Kim Valenta

Hospital Ward Antibiotic Prescribing and the Risks of Clostridium difficile Infection

IMPORTANCE Only a portion of hospital-acquired Clostridium difficile infections can be traced back to source patients identified as having symptomatic disease. Antibiotic exposure is the main risk factor for C difficile infection for individual patients and is also associated with increased asymptomatic shedding. Contact with patients taking antibiotics within the same hospital ward may be a transmission risk factor for C difficile infection, but this hypothesis has never been tested. OBJECTIVES To obtain a complete portrait of inpatient risk that incorporates innate patient risk factors and transmission risk factors measured at the hospital ward level and to investigate ward-level rates of antibiotic use and C difficile infection risk. DESIGN, SETTING, AND PATIENTS A 46-month (June 1, 2010, through March 31, 2014) retrospective cohort study of inpatients 18 years or older in a large, acute care teaching hospital composed of 16 wards, including 5 intensive care units and 11 non-intensive care unit wards. EXPOSURES Patient-level risk factors (eg, age, comorbidities, hospitalization history, antibiotic exposure) and ward-level risk factors (eg, antibiotic therapy per 100 patient-days, hand hygiene adherence, mean patient age) were identified from hospital databases. MAIN OUTCOMES AND MEASURES Incidence of hospital-acquired C difficile infection as identified prospectively by hospital infection prevention and control staff. RESULTS A total of 255 of 34 298 patients developed C difficile (incidence rate, 5.95 per 10,000 patient-days; 95% CI, 5.26-6.73). Ward-level antibiotic exposure varied from 21.7 to 56.4 days of therapy per 100 patient-days. Each 10% increase in ward-level antibiotic exposure was associated with a 2.1 per 10,000 (P < .001) increase in C difficile incidence. The association between C difficile incidence and ward antibiotic exposure was the same among patients with and without recent antibiotic exposure, and C difficile risk persisted after multilevel, multivariate adjustment for differences in patient-risk factors among wards (relative risk, 1.34 per 10% increase in days of therapy; 95% CI, 1.16-1.57). CONCLUSIONS AND RELEVANCE Among hospital inpatients, ward-level antibiotic prescribing is associated with a statistically significant and clinically relevant increase in C difficile risk that persists after adjustment for differences in patient-level antibiotic use and other patient- and ward-level risk factors. These data strongly support the use of antibiotic stewardship as a means of preventing C difficile infection.

Colour and odour drive fruit selection and seed dispersal by mouse lemurs

Animals and fruiting plants are involved in a complex set of interactions, with animals relying on fruiting trees as food resources, and fruiting trees relying on animals for seed dispersal. This interdependence shapes fruit signals such as colour and odour, to increase fruit detectability, and animal sensory systems, such as colour vision and olfaction to facilitate food identification and selection. Despite the ecological and evolutionary importance of plant-animal interactions for shaping animal sensory adaptations and plant characteristics, the details of the relationship are poorly understood. Here we examine the role of fruit chromaticity, luminance and odour on seed dispersal by mouse lemurs. We show that both fruit colour and odour significantly predict fruit consumption and seed dispersal by Microcebus ravelobensis and M. murinus. Our study is the first to quantify and examine the role of bimodal fruit signals on seed dispersal in light of the sensory abilities of the disperser.

Social Behaviours and Networks of Vervet Monkeys Are Influenced by Gastrointestinal Parasites

Substantial research has shown that while some parasite infections can be fatal to hosts, most infections are sub-clinical and non-lethal. Such sub-clinical infections can nonetheless have negative consequences for the long-term fitness of the host such as reducing juvenile growth and the host’s ability to compete for food and mates. With such effects, infected individuals are expected to exhibit behavioural changes. Here we use a parasite removal experiment to quantify how gastrointestinal parasite infections affect the behaviour of vervet monkeys (Chlorocebus aethiops) at Lake Nabugabo, Uganda. Behavioural profiles and the structure of nearest neighbour relationships varied significantly. As predicted, after deworming the duration of the resting events decreased, which is consistent with the idea that parasite infections are energetically costly. In contrast to what was predicted, we could not reject the null hypothesis and we observed no change in either the frequency or duration of grooming, but we found that the duration of travel events increased. A network analysis revealed that after deworming, individuals tended to have more nearest neighbours and hence probably more frequent interactions, with this effect being particularly marked for juveniles. The heightened response by juveniles may indicate that they are avoiding infected individuals more than other age classes because it is too costly to move energy away from growth. We consider that populations with high parasite burden may have difficulties developing social networks and behaviours that could have cascading effects that impact the population in general.

Sensory integration during foraging: the importance of fruit hardness, colour, and odour to brown lemurs

Animal reliance on fruit signals, such as hardness, colour, and odour, during foraging is poorly understood. Here, we present data on fruit foraging behaviour and efficiency (rate of fruit ingestion) of three groups of wild, frugivorous brown lemurs (Eulemur fulvus, N = 29 individuals) in Ankarafantsika National Park, Madagascar. We quantify fruit hardness using a modified force gauge, fruit colour using spectroscopy, and fruit odour using volatile organic compound (VOC) sampling with gas chromatography-mass spectrometry. We relate lemur foraging behaviour to fruit traits by calculating touching, visual inspection, and sniffing indices and relate lemur foraging efficiency to fruit traits by calculating acceptance indices. The use of different sensory modalities by lemurs is marginally predicted in one case by fruit traits—fruits with higher overall smell signals are sniffed less than fruits with lower overall smell signals. When controlling for all fruit traits, fruit size is the only significant predictor of fruit foraging efficiency—lemurs forage more rapidly on smaller fruits relative to larger fruits.

Long-term simian research sites: significance for theory and conservation

Simian primates (monkeys and apes) are typically long-lived animals with slow life histories. They also have varying social organization and can slowly impact their environment by either being seed dispersers or by overbrowsing their food trees. As a result, short-term studies and those focusing on just 1 location only provide a snapshot of simian life under a specific set of ecological conditions that typically do not represent the complete spatial and temporal picture. Long-term field studies are needed to obtain a true understanding of their behavior, life history, ecology, and the selective pressures acting on them. Fortunately, there have been many long-term studies of simians, so a great deal is known about many species. Here, we consider examples of long-term studies that have operated continuously for approximately a decade or more. We review studies that deal with ecophysiology, social organization, population and community ecology, or conservation. The information emerging from these sites is particularly helpful in the construction of informed conservation plans, which are desperately needed given the severity of threats to simians and the fact that responses do not occur over the duration of a Ph.D. or granting cycle (typically 1–3 years).

It’s Not Easy Being Blue: Are There Olfactory and Visual Trade-Offs in Plant Signalling?

Understanding the signals used by plants to attract seed disperses is a pervasive quest in evolutionary and sensory biology. Fruit size, colour, and odour variation have long been discussed in the controversial context of dispersal syndromes targeting olfactory-oriented versus visually-oriented foragers. Trade-offs in signal investment could impose important physiological constraints on plants, yet have been largely ignored. Here, we measure the reflectance and volatile organic compounds of a community of Malagasy plants and our results indicate that extant plant signals may represent a trade-off between olfactory and chromatic signals. Blue pigments are the most visually-effective – blue is a colour that is visually salient to all known seed dispersing animals within the study system. Additionally, plants with blue-reflecting fruits are less odiferous than plants that reflect primarily in other regions of the colour spectrum.

Plant attractants: integrating insights from pollination and seed dispersal ecology

Reproduction in many angiosperms depends on attracting animals that provide pollination and seed dispersal services. Flowers and fleshy fruits present various features that can attract animal mutualists through visual, olfactory, acoustic, and tactile cues and signals, and some of these traits may result from selection exerted by pollinators and seed dispersers. Plant attractants can provide information regarding the presence, location, and quality of the reward. However, because of the different functional outcomes of pollination and seed dispersal, pollination systems are thought to be more highly specialized than seed dispersal systems. Despite these interesting parallels and contrasts, theoretical and empirical insights in the sensory ecology of pollination and seed dispersal are rarely considered together. Here, we review extant theory and data of sensory attractants from both pollination and seed dispersal systems. We discuss theoretical and empirical similarities and differences between pollination and seed dispersal and offer suggestions for ways in which insights from each field may benefit the other in future.

The Ecology and Evolution of Fruit Odor: Implications for Primate Seed Dispersal

Primates are now known to possess a keen sense of smell that serves them in various contexts, including feeding. Many primate species are frugivorous and provide essential seed dispersal services to a variety of plants. Studies of pollination ecology, and recently seed dispersal ecology, indicate that animal mutualist behavior exerts selection pressures that drive changes in flower and fruit traits. As a result, the use of olfaction in in primate feeding ecology may have affected the evolution of fruit odor in species that rely on primate seed dispersal. However, this hypothesis is seldom tested. Here, we summarize the available information on how primates may have affected the evolution of fruit odor. We ask what the chemistry of primate fruit odor may look like, what information fruit odor may convey, whether there are geographical differences in fruit odor, and what other factors may affect the odor of fruits consumed by primates. We identify many gaps in the available data and offer research questions, hypotheses, and predictions for future studies. Finally, to facilitate standardization in the field, we discuss methodological issues in the process of odor sampling and analysis.

Fruit Ripening Signals and Cues in a Madagascan Dry Forest: Haptic Indicators Reliably Indicate Fruit Ripeness to Dichromatic Lemurs

Fruit ripeness can be indicated through changes in chromaticity, luminance, odor, hardness, and size to attract seed dispersing animals. We quantified these attributes for both ripe and unripe fruits of 31 lemur-dispersed plant species in Ankarafantsika National Park, a tropical dry forest in northwestern Madagascar. We used spectroscopy, gas-chromatography mass-spectrometry, and a modified force gauge to quantify chromaticity, luminance, odor, and hardness. We compared these traits between unripe and ripe fruits of each species to determine which traits reliably indicate fruit ripeness across species. Overall, ripe fruits were significantly heavier and softer than unripe fruits. Ripe fruits were not more chromatically-conspicuous or odiferous relative to unripe fruits, nor were ripe fruits more conspicuous in the luminance channel. Contrary to expectation, our findings indicate that, in this particular system, plant-lemur interactions may be strongly mediated by haptic traits, such as fruit hardness, which are consistent and reliable indicators of fruit ripeness. Despite the potential importance of haptic indicators of fruit ripeness, they are underrepresented in the literature on sensory ecology.

Protein Limitation Explains Variation in Primate Colour Vision Phenotypes: A Unified Model for the Evolution of Primate Trichromatic Vision

Primate colour vision has intrigued scientists for many decades and will likely continue to do so for the foreseeable future. Primates are the most visually adapted order of mammals and a considerable proportion of their large brain size is devoted to processing visual information (e.g. Barton, 2006). Most eutherian mammals have dichromatic (two-colour) vision, and chromatic distinctions are based on discriminating relatively shorter from relatively longer wavelengths within the visual spectrum (~400-700nm). These distinctions are made by neural comparison of cone cells possessing short (S) wavelength-sensitive photopigments, which are maximally sensitive to bluish light, and long (L) wavelengthsensitive pigments, which are maximally sensitive to greenish light. These photopigments are encoded by an autosomal S opsin gene and an X-chromosomal L opsin gene respectively. Primates have an additional colour channel enabling trichromatic vision via a duplication and divergence of the L opsin gene, resulting in long and middle (L-M) wavelength-sensitive photopigments (reviewed in Hunt et al., 2009; Regan et al., 2001). This arrangement permits enhanced discrimination of light and perception of different shades of green, yellow, orange and red.