolving memory response whereas in severe influenza activation is either delayed or excessive, and partially differentiated cells accumulate within blood indicating that recruitment of effector cells to the lung could be impaired. 相似文献58.
Vince JE Chau D Callus B Wong WW Hawkins CJ Schneider P McKinlay M Benetatos CA Condon SM Chunduru SK Yeoh G Brink R Vaux DL Silke J 《The Journal of cell biology》2008,182(1):171-184
Synthetic inhibitor of apoptosis (IAP) antagonists induce degradation of IAP proteins such as cellular IAP1 (cIAP1), activate nuclear factor kappaB (NF-kappaB) signaling, and sensitize cells to tumor necrosis factor alpha (TNFalpha). The physiological relevance of these discoveries to cIAP1 function remains undetermined. We show that upon ligand binding, the TNF superfamily receptor FN14 recruits a cIAP1-Tnf receptor-associated factor 2 (TRAF2) complex. Unlike IAP antagonists that cause rapid proteasomal degradation of cIAP1, signaling by FN14 promotes the lysosomal degradation of cIAP1-TRAF2 in a cIAP1-dependent manner. TNF-like weak inducer of apoptosis (TWEAK)/FN14 signaling nevertheless promotes the same noncanonical NF-kappaB signaling elicited by IAP antagonists and, in sensitive cells, the same autocrine TNFalpha-induced death occurs. TWEAK-induced loss of the cIAP1-TRAF2 complex sensitizes immortalized and minimally passaged tumor cells to TNFalpha-induced death, whereas primary cells remain resistant. Conversely, cIAP1-TRAF2 complex overexpression limits FN14 signaling and protects tumor cells from TWEAK-induced TNFalpha sensitization. Lysosomal degradation of cIAP1-TRAF2 by TWEAK/FN14 therefore critically alters the balance of life/death signals emanating from TNF-R1 in immortalized cells. 相似文献
59.
Dolecek C Tran TP Nguyen NR Le TP Ha V Phung QT Doan CD Nguyen TB Duong TL Luong BH Nguyen TB Nguyen TA Pham ND Mai NL Phan VB Vo AH Nguyen VM Tran TT Tran TC Schultsz C Dunstan SJ Stepniewska K Campbell JI To SD Basnyat B Nguyen VV Nguyen VS Nguyen TC Tran TH Farrar J 《PloS one》2008,3(5):e2188
Background
Drug resistant typhoid fever is a major clinical problem globally. Many of the first line antibiotics, including the older generation fluoroquinolones, ciprofloxacin and ofloxacin, are failing.Objectives
We performed a randomised controlled trial to compare the efficacy and safety of gatifloxacin (10 mg/kg/day) versus azithromycin (20 mg/kg/day) as a once daily oral dose for 7 days for the treatment of uncomplicated typhoid fever in children and adults in Vietnam.Methods
An open-label multi-centre randomised trial with pre-specified per protocol analysis and intention to treat analysis was conducted. The primary outcome was fever clearance time, the secondary outcome was overall treatment failure (clinical or microbiological failure, development of typhoid fever-related complications, relapse or faecal carriage of S. typhi).Principal Findings
We enrolled 358 children and adults with suspected typhoid fever. There was no death in the study. 287 patients had blood culture confirmed typhoid fever, 145 patients received gatifloxacin and 142 patients received azithromycin. The median FCT was 106 hours in both treatment arms (95% Confidence Interval [CI]; 94–118 hours for gatifloxacin versus 88–112 hours for azithromycin), (logrank test p = 0.984, HR [95% CI] = 1.0 [0.80–1.26]).Overall treatment failure occurred in 13/145 (9%) patients in the gatifloxacin group and 13/140 (9.3%) patients in the azithromycin group, (logrank test p = 0.854, HR [95% CI] = 0.93 [0.43–2.0]). 96% (254/263) of the Salmonella enterica serovar Typhi isolates were resistant to nalidixic acid and 58% (153/263) were multidrug resistant.Conclusions
Both antibiotics showed an excellent efficacy and safety profile. Both gatifloxacin and azithromycin can be recommended for the treatment of typhoid fever particularly in regions with high rates of multidrug and nalidixic acid resistance. The cost of a 7-day treatment course of gatifloxacin is approximately one third of the cost of azithromycin in Vietnam.Trial Registration
Controlled-Trials.com ISRCTN67946944 相似文献60.
Nghia HD Ho DT Tu le TP Le TP Wolbers M Thai CQ Cao QT Hoang NV Nguyen VM Nga TV Tran VT Thao le TP Le TP Phu NH Nguyen HP Chau TT Tran TH Sinh DX Dinh XS Diep TS To SD Hang HT Hoang TT Truong H Campbell J Chau NV Nguyen VV Chinh NT Nguyen TC Dung NV Nguyen VD Hoa NT Ngo TH Spratt BG Hien TT Tran TH Farrar J Schultsz C 《PloS one》2011,6(3):e17604