Salmonella is a significant zoonotic foodborne pathogen, and the global spread of multidrug-resistant (MDR) strains poses substantial challenges, necessitating alternatives to antibiotics. Among these alternatives, vaccines protect the community against infectious diseases effectively. This review aims to summarize the efficacy of developed Salmonella vaccines evaluated in various animal hosts and highlight key transitions for future vaccine studies. A total of 3221 studies retrieved from Web of Science, Google Scholar, and PubMed/Medline databases between 1970 and 2023 were evaluated. One hundred twenty-seven qualified studies discussed the vaccine efficacy against typhoidal and nontyphoidal serovars, including live-attenuated vaccines, killed inactivated vaccines, outer membrane vesicles, outer membrane complexes, conjugate vaccines, subunit vaccines, and the reverse vaccinology approach in different animal hosts. The most efficacious vaccine antigen candidate found was recombinant heat shock protein (rHsp60) with an incomplete Freund’s adjuvant evaluated in a murine model. Overall, bacterial ghost vaccine candidates demonstrated the highest efficacy at 91.25% (95% CI = 83.69–96.67), followed by the reverse vaccinology approach at 83.46% (95% CI = 68.21–94.1) across animal hosts. More than 70% of vaccine studies showed significant production of immune responses, including humoral and cellular, against Salmonella infection. Collectively, the use of innovative methods rather than traditional approaches for the development of new effective vaccines is crucial and warrants in-depth studies.

Nontyphoidal Salmonella (NTS) causes global outbreaks of foodborne disease. The main source of Salmonella for humans is animal-borne foods; however, the monitoring of Salmonella in the food chain via genomic platforms was limited in China. This study evaluated the prevalence, resistome, and virulome diversity of Salmonella strains identified from pork, retail environment, aquatic products, and poultry eggs of retail markets in Yichun city, Jiangxi province. The overall incidence of Salmonella was 9.4 %, with a higher contamination rate observed in pork at 13.5 %, followed by the retail environment at 7.69 %. The genomic analysis of the isolates revealed a total of fifteen distinct serovars, with serovar Enteritidis being the most prevalent (64.3 %). The phenotypic resistance analysis conducted by the broth microdilution method, revealed that 81.12 % of the isolates exhibited multidrug resistance (MDR), with high resistance to trimethoprim/sulphonamides (100 %), followed by tetracycline (99.3 %) and streptomycin (99.3 %). Genotypic analysis of antimicrobial resistance identified 80 antimicrobial-resistant genes (ARGs), with mdf(A), aph(3')-Ib, tet(A), dfrA12, floR, bla _TEM-1B , qnrS3, and sul2, conferring resistance to different antimicrobial classes, being the predominant ARGs. Additionally, forty ESBL genes, particularly critical genes such as bla _CTX-M and bla _NDM-1, were also identified in Salmonella isolates. The IncR, IncFIB (K), and IncX1 plasmid replicons were widely prevalent and served as significant reservoirs of horizontally acquired foreign genes. Moreover, key virulence genes such as cdtB, lpf and sef were also detected, in addition to Salmonella pathogenicity islands SPI-1 and SPI-2. This study reveals the prevalence of multidrug-resistant and virulent strains of Salmonella serovars in the markets of Yichuan city, posing a risk of human infections. The gained knowledge provided essential baseline information that may be utilized for regular tracking of MDR Salmonella transmission in the food chain to minimize potential future outbreaks.

Bacterial regional demonstration after global dissemination is an essential pathway for selecting distinct finesses. However, the evolution of the resistome during the transition to endemicity remains unaddressed. Using the most comprehensive whole-genome sequencing dataset of Salmonella enterica serovar Gallinarum ( S . Gallinarum) collected from 15 countries, including 45 newly recovered samples from two related local regions, we established the relationship among avian-specific pathogen genetic profiles and localization patterns. Initially, we revealed the international transmission and evolutionary history of S . Gallinarum to recent endemicity through phylogenetic analysis conducted using a spatiotemporal Bayesian framework. Our findings indicate that the independent acquisition of the resistome via the mobilome, primarily through plasmids and transposons shapes a unique antimicrobial resistance profile among different lineages. Notably, the mobilome-resistome combination among distinct lineages exhibits a geographical-specific manner, further supporting a localized endemic mobilome-driven process. Collectively, this study elucidates resistome adaptation in the endemic transition of an avian-specific pathogen, likely driven by the localized farming style, and provides valuable insights for targeted interventions.