Background/Objectives: Salmonella Saintpaul (SSa) is increasingly linked to foodborne outbreaks in Brazil and globally. Despite its rising public health significance, its epidemiology, genomic diversity, and pathogenic potential remain underexplored. This study addresses these gaps through a comprehensive global analysis of SSa population dynamics, outbreak patterns, and genetic structures, along with an in-depth phenotypic and genomic characterization of strain PP_BR059, isolated from a hospitalized patient in Ceará, Brazil. Methods: We analyzed 1,953 publicly available SSa genomes using core-genome multi-locus sequence typing (cgMLST), antimicrobial resistance (AMR) profiling, pan-genome analysis, and phylogenetic inference. A genome-wide association study (GWAS) identified genetic determinants of virulence and AMR. The invasiveness and intracellular survival of PP_BR059 were assessed using in vitro macrophage infection assays, while whole-genome sequencing (WGS) provided genetic insights. Results: Phylogenetic analysis identified 49 sequence types (STs), with ST-50 (787 genomes) and ST-27 (634 genomes) being most prevalent. ST-50 included all clinical strains from South America, including PP_BR059. AMR analysis showed 60% of SSa genomes were pan-susceptible, while ST-27 had the highest proportion of AMR strains. GWAS revealed distinct evolutionary lineages within ST-50 and ST-27. PP_BR059 exhibited lower macrophage invasion (3.82%) but significantly higher intracellular survival at 2 h (68.72%) and 20 h (25.68%) post-infection. WGS confirmed a pan-susceptible AMR profile and plasmid absence. Conclusions: This study highlights SSa’s global dissemination, evolutionary trends, and pathogenic variability, emphasizing the need for molecular surveillance to inform public health interventions.

This study, conducted in the State of Rio de Janeiro, aimed to genetically distinguish 29 isolates of S. Typhimurium isolated from 344 samples of swine carcasses by PFGE (pulse‑field gel electrophoresis) and to evaluate their antimicrobial resistance profile. Out of the 29 isolates, 26 (90%) were resistant to at least one antimicrobial. Sulfonamides (66%), nalidixic acid (66%), trimethoprim (66%) and tetracycline (52%) were the most frequent resistant drugs. Multidrug‑resistance (MDR) profile was frequent (60% of isolates). The profile Eno‑Na‑Nxn‑Fc‑C‑S‑Gm‑G‑T‑Te (14%), Cp‑Eno‑Na‑Fc‑C‑S‑G‑T‑Te (10%) and Na‑G‑T (7%) were the most frequent. Five isolates within the predominant PFGE pulsetype came from lymph nodes of distinct animals from multiple slaughterhouses indicating that this particular clone might be widespread in the Rio de Janeiro State. This paper reveals a threat to the population in the entire State and highlights the necessity of the strict control in the use of antimicrobials in swine production in the entire country.

Salmonella spp. are important foodborne pathogens often associated with infectious outbreaks caused by consuming contaminated food. Although these microorganisms are widely distributed in several animal production chains, there are few records of their occurrence in aquaculture. This study aimed to evaluate the presence and antimicrobial resistance of Salmonella spp. isolated from fish farms. Samples were collected from three fish farms, covering water, fish, and epilithic biofilm. Salmonella isolates were identified by PCR, and serotyping was performed using the slide agglutination method, according to the Kaufman-White system. Susceptibility to antimicrobial agents was assessed using the Kirby and Bauer disk diffusion method. The presence of class 1 and 2 integrons was determined by PCR. Ninety samples were examined, of which 13 (14.44%) were positive for S. enterica, of which 5 strains were isolated from lagoon water, 3 from fish, and 5 from epilithic biofilm. Among the samples, the serotypes S. Minnesota, S. Panamá, and S. Anatum were identified. Antimicrobial resistance rates were highest for sulfonamides (92.30%), trimethoprim (84.61%), tetracycline (46.15%), and streptomycin (46.15%). Multiple antibiotic resistance was confirmed in 84.61% of the isolates, with 100% presenting integron class 1 and 7.69% integron class 2. This study demonstrated a high prevalence of multiresistant bacteria in fish farms, which reinforces public health concerns due to the use of antibiotics and the risk associated with food from farmed freshwater fish. Given these results, the need for new external research into control and prevention strategies for Salmonella spp. is evident. in aquaculture, as well as greater regulation in fish production chains.

Bivalve mollusks play an essential role in the maintenance of two aquatic ecosystems and can act as bioindicators of environmental pollution due to their capacity to accumulate pollutants. In the state of Amapá, the exploration of these organisms is poorly studied, especially in relation to microbiological contamination and antimicrobial resistance. This study aims to analyze the occurrence of Escherichia coli and other enterobacteria in two species of water mollusks (Prisodon obliquus and Triplodon corrugatus) collected in the Amazon River, in Macapá (AP), as well as to evaluate their antimicrobial resistance profile. This is a transversal study carried out between October 2022 and March 2023. Foram colletadas 40 samples on three points along the banks of the Amazon River. Microbiological and molecular analyzes will include bacterial isolation, antimicrobial susceptibility tests using the disk diffusion method, and detection of resistance and virulence genes by PCR. Foram 62 bacterial isolates were identified, including 31 from E. coli, 18 from Klebsiella pneumoniae and others belonging to Enterobacter, Citrobacter and Serratia. The strains present high resistance to streptomycin (100%), nalidixic acid (93.5%) and ceftazidime (90.3%). The blaCMY gene, associated with cephalosporin resistance, was identified in E. coli samples. The presence of multiresistant bacteria in mollusks from the waters of the Amazon River represents a potential public health risk and evidence of the need for integrated environmental surveillance and antimicrobial resistance control actions based on a One Health approach.