Daptomycin eluted from calcium sulfate appears effective against Staphylococcus.

The emergence of resistant strains of Gram-positive organisms in osteomyelitis creates treatment challenges. Daptomycin is an antibiotic that shows promise for treating some resistant strains of Gram-positive infections; however, it has not been widely used clinically for the treatment of osteomyelitis. We determined whether daptomycin eluted from calcium sulfate-a local delivery vehicle used for the treatment of osteomyelitis-retained activity against Gram-positive bacteria. Daptomycin was mixed with calcium sulfate hemihydrate, with both laboratory powder and a commercial kit, to form a hardened pellet. Daptomycin was eluted from calcium sulfate and retained its ability to inhibit bacterial growth of Staphylococcus aureus and Staphylococcus epidermidis for eluates gathered up to 28 days. Our preliminary data demonstrates sterilized pellets with daptomycin retained their ability to inhibit bacterial growth of certain strains of Gram-positive organisms.

Arthrographic Anatomy of the Biceps Tendon Sheath: Potential Implications for Selective Injection.

The purpose of this investigation was to better define the anatomical features of the biceps tendon sheath, including the distance the sheath extends below the inferior margin of the subscapularis tendon and below the termination of the bony bicipital groove. A total of 110 magnetic resonance and computed tomography arthrograms performed during 1-year period at our institution were retrospectively reviewed, and the length of the biceps tendon sheath and distances from the inferior margin of the subscapularis tendon and from the termination of the bicipital groove to the inferior margin of the biceps tendon sheath were measured by 3 radiologists. The mean length of the biceps tendon sheath was 47.5mm. The mean distances from the inferior margin of the subscapularis tendon and from the inferior margin of the bicipital groove to the distal extent of the biceps tendon sheath were 24.5mm and 11.9mm, respectively. The relationships among these 3 anatomical measurements and biological confounders of sex and age were investigated while controlling for measurement variability. The anatomical relationships between the biceps tendon sheath and surrounding structures may have implications for needle placement when attempting to inject into the biceps tendon sheath for diagnostic or therapeutic purposes.

Can occupancy-abundance models be used to monitor wolf abundance?

Estimating the abundance of wild carnivores is of foremost importance for conservation and management. However, given their elusive habits, direct observations of these animals are difficult to obtain, so abundance is more commonly estimated from sign surveys or radio-marked individuals. These methods can be costly and difficult, particularly in large areas with heavy forest cover. As an alternative, recent research has suggested that wolf abundance can be estimated from occupancy-abundance curves derived from "virtual" surveys of simulated wolf track networks. Although potentially more cost-effective, the utility of this approach hinges on its robustness to violations of its assumptions. We assessed the sensitivity of the occupancy-abundance approach to four assumptions: variation in wolf movement rates, changes in pack cohesion, presence of lone wolves, and size of survey units. Our simulations showed that occupancy rates and wolf pack abundances were biased high if track surveys were conducted when wolves made long compared to short movements, wolf packs were moving as multiple hunting units as opposed to a cohesive pack, and lone wolves were moving throughout the surveyed landscape. We also found that larger survey units (400 and 576 km2) were more robust to changes in these factors than smaller survey units (36 and 144 km2). However, occupancy rates derived from large survey units rapidly reached an asymptote at 100% occupancy, suggesting that these large units are inappropriate for areas with moderate to high wolf densities (>15 wolves/1,000 km2). Virtually-derived occupancy-abundance relationships can be a useful method for monitoring wolves and other elusive wildlife if applied within certain constraints, in particular biological knowledge of the surveyed species needs to be incorporated into the design of the occupancy surveys. Further, we suggest that the applicability of this method could be extended by directly incorporating some of its assumptions into the modelling framework.

Prevalence of antibodies to canine parvovirus and distemper virus in wolves in the Canadian Rocky Mountains.

Wild carnivores are often exposed to diseases via contact with peridomestic host species that travel through the wildland-urban interfaces. To determine the antibody prevalences and relationships to human activity for two common canid pathogens, we sampled 99 wolves (Canis lupus) from 2000 to 2008 for antibodies to canine parvovirus (CPV) and canine distemper virus (CDV) in Banff and Jasper National Parks and surrounding areas of the Canadian Rockies. This population was the source for wolves reintroduced into the Northern Rockies of the US. Of 99 wolves sampled, 94 had detectable antibody to CPV (95%), 24 were antibody-positive for CDV (24%), and 24 had antibodies to both pathogens (24%). We tested whether antibody prevalences for CPV and CDV were higher closer to human activity (roads, town sites, First Nation reserves) and as a function of sex and age class. Wolves ≥2 yr old were more likely to be have antibodies to CPV. For CDV, male wolves, wolves ≥2 yr, and those closer to First Nation reserves were more likely to have antibodies. Overall, however, we found minimal support for human influence on antibody prevalence for CDV and CPV. The similarity between our antibody prevalence results and results from recent studies in Yellowstone National Park suggests that at least in the case of CDV, and perhaps CPV, these could be important pathogens with potential effects on wolf populations.

Building a mechanistic understanding of predation with GPS-based movement data.

Quantifying kill rates and sources of variation in kill rates remains an important challenge in linking predators to their prey. We address current approaches to using global positioning system (GPS)-based movement data for quantifying key predation components of large carnivores. We review approaches to identify kill sites from GPS movement data as a means to estimate kill rates and address advantages of using GPS-based data over past approaches. Despite considerable progress, modelling the probability that a cluster of GPS points is a kill site is no substitute for field visits, but can guide our field efforts. Once kill sites are identified, time spent at a kill site (handling time) and time between kills (killing time) can be determined. We show how statistical models can be used to investigate the influence of factors such as animal characteristics (e.g. age, sex, group size) and landscape features on either handling time or killing efficiency. If we know the prey densities along paths to a kill, we can quantify the 'attack success' parameter in functional response models directly. Problems remain in incorporating the behavioural complexity derived from GPS movement paths into functional response models, particularly in multi-prey systems, but we believe that exploring the details of GPS movement data has put us on the right path.

Elution behavior of daptomycin-loaded calcium sulfate pellets: a preliminary study.

Daptomycin is a new antibiotic active against many resistant Gram-positive organisms and seems an appropriate candidate for local delivery for severe musculoskeletal infections. Calcium sulfate dihydrate as a delivery vehicle is readily resorbable, allows new bone formation, and can be combined with therapeutic agents. We compared the elution of daptomycin and tobramycin in calcium sulfate pellets over time and determined the dissolution rates of the pellets. Unlike other water-soluble antibiotics, daptomycin required special techniques to convert the calcium sulfate from a hemihydrate powder to a hardened dihydrate shape. The elution of daptomycin on day 1 (537 microg/mL/g) was greater than that from days 2, 3, 7, 10, 14, 21, and 28. The concentration fell to 153 microg/mL/g and 37 microg/mL/g on days 2 and 3, respectively, then remained at between 5 microg/mL/g and 7 microg/mL/g for the remainder of the study. The elution behavior of the daptomycin pellets differed from that of the tobramycin-containing pellets on days 1 through 3, but was similar from day 7 through day 28. Daptomycin-containing pellets dissolved more rapidly in vitro than tobramycin-containing pellets, although the importance of this more rapid dissolution in an in vivo situation is unknown. Using the techniques described in this paper, daptomycin can be incorporated within a calcium sulfate matrix.