Salmonella remains a significant foodborne pathogen globally with S. Typhimurium presenting as a frequently occurring serovar. This study aimed to characterize 67 S. Typhimurium isolates from humans, food, farms, and slaughterhouses collected in Singapore from 2016 to 2017. Using whole-genome sequencing analysis, the isolates were found to belong to either ST19 (n = 33) or ST36 (n = 34). ST36 predominated in human intestinal and chicken isolates, while human extra-intestinal and non-chicken food isolates belonged to ST19. Plasmids were predicted in 88.1% (n = 59) of the isolates with the most common incompatibility group profiles being IncFIB(S), IncFII(S) and IncQ1. IncFIB(S) (adjusted p-value < 0.05) and IncFII(S) (adjusted p-value < 0.05) were significantly more prevalent in ST19 isolates, while Col156 (adjusted p-value < 0.05) was more significantly found in ST36 isolates. ST36 isolates exhibited higher resistance to multiple antibiotic classes such as penicillins, phenicols, folate pathway inhibitors, aminoglycosides, β-lactam/β-lactamase inhibitor combinations, tetracyclines, and fluoroquinolones. Phylogenetics analysis suggested potential shared routes of transmission among human, chicken, farm and slaughterhouse environments. Taken together, this study offers a cross-sectional epidemiological insight into the genomic epidemiology and antimicrobial landscape of S. Typhimurium isolates in Singapore, informing strategies for future public health and food safety surveillance.

The tilapia (Oreochromis) aquaculture industry in Malaysia has expanded rapidly to meet the increasing demand for animal protein. However, this growth is challenged by microbial infections, particularly those caused by the emerging pathogen Aeromonas dhakensis. This study aimed to investigate the microbial community composition across four distinct tilapia farming systems and assess associated water physicochemical parameters, with a focus on detecting the presence of A. dhakensis and elucidating its environmental associations. Water physicochemical parameters were measured to evaluate environmental conditions, microbial communities were characterized through 16S rDNA metabarcoding, and A. dhakensis was detected using both microbiological and molecular approaches. Principal component analysis (PCA) and canonical correspondence analysis (CCA) were employed to explore the influence of environmental variables and microbial community dynamics on pathogen occurrence. Our results indicated that floating cages exhibited higher levels of temperature, ammonium, and fecal coliform, while cement tanks showed signs of nutrient accumulation. PCA revealed that both systems were associated with degraded water quality. A total of 45 A. dhakensis strains with distinct fingerprints were isolated. The 16S metabarcoding revealed Proteobacteria, Actinobacteria, and Planctomycetota as the dominant phyla. Alpha diversity did not differ significantly among pond systems, while beta diversity revealed variations in microbial assemblages across aquaculture systems. CCA identified dissolved oxygen, temperature, macronutrients (phosphate, ammonium, nitrate, and nitrite), and turbidity as significant environmental drivers shaping the microbial community structure across the pond systems. In conclusion, this study highlights the importance of environmental factors, particularly dissolved oxygen, temperature, and nutrient levels, in shaping microbial community composition and potentially influencing the presence of pathogenic bacteria such as A. dhakensis. These findings underscore the need for improved environmental management in tilapia aquaculture to mitigate disease risks and support fish health.

Salmonella Saintpaul is a foodborne pathogen of public health relevance. This study characterised 79 S. Saintpaul isolates from human clinical and food sources collected in Singapore from 2015 to 2017. Isolates belonged to ST3602 (91.1%, n = 72), ST27 (6.33%, n = 5), ST49 (1.27%, n = 1) or ST50 (1.27%, n = 1). ST3602 predominated in both human (92.5%) and food (89.7%) isolates. Human and food isolates showed the highest resistance to penicillins and beta-lactam/beta-lactamase inhibitor combinations. The analysis identified beta-lactam resistance genes (bla_CTX-M-1, bla_TEM-1D), aminoglycoside resistance genes (aph(4)-Ia, aac(3)-IVa, aadA), and fluoroquinolone resistance genes (qnrS) as the most prevalent. Notably, 31.6% of isolates identified as extended-spectrum beta-lactamase (ESBL)-producing and all ESBL-positive isolates exhibited multidrug resistance. Plasmids were predicted in 75.9% (n = 60) of the isolates, with IncI1-I(Alpha) being the most common incompatibility group and showing a strong association with bla_CTX-M-1 (Fisher’s exact test, p < 0.001; Φ = 0.913). Single-nucleotide polymorphism (SNP) analysis revealed close genetic relatedness between chicken and human isolates at relatively low SNP distances (0–16 SNPs), suggesting potential shared transmission pathways. This study provides epidemiological insights and antimicrobial resistance landscape of S. Saintpaul in Singapore, informing strategies for food safety and public health surveillance.