Large-scale identification of rodenticide resistance in Rattus norvegicus and Mus musculus in the Netherlands based on Vkorc1 codon 139 mutations

BACKGROUND

Resistance to rodenticides has been reported globally and poses a considerable problem for efficacy in pest control. The most-documented resistance to rodenticides in commensal rodents is associated with mutations in the Vkorc1 gene, in particular in codon 139. Resistance to anticoagulant rodenticides has been reported in the Netherlands since 1989. A study from 2013 showed that 25% of 169 Norway rats (Rattus norvegicus) had a mutation at codon 139 of the Vkorc1 gene. To gain insight in the current status of rodenticide resistance amongst R. norvegicus and house mice Mus musculus in the Netherlands, we tested these rodents for mutations in codon 139 of the Vkorc1 gene. In addition, we collected data from pest controllers on their use of rodenticides and experience with rodenticide resistance.

RESULTS

A total of 1801 rodent samples were collected throughout the country consisting of 1404 R. norvegicus and 397 M. musculus. In total, 15% of R. norvegicus [95% confidence interval (CI): 13-17%] and 38% of M. musculus (95% CI: 33-43%) carried a genetic mutation at codon 139 of the Vkorc1 gene.

CONCLUSION

This study demonstrates genetic mutations at codon 139 of the Vkorc1 gene in M. musculus in the Netherlands. Resistance to anticoagulant rodenticides is present in R. norvegicus and M. musculus in multiple regions in the Netherlands. The results of this comprehensive study provide a baseline and facilitate trend analyses of Vkorc1 codon 139 mutations and evaluation of integrated pest management (IPM) strategies as these are enrolled in the Netherlands. © 2022 The Dutch Pest and Wildlife. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Nutritional implications of feeding free-living birds in public urban areas

Supplementary feeding can affect populations of birds. It reduces energy spent on foraging and reduces the risk of starvation, but it also increases the risk of disease transmission and predation. Supplementary feeding may reduce species richness if some species are better able to exploit supplementary food resources than others. Feeding may also artificially inflate the carrying capacity of the ecosystem, leading to bird nuisance in the form of droppings and noise. The aim of this study was to characterise and quantify the risk factors and consequences of feeding free‐living birds in public areas in the western part of the city of Amsterdam. In seven study areas, the following data were collected: bird population size and species composition, feeding events, and the type and amount of supplementary food offered. Estimations were made of the nutritional energy provided and the number of birds that could be supported by the food offered. Members of the public who fed the birds were invited to complete a questionnaire on various aspects of feeding. Results showed that supplementary feeding attracts juvenile gulls and feral pigeons, which could in the long‐term affect biodiversity. Bread was the main category of supplementary food being offered (estimated to be 67% of the total amount of food). The majority of respondents fed birds so as not to waste bread and meal leftovers. In six of the seven areas studied, an overabundance of nutritional energy was calculated. We conclude that the current type and extent of supplementary feeding in the city of Amsterdam is nutritionally unbalanced and affects species diversity at a local level. The overabundance is undesirable for reasons of both animal health, because it can lead to malnutrition, and public health, because surplus food attracts rats and may also have a negative effect on water quality.

Clostridium difficile in wild rodents and insectivores in the Netherlands

With wild rodents and insectivores being present around humans and their living, working and food production environments, it is important to gain knowledge of the zoonotic pathogens present in these animals. The enteropathogen Clostridium difficile, an opportunistic anaerobic bacteria, can be carried by both animals and humans, and is distributed globally. It is known that there is genetic overlap between human and animal sources of C. difficile. In this study, the aim was to assess the presence of C. difficile in rodents and insectivores trapped on and around pig and cattle farms in the Netherlands. In total 347 rodents and insectivores (10 different species) were trapped and 39·2% tested positive for presence of C. difficile. For all positive samples the ribotype (RT) was determined, and in total there were 13 different RTs found (in descending order of frequency: 057, 010, 029, 005, 073, 078, 015, 035, 454, 014, 058, 062, 087). Six of the RTs isolated from rodents and insectivores are known to be associated with human C. difficile infection; RT005, RT010, RT014, RT015, RT078 and RT087. The presence of rodents and insectivores in and around food production buildings (e.g. farms) could contribute to the spread of C. difficile in the human environment. In order to enable on-farm management for pathogen control, it is essential to comprehend the role of wild rodents and insectivores that could potentially affect the ecology of disease agents on farms. SIGNIFICANCE AND IMPACT OF THE STUDY: This study shows that rodents and insectivores in and around food production buildings (e.g. farms) can carry Clostridium difficile ribotypes associated with human C. difficile infection (CDI). C. difficile spores in rodent and insectivore droppings are able to survive in the environment for prolonged periods, leading to host-to-host exposure and transmission. Therefore we can state that rodent and insectivore presence on farms is a risk for zoonotic pathogen transmission of C. difficile.

Wild mice in and around the city of Utrecht, the Netherlands, are carriers of Clostridium difficile but not ESBL-producing Enterobacteriaceae, Salmonella spp. or MRSA

Mice in buildings are a hygiene hazard because they harbour several zoonoses and animal diseases. The aim of this study was to gather information on specific bacteria in house mice caught in the urban environment. Mice caught in snap traps during pest control activities were collected in and around the city of Utrecht, the Netherlands, during May-June 2014, October-November 2015 and September-November 2016. The gut contents were analysed for ESBL/AmpC-producing Enterobacteriaceae, Salmonella spp., and Clostridium difficile and the buccal cavities were swabbed for methicillin-resistant S. aureus (MRSA). In total, 109 house mice (Mus musculus) and 22 wood mice (Apodemus sylvaticus) were examined. One mouse was found positive for Enterobacter spp. Salmonella spp. and MRSA were not found. Of n = 80 mice, 35·0% carried C. difficile (ribotypes in descending order of frequency: 014/020, 258, 002, 005, 013, 056, 081 and two unknown ribotypes). In conclusion, mouse droppings are a hazard for transmission of C. difficile to humans and their environment.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows that mice in buildings can carry Clostridium difficile ribotypes that are associated with clinical disease in humans. Whether the mice are the source or whether they picked up these bacteria from the human environment has not been investigated. Either way, mouse droppings in the indoor environment are a hazard for transmission of C. difficile to humans.

Chlamydia psittaci and C. avium in feral pigeon (Columba livia domestica) droppings in two cities in the Netherlands

Background: Feral pigeons (Columba livia domestica) live and breed in many city centres and contact with their droppings can be a hazard for human health if the birds carry Chlamydia psittaci.

Objective: The aim of this study was to establish whether pigeon droppings in two Dutch cities (Utrecht and Haarlem) contain C. psittaci and/or C. avium, which could be a potential hazard for transmission to humans.

Methods: In May 2017 seven feral pigeon ‘hot spots’ with between 5 and 40+ pigeons present were identified in two cities by visual observations over two days. During the following ten days fresh droppings were collected at these hot spots and the samples were pooled per three droppings to achieve 40–41 samples per city. Samples were analysed for Chlamydia DNA with a broad range 23S Chlamydiaceae Real-Time PCR and positive samples were tested with a specific C. psittaci and C. avium Real-Time PCR. Positive C. psittaci samples were genotyped.

Results:C. psittaci and C. avium were detected in both cities. For C. psittaci the prevalences in Utrecht and Haarlem were 2.4% and 7.5%, respectively; for C. avium 36.6% and 20.0%, respectively. One sample contained both species. All C. psittaci samples belonged to genotype B.

Conclusion:C. psittaci and C. avium are present in feral pigeon droppings in Utrecht and Haarlem. Human contact with droppings from infected pigeons or inhalation of dust from dried droppings represent a potential hazard to public health.

Teaching Slaughter: Mapping Changes in Emotions in Veterinary Students during Training in Humane Slaughter

As part of their training, Dutch veterinary students learn how to carry out the humane slaughter of livestock, which many students consider emotionally challenging. The aims of this study were to plot changes in self-reported emotions in veterinary students at different time points during an educational program on humane slaughter using emotion cards and to assess the change in reported emotions after adding a video and a short period of self-reflection to the program. Emotions were mapped in five groups of students at the beginning, middle, and end of the program by asking them to select from 40 cards depicting emotions in photo and text. Then two changes were made to the course program: a video of an expert slaughterman stunning and bleeding a bovine was shown, and the students were requested to spend 2 minutes picturing themselves carrying out the same procedures. To evaluate the effect of these improvements to the course, the following five groups of students were asked in the same way to indicate their emotions at the same three time points. Adding the video and short period of self-reflection did not change the emotions reported by students. Our results indicate that instruction in humane slaughter techniques involves a significant mental challenge for students. The use of emotion cards by teachers could provide useful insights into emotional aspects of the more challenging programs for students.

Self-reported prevalence of pests in Dutch households and the use of the health belief model to explore householders' intentions to engage in pest control

Pests in the home are a health risk because they can be vectors for infectious disease, contribute to allergies and cause damage to buildings. The aims of this study were to record which categories of pests were reported in homes and to use a social cognition model, the health belief model, to investigate which psychological factors influence householders' intentions to control pests. An online questionnaire was completed by 413 respondents between 11 September and 31 November 2015. A large majority of respondents reported pests in or around their home within the previous year. The prevalences were: flying insects 98%, crawling insects 85%, rodents 62%, birds 58%, and moles 20%. Regression analysis for the health belief model revealed that perceiving greater benefits and fewer barriers to pest control and expecting severe consequences of zoonotic infections predicted higher intention to control pests. Intentions towards pest control were not influenced by perceiving oneself as susceptible to catching a disease from pests or health motivation (striving towards a healthy lifestyle). Intentions to engage in pest control were lower for households reporting bird prevalence. The findings suggest that interventions aimed at improving the effectiveness of domestic pest control should focus on increasing the benefits that individuals associate with effective pest control, lowering barriers, and on underlining the severity of the diseases that pests may carry.

Abstract P528: Modifiable Factors Affecting BP in Identical Twins

Background: Genetic factors determining blood pressure (BP) are largely unmodifiable. Understanding the effects of physiologic, environmental, and epigenetic (modifiable) factors on BP levels can improve strategies for hypertension (HTN) control. Monozygotic (MZ) twins with identical genetic background are a good model to study the effect of these factors on BP.

Methods: Seventy pairs of MZ twins were from Milwaukee, WI and Michigan State University Twin Registry, East Lansing, MI (62% women; age of 44 ± 10 years). BPs (measured in triplicate and averaged), anthropometrics, physical activity (Rapid Assessment of Physical Activity), and sodium intake measurements (Block Sodium Screener) were obtained. DNA was obtained from T-lymphocytes for methylation (epigenetic) sequencing analysis. Differences in systolic (SBP) and diastolic (DBP) BPs between co-twins were used as continuous variables for these analyses.

Results: Mean SBP was 124 ± 15 mm Hg (mean ± SD) and DBP was 78 ± 11 mm Hg. Average differences in SBP and DBP among co-twins were 8 ± 9 and 7 ± 6 mm Hg respectively. Twin pairs were considered concordant or discordant based on BP difference of 10 mm Hg between co-twins or one twin being hypertensive. Discordant twins as a group had higher BMI and waist circumference (WC) compared to concordant twins (p<0.05). Among discordant twins, the co-twin with higher BPs tended to have higher waist circumference (WC) (105 ± 15 vs. 98 ± 18 cm) and dietary salt intake (3900 ± 1437 vs. 3261 ± 1058 mg/d) even though they did not reach statistical significance. There were no differences in physical activity or education levels. Genome-wide methylation analyses revealed that 3 loci were associated with SBP difference and 2 were associated with DBP difference at an unadjusted significance level of p < 10 -4 . Two sites reached an adjusted significance level of 0.08 with SBP difference.

Conclusions: In this study, we identified several differentially methylated sites of interest in relation to BP among MZ twins. In addition, higher central adiposity and sodium intake may contribute to BP levels among MZ twins. Understanding the relationship of modifiable risk factors such as WC and sodium intake with methylation changes may shed light into novel pathogenic pathways for HTN.

Abstract P264: DNA Methylation and Differences in Blood Pressure Levels in Monozygotic Twins

Background: The development of common forms of hypertension (HTN) involves both genetic and environmental factors. Methylation changes (one of the epigenetic modifications) of DNA may play a role in the regulation of BP and development of HTN, and may result from interaction of specific genes with the environment. The current study investigates the relationship between genome-wide changes in DNA methylation in T-lymphocytes and BP level differences among monozygotic twins, who have identical DNA sequences.

Methods: In a preliminary study, we recruited 24 pairs of monozygotic twins (60% women) with a mean age of 44 ± 10 years. Zygosity was determined via self-report or participants’ responses to a standard zygosity questionnaire. BPs were measured in triplicate after 5 minutes of rest at one minute intervals and averaged. Anthropometrics measurements were obtained along with blood for isolation of T-lymphocytes. DNA from T-lymphocytes was used to perform reduced representation bisulfite sequencing (RRBS) to measure methylation levels at single-base resolution in these subjects. Average differences in systolic (SBP) and diastolic (DBP) BPs were used as continuous variables for these analyses.

Results: Mean SBP was 124 ± 15 (range (r): 97-174) mm Hg and mean DBP was 78 ± 11 (r: 49-106) mm Hg. Average differences in SBP and DBP among the co-twins (members of a twin pair) were 9 ± 10 (r: 0-40) mm Hg and 8 ± 6 (r: 0-26) mm Hg respectively. Average BMI was 29 ± 8 kg/m 2 . We observed that an average of 3063 (r: 757-7250) CpG islands were differentially methylated (DMRs) between co-twins. Among these DMRs, 10 were associated with average SBP difference and 5 were associated with average DBP difference at a significance level of p < 0.001. DMRs showing the strongest association (unadjusted p < 10 -4 ) between the co-twins were located in the transcriptional start site (TSS) of genes: CDC26 (cell division cycle protein) and NR2F6 (nuclear receptor) for average SBP difference and LEPRE1 (propyl 3 hydroxylase protein) for average DBP difference.

Conclusions: BP differences between monozygotic co-twins, which most likely result from environmental factors, appear to be associated with differences in DNA methylation in T lymphocytes.

Hepatitis E Virus in Farmed Rabbits, Wild Rabbits and Petting Farm Rabbits in the Netherlands

Rabbits have been suggested as a zoonotic source of Hepatitis E virus. Phylogenetic analysis of HEV isolates from farmed, wild and pet rabbits in the Netherlands (0, 60, and 23 % respectively) showed them to be grouped amongst published rabbit HEV sequences and distinct from most human isolates. Dutch rabbits are unlikely to be a zoonotic source.

Cinnamaldehyde, Carvacrol and Organic Acids Affect Gene Expression of Selected Oxidative Stress and Inflammation Markers in IPEC-J2 Cells Exposed to Salmonella typhimurium

Essential oils and organic acids are used as feed additives to improve health status and reduce colonization with pathogens. Although bactericidal in vitro, concentrations achieved in the animal gut are probably not lethal to pathogens. The aim of this study was to investigate the effects of cinnamaldehyde, carvacrol and cinnamic, lactic and propionic acids on the ability of Salmonella typhimurium ATCC 14028 (ST) to invade intestinal epithelial cells (IPEC-J2) and on the expression levels of immune related genes in the cells. The minimum inhibitory concentration (MIC) and non-inhibitory concentration (NIC) were determined and influence on the invasion capacity of ST was investigated. The structure of fimbriae and flagella was analysed by electron microscopy, and expression levels of HSP70, IkBa, IL-8 and IL-10 in the IPEC-J2 cells were carried out by q-PCR. Cinnamaldehyde, carvacrol and cinnamic and propionic acids inhibited ST invasion but not cell viability, bacterial viability and motility or the development of flagella. Propionic acid and cinnamaldehyde in combination with cinnamic acid caused structural impairment of fimbriae. Cinnamaldehyde up-regulated expression of HSP70 irrespective of the presence of organic acids or ST; exposure to carvacrol induced HSP70 only in the presence of propionic acid and ST. © 2016 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.

Neighborhood as a predictor of non-aggressive, but not aggressive, antisocial behaviors in adulthood

BACKGROUND

Prior meta-analytic work has highlighted important etiological distinctions between aggressive (AGG) and non-aggressive rule-breaking (RB) dimensions of antisocial behavior. Among these is the finding that RB is influenced by the environment more than is AGG. Relatively little research, however, has sought to identify the specific environmental experiences that contribute to this effect. The current study sought to do just this.

METHOD

We examined whether unrelated adults residing in the same neighborhood (n = 1915 participants in 501 neighborhoods) were more similar in their AGG and RB than would be expected by chance. Analyses focused on simple multi-level models, with the participant as the lower-level unit and the neighborhood as the upper-level unit.

RESULTS

Results revealed little to no evidence of neighborhood-level variance in AGG. By contrast, 11+% of the variance in RB could be predicted from participant neighborhood, results that persisted even when considering the possibility of genetic relatedness across participants and neighborhood selection effects. Moreover, 17% of this neighborhood-level variance in RB was accounted for by neighborhood structural characteristics and social processes.

CONCLUSIONS

Findings bolster prior suggestions that broader contextual experiences, like the structural and social characteristics of one's neighborhood, contribute in a meaningful way to RB in particular. Our results also tentatively imply that this association may be environmental in origin. Future work should seek to develop additional, stronger designs capable of more clearly leveraging genetic un-relatedness to improve causal inferences regarding the environment.

The quality of the interparental relationship does not moderate the etiology of child conduct problems

BACKGROUND

Although there is a clear phenotypic relationship between the quality of the interparental or marital relationship and child conduct problems (CP), the etiology of this association is as yet unclear. One possibility is that this association takes the form of a genotype-environment interaction (G × E), whereby the quality of the interparental relationship acts to moderate the etiology of child CP. The current study sought to evaluate this possibility.

METHOD

We examined multiple measures and informant reports of the quality of the interparental relationship in a sample of more than 700 child twin families from the Michigan State University Twin Registry (MSUTR). Analyses consisted of a series of latent G × E models.

RESULTS

The 'no moderation' model provided the best fit to the data in nearly all cases, findings that collectively provide strong evidence against the possibility that the etiology of CP is moderated by the quality of the interparental relationship.

CONCLUSIONS

Our findings suggest that, contrary to implicit (and sometimes explicit) assumptions in the field, it is not the case that every environmental risk (or protective) factor exacerbates (or suppresses) genetic influences on CP. Future research should seek to delineate the specific environmental experiences that do serve as etiologic moderators of CP, and to clarify how this G × E interplay might change over the course of development.

Prosocial peer affiliation suppresses genetic influences on non-aggressive antisocial behaviors during childhood

BACKGROUND

Available research has suggested that affiliation with prosocial peers reduces child and adolescent antisocial behavior. However, the etiologic mechanisms driving this association remain unclear. The current study sought to evaluate whether this association takes the form of a gene-environment interaction (G × E) in which prosocial peer affiliation acts to reduce the consequences of genetic risk for non-aggressive antisocial behavior during childhood.

METHOD

Our sample consisted of 500 twin pairs aged 6-10 years from the Michigan State University Twin Registry (MSUTR).

RESULTS

The results robustly support moderation by prosocial peer affiliation. Genetic influences on non-aggressive antisocial behavior were observed to be several times larger in those with lower levels of prosocial peer affiliation than in those with higher levels of prosocial peer affiliation. This pattern of results persisted even after controlling for gene-environment correlations and deviant peer affiliation, and when restricting our analyses to those twins who shared all or nearly all of their friends.

CONCLUSIONS

Such findings not only suggest that prosocial peer affiliation moderates genetic influences on non-aggressive antisocial behaviors during childhood but also provide support for the theoretical notion that protective environmental experiences may exert their influence by promoting resilience to genetic risk.

Do etiological influences on aggression overlap with those on rule breaking? A meta-analysis

BACKGROUND

Although aggressive (AGG) and non-aggressive rule-breaking (RB) dimensions of antisocial behavior have been shown to be differentially heritable, available studies have disagreed on the extent to which the genetic and environmental factors influencing AGG also influence RB. The current meta-analysis sought to clarify the extent of etiological overlap between AGG and RB. Method Thirteen twin/sibling studies examining the covariation between AGG and RB were collected, of which 11 (with 12 independent samples) were ultimately included in the analyses (n=12923 twin/sibling pairs). Genetic and environmental correlations between AGG and RB served as study effect sizes. When squared, these correlations directly index the proportion of genetic and environmental overlap. Data were analyzed using mixed effect models.

RESULTS

Analyses revealed that genetic influences on AGG were largely, but not entirely, distinct from those on RB: only 38.4% of the genetic influences on AGG overlapped with those on RB. Similarly, only 10.2% of the non-shared environmental influences on AGG overlapped with those on RB. Although the conclusion that etiological influences on AGG are partially distinct from those on RB persisted across several potential moderators, the age of the sample and the informant used were found to moderate the extent of overlap.

CONCLUSIONS

The findings underscore the presence of meaningful etiological distinctions between AGG and RB, and imply that future conceptualizations of antisocial behavior should be organized (at least in part) around the dimensions of AGG and RB.

Delinquent peer affiliation as an etiological moderator of childhood delinquency

BACKGROUND

Prior research has indicated that affiliation with delinquent peers activates genetic influences on delinquency during adolescence. However, because other studies have indicated that the socializing effects of delinquent peers vary dramatically across childhood and adolescence, it is unclear whether delinquent peer affiliation (DPA) also moderates genetic influences on delinquency during childhood. Method The current study sought to evaluate whether and how DPA moderated the etiology of delinquency in a sample of 726 child twins from the Michigan State University Twin Registry (MSUTR).

RESULTS

The results robustly supported etiological moderation of childhood delinquency by DPA. However, this effect was observed for shared environmental, rather than genetic, influences. Shared environmental influences on delinquency were found to be several-fold larger in those with higher levels of DPA as compared to those with lower levels. This pattern of results persisted even when controlling for the overlap between delinquency and DPA.

CONCLUSIONS

Our findings bolster prior work in suggesting that, during childhood, the association between DPA and delinquency is largely (although not solely) attributable to the effects of socialization as compared to selection. They also suggest that the process of etiological moderation is not specific to genetic influences. Latent environmental influences are also amenable to moderation by measured environmental factors.

The natural antimicrobial carvacrol inhibits Campylobacter jejuni motility and infection of epithelial cells

Background

Natural compounds with anti-microbial properties are attractive reagents to reduce the use of conventional antibiotics. Carvacrol, the main constituent of oregano oil, inhibits the growth of a variety of bacterial foodborne pathogens. As concentrations of carvacrol may vary in vivo or when used in animal feed, we here investigated the effect of subinhibitory concentrations of the compound on major virulence traits of the principal bacterial foodborne pathogen Campylobacter jejuni.

Methods/Principal Findings

Motility assays revealed that subinhibitory concentrations of carvacrol inhibited the motility of C. jejuni without affecting bacterial growth. Immunoblotting and electron microscopy showed that carvacrol-treated C. jejuni still expressed flagella. The loss of motility was not caused by reduced intracellular ATP levels. In vitro infection assays demonstrated that subinhibitory concentrations of carvacrol also abolished C. jejuni invasion of human epithelial cells. Bacterial uptake of invasive Escherichia coli was not blocked by carvacrol. Exposure of C. jejuni to carvacrol prior to infection also inhibited cellular infection, indicating that the inhibition of invasion was likely caused by an effect on the bacteria rather than inhibition of epithelial cell function.

Conclusions/Significance

Bacterial motility and invasion of eukaryotic cells are considered key steps in C. jejuni infection. Our results indicate that subinhibitory concentrations of carvacrol effectively block these virulence traits by interfering with flagella function without disturbing intracellular ATP levels. These results broaden the spectrum of anti-microbial activity of carvacrol and support the potential of the compound for use in novel infection prevention strategies.

In vitro inhibition of Eimeria tenella invasion of epithelial cells by phytochemicals

Resistance to coccidiostats and possible future restrictions on their use raise the need for alternative methods of reducing coccidiosis in poultry. The aim of this study was to evaluate the effect of selected phytochemicals on Eimeria tenella sporozoite invasion in vitro. Four phytochemicals were selected on the basis that they reduce the virulence of Eimeria spp. and/or provide immune modulatory benefits to host cells: betaine, carvacrol, curcumin and Echinacea purpurea extract (EP). Madin-Darby bovine kidney (MDBK) cells were covered by medium containing phytochemicals at the highest concentration which was non-toxic to the cells. Salinomycin 50 μg/ml was positive control; negative control was medium only. E. tenella (Houghton strain) sporozoites were added to wells and after incubation for 2, 4 or 20 h at 37°C, cells were fixed and stained with hematoxylin-eosin. Ten evenly spaced fields per well were photographed and the percentage of cells invaded by sporozoites was calculated and normalized to the control. At 2h, carvacrol, curcumin and EP showed a significantly lower percentage of sporozoite invasion than the untreated control; in contrast, betaine treatment represented a significantly higher invasion percentage. Combining carvacrol with EP inhibited E. tenella invasion more effectively than applying the compounds individually, but the further addition of curcumin did not reduce invasion further. In conclusion, this study shows that invasion of MDBK epithelial cells by E. tenella sporozoites is inhibited in the presence of carvacrol, curcumin, or EP and enhanced by betaine. There may be potential for developing these phytochemicals as anti-coccidial feed or water additives for poultry.

The effects of puberty on genetic risk for disordered eating: evidence for a sex difference

BACKGROUND

Differences in genetic influences on disordered eating are present across puberty in girls. Heritability is 0% before puberty, but over 50% during and after puberty. Emerging data suggest that these developmental differences may be due to pubertal increases in ovarian hormones. However, a critical piece of evidence is lacking, namely, knowledge of genetic influences on disordered eating across puberty in boys. Boys do not experience increases in ovarian hormones during puberty. Thus, if pubertal increases in genetic effects are present in boys, then factors in addition to ovarian hormones may drive increases in heritability in girls. The current study was the first to examine this possibility in a sample of 1006 male and female twins from the Michigan State University Twin Registry.

METHOD

Disordered eating was assessed with the Minnesota Eating Behavior Survey. Pubertal development was assessed with the Pubertal Development Scale.

RESULTS

No significant differences in genetic influences on disordered eating were observed in males across any developmental stage. Heritability was 51% in boys during pre-puberty, puberty and young adulthood. By contrast, in girls, genetic factors accounted for 0% of the variance in pre-puberty, but 51% of the variance during puberty and beyond. Sex differences in genetic effects were only significant during pre-puberty, as the best-fitting models constrained heritability to be equal across all males, pubertal females and young adult females.

CONCLUSIONS

The results highlight sex-specific effects of puberty on genetic risk for disordered eating and provide indirect evidence of a role for ovarian hormones and/or other female-specific factors.

Sub-lethal levels of carvacrol reduce Salmonella Typhimurium motility and invasion of porcine epithelial cells

The European ban on the use of antibiotic growth promotors has increased the search for new alternatives to prevent pig intestinal microbial diseases and to stimulate growth. The addition of essential oils or components thereof, such as carvacrol, to pig feed is a promising alternative. In this report we determined the effect of sub-lethal concentrations of carvacrol on Salmonella Typhimurium. At concentrations where growth of Salmonella was not inhibited, carvacrol completely inhibited motility of the bacterium. This loss of motility was not due to the loss of the flagellum or to ATP shortage upon carvacrol treatment. Adhesion of Salmonella to IPEC-J2, porcine intestinal epithelial cells, was not affected by carvacrol but invasion was significantly reduced. In addition, the epithelial gene expression of porcine β-defensin 2, an innate immune response to Salmonella infection, was reduced when Salmonella was exposed to carvacrol. This indicates that invasion but not adhesion of Salmonella triggers the porcine β-defensin 2 expression of porcine epithelial cells.

The death(s) of close friends and family moderate genetic influences on symptoms of major depressive disorder in adolescents

BACKGROUND

Prior work has suggested that genetic influences on major depressive disorder (MDD) may be activated by the experience of negative life events. However, it is unclear whether these results persist when controlling for the possibility of confounding active gene-environment correlations (rGE).

METHOD

We examined a sample of 1230 adopted and biological siblings between the ages of 10 and 20 years from the Sibling Interaction and Behavior Study. MDD was measured via a lifetime DSM-IV symptom count. Number of deaths experienced served as our environmental risk experience. Because this variable is largely independent of the individual's choices/behaviors, we were able to examine gene-environment interactions while circumventing possible rGE confounds.

RESULTS

Biometric analyses revealed pronounced linear increases in the magnitude of genetic influences on symptoms of MDD with the number of deaths experienced, such that genetic influences were estimated to be near-zero for those who had experienced no deaths but were quite large in those who had experienced two or more deaths (i.e. accounting for roughly two-thirds of the phenotypic variance). By contrast, shared and non-shared environmental influences on symptoms of MDD were not meaningfully moderated by the number of deaths experienced.

CONCLUSIONS

Such results constructively replicate prior findings of genetic moderation of depressive symptoms by negative life events, thereby suggesting that this effect is not a function of active rGE confounds. Our findings are thus consistent with the notion that exposure to specific negative life events may serve to activate genetic risk for depression during adolescence.

Preliminary evidence that estradiol moderates genetic influences on disordered eating attitudes and behaviors during puberty

BACKGROUND

Puberty moderates genetic influences on disordered eating attitudes and behaviors, with little genetic influence before puberty but large (50%) genetic effects during and after puberty. To date, however, nothing is known about the mechanisms that underlie these effects. Estradiol is a particularly promising candidate, as estrogens become elevated at puberty and regulate gene transcription within neurotransmitter systems important for eating-related phenotypes. The aim of this pilot study was to examine whether estradiol levels moderate genetic influences on disordered eating during puberty.

METHOD

Participants included 198 female twins (ages 10-15 years) from the Michigan State University Twin Registry. Disordered eating attitudes and behaviors were assessed with the total score, weight preoccupation, body dissatisfaction and binge eating/compensatory behavior subscales of the Minnesota Eating Behavior Survey (MEBS). Afternoon saliva samples were assayed for estradiol levels. Moderation of genetic effects was examined by comparing twin correlations in low versus high estradiol groups.

RESULTS

In the low estradiol group, monozygotic (MZ) and dizygotic (DZ) twin correlations for all MEBS scales were similar, suggesting little genetic influence. In the high estradiol group, the MZ twin correlation was more than double the DZ twin correlation, indicating the presence of genetic effects. Findings could not be accounted for by age, body mass index or the physical changes of puberty.

CONCLUSIONS

Estradiol may be one important moderator of genetic effects on disordered eating during puberty. Larger twin studies are needed to replicate this pilot work and quantify the extent of genetic moderation.

Inhibition of Salmonella enterica serotype Enteritidis on agar and raw chicken by carvacrol vapour

Carvacrol is known to inhibit a number of food borne pathogens. The activity of carvacrol vapour was evaluated against S. enterica serotype Enteritidis on tryptone soya agar and on pieces of raw chicken. On agar, the size of the inhibition zone increased with decreasing volume of agar, increasing vapour exposure period, increasing temperature, increasing volume of carvacrol used and with decreasing bacterial density. Inhibition was equally effective under aerobic and anaerobic conditions. On chicken pieces (10 x 10 x 5 mm, UV-sterilized and inoculated with approx. 5 x 10(3) cfu) carvacrol vapour significantly reduced viable numbers of salmonellae at 4, 20 and 37 degrees C and all viable cells were eliminated by a minimum of 3 h at 37 degrees C (p<0.05). A minimum concentration of 20% carvacrol v/v in ethanol was required to achieve a significant reduction and from 40% v/v no viable cells were recovered (p<0.05). In conclusion, carvacrol vapour is effective at inhibiting the growth of S. enterica serotype Enteritidis on agar and at inhibiting and eliminating these bacteria on the surface of raw chicken.

Low temperature and binding to food components inhibit the antibacterial activity of carvacrol against Listeria monocytogenes in steak tartare

Carvacrol is a major component of thyme and oregano essential oils and has potential uses as a food preservative. The effect of carvacrol on the growth of Listeria monocytogenes was investigated in vitro and in steak tartare. Carvacrol had strong antilisterial activity in growth medium (MIC = 1.6 mM), but no effect was observed when carvacrol was tested in steak tartare. There were two reasons for this reduced activity: the antilisterial activity of carvacrol was strongly reduced at lower temperatures (10 versus 30 degrees C), and the presence of food components interfered with the activity of carvacrol. Both bovine serum albumin and egg yolk inhibited carvacrol activity at > 0.2% (wt/vol) in growth medium. For the first time, carvacrol was found to bind to albumin, suggesting that the reduced antilisterial activity of carvacrol in foods such as dairy products and uncooked meats is the result of fewer free unbound carvacrol molecules available to interact with bacteria.

Carvacrol induces heat shock protein 60 and inhibits synthesis of flagellin in Escherichia coli O157:H7

The essential oils of oregano and thyme are active against a number of food-borne pathogens, such as Escherichia coli O157:H7. Carvacrol is one of the major antibacterial components of these oils, and p-cymene is thought to be its precursor in the plant. The effects of carvacrol and p-cymene on protein synthesis in E. coli O157:H7 ATCC 43895 cells were investigated. Bacteria were grown overnight in Mueller-Hinton broth with a sublethal concentration of carvacrol or p-cymene, and their protein compositions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and confirmed by Western blotting. The presence of 1 mM carvacrol during overnight incubation caused E. coli O157:H7 to produce significant amounts of heat shock protein 60 (HSP60) (GroEL) (P < 0.05) and inhibited the synthesis of flagellin highly significantly (P < 0.001), causing cells to be aflagellate and therefore nonmotile. The amounts of HSP70 (DnaK) were not significantly affected. p-Cymene at 1 mM or 10 mM did not induce HSP60 or HSP70 in significant amounts and did not have a significant effect on flagellar synthesis. Neither carvacrol (0.3, 0.5, 0.8, or 1 mM) nor p-cymene (0.3, 0.5, or 0.8 mM) treatment of cells in the mid-exponential growth phase induced significant amounts of HSP60 or HSP70 within 3 h, although numerical increases of HSP60 were observed. Motility decreased with increasing concentrations of both compounds, but existing flagella were not shed. This study is the first to demonstrate that essential oil components induce HSP60 in bacteria and that overnight incubation with carvacrol prevents the development of flagella in E. coli O157:H7.

Carvacrol induces heat shock protein 60 and inhibits synthesis of flagellin in Escherichia coli O157:H7

The essential oils of oregano and thyme are active against a number of food-borne pathogens, such as Escherichia coli O157:H7. Carvacrol is one of the major antibacterial components of these oils, and p-cymene is thought to be its precursor in the plant. The effects of carvacrol and p-cymene on protein synthesis in E. coli O157:H7 ATCC 43895 cells were investigated. Bacteria were grown overnight in Mueller-Hinton broth with a sublethal concentration of carvacrol or p-cymene, and their protein compositions were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and confirmed by Western blotting. The presence of 1 mM carvacrol during overnight incubation caused E. coli O157:H7 to produce significant amounts of heat shock protein 60 (HSP60) (GroEL) (P < 0.05) and inhibited the synthesis of flagellin highly significantly (P < 0.001), causing cells to be aflagellate and therefore nonmotile. The amounts of HSP70 (DnaK) were not significantly affected. p-Cymene at 1 mM or 10 mM did not induce HSP60 or HSP70 in significant amounts and did not have a significant effect on flagellar synthesis. Neither carvacrol (0.3, 0.5, 0.8, or 1 mM) nor p-cymene (0.3, 0.5, or 0.8 mM) treatment of cells in the mid-exponential growth phase induced significant amounts of HSP60 or HSP70 within 3 h, although numerical increases of HSP60 were observed. Motility decreased with increasing concentrations of both compounds, but existing flagella were not shed. This study is the first to demonstrate that essential oil components induce HSP60 in bacteria and that overnight incubation with carvacrol prevents the development of flagella in E. coli O157:H7.

Structural requirements for the antimicrobial activity of carvacrol

Carvacrol is a component of several essential oils and has been shown to exert antimicrobial activity. The structural requirements for the activity of carvacrol were determined by comparison to structurally related (nonessential oil) compounds. Removal of the aliphatic ring substituents of carvacrol slightly decreased the antimicrobial activity. The effect of the hydroxyl group of carvacrol on activity could not be determined by simply comparing it to p-cymene, because this compound is immiscible with water; therefore, 2-amino-p-cymene, the amino analogue of carvacrol, which has a similar hydrophobicity and structural characteristics, was used. 2-Amino-p-cymene had similar membrane disruption and bacterial killing characteristics as carvacrol showing that, contrary to previous reports, the hydroxyl group of carvacrol itself is not essential for the antimicrobial activity. However, the observed 3-fold lower activity for 2-amino-p-cymene as compared to carvacrol indicates special features in the antimicrobial mode of action of carvacrol due to the hydroxyl group.

Increase in activity of essential oil components carvacrol and thymol against Escherichia coli O157:H7 by addition of food stabilizers

The major components of oregano and thyme essential oils that had previously been shown to inhibit Escherichia coli O157:H7 were determined by high-performance liquid chromatography with UV detection and liquid chromatographic tandem mass spectrometry. The MICs and MBCs of carvacrol, thymol, p-cymene, and gamma-terpinene against a strain of E. coli O157: H7 phage type 34 isolated from bovine feces were determined by microdilution assay. The constituents were then tested in checkerboard assays to detect possible interactions. Carvacrol and thymol displayed bacteriostatic and bactericidal properties with MICs of 1.2 mmol/liter and were additive in combination. p-Cymene and gamma-terpinene displayed no measurable antibacterial activity up to 50 mmol/liter, and neither influenced the activity of carvacrol or thymol. Growth curves in the presence of nonlethal concentrations of carvacrol with the addition of agar (0.05%, wt/vol) or carrageenan (0.125%, wt/vol) as stabilizer were produced by optical density measurement. The stabilizers agar and carrageenan both significantly improved the effectiveness of carvacrol in broth, possibly because of a delay in the separation of the hydrophobic substrate from the aqueous phase of the medium. When carvacrol was dissolved in ethanol before addition to broth, stabilizers were not needed. Carvacrol and thymol, particularly when used in combination with a stabilizer or in an ethanol solution, may be effective in reducing the number or preventing growth of E. coli O157:H7 in liquid foods.

[Cleaning and disinfection: tips for the practice]

Cleaning (removal of visible dirt) and disinfection (reduction of the number of micro-organisms to an acceptable level) are necessary to limit 'carry over' of infections agents between patients and people as much as possible. Loose dirt should be removed prior to the use of a detergent. Apart from cases of contamination of an otherwise clean surface or in case of a highly infectious agent, thorough cleaning should always precede disinfection. Several active ingredients are approved for disinfection of animal accommodation. From the point of view of safety and effectiveness, individual chemicals should never be mixed or added to detergents. Queries about the use of chemical agents can be addressed to the College voor de Toelating van Bestrijdingsmiddelen or the manufacturer of the product.

Antibacterial activity of selected plant essential oils against Escherichia coli O157:H7

AIMS

To quantify the antibacterial properties of five essential oils (EO) on a non-toxigenic strain of Escherichia coli O157:H7 in the presence and absence of a stabilizer and an emulsifier and at three different temperatures.

METHODS AND RESULTS

Five EOs known to exhibit antibacterial properties were screened by disc diffusion assay and the most active were selected for further study in microdilution colorimetric assays. Oregano (Origanum vulgare) and thyme (Thymus vulgaris; light and red varieties) EO had the strongest bacteriostatic and bactericidal properties, followed by bay (Pimenta racemosa) and clove bud (Eugenia caryophyllata synonym: Syzygium aromaticum) EO. Oregano oil was colicidal at 625 microl l(-1) at 10, 20 and 37 degrees C. The addition of 0.05% (w/v) agar as stabilizer reinforced the antibacterial properties, particularly at 10 degrees C, whereas 0.25% (w/v) lecithin reduced antibacterial activity. Scanning electron micrographs showed extensive morphological changes to treated cells.

CONCLUSIONS

Oregano and thyme EO possess significant in vitro colicidal and colistatic properties, which are exhibited in a broad temperature range and substantially improved by the addition of agar as stabilizer. Bay and clove bud EO are less active. Lecithin diminished antibacterial properties. The bactericidal concentration of oregano EO irreversibly damaged E. coli O157:H7 cells within 1 min.

SIGNIFICANCE AND IMPACT OF THE STUDY

Oregano and light thyme EO, particularly when enhanced by agar stabilizer, may be effective in reducing the number or preventing the growth of E. coli O157:H7 in foods.

Surface form typicality and asymmetric transfer in episodic memory for spoken words

A series of experiments was conducted to determine whether the typicality of the surface form of speech would affect memory retention of spoken words. For each surface characteristic studied, a continuous-recognition-memory task was used in which listeners based recognition judgments on word identity alone. For "typical" items, repetition benefits did not depend on whether the surface forms of the 1st and 2nd occurrences matched or mismatched. For "atypical" items, a larger repetition benefit occurred when the surface forms of the 2 occurrences matched. These results suggest that episodic memory for spoken words may be directly related to the perceived typicality of particular surface characteristics.

Impact on human health of Salmonella spp. on pork in The Netherlands and the anticipated effects of some currently proposed control strategies

The impact on human health of Salmonella spp. on pork in The Netherlands is described. Subsequently, the effects of some currently proposed control strategies in the Dutch pork production chain are evaluated and quantified with the aid of a simple mathematical model. The estimated average incidence of cases of salmonellosis in the Netherlands is about 450 cases per 100,000 person years at risk (pyar). Some special risk groups for which the risks could be quantified are (1) persons with underlying diseases, such as neoplasms or diabetes mellitus (1200 cases/100,000 pyar); (2) persons with achlorhydria or who excessively use antacids (1100 cases/100,000 pyar); (3) persons who have recently been treated with antibiotics that disturb the normal gut flora (1700 cases/100,000 pyar); (4) nurses (900 cases/100,000 pyar); (5) caterers (900 cases/100,000 pyar); (6) slaughterline personnel (1800 cases/100,000 pyar). Furthermore, it is estimated that 15% (5-25%) of all cases of salmonellosis in The Netherlands are associated with the consumption of pork. Currently, proposed control measures regarding Salmonella in pigs and on pork in The Netherlands are codes of good manufacturing practices (GMP) that, in fact, formalize recommendations that can be found in many handbooks about pig breeding and pig slaughtering. When evaluated by a mathematical model constructed for this purpose, the proposed GMP codes from farm to cutting/retail could, at best, reduce the current levels of Salmonella-positive pigs and pork by 50-60%. If pigs were bred according to the rather costly specific pathogen-free concept (SPF), the prevalence of contaminated carcasses and pork could in total be reduced by 95% or more. However, implementing GMP codes from the transport phase up to the cutting/retail phase coupled with a decontamination step at the end of the slaughterline would be just as effective as GMP in combination with breeding using the SPF-concept. It is therefore concluded that the most efficient and cost-effective way of reducing the 'Salmonella problem' entailed by the consumption of pork would be to decontaminate carcasses under the precondition that the entire production chain strictly adheres to GMP principles. Therefore, the EU should also allow for more possibilities regarding the decontamination of carcasses than is currently the case. It is also concluded that current EU regulations relying on hazard analysis of critical control points (HACCP)-inspired production in cutting plants will not be effective in reducing the prevalence of Salmonella spp. on pork. This is mainly because (1) there is currently an almost steady stream of Salmonella-positive carcasses that enter the cutting process; (2) when contaminated carcasses are being processed, further cross-contamination during working hours is unavoidable; (3) no steps in the cutting process are intentionally designed to effectively reduce the risks or consequences of cross contamination of cuts and retail-ready products.

Salmonella spp. on pork at cutting plants and at the retail level and the influence of particular risk factors

This article describes the contamination of pork with Salmonella spp. in cutting plants and butchers' shops in The Netherlands and quantifies the influence of several risk factors. When contaminated carcasses are being processed, the main risk factors regarding cross contamination are inapt cleaning and disinfection (OR 12.8), manipulation of contaminated materials as such (OR 4.7) and (re)contaminated surfaces (OR 4.4). However, in the current situation, where contaminated carcasses are constantly being brought into cutting lines, interim cleaning and disinfection of surfaces and utensils during breaks and at the end of the working day will most likely prevent not more than about 10% of all cross contamination that takes place during a working day. Thus, as long as contaminated carcasses are being processed, about 90% of the cross contamination that occurs in cutting plants is practically unavoidable. It can therefore also be concluded that under these circumstances the implementation of codes of good manufacturing practices (GMP) and Hazard Analysis Critical Control Point (HACCP)-inspired production methods will only be marginally effective in the control of Salmonella spp. cross contamination in cutting lines. The same is more or less true for the processing of contaminated cuts or carcasses by butchers in shops and supermarkets. Furthermore, in contrast to the situation in cutting plants, it may be that up to 10% of butcher's shops or kitchens of restaurants become colonized for several weeks or months with their own endemic 'house flora' of Salmonella spp., which are originally introduced via the purchased contaminated products of animal origin. Though there are no hard data to substantiate this, it can be suspected that these shops and restaurants represent the more badly managed, i.e. poorly cleaned and disinfected, enterprises. However, several analytical limitations hinder an exact determination of the prevalence of Salmonella spp. contaminated pork and an exact quantification the influence of risk factors. The diagnostic value (i.e. the sensitivity, specificity, precision and predictive value) of the combination of swabbing of carcasses and cuts and the usually employed culturing methods, in particular, is largely unknown, and there are indications that it may be seriously questioned. Without a more thorough knowledge about the diagnostic value of current and future methods of sampling and identification, it is impossible to provide for more accurate estimations of the prevalence of Salmonella positive carcasses and cuts. Based on the research data, the incidence of contaminated cuts and retail-ready pork can not be estimated more precise than as somewhere between 5-40%. When compensating for the discussed methodological flaws, it must be assumed that currently the true prevalence of contaminated primal cuts and retail-ready pork in butchers' shops is about 25-30%, and that of minced pork and pork sausages about 50-55%. Lastly it is concluded that if carcasses were Salmonella-free, consumers could in principle be provided with virtually Salmonella-free pork. It is therefore recommended that the EU allows for a decontamination step in slaughterhouses with a substance that is generally recognized as safe, provided that the producers strictly adhere to GMP-principles.