Antimicrobial resistance and molecular epidemiology of Salmonella Rissen from animals, food products, and patients in Thailand and Denmark.

Recently we reported increases in both the number of Salmonella infections due to Salmonella Rissen in Thailand and the isolation of this serovar from pork products in Thailand. The objectives of the present study were to determine the genetic diversity and antimicrobial resistance of Salmonella Rissen isolates recovered from humans, food products, and animals in Denmark and Thailand. Additionally, risk factors due to travel and consumption of specific food products were analyzed and evaluated. A total of 112 Salmonella Rissen isolates were included in this study from Thailand and Denmark. Thai isolates were recovered from humans, uncooked food, and ready-to-eat food. Danish isolates were obtained from humans (with and without a history of travel to Thailand prior to the infection), Danish pig or pork products, imported pig or pork products, turkeys, and animal feed. A total of 63 unique XbaI PFGE patterns were observed. The predominant pattern was shared by 22 strains. Limited antimicrobial resistance was observed in the Danish strains, and a higher degree of resistance was observed in strains originating from Thailand. Virtually all isolates were resistant to tetracycline. The tet A gene was detected in tetracycline-resistant isolates. Statistical analysis and molecular subtyping identified the combination of travel to Thailand and consumption of imported pig or pork products as well consumption of as pig or pork products produced in Denmark as risk factors for Salmonella Rissen infection among the Danish patients. The outcome of this study might be used as a supplement for future Salmonella Rissen investigations and outbreak detection.