Introduction. Salmonella enterica is a significant enteric pathogen affecting human and livestock health. Pork production is a common source of Salmonella contamination, with emerging multidrug resistance (MDR) posing a global health threat. Gap statement. Salmonella contamination and antimicrobial resistance (AMR) profiles in the pig production chain are underreported. Aim. To investigate the prevalence of S. enterica in the pig production chain and characterise their AMR profiles. Methodology. We collected 485 samples from pig farms, a standard pig abattoir and retail markets in Patthalung and Songkhla provinces in southern Thailand. Antimicrobial susceptibility testing was performed on these samples, and AMR profiles were determined. Results. S. enterica was detected in 68.67% of farm samples, 45.95% of abattoir samples and 50.67% of retail market samples. Analysis of 264 isolates, representing 18 serotypes, identified S. enterica serotype Rissen as the most prevalent. The predominant resistance phenotypes included ampicillin (AMP, 91.29%), tetracycline (TET, 88.26%) and streptomycin (STR, 84.47%). Over 80% of isolates showed resistance to three or more antimicrobial classes, indicating MDR. The AMP–STR–TET resistance pattern was found in nearly 70% of all MDR isolates across the production chain. Conclusions. The high prevalence of MDR is consistent with extensive antimicrobial use in the livestock sector. The presence of extensively resistant S. enterica highlights the urgent need for antimicrobial stewardship. Strengthening preventive strategies and control measures is crucial to mitigate the risk of MDR Salmonella spreading from farm to fork.

Salmonella is an important enteric pathogen that poses a threat to human and livestock animal health, with emerging multidrug resistance (MDR) a major public health issue globally. We investigated the prevalence of Salmonella in healthy and diseased pigs from Thai pig farms and determined their phenotypic and genotypic antimicrobial resistance profiles. A total of 150 fecal samples were collected from pigs housed in pens from four separate pig farms in southern Thailand and tested for the presence of Salmonella . Confirmed Salmonella isolates were tested for their susceptibility to 11 antimicrobials, and PCR used to detect known antimicrobial resistance genes (ARGs). Salmonella isolates were cultured from 69% (103/150) of all fecal samples, with higher prevalence in disease pigs (12/15; 80%), compared with healthy pigs (91/135; 67%). Serotype Rissen was the most frequently identified serotype among the Salmonella isolates. Resistance to ampicillin (AMP) (97%), sulfonamide-trimethoprim (SXT) (97%), and tetracycline (TET) (94%) were the most common phenotypes observed. The most common ARGs identified were bla _TEM gene (99.%), tetA (87%), sul1 (77%), and dfrA1 (74%), and more than 95% of the Salmonella isolates tested were MDR - based on resistance to three or more antimicrobial classes. The most common antimicrobial resistance pattern exhibited was AMP-TET-SXT (76%), and resistance to colistin (via the mcr-1 gene) was observed in both healthy and diseased pigs. The clonal groups of PFGE analysis in serotype Typhimurium revealed the genetic relationship among Salmonella isolated from healthy and diseased pigs from different pig farms.

Salmonella spp. is an important foodborne pathogen associated with consumption of contaminated food, especially livestock products. Antimicrobial resistance (AMR) in Salmonella has been reported globally and increasing AMR in food production is a major public health issue worldwide. The objective of this study was to describe the genetic relatedness among Salmonella enterica isolates, which displayed identical DNA fingerprint profiles. Ten S. enterica isolates were selected from meat and human cases with an identical rep-PCR profile of serovars Rissen (n=4), Weltevreden (n=4), and Stanley (n=2). We used long-read whole genome sequencing (WGS) on the MinION sequencing platform to type isolates and investigate in silico the presence of specific AMR genes. Antimicrobial susceptibility testing was tested by disk diffusion and gradient diffusion method to corroborate the AMR phenotype. Multidrug resistance and resistance to more than one antimicrobial agent were observed in eight and nine isolates, respectively. Resistance to colistin with an accompanying mcr -1 gene was observed among the Salmonella isolates. The analysis of core genome and whole genome MLST revealed that the Salmonella from meat and human salmonellosis were closely genetic related. Hence, it could be concluded that meat is one of the important sources for Salmonella infection in human. Highlights: Colistin resistance detected in 2 clones from 2 different Salmonella enterica serovars (Rissen and Weltevreden) with accompanying plasmid-borne mcr -1 gene from the food production chain and human clinical salmonellosis. High prevalence of multidrug resistant isolates and resistance to more than one antimicrobial agent. MinION has potential for mobile, rapid and accurate application in veterinary genomic epidemiology studies.

Background: Salmonella is a foodborne pathogen that causes human gastroenteritis and is transmitted through the livestock production chain, with contamination occurring in pork across modern retail stores. In this study, we aimed to determine the prevalence of Salmonella contamination in pork, characterize antimicrobial resistance (AMR) profiles, and identify associated risk factors in urban southern Thailand. Methods: A total of 600 pork products were collected and tested for Salmonella identification by using ISO 6579:2017 and antimicrobial susceptibility. Associations between contamination and risk factors were assessed by Fisher’s exact test. A final model was developed using repeated logistic regression with a Generalized Estimating Equation (GEE) approach. Results: The prevalence of Salmonella contamination was 33.33%, with the serotype Rissen most frequently detected. Store type, packaging type, marketing target, and seasonal variation were significantly associated with contamination. Sealed packaging and products intended for household use were associated with lower contamination risk. High resistance was observed for ampicillin and tetracycline, while the rate of multidrug resistance was 12.5%, and 10.5% of the isolates were pan-susceptible. Conclusions: Salmonella contamination varies across pork products and retail conditions; proper handling and thorough cooking are essential. From a One Health perspective, these findings highlight links between animal production, food systems, and human health, supporting integrated strategies to reduce transmission and antimicrobial resistance.