Escherichia coli are major bacterial pathogens causing bovine mastitis, a disease of great economic impact on dairy production worldwide. This work aimed to study the virulence determinants of mammary pathogenic E. coli (MPEC). By whole-genome sequencing analysis of 40 MPEC and 22 environmental (“dairy-farm” E. coli [DFEC]) strains, we found that only the fec locus (fecIRABCDE) for ferric dicitrate uptake was present in the core genome of MPEC and that it was absent in DFEC genomes (P < 0.05). Expression of the FecA receptor in the outer membrane was shown to be citrate dependent by mass spectrometry. FecA was overexpressed when bacteria were grown in milk. Transcription of the fecA gene and of the inner membrane transport component fecB gene was upregulated in bacteria recovered from experimental intramammary infection. The presence of the fec system was shown to affect the ability of E. coli to grow in milk. While the rate of growth in milk of fec-positive (fec+) DFEC was similar to that of MPEC, it was significantly lower in DFEC lacking fec. Furthermore, deletion of fec reduced the rate of growth in milk of MPEC strain P4, whereas fec-transformed non-mammary gland-pathogenic DFEC strain K71 gained the phenotype of the level of growth in milk observed in MPEC. The role of fec in E. coli intramammary pathogenicity was investigated in vivo in cows, with results showing that an MPEC P4 mutant lacking fec lost its ability to induce mastitis, whereas the fec+ DFEC K71 mutant was able to trigger intramammary inflammation. For the first time, a single molecular locus was shown to be crucial in MPEC pathogenicity.
The potential for marine aquaculture development in the United States is significant and recent factors have highlighted the benefits of developing a shortened seafood supply chain to service domestic markets. Marine finfish in particular hold tremendous potential as technological advancements, improvements in production efficiencies, and market forces have aligned to create opportunities for growth within this sector of the aquaculture industry. Olive flounder, Paralichthys olivaceus, also commonly known as the Japanese flounder or hirame, is a candidate species for the U.S. aquaculture industry, which has a demonstrated track record of culture success and high market value. Although cultivation of the species is novel to the United States, olive flounder has been produced commercially for decades in other regions, notably Korea and Japan. With a number of favorable production characteristics, including a relatively short growout time compared with other flatfish species, an efficient food conversion ratio, and a wellestablished market presence, the species has been shown to be commercially viable. This study examines the opportunities for olive flounder to be developed in the United States, while also discussing the potential for land-based recirculating aquaculture systems culture of this species in
Cobia, Rachycentron canadum, is an important species for aquaculture worldwide. Production technology from egg to market was established in the early 1990s and continues to be perfected to this day. This species exhibits extraordinary scope for growth and can reach between 4 and 8 kg in 1 year, with females growing almost twice as fast and large as males. Despite continuous progress in maturation, spawning, larval rearing, fingerling production, nutrition, health management, genetics, and growout technology, overall cobia aquaculture production worldwide has been slow in the last decade. One of the biggest challenges remains the development of practical commercial feeds that are ecologically and economically efficient for this species.Feed conversion ratios are still very high, ranging from 2.0 to 3.0:1. In addition to nutritional challenges, diseases such as Photobacterium, Amyloodinium ocellatus, and Brooklynella hostilis continue to impact cobia aquaculture production worldwide. Genetics and breeding programs for cobia are still at their infancy. We report on current status of cobia
This research examined the effect of initial stocking density and feeding regime on larval growth and survival of Japanese flounder, Paralichthys olivaceus. Larval rearing trials were conducted in nine 50‐L tanks with different initial stocking densities combined with different feed rations (20 larvae/L with standard feed ration [LD], 80 larvae/L with standard feed ration [HD], and 80 larvae/L with four times the standard feed ration [HD+]). Larvae were stocked on 0 days posthatch (DPH) following hatching of the fertilized embryos. Larval total length (TL), survival rates, and final densities were observed on larval settlement (32 DPH) to evaluate larval rearing performance. At 32 DPH, there were no significant differences (p > .05) in TL or survival rates between the LD (46.5 ± 17.0%) and HD+ (40.3 ± 9.4%). The TL and survival rate of HD (23.1 ± 3.5%) were significantly lower than that of LD and HD+ (p < .05). However, the larval density of HD was significantly higher than that of LD (p < .05). HD+ achieved the best larvae production (32.27 ± 7.51 larvae/L), supported by sufficient food source, high water exchange, and proper water quality management (routine siphoning, surface skimming). The larval‐rearing protocols and larval development from hatching to metamorphosis is described in detail, with corresponding photographs taken during the experiment.
Vaccination against brucellosis using live attenuated strains is the primary approach in protecting livestock against the disease through a strong cellular immune response. Attenuated vaccine strains also induce serum anti-Brucella antibodies, mostly against Brucella O-polysaccharide, but their role in protection against the disease remains unclear. In this study, we show that Brucella OPS serum antibodies after vaccination or natural infection could kill Brucella in vitro as shown by the serum bactericidal activity (SBA) assay. We used serum samples of Rev. 1 vaccinated sheep that were negative or positive for Brucella OPS antibodies by either one of complement fixation test (CFT), microplate agglutination test (MAT) and ELISA, or sera of naturally infected sheep positive by CFT. We found a significant increase in the killing ability of sera 30 days after intraocular vaccination with Rev. 1 as compared with pre-vaccination. SBA was significantly higher in sera containing Brucella OPS IgG antibodies in comparison with sera lacking such antibodies (p < 0.001 against 16M & Rev. 1 strains). All 10 sera of convalescent sheep demonstrated significant killing ability against the 16M B. melitensis field strain. Specific OPS antibodies participate in the in vitro complement mediated Brucella killing suggesting a potential role in protection against the disease through this mechanism and relevance of developing OPS-based Brucella vaccines.
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