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Stochasticity is a core component of ecology, as it underlies key processes that structure and create variability in nature. Despite its fundamental importance in ecological systems, the concept is often treated as synonymous with unpredictability in community ecology, and studies tend to focus on single forms of stochasticity rather than taking a more holistic view. This has led to multiple narratives for how stochasticity me...
Columnaris disease can be problematic in tilapia ( O reochromis spp.) production. An understanding of the pathogenesis and virulence of F lavobacterium columnare is needed to develop prevention strategies. The objective of this study was to determine the virulence of genetically defined isolates of F . columnare in sex‐reversed hybrid tilapia, O reochromis niloticus ( L .) × O . aureus ( S teindachner). A series of immersion c...
Intragenomic heterogeneity in the 16 S r RNA genes of F lavobacterium columnare and standard protocol for genomovar assignmentNARA Subscribed
Genetic variability in 16 S r RNA gene sequences has been demonstrated among isolates of F lavobacterium columnare, and a restriction fragment length polymorphism ( RFLP ) assay is available for genetic typing of this important fish pathogen. Interpretation of restriction patterns can be difficult due to the lack of a formal description of the expected number and sizes of DNA fragments generated for each of the described genom...
Streptococcus iniae is a significant pathogen impacting aquaculture production worldwide. The objectives of this study were to determine whether a developed modified S. iniae (ARS‐98‐60) bacterin vaccine is efficacious in Nile tilapia, Oreochromis niloticus (L.), against challenge with heterologous isolates from diverse geographical locations and to evaluate protein and antigenic variability among the isolates tested. Two grou...
Using quantitative PCR (QPCR), the relative transcriptional levels of five toll‐like receptors (TLR2, TLR3, TLR5, TLR20a and TLR21) were studied in the channel catfish, Ictalurus punctatus (Rafinesque), under uninfected and acutely infected conditions [1‐, 2‐, 4‐, 6‐, 12‐, 24‐, 36‐ and 48‐h post‐injection (hpi)]. Under uninfected conditions, the transcriptional levels of the five TLRs were significantly lower than that of 18S...
Comparison of lipopolysaccharide and protein profiles between Flavobacterium columnare strains from different genomovarsNARA Subscribed
Lipopolysaccharide (LPS) and total protein profiles from four Flavobacterium columnare isolates were compar. These strains belonged to genetically different groups and/or presented distinct virulence properties. Flavobacterium columnare isolates ALG‐00‐530 and ARS‐1 are highly virulent strains that belong to different genomovars while F. columnare FC‐RR is an attenuated mutant used as a live vaccine against F. columnare . Stra...
Streptococcus agalactiae is a major bacterial pathogen that is the cause of serious economic losses in many species of freshwater, marine and estuarine fish worldwide. A highly efficacious S. agalactiae vaccine was developed using extracellular products (ECP) and formalin‐killed whole cells of S. agalactiae . The vaccine efficacy following storage of S. agalactiae ECP and formalin‐killed S. agalactiae cells at 4 °C for 1 year...
Flavobacterium columnare is an important pathogen of freshwater fish, implicated in skin and gill disease, often causing high mortality. An outbreak of skin disease in fingerling and adult Nile tilapia, Oreochromis niloticus (L.), cultivated in a recirculation system, was investigated. Four strains were isolated and characterized by biochemical reactions, enzyme production, fatty acid profile and analysis of the 16S‐23S rDNA i...
The biological properties of Edwardsiella ictaluri RE‐33 rifampicin‐mutant and its parent strain EILO were analysed. RE‐33 is an avirulent isolate used as a modified live vaccine against enteric septicaemia of catfish. Electrophoretic analysis of lipopolysaccharide (LPS) patterns showed high homology between both isolates. Further characterization of LPS by immunoblotting revealed the main differences in LPS composition. The R...
Streptococcus agalactiae was isolated from cultured gilthead seabream, Sparus auratus L., and diseased wild Klunzinger's mullet, Liza klunzingeri (Day), in Kuwait Bay, Arabian Gulf. Isolates were catalase negative, β‐haemolytic, Gram‐positive cocci and serogroup B. Experimental infectivity trials with mullet and seabream brain isolates in Nile tilapia, Oreochromis niloticus L., caused 100 and 90% mortality, respectively, withi...
Passive immunization of tilapia, Oreochromis niloticus (L.), with anti‐ Streptococcus iniae whole seraNARA Subscribed
Passive immunization of tilapia, Oreochromis niloticus, was conducted to determine whether anti‐ Streptococcus iniae whole sera (ASI), heat inactivated anti‐ S . iniae whole sera (HIASI) and normal whole sera (NWS) were protective when intraperitoneally (i.p.) injected into tilapia. The ASI was produced in tilapia actively immunized (challenged) with virulent S. iniae by i.p. injection. An antibody response against S. iniae wa...
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