This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library.

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library.

This music score was submitted for the Kaleidoscope 2020 Call for Scores, an open access collaboration with the UCLA Music Library.

Background

Whether or not animals habituate to repeated exposure to predator scents may depend upon whether there are predators associated with the cues. Understanding the contexts of habituation is theoretically important and has profound implication for the application of predator-based herbivore deterrents. We repeatedly exposed a mixed mob of macropod marsupials to olfactory scents (urine, feces) from a sympatric predator (Canis lupus dingo), along with a control (water). If these predator cues were alarming, we expected that over time, some red kangaroos (Macropus rufous), western grey kangaroos (Macropus fuliginosus) and agile wallabies (Macropus agilis) would elect to not participate in cafeteria trials because the scents provided information about the riskiness of the area.

Methodology/principal findings

We evaluated the effects of urine and feces independently and expected that urine would elicit a stronger reaction because it contains a broader class of infochemicals (pheromones, kairomones). Finally, we scored non-invasive indicators (flight and alarm stomps) to determine whether fear or altered palatability was responsible for the response. Repeated exposure reduced macropodid foraging on food associated with 40 ml of dingo urine, X = 986.75+/-3.97 g food remained as compared to the tap water control, X = 209.0+/-107.0 g (P<0.001). Macropodids fled more when encountering a urine treatment, X = 4.50+/-2.08 flights, as compared to the control, X = 0 flights (P<0.001). There was no difference in effect between urine or feces treatments (P>0.5). Macropodids did not habituate to repeated exposure to predator scents, rather they avoided the entire experimental area after 10 days of trials (R(2) = 83.8; P<0.001).

Conclusions/significance

Responses to urine and feces were indistinguishable; both elicited fear-based responses and deterred foraging. Despite repeated exposure to predator-related cues in the absence of a predator, macropodids persistently avoided an area of highly palatable food. Area avoidance is consistent with that observed from other species following repeated anti-predator conditioning, However, this is the first time this response has been experimentally observed among medium or large vertebrates - where a local response is observed spatially and an area effect is revealed over time.

The daunting complexity of ecosystems has led ecologists to use mathematical modelling to gain understanding of ecological relationships, processes and dynamics. In pursuit of mathematical tractability, these models use simplified descriptions of key patterns, processes and relationships observed in nature. In contrast, ecological data are often complex, scale-dependent, space-time correlated, and governed by nonlinear relations between organisms and their environment. This disparity in complexity between ecosystem models and data has created a large gap in ecology between model and data-driven approaches. Here, we explore data assimilation (DA) with the Ensemble Kalman filter to fuse a two-predator-two-prey model with abundance data from a 2600+ day experiment of a plankton community. We analyse how frequently we must assimilate measured abundances to predict accurately population dynamics, and benchmark our population model's forecast horizon against a simple null model. Results demonstrate that DA enhances the predictability and forecast horizon of complex community dynamics.

Background

Drivers of differences in Clostridium difficile incidence across acute and long-term care facilities are poorly understood. We sought to obtain a comprehensive picture of C. difficile incidence and risk factors in acute and long-term care.

Methods

We conducted a case-cohort study of persons spending at least 3 days in one of 131 acute care or 120 long-term care facilities managed by the United States Veterans Health Administration between 2006 and 2012. Patient (n = 8) and facility factors (n = 5) were included in analyses. The outcome was the incidence of facility-onset laboratory-identified C. difficile infection (CDI), defined as a person with a positive C. difficile test without a positive test in the prior 8 weeks.

Results

CDI incidence in acute care was 5 times that observed in long-term care (median, 15.6 vs 3.2 per 10000 person-days). History of antibiotic use was greater in acute care compared to long-term care (median, 739 vs 513 per 1000 person-days) and explained 72% of the variation in C. difficile rates. Importation of C. difficile cases (acute care: patients with recent long-term care attributable infection; long-term care: residents with recent acute care attributable infection) was 3 times higher in long-term care as compared to acute care (median, 52.3 vs 16.2 per 10000 person-days).

Conclusions

Facility-level antibiotic use was the main factor driving differences in CDI incidence between acute and long-term care. Importation of acute care C. difficile cases was a greater concern for long-term care as compared to importation of long-term care cases for acute care.

Background

Although clinical factors affecting a person's susceptibility to Clostridium difficile infection are well-understood, little is known about what drives differences in incidence across long-term care settings.

Objective

To obtain a comprehensive picture of individual and regional factors that affect C difficile incidence.

Design

Multilevel longitudinal nested case-control study.

Setting

Veterans Health Administration health care regions, from 2006 through 2012.

Participants

Long-term care residents.

Measurements

Individual-level risk factors included age, number of comorbid conditions, and antibiotic exposure. Regional risk factors included importation of cases of acute care C difficile infection per 10 000 resident-days and antibiotic use per 1000 resident-days. The outcome was defined as a positive result on a long-term care C difficile test without a positive result in the prior 8 weeks.

Results

6012 cases (incidence, 3.7 cases per 10 000 resident-days) were identified in 86 regions. Long-term care C difficile incidence (minimum, 0.6 case per 10 000 resident-days; maximum, 31.0 cases per 10 000 resident-days), antibiotic use (minimum, 61.0 days with therapy per 1000 resident-days; maximum, 370.2 days with therapy per 1000 resident-days), and importation (minimum, 2.9 cases per 10 000 resident-days; maximum, 341.3 cases per 10 000 resident-days) varied substantially across regions. Together, antibiotic use and importation accounted for 75% of the regional variation in C difficile incidence (R2 = 0.75). Multilevel analyses showed that regional factors affected risk together with individual-level exposures (relative risk of regional antibiotic use, 1.36 per doubling [95% CI, 1.15 to 1.60]; relative risk of importation, 1.23 per doubling [CI, 1.14 to 1.33]).

Limitations

Case identification was based on laboratory criteria. Admission of residents with recent C difficile infection from non-Veterans Health Administration acute care sources was not considered.

Conclusion

Only 25% of the variation in regional C difficile incidence in long-term care remained unexplained after importation from acute care facilities and antibiotic use were accounted for, which suggests that improved infection control and antimicrobial stewardship may help reduce the incidence of C difficile in long-term care settings.

Primary funding source

U.S. Department of Veterans Affairs and Centers for Disease Control and Prevention.

From micro to planetary scales, spatial heterogeneity-patchiness-is ubiquitous in ecosystems, defining the environments in which organisms move and interact. However, most large-scale models still use spatially averaged 'mean fields' to represent natural populations, while fine-scale spatially explicit models are mostly restricted to particular organisms or systems. In a conceptual paper, Grünbaum (2012, Interface Focus 2: 150-155) introduced a heuristic, based on three dimensionless ratios quantifying movement, reproduction and resource consumption, to characterise patchy ecological interactions and identify when mean-field assumptions are justifiable. We calculated these dimensionless numbers for 33 interactions between consumers and their resource patches in terrestrial, aquatic and aerial environments. Consumers ranged in size from bacteria to whales, and patches lasted from minutes to millennia, with separation scales from mm to hundreds of km. No interactions could be accurately represented by naive mean-field models, though 19 (58%) could be partially simplified by averaging out movement, reproductive or consumption dynamics. Clustering interactions by their non-dimensional ratios revealed several unexpected dynamic similarities. For example, bacterial Pseudoalteromonas exploit nutrient plumes similarly to Mongolian gazelles grazing on ephemeral steppe vegetation. We argue that dimensional analysis is valuable for characterising ecological patchiness and can link widely different systems into a single quantitative framework.

Collective cell behavior contributes to all stages of cancer progression. Understanding how collective behavior emerges through cell-cell interactions and decision-making will advance our understanding of cancer biology and provide new therapeutic approaches. Here, we summarize an interdisciplinary discussion on multicellular behavior in cancer, draw lessons from other scientific disciplines, and identify future directions.