Dispersal dynamics in food webs

Studies of food webs suggest that limited nonrandom dispersal can play an important role in structuring food webs. It is not clear, however, whether density-dependent dispersal fits empirical patterns of food webs better than density-independent dispersal. Here, we study a spatially distributed food web, using a series of population-dispersal models that contrast density-independent and density-dependent dispersal in landscapes where sampled sites are either homogeneously or heterogeneously distributed. These models are fitted to empirical data, allowing us to infer mechanisms that are consistent with the data. Our results show that models with density-dependent dispersal fit the α, β, and γ tritrophic richness observed in empirical data best. Our results also show that density-dependent dispersal leads to a critical distance threshold beyond which site similarity (i.e., β tritrophic richness) starts to decrease much faster. Such a threshold can also be detected in the empirical data. In contrast, models with density-independent dispersal do not predict such a threshold. Moreover, preferential dispersal from more centrally located sites to peripheral sites does not provide a better fit to empirical data when compared with symmetric dispersal between sites. Our results suggest that nonrandom dispersal in heterogeneous landscapes is an important driver that shapes local and regional richness (i.e., α and γ tritrophic richness, respectively) as well as the distance-decay relationship (i.e., β tritrophic richness) in food webs.

Eco-Evolutionary Spatial Dynamics. Rapid Evolution and Isolation Explain Food Web Persistence

One of the current challenges in evolutionary ecology is understanding the long-term persistence of contemporary-evolving predator–prey interactions across space and time. To address this, we developed an extension of a multi-locus, multi-trait eco-evolutionary individual-based model that incorporates several interacting species in explicit landscapes. We simulated eco-evolutionary dynamics of multiple species food webs with different degrees of connectance across soil-moisture islands. A broad set of parameter combinations led to the local extinction of species, but some species persisted, and this was associated with (1) high connectance and omnivory and (2) ongoing evolution, due to multi-trait genetic variability of the embedded species. Furthermore, persistence was highest at intermediate island distances, likely because of a balance between predation-induced extinction (strongest at short island distances) and the coupling of island diversity by top predators, which by travelling among islands exert global top-down control of biodiversity. In the simulations with high genetic variation, we also found widespread trait evolutionary changes indicative of eco-evolutionary dynamics. We discuss how the ever-increasing computing power and high-resolution data availability will soon allow researchers to start bridging the in vivo–in silico gap.

Prevalence, genetic diversity and antimicrobial susceptibility of Listeria monocytogenes isolated from open-air food markets in Greece

A total of 210 food samples originating from milk products, ready-to-eat salads, raw meat and raw meat products purchased in ten open-air market places in Thessaloniki, Greece, were analyzed for the presence of Listeria monocytogenes. Thirty (14.3%) contained L. monocytogenes with the highest prevalence in raw meat (27.5%), raw meat products (18%) and cheese (8%). The strains were susceptible to 16 antimicrobials as determined by microbroth dilution, except one strain which displayed resistance to tetracycline (MIC > 32 μg/ml). This strain carried the tetracycline resistance gene tet(M). Pulsed-field gel electrophoresis (PFGE) revealed a low genetic diversity among the isolates, irrespective of their origin. This suggests that dominant L. monocytogenes clones are widespread in different food product types in open-air food markets in Greece. The high prevalence of L. monocytogenes in these products indicates that appropriate hygienic measures and periodic bacteriological controls are also necessary in open-air food markets to reduce contamination with food-borne pathogens. Greek specialties made with raw meat and raw milk may contain L. monocytogenes and should not be consumed by persons at risk.

Commensal bacteria protect against food allergen sensitization.

Environmentally induced alterations in the commensal microbiota have been implicated in the increasing prevalence of food allergy. We show here that sensitization to a food allergen is increased in mice that have been treated with antibiotics or are devoid of a commensal microbiota. By selectively colonizing gnotobiotic mice, we demonstrate that the allergy-protective capacity is conferred by a Clostridia-containing microbiota. Microarray analysis of intestinal epithelial cells from gnotobiotic mice revealed a previously unidentified mechanism by which Clostridia regulate innate lymphoid cell function and intestinal epithelial permeability to protect against allergen sensitization. Our findings will inform the development of novel approaches to prevent or treat food allergy based on modulating the composition of the intestinal microbiota.

High Prevalence of Extended-Spectrum β-Lactamase, Plasmid-Mediated AmpC and Carbapenemase genes in Food for Pets

We evaluated the pet food contained in thirty packages as potential origin of extended-spectrum cephalosporin-resistant Gram-negative organisms and β-lactamase genes (bla). Alive bacteria were not detected by selective culture. However, PCR investigations on food DNA extracts indicated that samples harbored blaCTX-M-15 (53.3%), blaCMY-4 (20%), and blaVEB-4-like (6.7%). Particularly worrisome was the presence of blaOXA-48-like carbapenemases (13.3%). Original pet food ingredients and/or the production process were highly contaminated with bacteria carrying clinically relevant acquired bla genes.

Food Recognition for Dietary Assessment Using Deep Convolutional Neural Networks

Diet management is a key factor for the prevention and treatment of diet-related chronic diseases. Computer vision systems aim to provide automated food intake assessment using meal images. We propose a method for the recognition of already segmented food items in meal images. The method uses a 6-layer deep convolutional neural network to classify food image patches. For each food item, overlapping patches are extracted and classified and the class with the majority of votes is assigned to it. Experiments on a manually annotated dataset with 573 food items justified the choice of the involved components and proved the effectiveness of the proposed system yielding an overall accuracy of 84.9%.

Listeria monocytogenes infection in ruminants: Is there a link to the environment, food and human health? A review.

Listeria (L.) monocytogenes is widely distributed in the environment, but also has the ability to cause serious invasive disease in ruminants and humans. This review provides an overview of listeriosis in ruminants and discusses our insufficient understanding of reservoirs and possible cycling ofL. monocytogenes between animal and human hosts, food and the environment. It indicates gaps in our knowledge of the role of genetic subtypes in L. monocytogenes ecology and virulence as well as risk factors, in vivo diagnostics and pathogenesis of listeriosis in ruminants. Filling these gaps will contribute to improving the control of L. monocytogenes and enhancing disease prevention. As the prevalence of listeriosis in ruminants in Switzerland is likely to be underestimated, propositions concerning improvement options for surveillance of listeriosis in ruminants are provided.

Effects of Food Primes and Thought Suppression on Eating Habits

Food primes and thought suppression have been identified as factors influencing poor eating choices. Primes affect people non-consciously by activating thoughts of food. Suppression of food thoughts leads to a preoccupation with food that is often followed by a hyperaccessibility of food thoughts and increased binging. The current study paired these two processes to examine their interactional effects. We manipulated exposure to food primes and instructions to suppress thoughts of a tasty snack food (M&Ms) for 76 college-aged women. We hypothesized that participants both primed with food images and asked to suppress would consume the most M&Ms at the end of the study. Contrary to predictions, results showed no effects for the manipulations. Perceived weight category, however, did interact with the manipulations, with overweight participants eating more when they got either the food prime or the suppression (but not both together). These findings have important implications for weight-loss strategies.

Estimated current patterns of food consumption and perceived changes among patients with lymphoma

Usual food choices during the past year, self-reported changes in consumption of three important food groups, and weight changes or stability were the questions addressed in this cross-sectional survey and retrospective review. The subjects were 141 patients with Hodgkin's disease or other B-cell types of lymphoma within their first three years following completion of initial treatments for lymphoma at the University of Texas M. D. Anderson Cancer Center in Houston, Texas. ^ The previously validated Block-98 Food Frequency Questionnaire was used to estimate usual food choices during the past year. Supplementary questions asked about changes breads and cereals (white or whole grain) and relative amounts of fruits and vegetables compared with before diagnosis and treatment. Over half of the subjects reported consuming more whole grains, fruits, and/or vegetables and almost three quarters of those not reporting such changes had been consuming whole grains before diagnosis and treatment. ^ Various dietary patterns were defined in order to learn whether proportionately more patients who changed in healthy directions fulfilled recognized nutritional guidelines such as 5-A-day fruits and vegetables and Dietary Reference Intakes (DRIB) for selected nutrients. ^ Small sizes of dietary pattern sub-groups limited the power of this study to detect differences in meeting recommended dietary guidelines. Nevertheless, insufficient and excessive intakes were detected among individuals with respect to fruits and vegetables, fats, calcium, selenium, iron, folate, and Vitamin A. The prevalence of inadequate or excess intakes of foods or nutrients even among those who perceived that they had increased or continued to eat whole grains and/or fruits and vegetables is of concern because of recognized effects upon general health and potential cancer related effects. ^ Over half of the subjects were overweight or obese (by BMI category) on their first visit to this cancer center and that proportion increased to almost three-quarters by their last follow-up visits. Men were significantly heavier than women, but no other significant differences in BMI measures were found even after accounting for prescribed steroids and dietary patterns. ^

Risk of adult-onset asthma in Mexican-American women employed in food preparation or food service

Existing literature examining the association between occupation and asthma has not been adequately powered to address this question in the food preparation or food service industries. Few studies have addressed the possible link between occupational exposure to cooking fumes and asthma. This secondary analysis of cohort study data aimed to investigate the association between adult-onset asthma and exposure to: (a) cooking fumes at work or (b) longest-held employment in food preparation or food service (e.g. waiters and waitresses, food preparation workers, non-restaurant food servers, etc.). Participants arose from a cohort of Mexican-American women residing in Houston, TX, recruited between July 2001 and June 2007. This analysis used Cox proportional-hazards regression to estimate the hazard ratio of adult-onset asthma given the exposures of interest, adjusting for age, BMI, smoking status, acculturation, and birthplace. We found a strong association between adult-onset asthma and occupational exposure to cooking fumes (hazard ratio [HR] = 1.77; 95% confidence interval [CI], 1.15, 2.72), especially in participants whose longest-held occupation was not in the food-related industry (HR = 2.12; 95% CI, 1.21, 3.60). In conclusion, adult-onset asthma is a serious public health concern for food industry workers. ^

The prevalence of food insecurity and associated factors among households with children in Head Start programs in Houston, Texas and Birmingham, Alabama

The purposes of this study were to determine the prevalence of food insecurity and factors associated with food insecurity among households with children enrolled in Head Start programs in Houston, Texas, and Birmingham, Alabama. This cross-sectional study utilized data gathered from 688 households recruited by convenience sample from two Head Start districts in each city. Interviewers collected data from primary caregivers on demographic characteristics, dietary intake, and the six-item USDA food security module. Chi-square and logistic regression analysis were used to determine the association of food security and demographic characteristics. Comparison of means was used to analyze the association between the child's fruit and vegetable intake and the household's food security status. The prevalence of food insecurity among the sample was 34.9% (95% CI: 31.3%, 38.5%). Characteristics associated with food insecurity were the caregiver's national origin (Foreign-born (ref.) v. U.S.-born, adjusted OR = 0.36, 95% CI: 0.14, 0.94), gender of the child (male (ref.) v. female, adjusted OR = 1.44, 95% CI: 1.03, 2.01), and city of residence (Birmingham (ref.) v. Houston, adjusted OR = 0.20, 95% CI: 0.10, 0.39). Children in food insecure households consumed more daily servings of fruits and vegetables on average (mean = 2.44) than children in food secure households (mean = 2.16, p = 0.04). ^

The association of food sources of calcium with weight class in adolescent girls

To determine the association of food sources of calcium with weight class in adolescent girls, the major food sources of calcium were determined for 718 sixth grade girls at three different time periods during an 18 month school-based health intervention program using a FFQ. To determine weight class, the BMI of each girl was stratified using CDC age and gender specific criteria at each time period. The percent contribution of the major food sources of calcium to total calcium intake was compared among the different weight classes at each time period, among those girls who had changed weight class at the different time periods and for those girls who did not change weight class at the different time periods. The mean total calcium intake increased by 20% between the first two time periods and by 12% between the first and last time periods with the intervention despite baseline total calcium intake already being greater than the recommended 1300 mg/day. The percent contribution of the major food sources of calcium were highly correlated among the weight classes that were compared throughout the study. Those girls who remained in the normal weight class throughout the study had the most consistent intake of food sources of calcium. Their top four food sources of calcium were different types of milk which provided greater than 50% of their total calcium intake. Despite there being no significant differences in the major food sources of calcium among the different weight classes, these data show a successful intervention for increasing calcium intake among adolescent girls. ^

Analyzing the effectiveness of Kinderworld's food program on lowering & controlling childhood obesity

This is an analysis of previously collected data at Kinderworld Child Care and Early Learning Center, as part of an evaluation done to determine the program's effectiveness in reducing/controlling childhood obesity. Kinderworld is a private, for-profit organization that provides healthy, nutritious meals and snacks to children under the guidelines of the Child and Adult Care Food Program, and is reimbursed by the Texas Department of Agriculture on a fixed price-per-meal basis. The primary goal of the program is to reduce childhood obesity. Previous studies have shown a link between obesity and diet. Other, similar programs have shown success in reducing obesity among children with a healthy diet and exercise. The results from the outcome evaluation indicated that time spent in the center was positively related to higher proportions of healthy-weight children, and inversely related to BMI levels. ^

Food advertisements during children's television programming in 2007: Comparison with ads in 1994 and the 2005 dietary recommendations

Childhood overweight and obesity are two major public health problems that are of economic and medical concern in the world today (Lobstein, Baur, & Uauy, 2004). Overweight conditions in childhood are important because they are widely prevalent, serious, and carry lifetime consequences for health and well being (Lobstein et al., 2004). Several studies have shown an association between television viewing and obesity in all age groups (Caroli, Argentieri, Cardone, & Masi, 2004; Harper, 2006; Vandewater & Huang, 2006; Wiecha et al., 2006). One mechanism that potentially links television viewing to childhood obesity is food advertising (Story, 2003). ^ The purpose of this study was to examine the types of foods advertised on children's television programming and to determine if there have been any changes in the number and types of commercials over the last 13 years. In addition, the food content of the advertisements was compared to the 2005 Dietary Guidelines to determine if the foods targeted were consistent with the current recommendations. Finally, each television network was analyzed individually to determine any differences between advertising on cable and regular programming. ^ A descriptive analysis was conducted on the most commonly advertised commercials during children's television programming on Saturday morning from 7 a.m. to 10:30 a.m. A total of 10 major television networks were viewed on three different Saturday mornings during June and July 2007. Commercial advertising accounted for approximately 19% of children's total viewing time. Of the 3,185 commercials, 28.5% were for foods, 67.7% were for non-food items, and 3.8% were PSAs. On average, there were 30 commercial advertisements and PSAs per hour, of which approximately nine were for food. ^ Of the 907 food advertisements, 72.0% were for foods classified in the fats, oils, and sugar group. The next largest group (17.3%) was for restaurant food of which 15.3% were for unhealthy/fast food restaurant fare. The most frequently advertised food product on Saturday morning television was regular cereal, accounting for 43.9% of all food advertisements. ^ Cable and regular programming stations varied slightly in the amount, length, and category of commercials. Cable television had about 50% less commercials and PSAs (1098) than regular programming (2087), but only had approximately 150 minutes less total commercial and PSA time; therefore, cable, in general, had longer commercials than regular programming. Overall, cable programming had more advertisements encouraging increased physical activity and positive nutrition behavior with less commercials focusing on the fats, oils, and sugar groups, compared to regular programming. ^ During the last 13 years, food advertisements have not improved, despite the recent IOM report on marketing foods to children (Institute of Medicine-Committee on Food Marketing and the Diets of Children and Youth, 2005), although the frequency of food advertisements has improved slightly. Children are now viewing an average of one food advertisement every 7 minutes, compared to one food advertisement every 5 minutes in 1994 (Kotz & Story, 1994). Therefore, manufacturers are putting a greater emphasis on advertising other products to children. Despite the recent attention to the issue of marketing unhealthy foods to children through television advertisements, not much progress has been noted since 1994. Further advocacy and regulatory issues concerning the content of advertisements during Saturday morning TV need to be explored. ^