Salmonella Kentucky is commonly found in poultry and rarely associated with human disease. However, a multidrug-resistant (MDR) S. Kentucky clone [sequence type (ST)198] has been increasingly reported globally in humans and animals. Our aim here was to assess if the recently reported increase of S. Kentucky in poultry in Spain was associated with the ST198 clone and to characterize this MDR clone and its distribution in Spain. Sixty-six isolates retrieved from turkey, laying hen and broiler in 2011–2017 were subjected to whole-genome sequencing to assess their sequence type, genetic relatedness, and presence of antimicrobial resistance genes (ARGs), plasmid replicons and virulence factors. Thirteen strains were further analysed using long-read sequencing technologies to characterize the genetic background associated with ARGs. All isolates belonged to the ST198 clone and were grouped in three clades associated with the presence of a specific point mutation in the gyrA gene, their geographical origin and isolation year. All strains carried between one and 16 ARGs whose presence correlated with the resistance phenotype to between two and eight antimicrobials. The ARGs were located in the Salmonella genomic island (SGI-1) and in some cases (bla _SHV-12 , catA1, cmlA1, dfrA and multiple aminoglycoside-resistance genes) in IncHI2/IncI1 plasmids, some of which were consistently detected in different years/farms in certain regions, suggesting they could persist over time. Our results indicate that the MDR S. Kentucky ST198 is present in all investigated poultry hosts in Spain, and that certain strains also carry additional plasmid-mediated ARGs, thus increasing its potential public health significance.

Salmonella Enteritidis, the most prevalent serovar-causing human gastroenteritis, has been traditionally linked to poultry sources. Although antimicrobial resistance (AMR) is not common in this serovar, increasing levels of resistance to fluoroquinolones and ampicillin have been reported in the last few years. Here, 298 isolates retrieved from different sources (human, livestock, wildlife, food, and environment) and years (2002–2021) in Spain were analyzed to evaluate their diversity, the distribution of AMR-conferring genes (ARGs), and mutations and reconstruct the epidemiology of infection due to this serovar. Isolates were clustered in two major clades (I and II), with strains in clade I (including 61.5% of all human isolates) displaying a pan-susceptible phenotype and not carrying AMR determinants. In contrast, clade II included 80.7% of isolates from animal/food/environmental sources, with the majority (69.8%) harboring mutations in the quinolone resistance determinant regions (QRDR). ARGs, although rare, were mostly found in clade II strains that also carried plasmid replicons, among which IncX1 was the most common. Although higher levels of phenotypic resistance were found in animal isolates, extended-spectrum beta-lactamase, plasmid-mediated AmpC, and carbapenemase-encoding genes were only found among human isolates. In summary, the majority of human and animal isolates from Spanish sources in our collection were classified in different phylogenetic branches, suggesting that additional sources are contributing to the occurrence of foodborne infections in Spain. Furthermore, the different distributions of virulence factors and ARGs in isolates from different sources and their association with specific plasmids suggest the presence of different dynamics contributing to the selection of resistant strains.

Bluetongue (BT) is an infectious, non-contagious, arthropod-borne viral disease of ruminants, and has a severe impact on livestock. It is caused by Bluetongue virus (BTV), a double-stranded (ds) RNA virus with a segmented genome (10 segments), belonging to the Seoreoviridae family, Orbivirus genus. Over the last 25 years, Europe has suffered multiple incursions of different BTV serotypes with serious consequences, which have mainly been controlled thanks to vaccination. In the case of Spain, from 2000 to 2023, BTV serotypes 1, 2, 4 and 8 have caused epidemics, and, sporadically, BTV-1 and -4 were detected in the same area and period. In 2024, BTV serotypes 1, 3 and 8 circulated simultaneously in the southwest of the country, causing a severe clinical impact in sheep but also in cattle and a multitude of outbreaks. Additionally, despite vaccination, serotype 4 also circulated that year, especially in areas where the other serotypes were already circulating. Whole-genome sequencing and phylogenetic analyses allowed us to confirm that serotypes 1 and 4 were homologous to viruses circulating in the country since 2000s, while serotypes 3 and 8 were homologous to BTVs recently notified in neighboring countries. In this context, many BTV co-infections of two or more different serotypes were confirmed by serotype-specific RT-PCRs, both in farms and individual animals. An epidemic caused by four serotypes coinciding in space and time had never occurred before in Spain, being a challenge for the diagnosis and control of this disease. Moreover, it could have favored the appearance of reassortant viruses with an unknown virulence, posing an additional risk. The data presented here raise the question of whether the co-circulation of different BTV strains, an exceptional situation, could become the new normal in certain areas of Europe.

Bluetongue (BT) is an infectious, non-contagious, arthropod-borne viral diseases of ruminants, producing severe impacts in livestock. It is caused by Bluetongue virus (BTV), a double-stranded (ds) RNA virus with segmented genome (10 segments), belonging to Seoreoviridae family, Orbivirus genus. Over the last 25 years, Europe has suffered multiple incursions of different BTV serotypes with serious consequences, which have been controlled mainly thanks to vaccination. In the case of Spain, since 2000 to 2023, BTV serotypes 1, 2, 4 and 8 have caused epidemics, and sporadically BTV-1 and -4 were detected in the same area and period. In 2024, BTV serotypes 1, 3 and 8 circulated simultaneously in the southwest of the country, causing a severe clinical impact especially on sheep but also in cattle and a multitude of outbreaks. Additionally, despite vaccination, also circulated serotype 4 that year, especially in areas where the other serotypes were already circulating. Whole Genome Sequencing and phylogenetic analyses allowed us to confirm that serotypes 1 and 4 were homologous to viruses circulating in the country since 2000s, while serotypes 3 and 8 were homologous to BTV viruses recently notified in neighboring countries. In this context, many BTV co-infections of two or more different serotypes were confirmed by serotype specific RT-PCRs both in farms and individual animals. An epidemic caused by four serotypes coinciding in space and time had never occurred before in Spain, being a challenge for the diagnosis and control of this disease. Moreover, it could have favored the appearance of reassortant viruses with an unknown virulence, posing an additional risk. The data presented here raises the question of whether the co-circulation of different BTV strains, an exceptional situation, could become the new normal in certain areas of Europe.