Lactococcus garvieae is the etiological agent of lactococcosis, a clinically and economically significant infectious disease affecting farmed rainbow trout. L. garvieae had been considered the only cause of lactococcosis for a long time; however, L. petauri, another species of the genus Lactococcus, has lately been linked to the same disease. The genomes and biochemical profiles of L. petauri and L. garvieae have a high degree of similarity. Traditional diagnostic tests currently available cannot distinguish between these two species. The aim of this study was to use the transcribed spacer (ITS) region between 16S rRNA and 23S rRNA as a potential useful molecular target to differentiate L. garvieae from L. petauri, saving time and money compared to genomics methods currently used as diagnostic tools for accurate discrimination between these two species. The ITS region of 82 strains was amplified and sequenced. The amplified fragments varied in size from 500 to 550 bp. Based on the sequence, seven SNPs were identified that separate L. garvieae from L. petauri. The 16S-23S rRNA ITS region has enough resolution to distinguish between closely related L. garvieae and L. petauri and it can be used as a diagnostic marker to quickly identify the pathogens in a lactococcosis outbreak.

Infectious diseases place an economic burden on aquaculture and a limitation to its growth. An innovative approach to mitigate their impact on production is breeding for disease resistance: selection for domestication, family-based selection, marker-assisted selection, and more recently, genomic selection. Advances in genetics and genomics approaches to the control of infectious diseases are key to increasing aquaculture efficiency, profitability, and sustainability and to reducing its environmental footprint. Interaction and co-evolution between a host and pathogen can, however, turn breeding to boost infectious disease resistance into a potential driver of pathogenic change. Parallel molecular characterization of the pathogen and its virulence and antimicrobial resistance genes is therefore essential to understand pathogen evolution over time in response to host immunity, and to apply appropriate mitigation strategies.

The genus Vibrio currently contains 147 recognized species widely distributed, including pathogens for aquatic organisms. Vibrio infections in elasmobranchs are poorly reported, often with identifications as Vibrio sp. and without detailed diagnostic insights. The purpose of this paper is the description of the isolation and identification process of Vibrio spp. following a mortality event of Scyliorhinus canicula juvenile reared in an Italian public aquarium. Following investigations aimed at excluding the presence of different pathogens of marine fish species (parasites, bacteria, Betanodavirus), several colonies were isolated and subjected to species identification using the available diagnostic techniques (a biochemical test, MALDI-TOF MS, and biomolecular analysis). Discrepancies were observed among the methods; the limits of biochemistry as a unique tool for Vibrio species determination were detected through statistical analysis. The use of the rpoB gene, as a diagnostic tool, allowed the identification of the isolates as V. crassostreae and V. cyclotrophicus. Although the pathogenic role of these microorganisms in lesser-spotted dogfish juveniles has not been demonstrated, and the presence of further pathogens cannot be excluded, this study allowed the isolation of two Vibrio species in less-studied aquatic organisms, highlighting the weaknesses and strengths of the different diagnostic methods applied.

This study investigated the hepatic expression of genes involved in stress response (CASP6, CAT, SOD1, HSPA2) and lipid metabolism (LPL, SREBF, FABP1, ACOX1, FADS2) in a local slow-growing chicken breed, the Bionda Piemontese (BP), following two isonitrogenous diets (crude protein, 170 g/kg as fed): a control diet (L) and a high-fat diet (H) obtained by supplementing 6 % palm kernel oil, during the finisher period. Sixty (male and female) chickens were included in the study and slaughtered at five months of age. RNA was extracted from 36 liver samples (18 male and 18 female) and sequenced using the targeted RNA-seq method followed by bioinformatic analysis using DESeq2 to detect differences in gene expression. Overall, the high-fat dietary supplementation did not significantly alter the expression of most stress-related genes, indicating that the high-fat diet did not elicit a hepatic stress response in BP chickens. However, within each sex, the high-fat diet tended to upregulate FADS2 and FABP1 in females, and slightly downregulate ACOX1 in males. Considering sex as an independent factor, FABP1 expression was higher in females, whereas males exhibited significantly higher LPL expression. These findings highlight a clear sexual dimorphism in hepatic lipid gene expression in BP chickens. While dietary fat supplementation had limited impact on differentially expressed genes, the study underscores the importance of sex in shaping metabolic gene expression. It also provides evidence supporting the possible metabolic resilience of the BP breed to tolerate changes in dietary fat content. Further studies are needed to substantiate this claim, and to investigate the long-term effects and the tissue-specific responses of dietary fat supplementation in other organs.

• NIR spectroscopy effectively assessed meat quality in a local chicken breed. • Freeze-dried samples provided the highest prediction accuracy, for EE and CP. • NIR successfully discriminated chicken parts and sex in chicken meat. • It did not discriminate the diets due to minimal compositional differences in meat.