UK likely introduced Salmonella strain into Korea

A type of Salmonella was likely introduced into South Korea from the United Kingdom, according to researchers.

Scientists analyzed whole genome sequences of Salmonella Enteritidis isolates in South Korea that had a specific pulsed-field gel electrophoresis (PFGE) pattern, which has emerged and circulated in South Korea since 2020, leading to two fatal infections.

Isolates with this pattern were submitted to the Korea Disease Control and Prevention Agency (KDCA). According to clinical data at KDCA, both fatalities were in patients who had no documented underlying health conditions.

The study, published in Emerging Infectious Diseases, included isolates from eight outbreaks during 2020 to 2023, other Salmonella Enteritidis strains from chicken farms in South Korea, and human isolates from the UK.

Data from the Food and Agriculture Organization of the United Nations showed that an average of 177,000 live chickens per year were imported into South Korea from the UK during 2015 to 2020. This trade route represents a plausible pathway, said scientists.

Breeding stock trade
In South Korea, Salmonella Enteritidis is a leading cause of foodborne illness. Poultry products, especially eggs, have been consistently identified as primary sources of transmission.

Surveillance of Salmonella Enteritidis in the PulseNet Korea network moved from pulsed-field gel electrophoresis (PFGE) to the use of whole genome sequencing (WGS) in 2020.

The frequency of isolates with the studied pattern increased from 3.2 percent in 2018 to 96.5 percent by August 2024. The percentage of related outbreaks rose from 33.3 percent in 2020 to 91.7 percent in 2024. Among the 23 outbreaks during 2020 to 2024, 13 were caused by egg-associated foods, nine from unknown sources, and one from another food type.

Researchers compared isolates from the study with 223 other Salmonella Enteritidis genome sequences from South Korea or 1,230 global genome sequences.

Isolates from South Korea within a certain clade shared recent common ancestors with human isolates from the UK. Analysis supported the likely introduction of Salmonella Enteritidis into South Korea from the UK. After the introduction, poultry products played a role in dissemination of the strain, leading to foodborne outbreaks.

“Enhanced biosecurity is required to prevent the introduction and dissemination of Salmonella Enteritidis across the poultry industry; the role that human activity can play in spread should not be underestimated. Continued genomic surveillance remains invaluable to monitor the spread of foodborne pathogens; such efforts could further the design of improved prevention strategies,” said researchers.