Background.Almost one-fifth of United States tuberculosis cases are extrapulmonary; unexplained slower annual case count decreases have occurred in extrapulmonary tuberculosis (EPTB), compared with ...annual case count decreases in pulmonary tuberculosis (PTB) cases. We describe the epidemiology of EPTB by means of US national tuberculosis surveillance data. Methods.US tuberculosis cases reported from 1993 to 2006 were classified as either EPTB or PTB. EPTB encompassed lymphatic, pleural, bone and/or joint, genitourinary, meningeal, peritoneal, and unclassified EPTB cases. We excluded cases with concurrent extrapulmonary-pulmonary tuberculosis and cases of disseminated (miliary) tuberculosis. Demographic characteristics, drug susceptibility test results, and risk factors, including human immunodeficiency virus (HIV) status, were compared for EPTB and PTB cases. Results.Among 253,299 cases, 73.6% were PTB and 18.7% were EPTB, including lymphatic (40.4%), pleural (19.8%), bone and/or joint (11.3%), genitourinary (6.5%), meningeal (5.4%), peritoneal (4.9%), and unclassified EPTB (11.8%) cases. Compared with PTB, EPTB was associated with female sex (odds ratio OR, 1.7; 95% confidence interval CI, 1.7–1.8) and foreign birth (OR, 1.5; CI, 1.5–1.6), almost equally associated with HIV status (OR, 1.1; CI, 1.1–1.1), and negatively associated with multidrug resistance (OR, 0.6; CI, 0.5–0.6) and several tuberculosis risk factors, especially homelessness (OR, 0.3; CI, 0.3–0.3) and excess alcohol use (OR, 0.3; CI, 0.3–0.3). Slower annual decreases in EPTB case counts, compared with annual decreases in PTB case counts, from 1993 through 2006 have caused EPTB to increase from 15.7% of tuberculosis cases in 1993 to 21.0% in 2006. Conclusions.EPTB epidemiology and risk factors differ from those of PTB, and the proportion of EPTB has increased from 1993 through 2006. Further study is needed to identify causes of the proportional increase in EPTB.
Staphylococcus aureus is a major cause of healthcare associated mortality, but like many important bacterial pathogens, it is a common constituent of the normal human body flora. Around a third of ...healthy adults are carriers. Recent evidence suggests that evolution of S. aureus during nasal carriage may be associated with progression to invasive disease. However, a more detailed understanding of within-host evolution under natural conditions is required to appreciate the evolutionary and mechanistic reasons why commensal bacteria such as S. aureus cause disease. Therefore we examined in detail the evolutionary dynamics of normal, asymptomatic carriage. Sequencing a total of 131 genomes across 13 singly colonized hosts using the Illumina platform, we investigated diversity, selection, population dynamics and transmission during the short-term evolution of S. aureus.
We characterized the processes by which the raw material for evolution is generated: micro-mutation (point mutation and small insertions/deletions), macro-mutation (large insertions/deletions) and the loss or acquisition of mobile elements (plasmids and bacteriophages). Through an analysis of synonymous, non-synonymous and intergenic mutations we discovered a fitness landscape dominated by purifying selection, with rare examples of adaptive change in genes encoding surface-anchored proteins and an enterotoxin. We found evidence for dramatic, hundred-fold fluctuations in the size of the within-host population over time, which we related to the cycle of colonization and clearance. Using a newly-developed population genetics approach to detect recent transmission among hosts, we revealed evidence for recent transmission between some of our subjects, including a husband and wife both carrying populations of methicillin-resistant S. aureus (MRSA).
This investigation begins to paint a picture of the within-host evolution of an important bacterial pathogen during its prevailing natural state, asymptomatic carriage. These results also have wider significance as a benchmark for future systematic studies of evolution during invasive S. aureus disease.
Approximately 30-40% of children <1 year of age are Clostridium difficile colonized, and may represent a reservoir for adult C. difficile infections (CDI). Risk factors for colonization with ...toxigenic versus non-toxigenic C. difficile strains and longitudinal acquisition dynamics in infants remain incompletely characterized.
Predominantly healthy infants (≤2 years) were recruited in Oxfordshire, UK, and provided ≥1 fecal samples. Independent risk factors for toxigenic/non-toxigenic C. difficile colonization and acquisition were identified using multivariable regression. Infant C. difficile isolates were whole-genome sequenced to assay genetic diversity and prevalence of toxin-associated genes, and compared with sequenced strains from Oxfordshire CDI cases.
338/365 enrolled infants provided 1332 fecal samples, representing 158 C. difficile colonization or carriage episodes (10768% toxigenic). Initial colonization was associated with age, and reduced with breastfeeding but increased with pet dogs. Acquisition was associated with older age, Caesarean delivery, and diarrhea. Breastfeeding and pre-existing C. difficile colonization reduced acquisition risk. Overall 13% of CDI C. difficile strains were genetically related to infant strains. 29(18%) infant C. difficile sequences were consistent with recent direct/indirect transmission to/from Oxfordshire CDI cases (≤2 single nucleotide variants SNVs); 79(50%) shared a common origin with an Oxfordshire CDI case within the last ~5 years (0-10 SNVs). The hypervirulent, epidemic ST1/ribotype 027 remained notably absent in infants in this large study, as did other lineages such as STs 10/44 (ribotype 015); the most common strain in infants was ST2 (ribotype 020/014)(22%).
In predominantly healthy infants without significant healthcare exposure C. difficile colonization and acquisition reflect environmental exposures, with pet dogs identified as a novel risk factor. Genetic overlap between some infant strains and those isolated from CDI cases suggest common community reservoirs of these C. difficile lineages, contrasting with those lineages found only in CDI cases, and therefore more consistent with healthcare-associated spread.
Horizontal gene transfer is an important driver of bacterial evolution, but genetic exchange in the core genome of clonal species, including the major pathogen Staphylococcus aureus, is incompletely ...understood. Here we reveal widespread homologous recombination in S. aureus at the species level, in contrast to its near-complete absence between closely related strains. We discover a patchwork of hotspots and coldspots at fine scales falling against a backdrop of broad-scale trends in rate variation. Over megabases, homoplasy rates fluctuate 1.9-fold, peaking towards the origin-of-replication. Over kilobases, we find core recombination hotspots of up to 2.5-fold enrichment situated near fault lines in the genome associated with mobile elements. The strongest hotspots include regions flanking conjugative transposon ICE6013, the staphylococcal cassette chromosome (SCC) and genomic island νSaα. Mobile element-driven core genome transfer represents an opportunity for adaptation and challenges our understanding of the recombination landscape in predominantly clonal pathogens, with important implications for genotype-phenotype mapping.
Whole-genome sequencing offers new insights into the evolution of bacterial pathogens and the etiology of bacterial disease. Staphylococcus aureus is a major cause of bacteria-associated mortality ...and invasive disease and is carried asymptomatically by 27% of adults. Eighty percent of bacteremias match the carried strain. However, the role of evolutionary change in the pathogen during the progression from carriage to disease is incompletely understood. Here we use high-throughput genome sequencing to discover the genetic changes that accompany the transition from nasal carriage to fatal bloodstream infection in an individual colonized with methicillin-sensitive S. aureus. We found a single, cohesive population exhibiting a repertoire of 30 single-nucleotide polymorphisms and four insertion/deletion variants. Mutations accumulated at a steady rate over a 13-mo period, except for a cluster of mutations preceding the transition to disease. Although bloodstream bacteria differed by just eight mutations from the original nasally carried bacteria, half of those mutations caused truncation of proteins, including a premature stop codon in an AraC-family transcriptional regulator that has been implicated in pathogenicity. Comparison with evolution in two asymptomatic carriers supported the conclusion that clusters of protein-truncating mutations are highly unusual. Our results demonstrate that bacterial diversity in vivo is limited but nonetheless detectable by whole-genome sequencing, enabling the study of evolutionary dynamics within the host. Regulatory or structural changes that occur during carriage may be functionally important for pathogenesis; therefore identifying those changes is a crucial step in understanding the biological causes of invasive bacterial disease.
Summary Background Low-dose aspirin is of definite and substantial net benefit for many people who already have occlusive vascular disease. We have assessed the benefits and risks in primary ...prevention. Methods We undertook meta-analyses of serious vascular events (myocardial infarction, stroke, or vascular death) and major bleeds in six primary prevention trials (95 000 individuals at low average risk, 660 000 person-years, 3554 serious vascular events) and 16 secondary prevention trials (17 000 individuals at high average risk, 43 000 person-years, 3306 serious vascular events) that compared long-term aspirin versus control. We report intention-to-treat analyses of first events during the scheduled treatment period. Findings In the primary prevention trials, aspirin allocation yielded a 12% proportional reduction in serious vascular events (0·51% aspirin vs 0·57% control per year, p=0·0001), due mainly to a reduction of about a fifth in non-fatal myocardial infarction (0·18% vs 0·23% per year, p<0·0001). The net effect on stroke was not significant (0·20% vs 0·21% per year, p=0·4: haemorrhagic stroke 0·04% vs 0·03%, p=0·05; other stroke 0·16% vs 0·18% per year, p=0·08). Vascular mortality did not differ significantly (0·19% vs 0·19% per year, p=0·7). Aspirin allocation increased major gastrointestinal and extracranial bleeds (0·10% vs 0·07% per year, p<0·0001), and the main risk factors for coronary disease were also risk factors for bleeding. In the secondary prevention trials, aspirin allocation yielded a greater absolute reduction in serious vascular events (6·7% vs 8·2% per year, p<0.0001), with a non-significant increase in haemorrhagic stroke but reductions of about a fifth in total stroke (2·08% vs 2·54% per year, p=0·002) and in coronary events (4·3% vs 5·3% per year, p<0·0001). In both primary and secondary prevention trials, the proportional reductions in the aggregate of all serious vascular events seemed similar for men and women. Interpretation In primary prevention without previous disease, aspirin is of uncertain net value as the reduction in occlusive events needs to be weighed against any increase in major bleeds. Further trials are in progress. Funding UK Medical Research Council, British Heart Foundation, Cancer Research UK, and the European Community Biomed Programme.
The current study has investigated the use of decellularised, demineralised bone extracellular matrix (ECM) hydrogel constructs for in vivo tissue mineralisation and bone formation. Stro-1-enriched ...human bone marrow stromal cells were incorporated together with select growth factors including VEGF, TGF-β3, BMP-2, PTHrP and VitD3, to augment bone formation, and mixed with alginate for structural support. Growth factors were delivered through fast (non-osteogenic factors) and slow (osteogenic factors) release PLGA microparticles. Constructs of 5 mm length were implanted in vivo for 28 days within mice. Dense tissue assessed by micro-CT correlated with histologically assessed mineralised bone formation in all constructs. Exogenous growth factor addition did not enhance bone formation further compared to alginate/bone ECM (ALG/ECM) hydrogels alone. UV irradiation reduced bone formation through degradation of intrinsic growth factors within the bone ECM component and possibly also ECM cross-linking. BMP-2 and VitD3 rescued osteogenic induction. ALG/ECM hydrogels appeared highly osteoinductive and delivery of angiogenic or chondrogenic growth factors led to altered bone formation. All constructs demonstrated extensive host tissue invasion and vascularisation aiding integration and implant longevity. The proposed hydrogel system functioned without the need for growth factor incorporation or an exogenous inducible cell source. Optimal growth factor concentrations and spatiotemporal release profiles require further assessment, as the bone ECM component may suffer batch variability between donor materials. In summary, ALG/ECM hydrogels provide a versatile biomaterial scaffold for utilisation within regenerative medicine which may be tailored, ultimately, to form the tissue of choice through incorporation of select growth factors.
Summary Background Lithium carbonate and valproate semisodium are both recommended as monotherapy for prevention of relapse in bipolar disorder, but are not individually fully effective in many ...patients. If combination therapy with both agents is better than monotherapy, many relapses and consequent disability could be avoided. We aimed to establish whether lithium plus valproate was better than monotherapy with either drug alone for relapse prevention in bipolar I disorder. Methods 330 patients aged 16 years and older with bipolar I disorder from 41 sites in the UK, France, USA, and Italy were randomly allocated to open-label lithium monotherapy (plasma concentration 0·4–1·0 mmol/L, n=110), valproate monotherapy (750–1250 mg, n=110), or both agents in combination (n=110), after an active run-in of 4–8 weeks on the combination. Randomisation was by computer program, and investigators and participants were informed of treatment allocation. All outcome events were considered by the trial management team, who were masked to treatment assignment. Participants were followed up for up to 24 months. The primary outcome was initiation of new intervention for an emergent mood episode, which was compared between groups by Cox regression. Analysis was by intention to treat. This study is registered, number ISRCTN 55261332. Findings 59 (54%) of 110 people in the combination therapy group, 65 (59%) of 110 in the lithium group, and 76 (69%) of 110 in the valproate group had a primary outcome event during follow-up. Hazard ratios for the primary outcome were 0·59 (95% CI 0·42–0·83, p=0·0023) for combination therapy versus valproate, 0·82 (0·58–1·17, p=0·27) for combination therapy versus lithium, and 0·71 (0·51–1·00, p=0·0472) for lithium versus valproate. 16 participants had serious adverse events after randomisation: seven receiving valproate monotherapy (three deaths); five lithium monotherapy (two deaths); and four combination therapy (one death). Interpretation For people with bipolar I disorder, for whom long-term therapy is clinically indicated, both combination therapy with lithium plus valproate and lithium monotherapy are more likely to prevent relapse than is valproate monotherapy. This benefit seems to be irrespective of baseline severity of illness and is maintained for up to 2 years. BALANCE could neither reliably confirm nor refute a benefit of combination therapy compared with lithium monotherapy. Funding Stanley Medical Research Institute; Sanofi-Aventis.
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