A study has identified that a strain of Salmonella Enteritidis was likely introduced into South Korea from the United Kingdom. Researchers analyzed whole genome sequences of Salmonella isolates in South Korea, specifically those exhibiting a distinct pulsed-field gel electrophoresis (PFGE) pattern. This pattern has been prevalent in the country since 2020, resulting in two fatal infections among individuals without documented underlying health conditions.
The findings, published in the journal Emerging Infectious Diseases, indicate that isolates with the identified PFGE pattern were submitted to the Korea Disease Control and Prevention Agency (KDCA). The KDCA reported that both fatalities occurred in patients who had not previously exhibited any significant health issues.
Analysis of Outbreak Patterns
The researchers’ study encompassed isolates from eight outbreaks spanning from 2020 to 2023, as well as other Salmonella Enteritidis strains sourced from chicken farms in South Korea. They also included human isolates from the UK for a comprehensive analysis. Data from the Food and Agriculture Organization of the United Nations indicated that an average of 177,000 live chickens were imported annually from the UK to South Korea between 2015 and 2020. Scientists suggest that this trade route is a plausible pathway for the introduction of the Salmonella strain.
In South Korea, Salmonella Enteritidis is a leading cause of foodborne illness, with poultry products, particularly eggs, consistently recognized as primary sources of contamination. Surveillance efforts in the PulseNet Korea network transitioned from PFGE to whole genome sequencing (WGS) in 2020. The frequency of isolates exhibiting the studied pattern surged from 3.2 percent in 2018 to 96.5 percent by August 2024. Additionally, the proportion of related outbreaks escalated from 33.3 percent in 2020 to 91.7 percent in 2024.
Among the 23 outbreaks documented from 2020 to 2024, 13 were linked to egg-associated foods, nine had unknown sources, and one was attributed to another food type. Researchers compared the isolates from the South Korean study with 223 other Salmonella Enteritidis genome sequences from South Korea and 1,230 global sequences. The analysis revealed that isolates from South Korea within a specific clade shared recent common ancestors with human isolates from the UK, reinforcing the hypothesis of the strain’s introduction from that region.
Recommendations for Biosecurity and Surveillance
Following the introduction of Salmonella Enteritidis, poultry products played a significant role in the strain’s spread, leading to foodborne outbreaks. Researchers emphasize the necessity for enhanced biosecurity measures to prevent both the introduction and dissemination of this pathogen throughout the poultry industry. They highlight that the influence of human activity on the spread of such pathogens should not be underestimated.
Furthermore, the study underscores the importance of ongoing genomic surveillance to monitor the emergence and spread of foodborne pathogens. Such initiatives are crucial for improving prevention strategies and safeguarding public health against Salmonella outbreaks.