Evaluation of clinicians' knowledge and use of minimum inhibitory concentration values.

Routinely reporting minimum inhibitory concentration (MIC) values to clinicians remains controversial. We surveyed clinicians to assess their knowledge and usage of MIC in clinical scenarios. The majority of respondents used MIC values to select antibiotic therapy, with a tendency to use those antibiotics with lower MICs, regardless of clinical appropriateness.

Tree diversity effects through a temporal lens: Implications for the abundance, diversity and stability of foraging birds.

Tree diversity exerts a strong influence on consumer communities, but most work has involved single time point measurements over short time periods. Describing temporal variation associated with diversity effects over longer time periods is necessary to fully understand the effects of tree diversity on ecological function. We conducted a year-long study in an experimental system in southern Mexico assessing the effects of tree diversity on the abundance and diversity of foraging birds. To this end, we recorded bird visitation patterns in 32 tree plots (21 × 21 m; 12 tree species monocultures, 20 four-species polycultures) every 45 days (n = 8 surveys) and for each plot estimated bird abundance, richness, functional diversity (FD) and phylogenetic diversity (PD). In each case, we reported temporal (intra-annual) variation in the magnitude of tree diversity effects, and calculated the temporal stability of these bird responses. Across surveys, tree diversity noticeably affected bird responses, demonstrated by significantly higher abundance (43%), richness (32%), PD (25%) and FD (25%) of birds visiting polyculture plots compared to monoculture plots, as well as a distinct species composition between plot types. We also found intra-annual variation in tree diversity effects on these response variables, ranging from surveys for which the diversity effect was not significant to surveys where a significant 80% increase (e.g. for bird FD and PD) was observed in polyculture relative to monoculture plots. Notably, tree diversity increased the stability of all bird responses, with polycultures having a greater stability abundance (18%), richness (38%), PD (32%), and FD (35%) of birds visiting tree species polycultures compared to monocultures. These results show that tree diversity not only increases bird visitation to plots, but also stabilizes bird habitat usage over time in ways that could implicate insurance-related mechanisms. Such findings are highly relevant for understanding the long-term effects of plant diversity on vertebrates and the persistence of bird-related ecosystem functions. More work is needed to unveil the ecological mechanisms behind temporal variation in vertebrate responses to tree diversity and their consequences for community structure and function.

Tropical tree diversity mediates foraging and predatory effects of insectivorous birds.

Biodiversity affects the structure of ecological communities, but little is known about the interactive effects of diversity across multiple trophic levels. We used a large-scale forest diversity experiment to investigate the effects of tropical tree species richness on insectivorous birds, and the subsequent indirect effect on predation rates by birds. Diverse plots (four tree species) had higher bird abundance (61%), phylogenetic diversity (61%), and functional diversity (55%) than predicted based on single-species monocultures, which corresponded to higher attack rates on artificial caterpillars (65%). Tree diversity effects on attack rate were driven by complementarity among tree species, with increases in attack rate observed on all tree species in polycultures. Attack rates on artificial caterpillars were higher in plots with higher bird abundance and diversity, but the indirect effect of tree species richness was mediated by bird diversity, providing evidence that diversity can interact across trophic levels with consequences tied to ecosystem services and function.

Population Genomics of Reduced Vancomycin Susceptibility in Staphylococcus aureus.

The increased prevalence of vancomycin-intermediate Staphylococcus aureus (VISA) is an emerging health care threat. Genome-based comparative methods hold great promise to uncover the genetic basis of the VISA phenotype, which remains obscure. S. aureus isolates were collected from a single individual that presented with recurrent staphylococcal bacteremia at three time points, and the isolates showed successively reduced levels of vancomycin susceptibility. A population genomic approach was taken to compare patient S. aureus isolates with decreasing vancomycin susceptibility across the three time points. To do this, patient isolates were sequenced to high coverage (~500×), and sequence reads were used to model site-specific allelic variation within and between isolate populations. Population genetic methods were then applied to evaluate the overall levels of variation across the three time points and to identify individual variants that show anomalous levels of allelic change between populations. A successive reduction in the overall levels of population genomic variation was observed across the three time points, consistent with a population bottleneck resulting from antibiotic treatment. Despite this overall reduction in variation, a number of individual mutations were swept to high frequency in the VISA population. These mutations were implicated as potentially involved in the VISA phenotype and interrogated with respect to their functional roles. This approach allowed us to identify a number of mutations previously implicated in VISA along with allelic changes within a novel class of genes, encoding LPXTG motif-containing cell-wall-anchoring proteins, which shed light on a novel mechanistic aspect of vancomycin resistance. IMPORTANCE The emergence and spread of antibiotic resistance among bacterial pathogens are two of the gravest threats to public health facing the world today. We report the development and application of a novel population genomic technique aimed at uncovering the evolutionary dynamics and genetic determinants of antibiotic resistance in Staphylococcus aureus. This method was applied to S. aureus cultures isolated from a single patient who showed decreased susceptibility to the vancomycin antibiotic over time. Our approach relies on the increased resolution afforded by next-generation genome-sequencing technology, and it allowed us to discover a number of S. aureus mutations, in both known and novel gene targets, which appear to have evolved under adaptive pressure to evade vancomycin mechanisms of action. The approach we lay out in this work can be applied to resistance to any number of antibiotics across numerous species of bacterial pathogens.

Dysregulated coagulation associated with hypofibrinogenaemia and plasma hypercoagulability: implications for identifying coagulopathic mechanisms in humans.

Identifying coagulation abnormalities in patients with combined bleeding and thrombosis history is clinically challenging. Our goal was to probe the complexity of dysregulated coagulation in humans by characterizing pathophysiologic mechanisms in a patient with both bleeding and thrombosis. The patient is a 56-year-old female with a history of haematomas, poor wound healing, and thrombosis (retinal artery occlusion and transient cerebral ischaemia). She had a normal activated partial thromboplastin time, prolonged thrombin and reptilase times, and decreased functional and antigenic fibrinogen levels, and was initially diagnosed with hypodysfibrinogenaemia. This diagnosis was supported by DNA analysis revealing a novel FGB mutation (c.656A>G) predicting a Q189R mutation in the mature chain that was present in the heterozygote state. However, turbidity analysis showed that purified fibrinogen polymerisation and degradation were indistinguishable from normal, and Bß chain subpopulations appeared normal by two-dimensional difference in-gel electrophoresis, indicating the mutated chain was not secreted. Interestingly, plasma thrombin generation testing revealed the patient's thrombin generation was higher than normal and could be attributed to elevated levels of factor VIII (FVIII, 163-225%). Accordingly, in an arterial injury model, hypofibrinogenaemic mice (Fgn(+/-)) infused with factor VIII demonstrated significantly shorter vessel occlusion times than saline-infused Fgn(+/-) mice. Together, these data associate the complex bleeding and thrombotic presentation with combined hypofibrinogenaemia plus plasma hypercoagulability. These findings suggest previous cases in which fibrinogen abnormalities have been associated with thrombosis may also be complicated by co-existing plasma hypercoagulability and illustrate the importance of "global" coagulation testing in patients with compound presentations.

Camina por Salud: walking in Mexican-American women.

Forty-six percent of older Mexican-American women report that they do not engage in leisure time physical activity (PA); 38.1% of them are obese. This study (1) evaluated a PA intervention for coronary heart disease risk reduction and (2) determined which variables affect adherence to PA. For 36 weeks, Group I members walked for 3 days a week and Group II members walked for 5 days a week. We measured the participants' total body fat, regional fat, blood lipids, and adherence to PA The walking interventions favorably affected body fat, with significant differences in body mass index reduction, F(2, 16) = 12.86, p = .001. No statistical difference was noted in the anthropometric and blood lipid results between the baseline and 36-week measures.