Comparison of intestinal mucosa homogenate and pure culture of the homologous Lawsonia intracellularis isolate in reproducing proliferative enteropathy in swine

Little information is available on reproduction of proliferative enteropathy (PE) using a virulent pure culture of Lawsonia intracellularis. Reproduction of the disease using PE-diseased mucosa homogenates, however, is well-characterized. The aims of this study were to evaluate and compare clinical signs, growth performance and the severity of lesions in pigs inoculated with intestinal mucosa homogenate or pure culture of the homologous L. intracellularis isolate. Five-week-old pigs were inoculated with pure culture of L. intracellularis (isolate PHE/MN1-00; n=10), PE-diseased mucosa (n=10), or control media (n=4). The L. intracellularis isolate PHE/MN1-00 used in the pure culture inoculum was extracted from a fragment of the same intestine used to prepare the mucosa homogenate. Clinical signs and growth performance were evaluated throughout the study. Fecal shedding was evaluated in all animals weekly during the experiment. All animals were euthanized 22 days post-inoculation, the intestines were examined grossly and histologically. Results showed that both the infection procedures reproduced clinical disease, macroscopic and histologic lesions typical of PE. Fecal shedding was detected in animals in both challenge groups. In conclusion, the L. intracellularis isolate PHE/MN1-00 reproduces typical clinical signs and lesions of PE similar to the homologous infection with an intestinal mucosa homogenate.     

Detection and characterisation of Shiga toxin-producing Escherichia coli other than Escherichia coli O157:H7 in wild ruminants

Shiga toxin-producing Escherichia coli (STEC) are an important group of emerging pathogens, with ruminants recognised as their main natural reservoir. The aim of this work was to establish the prevalence of non-O157 STEC in free-ranging wild ruminants in the Extremadura region of Spain and to characterise them phenogenotypically. Faecal samples were collected from 243 wild ruminants, including Cervus elaphus, Capreolus capreolus, Dama dama and Ovis musimon and were examined for STEC using both phenotypic (Vero cells) and genotypic (PCR and PFGE) methods.Shiga toxin-producing Escherichia coli were isolated from 58 (23.9%) of the samples and a total of 65 isolates were characterised. A PCR method indicated that 11 (16.9%) strains carried the stx₁ gene, 44 (67.7%) carried the stx₂ gene and 10 (15.4%) carried both these genes. The ehxA gene was detected in 37 (57%) of the isolates but none contained either the eae or saa genes. The isolates were from a total of 12 ‘O’ serogroups, although 80% were restricted to the O2, O8, O128, O146, O166 and O174 serogroups. The most commonly isolated STEC bacteria, which were from the O146 serogroup, exhibited a high degree of polymorphism as indicated by PFGE. Shiga toxin-producing Escherichia coli isolates of serogroups O20, O25, O166, O171, O174 and O176 had not previously been found in wild ruminants. This is the first study to confirm that wild ruminants in Spain are a reservoir of STEC and are thus a potential source of human infection.     

Production of L-lactic acid and oligomeric compounds from apple pomace by simultaneous saccharification and fermentation: a response surface methodology assessment

The potential of apple pomace for lactic acid production by simultaneous saccharification and fermentation (SSF) was evaluated. The effects of the cellulase to solid ratio (CSR), the liquor to solid ratio (LSR), and the beta-glucosidase to cellulase ratio (BCR) on the kinetics of lactic acid generation were assessed, and a set of mathematical models was developed to reproduce and predict the lactic acid concentration of fermentation broths. Operating at low cellulase and cellobiase charges (1 FPU/g and 0.25 IU/FPU, respectively) and short reaction times (10 h), SSF media containing 27.8 g of lactic acid/L were obtained with a volumetric productivity of 2.78 g/Lh. Material balances showed that the SSF processing of 100 kg of dry apple pomace results in the production of 36.6 kg of lactic acid, 18.3 kg of oligomeric carbohydrates (which can be used as ingredients for functional foods), 8.4 kg of microbial biomass, and 8 kg uronic acids.     

Identification and characterization of proteases from skin mucus of tambacu,a Neotropical hybrid fish

Skin secretions of fishes constitute a rich source of proteins with a broad spectrum of antimicrobial properties. We report here the characterization of proteases from skin mucus of tambacu, an economically important Neotropical hybrid fish. The effects of pH on the proteolytic activities of the mucus acting on various substracts – hemoglobin, casein, bovine serum albumin (BSA) and ovalbumin (OVA) – were tested. Optimal pH values for protease activity on hemoglobin were 4.5 and 8.5, on casein, 8.5, on BSA, 5.0 and 7.5, and on ovalbumin, 4.5 and 6.5. The proteolytic activity was inhibited on all of these substrates in the presence of specific inhibitors: caseinolytic activity was inhibited by inhibitors of serine and metalloproteases; hemoglobinolytic activity was inhibited by serine, aspartic and metalloproteases inhibitors; albuminolytic activity on BSA was inhibited by serine and aspartic proteases inhibitors, and on ovalbumin, by cysteine and aspartic proteases inhibitors. Gelatin zymography revealed that the skin mucus of tambacu consisted primarily of serine and metalloproteases. Hemoglobin zymography showed one proteolytic band inhibited by EDTA, whereas casein zymography showed two proteases inhibited by serine proteases inhibitors. We were able to identify all classes of proteases in the mucus from the skin of tambacu. These, and these results suggest that the proteolytic activities of the skin mucus of fish may play an important role in the defense against microorganisms and ectoparasites.     

Energy acquisition and allocation to egg production in relation to fish reproductive strategies

Oogenesis in fishes follows a universal plan; yet, due to differences in the synchrony and rate of egg development, spawning frequency varies from daily to once in a lifetime. Some species spawn and feed in separate areas, during different seasons, by storing energy and drawing on it later for reproduction (i.e. capital breeding). Other species spawn using energy acquired locally, throughout a prolonged spawning season, allocating energy directly to reproduction (i.e. income breeding). Capital breeders tend to ovulate all at once and are more likely to be distributed at boreal latitudes. Income breeding allows small fish to overcome allometric constraints on egg production. Income breeders can recover more quickly when good‐feeding conditions are re‐established, which is a benefit to adults regarding bet‐hedging spawning strategies. Many species exhibit mixed capital‐ and income‐breeding patterns. An individual's position along this capital–income continuum may shift with ontogeny or in relation to environmental conditions, so breeding patterns are a conditional reproductive strategy. Poor‐feeding environments can lead to delayed maturation, skipped spawning, fewer spawning events per season or fewer eggs produced per event. In a few cases, variations in feeding environments appear to affect recruitment variability. These flexible processes of energy acquisition and allocation allow females to prioritize their own condition over their propagules' condition at any given spawning opportunity, thereby investing energy cautiously to maximize lifetime reproductive value. These findings have implications for temporal and spatial sampling designs, for measurement and interpretation of fecundity, and for interpreting fishery and ecosystem assessments.     

Assessment of changes in the ichthyofauna in a tropical reservoir in south-eastern Brazil: Consequences of global warming?

Increases in temperatures over the last century, more intensively after the eighties, were recorded in several databases for the south-eastern Brazil. These increases are likely to change fish communities in aquatic systems by decreasing abundances, biomass and sizes of some species more sensitive to climate change. Reservoirs may be particularly susceptible to the effects of climate change, as they isolate previously connected areas limiting fish dispersal and migration, as well as increasing water temperature and thermal stratification. We assessed temporal changes in the abundance and biomass of the ichthyofauna in an isolate reservoir (inflowing waters from small tributaries in a highland region) aiming to associate changes with climate effects over three decades (1990, 2000, 2010). Two abundant native species, a loricariid Loricariichthys castaneus (Castelnau, 1855) and a cichlid Geophagus brasiliensis (Quoy & Gaimard, 1824), were selected to assess eventual response to climate changes in their geographical distribution in the Southeast Atlantic Hydrographic Region, considering different carbon emission scenarios using ecological niche models. A decrease in the densities and biomass of the ichthyofauna and of the two selected species were observed in both summer and winter over the three decades, coinciding with increases in temperatures. These decreases were correlated with increases in positive anomalies of temperature, which may be an indicator of climatic changes, although with low explanation of the data variation. The mean size of L. castaneus decreased between the nineties and 2010, whereas no significant trend was found for the size of G. brasiliensis. Our predictions of new area for future adequacy indicated a loss in the distribution area for both species (mainly for G. brasiliensis), considering the most pessimistic scenario for 2050 and 2070, possibly due to climatic changes. Both hydroelectric dams and global warming pose threats to freshwater fish diversity, and both will interact. Changes observed in the fish assemblage over the last decades were essential for an assessment of the consequences of global warming in this type of reservoir combining larger scale studies with future projections.