Prevalence of verotoxigenic Escherichia coli O157 (VTEC O157) and compliance with microbiological safety standards in bovine carcasses from an industrial beef slaughter plant

The presence of Salmonella spp. and levels of Enterobacteriaceae and aerobic plate count were determined in 300 bovine carcasses randomly collected in an industrial cattle slaughterhouse in Catalonia (Spain) as part of a control programme to validate good slaughter practices according to Commission Regulation No 2073/2005. The verotoxigenic Escherichia coli O157 (VTEC O157), although not currently legislated, was also investigated in the same carcasses due to the importance of bovines as a reservoir for this micro‐organism. Virulence genes (vtx1, vtx2 and eae), the presence of fliC_H7 and antimicrobial susceptibility were studied in E. coli O157 isolates. Levels of Enterobacteriaceae and aerobic colonies and the presence of Salmonella were within the admissible range stipulated by current legislation. However, VTEC O157 was detected in 14·7% of carcasses. Among the VTEC O157 strains tested for antimicrobial susceptibility, 65% were multiresistant. Overall, the results of this study indicate that even with good manufacturing practices, contamination with VTEC O157 can occur and cattle meat can pose a risk to human health. These results confirm the need for a review of the appropriateness of introducing antimicrobial treatments in the processing of cattle carcasses in Europe.

Significance and Impact of the Study

This study describes the prevalence of verotoxigenic and multidrug‐resistant E. coli O157 strains in bovine carcasses. These results suggest that despite the good manufacturing practices used in the slaughterhouse studied (the largest in Catalonia slaughtering over 81 000 cattle per year), the absence of verotoxigenic E. coli O157 in bovine carcasses cannot be guaranteed.     

Bacteria in Weathered Basaltic Glass,Iceland

Bacteria play an important role in rock weathering and yet their diversity and potential activity in the terrestrial rock weathering environment is poorly understood. Culture and culture-independent methods (16S rDNA) were used to investigate the populations of bacteria inhabiting a basaltic glass/palagonite subglacial (hyaloclastite) deposit subject to weathering in Iceland. The rock hosts a diverse microbial community. The 16S rDNA clones were dominated by Actinobacteria, Proteobacteria, Bacteroidetes and Acidobacteria. Representatives of Gemmatimonadetes and Verrucomicrobia were present. Isolation of organisms on basalt/palagonite yielded only two isolates, an actinobacterium and a Bacteroidetes, showing that the active species, at least in the time scale of laboratory cultivation, are a small proportion of the total diversity. Firmicutes and Actinobacteria were isolated when basalt/palagonite was supplemented with an organic source. Many of the isolates demonstrated tolerance to transition metals (Cr, Cu, Zn, Ni, Co) naturally present in the rock. The growth of the isolates was inhibited at typical pH values for Icelandic rain, which suggests that the increase in pH caused by the consumption of protons in rock weathering, for example by palagonite formation, may play a role in defining which organisms are active. Colonization experiments show that the filamentous growth habit of the actinobacterium isolated on basalt/palagonite allows it to actively invade and colonise the basaltic glass. The filamentous growth of some actinobacteria may be an important contributor to their role in systemic interstitial rock weathering in the natural environment.     

Sex-Specific Effects on Spatial Learning and Memory,and Sex-Independent Effects on Blood Pressure of a <3.3 Mbp Rat Chromosome 2 QTL Region in Dahl Salt-Sensitive Rats

Epidemiological studies have consistently found that hypertension is associated with poor cognitive performance. We hypothesize that a putative causal mechanism underlying this association is due to genetic loci affecting both blood pressure and cognition. Consistent with this notion, we reported several blood pressure (BP) quantitative trait loci (QTLs) that co-localized with navigational performance (Nav)-QTLs influencing spatial learning and memory in Dahl rats. The present study investigates a chromosome 2 region harboring BP-f4 and Nav-8 QTLs. We developed two congenic strains, S.R2A and S.R2B introgressing Dahl R-chromosome 2 segments into Dahl S chromosome 2 region spanning BP-f4 and Nav-8 QTLs. Radiotelemetric blood pressure analysis identified only S.R2A congenic rats with lower systolic blood pressure (females: −26.0 mmHg, P = 0.003; males: −30.9 mmHg, P<1×10⁻⁵), diastolic blood pressure (females: −21.2 mmHg, P = 0.01; males: −25.7 mmHg, P<1×10⁻⁵), and mean arterial pressure (females: −23.9 mmHg, P = 0.004; males: −28.0 mmHg, P<1×10⁻⁵) compared with corresponding Dahl S controls, confirming the presence of BP-f4 QTL on rat chromosome 2. The S.R2B congenic segment did not affect blood pressure. Testing of S.R2A, S.R2B, and Dahl S male rats in the Morris water maze (MWM) task revealed significantly decreased spatial navigation performance in S.R2A male congenic rats when compared with Dahl S male controls (P<0.05). The S.R2B congenic segment did not affect performance of the MWM task in males. The S.R2A female rats did not differ in spatial navigation when compared with Dahl S female controls, indicating that the Nav-8 effect on spatial navigation is male-specific. Our results suggest the existence of a single QTL on chromosome 2 176.6–179.9 Mbp region which affects blood pressure in both males and females and cognition solely in males.     

Trypanosoma cruzi Infection in Neotropical Wild Carnivores (Mammalia: Carnivora): At the Top of the T. cruzi Transmission Chain

Little is known on the role played by Neotropical wild carnivores in the Trypanosoma cruzi transmission cycles. We investigated T. cruzi infection in wild carnivores from three sites in Brazil through parasitological and serological tests. The seven carnivore species examined were infected by T. cruzi, but high parasitemias detectable by hemoculture were found only in two Procyonidae species. Genotyping by Mini-exon gene, PCR-RFLP (1f8/Akw21I) and kDNA genomic targets revealed that the raccoon (Procyon cancrivorus) harbored TcI and the coatis (Nasua nasua) harbored TcI, TcII, TcIII-IV and Trypanosoma rangeli, in single and mixed infections, besides four T. cruzi isolates that displayed odd band patterns in the Mini-exon assay. These findings corroborate the coati can be a bioaccumulator of T. cruzi Discrete Typing Units (DTU) and may act as a transmission hub, a connection point joining sylvatic transmission cycles within terrestrial and arboreal mammals and vectors. Also, the odd band patterns observed in coatis’ isolates reinforce that T. cruzi diversity might be much higher than currently acknowledged. Additionally, we assembled our data with T. cruzi infection on Neotropical carnivores’ literature records to provide a comprehensive analysis of the infection patterns among distinct carnivore species, especially considering their ecological traits and phylogeny. Altogether, fifteen Neotropical carnivore species were found naturally infected by T. cruzi. Species diet was associated with T. cruzi infection rates, supporting the hypothesis that predator-prey links are important mechanisms for T. cruzi maintenance and dispersion in the wild. Distinct T. cruzi infection patterns across carnivore species and study sites were notable. Musteloidea species consistently exhibit high parasitemias in different studies which indicate their high infectivity potential. Mesocarnivores that feed on both invertebrates and mammals, including the coati, a host that can be bioaccumulator of T. cruzi DTU’s, seem to take place at the top of the T. cruzi transmission chain.     

Frugivore Behavioural Details Matter for Seed Dispersal: A Multi-Species Model for Cantabrian Thrushes and Trees

Animal movement and behaviour is fundamental for ecosystem functioning. The process of seed dispersal by frugivorous animals is a showcase for this paradigm since their behaviour shapes the spatial patterns of the earliest stage of plant regeneration. However, we still lack a general understanding of how intrinsic (frugivore and plant species traits) and extrinsic (landscape features) factors interact to determine how seeds of a given species are more likely to be deposited in some places more than in others. We develop a multi-species mechanistic model of seed dispersal based on frugivore behavioural responses to landscape heterogeneity. The model was fitted to data from three-years of spatially-explicit field observations on the behaviour of six frugivorous thrushes and the fruiting patterns of three fleshy-fruited trees in a secondary forest of the Cantabrian range (N Spain). With such model we explore how seed rain patterns arise from the interaction between animal behaviour and landscape heterogeneity. We show that different species of thrushes respond differently to landscape heterogeneity even though they belong to the same genus, and that provide complementary seed dispersal functions. Simulated seed rain patterns are only realistic when at least some landscape heterogeneity (forest cover and fruit abundance) is taken into account. The common and simple approach of re-sampling movement data to quantify seed dispersal produces biases in both the distance and the habitat at which seeds arrive. Movement behaviour not only affects dispersal distance and seed rain patterns but also can affect frugivore diet composition even if there is no built-in preference for fruiting species. In summary, the fate of seeds produced by a given plant species is strongly affected by both the composition of the frugivore assemblage and the landscape-scale context of the plant location, including the presence of fruits from other plants (from the same or different species).     

Genome-Wide Association Mapping of Root Traits in a Japonica Rice Panel

Rice is a crop prone to drought stress in upland and rainfed lowland ecosystems. A deep root system is recognized as the best drought avoidance mechanism. Genome-wide association mapping offers higher resolution for locating quantitative trait loci (QTLs) than QTL mapping in biparental populations. We performed an association mapping study for root traits using a panel of 167 japonica accessions, mostly of tropical origin. The panel was genotyped at an average density of one marker per 22.5 kb using genotyping by sequencing technology. The linkage disequilibrium in the panel was high (r²>0.6, on average, for 20 kb mean distances between markers). The plants were grown in transparent 50 cm × 20 cm × 2 cm Plexiglas nailboard sandwiches filled with 1.5 mm glass beads through which a nutrient solution was circulated. Root system architecture and biomass traits were measured in 30-day-old plants. The panel showed a moderate to high diversity in the various traits, particularly for deep (below 30 cm depth) root mass and the number of deep roots. Association analyses were conducted using a mixed model involving both population structure and kinship to control for false positives. Nineteen associations were significant at P<1e-05, and 78 were significant at P<1e-04. The greatest numbers of significant associations were detected for deep root mass and the number of deep roots, whereas no significant associations were found for total root biomass or deep root proportion. Because several QTLs for different traits were co-localized, 51 unique loci were detected; several co-localized with meta-QTLs for root traits, but none co-localized with rice genes known to be involved in root growth. Several likely candidate genes were found in close proximity to these loci. Additional work is necessary to assess whether these markers are relevant in other backgrounds and whether the genes identified are robust candidates.     

Putative Panmixia in Restricted Populations of Trypanosoma cruzi Isolated from Wild Triatoma infestans in Bolivia

Trypanosoma cruzi, the causative agent of Chagas disease, is subdivided into six discrete typing units (DTUs; TcI–TcVI) of which TcI is ubiquitous and genetically highly variable. While clonality is the dominant mode of propagation, recombinant events play a significant evolutive role. Recently, foci of wild Triatoma infestans have been described in Bolivia, mainly infected by TcI. Hence, for the first time, we evaluated the level of genetic exchange within TcI natural potentially panmictic populations (single DTU, host, area and sampling time). Seventy-nine TcI stocks from wild T. infestans, belonging to six populations were characterized at eight microsatellite loci. For each population, Hardy-Weinberg equilibrium (HWE), linkage disequilibrium (LD), and presence of repeated multilocus genotypes (MLG) were analyzed by using a total of seven statistics, to test the null hypothesis of panmixia (H₀). For three populations, none of the seven statistics allowed to rejecting H₀; for another one the low size did not allow us to conclude, and for the two others the tests have given contradictory results. Interestingly, apparent panmixia was only observed in very restricted areas, and was not observed when grouping populations distant of only two kilometers or more. Nevertheless it is worth stressing that for the statistic tests of "HWE", in order to minimize the type I error (i. e. incorrect rejection of a true H₀), we used the Bonferroni correction (BC) known to considerably increase the type II error ( i. e. failure to reject a false H₀). For the other tests (LD and MLG), we did not use BC and the risk of type II error in these cases was acceptable. Thus, these results should be considered as a good indicator of the existence of panmixia in wild environment but this must be confirmed on larger samples to reduce the risk of type II error.     

Assessment of snake antivenom purity by comparing physicochemical and immunochemical methods

Purity is a characteristic that, together with effectiveness and safety, must be tested to determine the quality of biopharmaceutical products. In therapeutic immunoglobulins, such as human intravenous immunoglobulin (IVIG), purity is evaluated on the basis of physicochemical properties, and is usually assessed by chromatography and electrophoresis. However, in the case of antivenoms these methods fail to discriminate between antibodies towards venom antigens, which constitute the active substance, and antibodies towards non-venom antigens, which are the major impurities in most of the current formulations. The assessment of this aspect of purity requires the use of the immunochemical methods. In this study, it was demonstrated that antivenoms showing physicochemical purity higher than 90% might present immunochemical purity lower than 40%. It is proposed that a comprehensive analysis of antivenom purity should combine physicochemical and immunochemical parameters. In addition, these results are crucial to decide the more appropriate strategies to improve antivenom purity. Taking into account that the current methods of antivenom purification remove most non-antibodies proteins, we propose that efforts must be primarily directed to the improvement of immunization protocols to enhance the antibody response towards venom components in hyperimmunized animals, and secondarily, in the realm of immunoglobulin purification technology.