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1.
J Appl Microbiol ; 130(3): 832-842, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-32881179

RESUMO

AIMS: Antimicrobial resistance genes (ARGs) are often associated with mobile genetic elements (MGEs), which facilitate their movement within and between bacterial populations. Detection of mobility is therefore important to understand the dynamics of MGE dissemination and their associated genes, especially in resistant clinical isolates that often have multiple ARGs associated with MGEs. Therefore, this study aimed to develop an entrapment vector to capture active MGEs and ARGs in clinical isolates of Escherichia coli. METHODS AND RESULTS: We engineered an entrapment vector, called pBACpAK, to capture MGEs in clinical E. coli isolates. It contains a cI-tetA positive selection cartridge in which the cI gene encodes a repressor that inhibits the expression of tetA. Therefore, any disruption of cI, for example, by insertion of a MGE, will allow tetA to be expressed and result in a selectable tetracycline-resistant phenotype. The pBACpAK was introduced into clinical E. coli isolates and grown on tetracycline-containing agar to select for clones with the insertion of MGEs into the entrapment vector. Several insertion sequences were detected within pBACpAK, including IS26, IS903B and ISSbo1. A novel translocatable unit (TU), containing IS26 and dfrA8 was also captured, and dfrA8 was shown to confer trimethoprim resistance when it was cloned into E. coli DH5α. CONCLUSIONS: The entrapment vector, pBACpAK was developed and shown to be able to capture MGEs and their associated ARGs from clinical E. coli isolates. We have captured, for the first time, a TU encoding antibiotic resistance. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first time that a TU and associated resistance gene has been captured from clinical E. coli isolates using an entrapment vector. The pBACpAK has the potential to be used not only as a tool to capture MGEs in clinical E. coli isolates, but also to study dynamics, frequency and potentiators of mobility for MGEs.


Assuntos
Farmacorresistência Bacteriana/genética , Escherichia coli/genética , Sequências Repetitivas Dispersas/genética , Antibacterianos/farmacologia , Farmacorresistência Bacteriana/efeitos dos fármacos , Escherichia coli/efeitos dos fármacos , Escherichia coli/isolamento & purificação , Proteínas de Escherichia coli/genética , Proteínas de Escherichia coli/metabolismo , Genes Bacterianos , Vetores Genéticos , Humanos , Resistência a Trimetoprima/efeitos dos fármacos , Resistência a Trimetoprima/genética
2.
Nat Commun ; 10(1): 2170, 2019 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-31092826

RESUMO

During the Last Glacial Maximum (LGM; ~20,000 years ago), the global ocean sequestered a large amount of carbon lost from the atmosphere and terrestrial biosphere. Suppressed CO2 outgassing from the Southern Ocean is the prevailing explanation for this carbon sequestration. By contrast, the North Atlantic Ocean-a major conduit for atmospheric CO2 transport to the ocean interior via the overturning circulation-has received much less attention. Here we demonstrate that North Atlantic carbon pump efficiency during the LGM was almost doubled relative to the Holocene. This is based on a novel proxy approach to estimate air-sea CO2 exchange signals using combined carbonate ion and nutrient reconstructions for multiple sediment cores from the North Atlantic. Our data indicate that in tandem with Southern Ocean processes, enhanced North Atlantic CO2 absorption contributed to lowering ice-age atmospheric CO2.

3.
Nat Commun ; 9(1): 3026, 2018 08 02.
Artigo em Inglês | MEDLINE | ID: mdl-30072688

RESUMO

Tibetan Plateau uplift has been suggested as the main driving force for mid-latitude Asian inland aridity (AIA) and for deposition of thick aeolian sequences in northern China since the Miocene. However, the relationship between earlier AIA and Tibetan Plateau mountain building is uncertain because of a lack of corresponding thick aeolian sequences with accurate age constraints. We here present results for a continuous aeolian sequence that spans the interval from >51 to 39 Ma from the eastern Xorkol Basin, Altun Shan, northeastern Tibetan Plateau. The basal age of the studied sequence postdates initial uplift of the Tibetan Plateau by several million years. Our results indicate that the local palaeoclimate was teleconnected strongly to the overall global cooling pattern, so that local enhanced aridification recorded by the studied aeolian sequence is dominantly a response to global climatic forcing rather than plateau uplift.

4.
Environ Microbiol Rep ; 10(3): 337-343, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29611897

RESUMO

Magnetotactic bacteria are a multi-phyletic group of bacteria that synthesize membrane-bound magnetic minerals. Understanding the preservation of these minerals in various environments (e.g., with varying oxygen concentrations and iron supply) is important for understanding their role as carriers of primary magnetizations in sediments and sedimentary rocks. Here we present X-ray near edge structure (XANES) spectra for Fe in magnetotactic bacteria samples from recent sediments to assess surface oxidation and crystal structure changes in bacterial magnetite during early burial. Our results are compared with a XANES spectrum of cultivated Magnetofaba australis samples, and with magnetic properties, and indicate that oxidation of magnetite to maghemite increases with depth in the sediment due to longer exposure to molecular oxygen. These results are relevant to understanding magnetic signatures carried by magnetofossils in oxic sediments and sedimentary rocks of different ages.


Assuntos
Alphaproteobacteria/metabolismo , Organismos Aquáticos/metabolismo , Óxido Ferroso-Férrico/metabolismo , Magnetossomos/metabolismo , Alphaproteobacteria/efeitos da radiação , Organismos Aquáticos/efeitos da radiação , Compostos Férricos/análise , Compostos Férricos/metabolismo , Óxido Ferroso-Férrico/análise , Magnetossomos/química , Oxirredução , Síncrotrons , Espectroscopia por Absorção de Raios X
5.
Gait Posture ; 55: 109-115, 2017 06.
Artigo em Inglês | MEDLINE | ID: mdl-28437757

RESUMO

Unilateral knee replacement is often followed by a contralateral replacement in time and the biomechanics of the other knee before and after knee replacement remains poorly understood. The aim of this paper is to distinguish the features of arthritic gait in the affected and unaffected legs relative to a normal population and to assess the objective recovery of gait function post-operatively, with the aim of defining patients at risk of poor post-operative function. Twenty patients with severe knee OA but no pain or deformity in any other lower limb joint were compared to twenty healthy subjects of the same age. Gait analysis was performed and quadriceps and hamstrings co-contraction was measured. Fifteen subjects returned 1year following knee arthroplasty. Moments and impulses were calculated, principal component analysis was used to analyse the waveforms and a classification technique (the Cardiff Classifier) was used to select the most discriminant data and define functional performance. Comparing pre-operative function to healthy function, classification accuracies for the affected and unaffected knees were 95% and 92.5% respectively. Post-operatively, the affected limb returned to the normal half of the classifier in 8 patients, and 7 of those patients returned to normal function in the unaffected limb. Recovery of normal gait could be correctly predicted 13 out of 15 times at the affected knee, and 12 out of 15 times at the unaffected knee based on pre-operative gait function. Focused rehabilitation prior to surgery may be beneficial to optimise outcomes and protect the other joints following knee arthroplasty.


Assuntos
Artroplastia do Joelho , Marcha/fisiologia , Articulação do Joelho/fisiopatologia , Osteoartrite do Joelho/fisiopatologia , Suporte de Carga/fisiologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Estudos de Casos e Controles , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Osteoartrite do Joelho/cirurgia , Período Pós-Operatório , Análise de Componente Principal , Músculo Quadríceps/fisiopatologia , Adulto Jovem
6.
J Dent Res ; 95(9): 969-76, 2016 08.
Artigo em Inglês | MEDLINE | ID: mdl-27183895

RESUMO

Antibiotic resistance is considered one of the greatest threats to global public health. Resistance is often conferred by the presence of antibiotic resistance genes (ARGs), which are readily found in the oral microbiome. In-depth genetic analyses of the oral microbiome through metagenomic techniques reveal a broad distribution of ARGs (including novel ARGs) in individuals not recently exposed to antibiotics, including humans in isolated indigenous populations. This has resulted in a paradigm shift from focusing on the carriage of antibiotic resistance in pathogenic bacteria to a broader concept of an oral resistome, which includes all resistance genes in the microbiome. Metagenomics is beginning to demonstrate the role of the oral resistome and horizontal gene transfer within and between commensals in the absence of selective pressure, such as an antibiotic. At the chairside, metagenomic data reinforce our need to adhere to current antibiotic guidelines to minimize the spread of resistance, as such data reveal the extent of ARGs without exposure to antimicrobials and the ecologic changes created in the oral microbiome by even a single dose of antibiotics. The aim of this review is to discuss the role of metagenomics in the investigation of the oral resistome, including the transmission of antibiotic resistance in the oral microbiome. Future perspectives, including clinical implications of the findings from metagenomic investigations of oral ARGs, are also considered.


Assuntos
Antibacterianos/farmacologia , Farmacorresistência Bacteriana/genética , Transferência Genética Horizontal/genética , Metagenômica , Microbiota/efeitos dos fármacos , Boca/microbiologia , Genes Bacterianos/genética , Humanos , Microbiota/genética
8.
Nature ; 522(7555): 197-201, 2015 Jun 11.
Artigo em Inglês | MEDLINE | ID: mdl-26062511

RESUMO

Our current understanding of ocean-atmosphere-cryosphere interactions at ice-age terminations relies largely on assessments of the most recent (last) glacial-interglacial transition, Termination I (T-I). But the extent to which T-I is representative of previous terminations remains unclear. Testing the consistency of termination processes requires comparison of time series of critical climate parameters with detailed absolute and relative age control. However, such age control has been lacking for even the penultimate glacial termination (T-II), which culminated in a sea-level highstand during the last interglacial period that was several metres above present. Here we show that Heinrich Stadial 11 (HS11), a prominent North Atlantic cold episode, occurred between 135 ± 1 and 130 ± 2 thousand years ago and was linked with rapid sea-level rise during T-II. Our conclusions are based on new and existing data for T-II and the last interglacial that we collate onto a single, radiometrically constrained chronology. The HS11 cold episode punctuated T-II and coincided directly with a major deglacial meltwater pulse, which predominantly entered the North Atlantic Ocean and accounted for about 70 per cent of the glacial-interglacial sea-level rise. We conclude that, possibly in response to stronger insolation and CO2 forcing earlier in T-II, the relationship between climate and ice-volume changes differed fundamentally from that of T-I. In T-I, the major sea-level rise clearly post-dates Heinrich Stadial 1. We also find that HS11 coincided with sustained Antarctic warming, probably through a bipolar seesaw temperature response, and propose that this heat gain at high southern latitudes promoted Antarctic ice-sheet melting that fuelled the last interglacial sea-level peak.


Assuntos
Camada de Gelo , Água do Mar/análise , Regiões Antárticas , Organismos Aquáticos/metabolismo , Oceano Atlântico , Clima , Foraminíferos/metabolismo , História Antiga , Região do Mediterrâneo , Mar Mediterrâneo , Plâncton/metabolismo , Temperatura
9.
Artigo em Inglês | MEDLINE | ID: mdl-25819741

RESUMO

Noradrenaline (NA) is the active component of novel antifouling agents and acts by preventing attachment of fouling organisms. The goal of this study was to examine the toxicity of NA to the non-target zooplankton D. magna and C. dubia. Neonates were exposed to one of five concentrations of NA and effects on survival, reproduction and molting were determined. Calculated LC50 values were determined to be 46 and 38 µM in C. dubia and D. magna, respectively. A 10-day C. dubia study found that reproduction metrics were significantly impacted at non-lethal concentrations. In D. magna, concentrations greater than 40 µM significantly impacted molting. A toxicity test was conducted with D. magna using oxidized NA, which yielded similar results. These data indicate that both NA and oxidized NA are toxic to non-target zooplankton. Results obtained from this study can be used to guide future ecological risk assessments of catecholamine-based antifouling agents.


Assuntos
Cladóceros/efeitos dos fármacos , Muda/efeitos dos fármacos , Norepinefrina/toxicidade , Praguicidas/toxicidade , Reprodução Assexuada/efeitos dos fármacos , Poluentes Químicos da Água/toxicidade , Zooplâncton/efeitos dos fármacos , Animais , Cladóceros/crescimento & desenvolvimento , Cladóceros/fisiologia , Daphnia/efeitos dos fármacos , Daphnia/crescimento & desenvolvimento , Daphnia/fisiologia , Resistência a Medicamentos , Feminino , Dose Letal Mediana , Masculino , Norepinefrina/química , Concentração Osmolar , Oxirredução , Praguicidas/química , Especificidade da Espécie , Testes de Toxicidade Aguda , Testes de Toxicidade Crônica , Poluentes Químicos da Água/química , Zooplâncton/crescimento & desenvolvimento , Zooplâncton/fisiologia
10.
Chemosphere ; 120: 206-10, 2015 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-25062026

RESUMO

Titanium dioxide nanoparticles (TiO2 NP) are one of the most abundantly utilized nanoparticles in the world. Studies have demonstrated the ability of the anatase crystal of TiO2 NP to produce reactive oxygen species (ROS) in the presence of ultraviolet radiation (UVR), a co-exposure likely to occur in aquatic ecosystems. The goal of this study was to examine the photo-induced toxicity of anatase TiO2 NP under natural sunlight to Daphnia magna. D. magna were exposed to a range of UVR intensities and anatase TiO2 concentrations in an outdoor exposure system using the sun as the source of UVR. Different UVR intensities were achieved using UVR opaque and transparent plastics. AnataseTiO2-NP demonstrated the reciprocal relationship seen in other phototoxic compounds such as polycyclic aromatic hydrocarbons (PAHs) at higher UVR treatments. The calculated 8h LC50 of anatase TiO2 NP was 139 ppb under full intensity ambient natural sunlight, 778 ppb under 50% natural sunlight, and >500 ppm under 10% natural sunlight. Mortality was also compared between animals allowed to accumulate a body burden of anatase TiO2 for 1h and organisms whose first exposure to anatase TiO2 aqueous suspensions occurred under UVR. A significantly greater toxic effect was observed in aqueous, low body burden suspensions than that of TiO2 1h body burdens, which is dissimilar from the model presented in PAHs. Anatase TiO2 presents a unique photo-induced toxic model that is different than that of established phototoxic compounds.


Assuntos
Daphnia/efeitos dos fármacos , Nanopartículas Metálicas/toxicidade , Luz Solar , Titânio/toxicidade , Poluentes Químicos da Água/toxicidade , Animais
12.
Nat Commun ; 5: 5076, 2014 Sep 25.
Artigo em Inglês | MEDLINE | ID: mdl-25254503

RESUMO

Research on global ice-volume changes during Pleistocene glacial cycles is hindered by a lack of detailed sea-level records for time intervals older than the last interglacial. Here we present the first robustly dated, continuous and highly resolved records of Red Sea sea level and rates of sea-level change over the last 500,000 years, based on tight synchronization to an Asian monsoon record. We observe maximum 'natural' (pre-anthropogenic forcing) sea-level rise rates below 2 m per century following periods with up to twice present-day ice volumes, and substantially higher rise rates for greater ice volumes. We also find that maximum sea-level rise rates were attained within 2 kyr of the onset of deglaciations, for 85% of such events. Finally, multivariate regressions of orbital parameters, sea-level and monsoon records suggest that major meltwater pulses account for millennial-scale variability and insolation-lagged responses in Asian monsoon records.

13.
Nature ; 508(7497): 477-82, 2014 Apr 24.
Artigo em Inglês | MEDLINE | ID: mdl-24739960

RESUMO

Ice volume (and hence sea level) and deep-sea temperature are key measures of global climate change. Sea level has been documented using several independent methods over the past 0.5 million years (Myr). Older periods, however, lack such independent validation; all existing records are related to deep-sea oxygen isotope (δ(18)O) data that are influenced by processes unrelated to sea level. For deep-sea temperature, only one continuous high-resolution (Mg/Ca-based) record exists, with related sea-level estimates, spanning the past 1.5 Myr. Here we present a novel sea-level reconstruction, with associated estimates of deep-sea temperature, which independently validates the previous 0-1.5 Myr reconstruction and extends it back to 5.3 Myr ago. We find that deep-sea temperature and sea level generally decreased through time, but distinctly out of synchrony, which is remarkable given the importance of ice-albedo feedbacks on the radiative forcing of climate. In particular, we observe a large temporal offset during the onset of Plio-Pleistocene ice ages, between a marked cooling step at 2.73 Myr ago and the first major glaciation at 2.15 Myr ago. Last, we tentatively infer that ice sheets may have grown largest during glacials with more modest reductions in deep-sea temperature.


Assuntos
Água do Mar/análise , Temperatura , Foraminíferos , História Antiga , Camada de Gelo , Mar Mediterrâneo , Isótopos de Oxigênio , Reprodutibilidade dos Testes , Fatores de Tempo
14.
J Antimicrob Chemother ; 69(2): 343-8, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-24092655

RESUMO

OBJECTIVES: Large amounts of biocides are used to reduce and control bacterial growth in the healthcare sector, food production and agriculture. This work explores the effect of subinhibitory concentrations of four commonly used biocides (ethanol, hydrogen peroxide, chlorhexidine digluconate and sodium hypochlorite) on the conjugative transposition of the mobile genetic element Tn916. METHODS: Conjugation assays were carried out between Bacillus subtilis strains. The donor containing Tn916 was pre-exposed to subinhibitory concentrations of each biocide for a defined length of time, which was determined by an analysis of the transcriptional response of the promoter upstream of tet(M) using ß-glucuronidase reporter assays. RESULTS: Ethanol significantly (P = 0.01) increased the transfer of Tn916 by 5-fold, whereas hydrogen peroxide, chlorhexidine digluconate and sodium hypochlorite did not significantly affect the transfer frequency. CONCLUSIONS: These results suggest that exposure to subinhibitory concentrations of ethanol may induce the transfer of Tn916-like elements and any resistance genes they contain.


Assuntos
Bacillus subtilis/efeitos dos fármacos , Bacillus subtilis/genética , Conjugação Genética/efeitos dos fármacos , Conjugação Genética/genética , Desinfetantes/administração & dosagem , Humanos , Testes de Sensibilidade Microbiana/métodos , Resultado do Tratamento
15.
Bone Joint J ; 95-B(3): 348-53, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23450019

RESUMO

The aim of this study was to examine the loading of the other joints of the lower limb in patients with unilateral osteoarthritis (OA) of the knee. We recruited 20 patients with no other symptoms or deformity in the lower limbs from a consecutive cohort of patients awaiting knee replacement. Gait analysis and electromyographic recordings were performed to determine moments at both knees and hips, and contraction patterns in the medial and lateral quadriceps and hamstrings bilaterally. The speed of gait was reduced in the group with OA compared with the controls, but there were only minor differences in stance times between the limbs. Patients with OA of the knee had significant increases in adduction moment impulse at both knees and the contralateral hip (adjusted p-values: affected knee: p < 0.01, unaffected knee p = 0.048, contralateral hip p = 0.03), and significantly increased muscular co-contraction bilaterally compared with controls (all comparisons for co-contraction, p < 0.01). The other major weight-bearing joints are at risk from abnormal biomechanics in patients with unilateral OA of the knee.


Assuntos
Articulação do Quadril/fisiopatologia , Articulação do Joelho/fisiopatologia , Osteoartrite do Joelho/fisiopatologia , Adulto , Idoso , Idoso de 80 Anos ou mais , Fenômenos Biomecânicos , Estudos de Casos e Controles , Estudos de Coortes , Eletromiografia , Feminino , Marcha/fisiologia , Humanos , Masculino , Pessoa de Meia-Idade , Músculo Quadríceps/fisiopatologia , Análise de Regressão , Suporte de Carga
16.
Nature ; 491(7426): 744-7, 2012 Nov 29.
Artigo em Inglês | MEDLINE | ID: mdl-23151478

RESUMO

Current global warming necessitates a detailed understanding of the relationships between climate and global ice volume. Highly resolved and continuous sea-level records are essential for quantifying ice-volume changes. However, an unbiased study of the timing of past ice-volume changes, relative to polar climate change, has so far been impossible because available sea-level records either were dated by using orbital tuning or ice-core timescales, or were discontinuous in time. Here we present an independent dating of a continuous, high-resolution sea-level record in millennial-scale detail throughout the past 150,000 years. We find that the timing of ice-volume fluctuations agrees well with that of variations in Antarctic climate and especially Greenland climate. Amplitudes of ice-volume fluctuations more closely match Antarctic (rather than Greenland) climate changes. Polar climate and ice-volume changes, and their rates of change, are found to covary within centennial response times. Finally, rates of sea-level rise reached at least 1.2 m per century during all major episodes of ice-volume reduction.


Assuntos
Mudança Climática/história , Clima , Camada de Gelo , Temperatura , Animais , Regiões Antárticas , Antozoários , Mudança Climática/estatística & dados numéricos , Retroalimentação , Foraminíferos/isolamento & purificação , Sedimentos Geológicos/análise , Groenlândia , História Antiga , Camada de Gelo/química , Oceano Índico , Mar Mediterrâneo , Plâncton/isolamento & purificação , Água do Mar/análise , Água do Mar/química , Fatores de Tempo
17.
Diabet Med ; 29(6): 716-20, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22150786

RESUMO

AIMS: The efficacy and safety of insulin degludec (degludec), a new-generation ultra-long-acting basal insulin, was compared with insulin glargine (glargine) in people with Type 1 diabetes mellitus in a 16-week, open-label, randomized trial. Health status, an important aspect of effective diabetes management, was also assessed. METHODS: Degludec (n = 59) or glargine (n = 59) were injected once daily, with insulin aspart at mealtimes. Health status assessment utilized the validated Short Form 36 Health Survey, version 2, which has two summary component scores for mental and physical well-being, each comprising four domains. RESULTS: At study end, HbA(1c) reductions were comparable between groups, but confirmed nocturnal hypoglycaemia was significantly less frequent with degludec [relative rate 0.42 (95% CI 0.25-0.69)], and overall hypoglycaemia numerically less frequent [relative rate 0.72 (95% CI 0.52-1.00)]. After 16 weeks, a significant improvement in Short Form 36 Health Survey mental component score of +3.01 (95% CI 0.32-5.70) was obtained for degludec against glargine, attributable to significant differences in the social functioning [+8.04 (95% CI 1.89-14.18)] and mental health domains [+2.46 (95% CI 0.10-4.82)]. For mental component score, Cohen's effect size was 0.42, indicating a small-to-medium clinically meaningful difference. The physical component score [+0.66 (95% CI -2.30 to 3.62)] and remaining domains were not significantly different between degludec and glargine. CONCLUSIONS: In the context of comparable overall glycaemic control with glargine, degludec improved mental well-being as measured using the mental component score of the Short Form 36 Health Survey. The improvements in overall mental component score and the underlying social functioning and mental health domains with degludec compared with glargine may relate to the observed reduction in hypoglycaemic events.


Assuntos
Glicemia/efeitos dos fármacos , Diabetes Mellitus Tipo 1/tratamento farmacológico , Hemoglobina A Glicada/metabolismo , Hipoglicemiantes/administração & dosagem , Insulina de Ação Prolongada/administração & dosagem , Adolescente , Adulto , Idoso , Glicemia/metabolismo , Diabetes Mellitus Tipo 1/sangue , Esquema de Medicação , Feminino , Hemoglobina A Glicada/efeitos dos fármacos , Inquéritos Epidemiológicos , Humanos , Injeções Subcutâneas , Insulina Glargina , Masculino , Pessoa de Meia-Idade , Qualidade de Vida , Inquéritos e Questionários , Resultado do Tratamento , Adulto Jovem
19.
Phys Rev E Stat Nonlin Soft Matter Phys ; 79(3 Pt 1): 031111, 2009 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-19391906

RESUMO

The probability that a random walker returns to its origin for large times scales as t;{-d[over ]2} , where d[over ] is the spectral dimension. We calculate d[over ] for a class of tree structures using a renormalization technique on an infinite continued fraction. We consider a wide range of homogeneous networks based on replacing the branches of a self-similar tree with arbitrary fractals and composite fractals. We also consider a new class of inhomogeneous hyperbranched trees.

20.
Int J Antimicrob Agents ; 33(4): 364-7, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19097761

RESUMO

Pneumococcal resistance to tetracycline, chloramphenicol, erythromycin and clindamycin is often attributed to carriage of conjugative transposons of the Tn916 family. The less well studied conjugative transposon Tn5253 is a composite transposon consisting of a Tn916-like element inserted within the unrelated Tn5252 element, which has also been associated with chloramphenicol and tetracycline resistance. Here, carriage of the Tn5252 integrase (int(5252)), Tn5252-encoded umuC and umuD homologues and Tn916 integrase (int(916)) was examined among 55 clinical isolates of Streptococcus pneumoniae resistant to one or more of the above mentioned antibiotics. Tn5253-associated genes were common among the antibiotic-resistant S. pneumoniae examined, including members of international clones, although the spectrum of genes and resistances carried was diverse. Analysis of five isolates demonstrated insertion of a Tn5253-related element at the same chromosomal locus but sequence and restriction site diversity. This study shows for the first time a high degree of variability of Tn5253-related elements within clinical isolates of pneumococci. The fact that these elements are prevalent among internationally recognised pandemic clones warrants a more intensive investigation.


Assuntos
Elementos de DNA Transponíveis , DNA Bacteriano/genética , Polimorfismo Genético , Streptococcus pneumoniae/genética , Antibacterianos/farmacologia , DNA Bacteriano/química , Farmacorresistência Bacteriana , Ordem dos Genes , Genes Bacterianos , Integrases/genética , Dados de Sequência Molecular , Análise de Sequência de DNA , Streptococcus pneumoniae/efeitos dos fármacos
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