Distinct Sensory Hedonic Functions for Sourness in Adults.

Over the last half-century, variable responses to sweetness have repeatedly been shown to fall into a small number of hedonic responses, implying that looking only at group means may can obfuscate meaningfully different response patterns. Comparative data for sourness is quite sparse, especially in adults. While increased liking with higher acid concentration has been reported for some children, in adults, sourness is classically assumed to be aversive, with a monotonic drop in liking with increasing sourness. Here, we test this assumption using a simple model system or experimental beverage in convenience samples of adults from the United States (increasing citric acid in water) and Italy (increasing citric acid in pear juice). Participants rated intensity and liking of sampled stimuli. For both cohorts, we find clear evidence of three distinct patterns of responses: a strong negative group where liking dropped with increased sourness, an intermediate group who showed a more muted drop in liking with more sourness, and a strong positive group where liking increased with more sourness. Strikingly, both cohorts showed similar proportions of response patterns, with ~63-70% in the strong negative group, and 11-12% in the strong positive group, suggesting these proportions may be stable across cultures. Notably, the three groups did not differ by age or gender. These data support the existence of different hedonic response profiles to sour stimuli in adults, once again highlighting the importance of looking at individual differences and potential consumer segments, rather than merely averaging hedonic responses across all individuals within a group.

Associations between human fungiform papillae and responsiveness to oral stimuli: effects of individual variability, population characteristics, and methods for papillae quantification.

Fungiform papillae (FP) on human tongue are the proxy structures designated to oral stimuli detection and transduction. However, the role of their density (fungiform papillae/cm2) in explaining oral sensitivity is still controversial. While early studies generally found that the responsiveness to oral stimuli increased as the number of papillae increased, recent large-scale studies failed to confirm this finding. The present paper reviews relevant studies dealing with the relationship between FP density and responsiveness to oral sensations including: fundamental tastes, 6-n-propyl-2-thiouracil (PROP), and sensations from trigeminal stimulation. Manual methods and automated methods for papillae detection and quantification are reviewed and their advantages and limitations highlighted. The main factors affecting FP density and functionality (age, gender, pathologic impairments) are also considered. Possible bias related to methodological issues in counting technique (equipment used, area and location of the tongue to count, procedures to validate the count), population sample (demographics), and sensory response collection (threshold or supra-threshold stimuli, intensity scaling) are illustrated. The lack of information related to the variability in taste pores density and the possible impairments due to nerve damages, may obscure the relationship between FPD and oral responsiveness.

Individual Variation in PROP Status, Fungiform Papillae Density, and Responsiveness to Taste Stimuli in a Large Population Sample.

Despite considerable research investigating the role of 6-n-propylthiouracil bitterness perception and variation of fungiform papillae density in food perception, this relationship remains controversial as well as the association between the 2 phenotypes. Data from 1119 subjects (38.6% male; 18-60 years) enrolled in the Italian Taste project were analyzed. Responsiveness to the bitterness of 6-n-propylthiouracil was assessed on the general Labeled Magnitude Scale. Fungiform papillae density was determined from manual counting on digital images of the tongue. Solutions of tastes, astringent, and pungent sensations were prepared to be moderate/strong on a general Labeled Magnitude Scale. Four foods had tastants added to produce 4 variations in target sensations from weak to strong (pear juice: citric acid, sourness; chocolate pudding: sucrose, sweetness; bean purée: sodium chloride, saltiness; and tomato juice: capsaicin, pungency). Women gave ratings to 6-n-propylthiouracil and showed fungiform papillae density that was significantly higher than men. Both phenotype markers significantly decreased with age. No significant correlations were found between 6-n-propylthiouracil ratings and fungiform papillae density. Fungiform papillae density variation does not affect perceived intensity of solutions. Responsiveness to 6-n-propylthiouracil positively correlated to perceived intensity of most stimuli in solution. A significant effect of fungiform papillae density on perceived intensity of target sensation in foods was found in a few cases. Responsiveness to 6-n-propylthiouracil positively affected all taste intensities in subjects with low fungiform papillae density whereas there were no significant effects of 6-n-propylthiouracil in those with high fungiform papillae density. These data highlight a complex interplay between 6-n-propylthiouracil status and fungiform papillae density and the need of a critical reconsideration of their role in food perception and acceptability.

The Agr-Like Quorum Sensing System Is Required for Pathogenesis of Necrotic Enteritis Caused by Clostridium perfringens in Poultry.

Clostridium perfringens encodes at least two different quorum sensing (QS) systems, the Agr-like and LuxS, and recent studies have highlighted their importance in the regulation of toxin production and virulence. The role of QS in the pathogenesis of necrotic enteritis (NE) in poultry and the regulation of NetB, the key toxin involved, has not yet been investigated. We have generated isogenic agrB-null and complemented strains from parent strain CP1 and demonstrated that the virulence of the agrB-null mutant was strongly attenuated in a chicken NE model system and restored by complementation. The production of NetB, a key NE-associated toxin, was dramatically reduced in the agrB mutant at both the transcriptional and protein levels, though not in a luxS mutant. Transwell assays confirmed that the Agr-like QS system controls NetB production through a diffusible signal. Global gene expression analysis of the agrB mutant identified additional genes modulated by Agr-like QS, including operons related to phospholipid metabolism and adherence, which may also play a role in NE pathogenesis. This study provides the first evidence that the Agr-like QS system is critical for NE pathogenesis and identifies a number of Agr-regulated genes, most notably netB, that are potentially involved in mediating its effects. The Agr-like QS system thus may serve as a target for developing novel interventions to prevent NE in chickens.

Comparative transcriptome analysis by RNAseq of necrotic enteritis Clostridium perfringens during in vivo colonization and in vitro conditions.

BACKGROUND: Necrotic enteritis (NE) caused by netB-positive type A Clostridium perfringens is an important bacterial disease of poultry. Through its complex regulatory system, C. perfringens orchestrates the expression of a collection of toxins and extracellular enzymes that are crucial for the development of the disease; environmental conditions play an important role in their regulation. In this study, and for the first time, global transcriptomic analysis was performed on ligated intestinal loops in chickens colonized with a netB-positive C. perfringens strain, as well as the same strain propagated in vitro under various nutritional and environmental conditions. RESULTS: Analysis of the respective pathogen transcriptomes revealed up to 673 genes that were significantly expressed in vivo. Gene expression profiles in vivo were most similar to those of C. perfringens grown in nutritionally-deprived conditions. CONCLUSIONS: Taken together, our results suggest a bacterial transcriptome responses to the early stages of adaptation, and colonization of, the chicken intestine. Our work also reveals how netB-positive C. perfringens reacts to different environmental conditions including those in the chicken intestine.

Experimental reproduction of necrotic enteritis in chickens: a review.

This review discusses key factors important in successful experimental reproduction of necrotic enteritis (NE) in chickens, and how these factors can be adjusted to affect the severity of the lesions induced. The critical bacterial factor is the need to use virulent, netB-positive, strains of Clostridium perfringens; disease severity can be enhanced by using netB-positive C. perfringens strains that are also tpeL-positive, by the use of young rather than old broth cultures, and by the number of days of inoculation and the number of bacteria used. Use of cereals rich in non-starch polysaccharides can enhance disease, as does use of animal proteins. Administration of coccidia, including coccidial vaccines, combined with netB-positive C. perfringens, increases the severity of experimentally-induced NE. Dietary manipulation may be less important in coccidia-based models since the latter are so effective. Disease scoring systems and welfare considerations are discussed.

The pathogenesis of necrotic enteritis in chickens: what we know and what we need to know: a review.

This review summarizes advances in understanding the pathogenesis of necrotic enteritis of chickens caused by netB-positive Clostridium perfringens. The discovery of NetB as the essential toxin trigger for the disease was followed by recognition that it forms part of a large plasmid-encoded 42 kb pathogenicity locus (NELoc-1). While the locus is critical for toxin production, it likely has additional functions related to colonization and degradation of the mucus barrier, which are essential both to multiplication and to bringing NetB close to the intestinal epithelium. Two "chitinases" (glycoside hydrolases (GHs)) present on NELoc-1 are predicted to be involved in mucin degradation, as is the large carbohydrate-binding metalloprotease, shown to be involved in mucinase activity in other clostridia. A second pathogenicity locus found in netB-positive C. perfringens, NELoc-2, also encodes a GH likely involved in mucin degradation. Upon reaching a sufficient cell density on the intestinal mucosa, the Agr-like quorum-sensing system is triggered, which in turn up-regulates the VirR/VirS regulon. This regulon includes NetB. Where NetB initiates damage is unresolved, but it may be deep in the intestinal mucosa, rather than superficially. As the disease progresses, C. perfringens line what remains of the intestinal epithelium in large numbers. This likely involves a number of different bacterial adhesins, including additional NELoc-1-encoded bacterial surface proteins, some of which may adhere to epithelial cell ligands exposed by bacterial sialidases. Further studies of the pathogenesis of necrotic enteritis should lead to development of novel ways to control the infection.

Novel flavours paired with glutamate condition increased intake in older adults in the absence of changes in liking.

Previous research on the repeat exposure to a novel flavour combined with monosodium glutamate (MSG) has shown an increase in liking and consumption for the particular flavour. The aim of the current work was to investigate whether this could also be observed in the case of older people, since they are most affected by undernutrition in the developed world and ways to increase consumption of food are of significant importance for this particular age group. For this study, 40 older adults (age 65-88) repeatedly consumed potato soup with two novel flavours (lemongrass and cumin) which were either with or without a high level of MSG (5% w/w). A randomized single blind within-subject design was implemented, where each participant was exposed to both soup flavours three times over 6 days, with one of the soup flavours containing MSG. After three repeat exposures, consumption increased significantly for the soups where the flavours had contained MSG during the repeated exposure (mean weight consumed increased from 123 to 164 g, p = 0.017), implying that glutamate conditioned for increased wanting and consumption, despite the fact that the liking for the soup had not increased.

Diversion of phagosome trafficking by pathogenic Rhodococcus equi depends on mycolic acid chain length.

Rhodococcus equi is a close relative of Mycobacterium spp. and a facultative intracellular pathogen which arrests phagosome maturation in macrophages before the late endocytic stage. We have screened a transposon mutant library of R. equi for mutants with decreased capability to prevent phagolysosome formation. This screen yielded a mutant in the gene for ß-ketoacyl-(acyl carrier protein)-synthase A (KasA), a key enzyme of the long-chain mycolic acid synthesizing FAS-II system. The longest kasA mutant mycolic acid chains were 10 carbon units shorter than those of wild-type bacteria. Coating of non-pathogenic E. coli with purified wild-type trehalose dimycolate reduced phagolysosome formation substantially which was not the case with shorter kasA mutant-derived trehalose dimycolate. The mutant was moderately attenuated in macrophages and in a mouse infection model, but was fully cytotoxic.Whereas loss of KasA is lethal in mycobacteria, R. equi kasA mutant multiplication in broth was normal proving that long-chain mycolic acid compounds are not necessarily required for cellular integrity and viability of the bacteria that typically produce them. This study demonstrates a central role of mycolic acid chain length in diversion of trafficking by R. equi.

Perfrin, a novel bacteriocin associated with netB positive Clostridium perfringens strains from broilers with necrotic enteritis.

Necrotic enteritis in broiler chickens is associated with netB positive Clostridium perfringens type A strains. It is known that C. perfringens strains isolated from outbreaks of necrotic enteritis are more capable of secreting factors inhibiting growth of other C. perfringens strains than strains isolated from the gut of healthy chickens. This characteristic could lead to extensive and selective presence of a strain that contains the genetic make-up enabling to secrete toxins that cause gut lesions. This report describes the discovery, purification, characterization and recombinant expression of a novel bacteriocin, referred to as perfrin, produced by a necrotic enteritis-associated netB-positive C. perfringens strain. Perfrin is a 11.5 kDa C-terminal fragment of a 22.9 kDa protein and showed no sequence homology to any currently known bacteriocin. The 11.5 kDa fragment can be cloned into Escherichia coli, and expression yielded an active peptide. PCR detection of the gene showed its presence in 10 netB-positive C. perfringens strains of broiler origin, and not in other C. perfringens strains tested (isolated from broilers, cattle, sheep, pigs, and humans). Perfrin and NetB are not located on the same genetic element since NetB is plasmid-encoded and perfrin is not. The bacteriocin has bactericidal activity over a wide pH-range but is thermolabile and sensitive to proteolytic digestion (trypsin, proteinase K). C. perfringens bacteriocins, such as perfrin, can be considered as an additional factor involved in the pathogenesis of necrotic enteritis in broilers.

Arousal and the modulation of sensory experience: evidence from food-related emotions.

Across sensory systems, several stimulus collative characteristics, including intensity, novelty, complexity and perceived dangerousness, are known to elicit high levels of physiological and psychological arousal. It has become apparent that food rejections by both children and adults are frequently linked to such arousal-inducing characteristics. This paper examines how arousal and arousability are important elements in responding to stimuli generally, but specifically to foods, ultimately influencing food preferences and choices. It is clear that responses to sensory properties are subject not just to variations in perceptual sensitivity due to genetics or experience-as in the case of widely rejected qualities such as bitterness or pungency-but also to the arousal potential of those stimuli. Moreover, this is linked to various enduring aspects of personality, suggesting that the impact of arousal on food choices is merely one aspect of a more general sensory sensitivity. The impact of diet on various health outcomes underlines the importance of understanding the relationship of arousal to food choices. This article is part of the theme issue 'Sensing and feeling: an integrative approach to sensory processing and emotional experience'.

The genome of a pathogenic rhodococcus: cooptive virulence underpinned by key gene acquisitions.

We report the genome of the facultative intracellular parasite Rhodococcus equi, the only animal pathogen within the biotechnologically important actinobacterial genus Rhodococcus. The 5.0-Mb R. equi 103S genome is significantly smaller than those of environmental rhodococci. This is due to genome expansion in nonpathogenic species, via a linear gain of paralogous genes and an accelerated genetic flux, rather than reductive evolution in R. equi. The 103S genome lacks the extensive catabolic and secondary metabolic complement of environmental rhodococci, and it displays unique adaptations for host colonization and competition in the short-chain fatty acid-rich intestine and manure of herbivores--two main R. equi reservoirs. Except for a few horizontally acquired (HGT) pathogenicity loci, including a cytoadhesive pilus determinant (rpl) and the virulence plasmid vap pathogenicity island (PAI) required for intramacrophage survival, most of the potential virulence-associated genes identified in R. equi are conserved in environmental rhodococci or have homologs in nonpathogenic Actinobacteria. This suggests a mechanism of virulence evolution based on the cooption of existing core actinobacterial traits, triggered by key host niche-adaptive HGT events. We tested this hypothesis by investigating R. equi virulence plasmid-chromosome crosstalk, by global transcription profiling and expression network analysis. Two chromosomal genes conserved in environmental rhodococci, encoding putative chorismate mutase and anthranilate synthase enzymes involved in aromatic amino acid biosynthesis, were strongly coregulated with vap PAI virulence genes and required for optimal proliferation in macrophages. The regulatory integration of chromosomal metabolic genes under the control of the HGT-acquired plasmid PAI is thus an important element in the cooptive virulence of R. equi.

How do swine practitioners and veterinary pathologists arrive at a diagnosis of Clostridium perfringens type A enteritis in neonatal piglets?

A questionnaire was administered to 22 veterinary practitioners and 17 veterinary pathologists to investigate the methods used for diagnosis of Clostridium perfringens type A enteritis in neonatal pigs. Practitioners generally diagnosed C. perfringens type A associated enteritis by age of onset of diarrhea (between 1 to 7 days of age). Most practitioners (95%) were moderately to very confident in their diagnosis. Pathologists generally diagnosed C. perfringens type A associated enteritis by combinations of isolation of the organism, genotyping or detecting the toxins of the organism, and ruling out other pathogens through histopathology. Almost half (41%) of the pathologists were not confident of their diagnosis. This study reports that the current diagnostic method for C. perfringens type A enteritis is not specific, and although many pathologists expressed reservations about making a diagnosis of C. perfringens type A enteritis, most practitioners were confident in their diagnosis, even though reported clinical signs of clostridial diarrhea are similar to those of a number of other enteric diseases.

Comment les praticiens porcins et les pathologistes vétérinaires parviennent-ils à un diagnostic d'entérite àClostridium perfringenstype A chez les porcelets nouveau-nés? Un questionnaire a été administré à 22 praticiens vétérinaires et à 17 pathologistes vétérinaires afin de faire enquête sur les méthodes utilisées pour le diagnostic de l'entérite à Clostridium perfringens type A chez les porcs nouveau-nés. Les praticiens diagnostiquaient généralement une entérite associée à C. perfringens type A selon l'âge à l'apparition de la diarrhée (âge d'entre 1 et 7 jours). La plupart des praticiens (95 %) ont déclaré un niveau de confiance de modérément confiant à très confiant à l'égard de leur diagnostic. Les pathologistes diagnostiquaient généralement l'entérite associée à C. perfringens type A par une combinaison d'isolement de l'organisme, du génotypage ou de la détection des toxines de l'organisme et éliminaient les autres agents pathogènes à l'aide d'une histopathologie. Près de la moitié (41 %) des pathologistes n'étaient pas confiants de leur diagnostic. Cette étude signale que la méthode diagnostique actuelle pour l'entérite à C. perfringens type A n'est pas spécifique et, même si beaucoup de pathologistes ont exprimé des réserves à propos d'un diagnostic d'entérite à C. perfringens type A, la plupart des praticiens éprouvaient de la confiance face à leur diagnostic, même si les signes cliniques signalés de la diarrhée clostridiale sont semblables à plusieurs autres maladies entériques.(Traduit par Isabelle Vallières).

High arousal as the source of food rejection in food neophobia.

Food neophobia (FN) at moderate to high levels is very common among adult populations in all cultures and is usually defined in terms of rejection of unfamiliar foods. However, food rejection in FN is only partly related to food familiarity. Experimental and survey studies have suggested that unpleasantly high arousal may be induced by food novelty, but also be produced by foods with intense or complex flavours, that are perceived as dangerous or foreign, or that have unusual ingredients. Liking for foods with these characteristics have recently been shown to be strongly negatively associated with FN. Thus, induced high arousal may underlie food rejection in FN. Here, we collected familiarity, liking and arousal ratings, and scores on the standard Food Neophobia Scale from more than 7000 consumers in four countries - Australia, United Kingdom, Singapore, Malaysia - for a series of food names that were manipulated to produce standard and 'high arousal' (variant) versions of the same foods. Consistent across all four countries, arousal ratings increased, and liking decreased, with decreases in food familiarity. Variant food names were always associated with ratings of higher arousal than the standard names. The variant foods were generally less familiar than the standard foods, although this was not a necessary condition for their higher arousal ratings, suggesting that the other arousal-inducing factors (e.g., flavour intensity) also played a role. Across all foods, arousal ratings increased, and liking ratings decreased, as FN increased, but these effects were accentuated for the variant foods. The consistency of these effects across multiple countries supports a view that arousal is universally a strong determinant of liking for foods and that this underlies the rejection of foods, familiar and novel, in FN.