A set of 207 Streptococcus suis isolates were collected from ten autonomous communities from Spain in 2019 to 2020 from pigs with meningitis, pneumonic lungs, arthritic joints or other swollen viscera, to a lesser extent. Thirteen capsular types were detected being the most prevalent serotype 2 (21.7%), followed by serotypes 1 (21.3%), 9 (19.3%) and 3 (6.3%). Serotypes 2 and 9 were recovered mainly from the central nervous system (CNS), while serotype 1 was isolated mostly from swollen joints and serotype 3 from the lungs. Twenty-five isolates (12.1%) could not be typed. The most prevalent pathotype was epf + mrp + sly + luxS (49 isolates, 23.8%), and it was related mainly to serotypes 1 and 2. Serotypes 1–3 and 9 were significantly associated with anatomical sites of isolation and virulence factors, serotype 9 (CNS) and serotypes 3 and 9 (lungs) being associated with virulence profiles without the epf gene. S. suis isolates showed globally high antimicrobial resistances, but ampicillin followed by spectinomycin and tiamulin resulted in the highest activities, while the greatest resistances were detected for sulphadimethoxine, tetracyclines, neomycin, clindamycin and macrolides. A total of 87.4% isolates were positive to the tetO gene, 62.4% to the ermB gene and 25.2% to the fexA gene, while 14.6% were positive to all three genes simultaneously. A significative association between isolate resistances to tetracyclines and macrolides and the resistance genes tested was established, except for phenicol resistance and the fexA gene. A set of 14 multiresistance patterns were obtained according to the number of antimicrobials to which the isolates were resistant, the resistances to 12 or more agents being the most prevalent ones. A remarkable amount of multiresistance profiles could be seen among the S. suis serotype 9 isolates.

This study aimed to update the Streptococcus suis serotype distribution in Spain by analysing 302 clinical isolates recovered from diseased pigs between 2020 and 2022. The main objectives were to identify prevalent serotypes, differentiate specific serotypes 1, 14, 2, and 1/2, investigate specific genotypic and phenotypic antimicrobial resistance features, and explore associations between resistance genes and phenotypic resistances. Serotypes 9 (21.2%), 1 (16.2%), 2 (15.6%), 3 (6%), and 7 (5.6%) were the most prevalent, whereas serotypes 14 and 1/2 corresponded with 4.3% and 0.7% of all isolates. Antimicrobial resistance genes, including tet(O), erm(B), lnu(B), lsa(E), tet(M), and mef(A/E), were analysed, which were present in 85.8%, 65.2%, 7%, 7%, 6.3%, and 1% of the samples, respectively. Susceptibility testing for 18 antimicrobials revealed high resistance levels, particularly for clindamycin (88.4%), chlortetracycline (89.4%), and sulfadimethoxine (94.4%). Notably, seven significant associations (p < 0.0001) were detected, correlating specific antimicrobial resistance genes to the observed phenotypic resistance. These findings contribute to understanding the S. suis serotype distribution and its antibiotic resistance profiles in Spain, offering valuable insights for veterinary and public health efforts in managing S. suis-associated infections.

Staphylococcus hyicus is a significant pathogen in swine, primarily causing exudative epidermitis. Addressing S. hyicus infections requires both the characterization of virulence and antimicrobial resistance (AMR) in farm-recovered isolates. This study aimed to characterize the virulence, AMR, and biofilm formation of S. hyicus isolates from Spanish swine farms. A total of 49 isolates were analyzed, originating from animals with cutaneous, reproductive, and systemic clinical signs. Half of the isolates (49.0%) were positive for at least one virulence factor (VF) gene, with SHETA being the most frequent (28.6%). A high frequency of multidrug resistant (MDR) isolates was observed (83.7%), with significant resistance to commonly used antimicrobials, including lincosamides (83.7%), pleuromutilins (81.6%), penicillins (75.5%), and tetracyclines (73.5%). All isolates exhibited robust in vitro biofilm formation capacity (DC = 15.6 ± 7.0). Significant associations were found between VFs, biofilm formation, and AMR patterns, highlighting the link between the resistance to lincosamides and pleuromutilins (p < 0.001; Φ = 0.57) and macrolides (p < 0.001; Φ = 0.48), and the association of AMR with the ExhC and ExhD VF genes. These findings underscore the need for targeted diagnostics to improve management and therapeutic strategies to mitigate the impact of S. hyicus on swine production.