Genomic characterization of a hypervirulent Aeromonas veronii NN0115 from Nile tilapia and head kidney transcriptome of infected fish reveals B-cell-dominated immune response with specific immunoglobulin downregulation.

Pathogenicity and Genomic Analysis of Hypervirulent Aeromonas hydrophila NN0116 From Nile Tilapia and Head Kidney Transcriptome of Infected Fish Reveals a B-Cell-Dominated Immune Response.

Aeromonas hydrophila is a major pathogen of Motile Aeromonad Septicemia (MAS) in Nile tilapia, with pathogenesis and immunity poorly understood. In early 2026, a > 70% mortality outbreak occurred at a Nanning tilapia farm. The dominant strain NN0116 was identified as A. hydrophila by 16S rRNA and whole-genome ANI analysis. It exhibited high virulence (LD50 = 5.2 × 103 CFU/fish). Its 5.37 Mb genome encodes 5065 proteins and contains T2SS, T3SS, T6SS, and pore-forming toxins. Virulence and antimicrobial resistance genes co-localized on genomic islands GI2 and GI7. The strain was resistant to 12 antibiotic classes but susceptible to third-generation cephalosporins and fluoroquinolones. Head kidney transcriptomics at 24 h identified 1066 differentially expressed genes, including 61 immunoglobulin (Ig) genes. KEGG enrichment revealed 43 significant pathways; the top ten were driven by 26 Ig genes. Network analysis of the top 20 pathways identified B cell receptor signalling (ko04662) and COVID-19 (ko05171) as central nodes, alongside 10 secondary core pathways, all Ig-driven. Integration of bacterial genomic and host transcriptomic data characterizes hypervirulent A. hydrophila NN0116 and demonstrates that Ig-mediated B cell responses are central to host defence, offering targets for vaccines and therapeutics.

Genomic Insights Into Bacillus thuringiensis Strain JSd1 From Bangladesh: A Whole Genome Sequencing Approach

The findings suggest that B. thuringiensis JSd1 is a promising candidate for development as a biopesticide targeting insect pests in Bangladeshi agriculture, and lays the groundwork for further functional validation and field applications, contributing to sustainable pest management strategies in the region.

Comparative genomic analysis of two virulent Metarhizium rileyi (Hypocreales: Clavicipitaceae) isolates reveals enhanced virulence potential

Pathogenicity and systemic virulence of Aeromonas veronii in red-bellied pacu (Piaractus brachypomus): an experimental disease model

Aeromonas veronii is an important etiological agent of motile aeromonas septicemia (MAS) in aquaculture; however, its pathogenicity in the emerging cultured species red-bellied pacu (Piaractus brachypomus) remains poorly understood. Pacu fingerlings (10±2 g; n = 180) were intraperitoneally challenged with A. veronii strain BLB-01 (GenBank accession: MF370515) at concentrations ranging from 10⁵ to 10⁹ CFU mL⁻¹, following OECD guideline 203. The median lethal dose (LD₅₀) was estimated using probit analysis. Clinical signs, haematological and biochemical parameters, and histopathological alterations were evaluated at 96 h post-LD₅₀ exposure. Probit analysis (Y = 0.591 + 2.185 log₁₀ concentration; R² = 0.984) estimated the LD₅₀ as 7.8×10⁶ CFU mL⁻¹ (95% CI: 5.2–11.4 ×10⁶ CFU mL⁻¹). Infected fish exhibited progressive MAS symptoms over 7 days. Haematological analysis revealed significant anaemia (decreased haemoglobin and total erythrocyte count), leukocytosis (increased total leukocyte count), and thrombocytopenia (reduced platelet count). Biochemical changes included stress-induced hyperglycaemia (elevated glucose), hepatocellular damage (increased ALP, AST, and ALT), and hypoalbuminemia (reduced albumin). Histopathological examination demonstrated severe lesions, including gill lamellar fusion (2.8±0.3), hepatic vacuolation (2.9±0.2), and renal tubular necrosis (2.8±0.2). Aeromonas veronii exhibits high pathogenicity in pacu, with an LD₅₀ of 7.8×10⁶ CFU mL⁻¹, providing baseline data for challenge studies and the development of vaccines and probiotics. A combination of haematological and biochemical markers particularly increased TLC, reduced platelet count, and elevated liver enzymes offers a practical tool for rapid field-level diagnosis and surveillance of MAS, supporting improved health management in Indian pacu aquaculture.

Comprehensive Genomic Analysis of the pO157 Plasmid in Enterohemorrhagic Escherichia coli O157:H7 Reveals Non-synonymous Variation in Virulence Factors

Isolation and genomic characterization of a lytic siphoviridae phage infecting lactococcus garvieae from rainbow trout ( Oncorhynchus mykiss )

During intensive rainbow trout ( Oncorhynchus mykiss ) farming operations conducted between 2021 and 2024 in the Karkamış and Keban Dam Lakes, ten Lactococcus garvieae isolates were recovered from moribund fish. Bacterial identification was performed using classical microbiological procedures, the Biolog GEN III system, and Sanger sequencing. To detect lytic bacteriophages targeting L. garvieae , water samples collected from farming areas were processed using both spot testing and the double agar overlay assay. Host-range assessment revealed that two of the ten sequenced isolates were susceptible in spot tests, while only one produced clear plaques in the double agar method. Transmission electron microscopy characterized the isolated phage possessing an icosahedral capsid with an approximate diameter of 200 nm. Whole-genome sequencing of the phage revealed a genome size of 34,324 bp with a GC content of 58.41%. Metagenomic classification identified the phage as a member of the family Siphoviridae . These findings provide new insights into the diversity of L. garvieae strains circulating in Turkish aquaculture systems and contribute to the development of phage-based alternatives for managing bacterial infections in aquaculture.