Sequence types and antimicrobial resistance profiles of salmonella typhimurium in the food chain in Singapore

• Main Authors: Lim, Yen Ching, Ong, Kar Hui, Khor, Wei Ching, Chua, Favian Yue Xuan, Lim, Jia Qi, Tan, Li Kiang, Chen, Swaine L., Wong, Wai Kwan, Maiwald, Matthias, Barkham, Timothy, Koh, Tse Hsien, Khoo, Joanna, Chan, Joanne Sheot Harn, Aung, Kyaw Thu
• Other Authors: School of Biological Sciences
• Format: Article
• Language: English
• Published: 2024
• Subjects: Medicine, Health and Life Sciences; Salmonella Typhimurium; Antimicrobial resistance
• Online Access: https://hdl.handle.net/10356/181463
• Institution: Nanyang Technological University

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.