Summary
The Salmonella enterica subspecies serovar Enteritidis is the one
of main serovars isolated from human patients with food poisoning and
poultry without clinical signs. Consumption of poultry products
contaminated with Salmonella Enteritidis is a common source of
human salmonellosis. This study was aimed to determine the genetic
relationships between Salmonella Enteritidis strains isolated
from human patients and those isolated from poultry sources using
whole-genome sequencing analysis.
Seven of multi-drug resistant (MDR) strains of SalmonellaEnteritidis were isolated from 234 retail chicken meats, internal organs
of chicken, and straw bedding samples at chicken farms. Whole genome
sequences of the MDR strains were determined using the Oxford Nanopore
sequencing and compared with available whole genome sequences of theSalmonella Enteritidis strains previously isolated in Korea.
Single-nucleotide polymorphism analysis of the whole genomes showed that
all MDR Salmonella Enteritidis strains were genetically close and
related to the FORC_019 strain isolated from human blood in 2015 in
Korea. All of the MDR Salmonella Enteritidis strains contained a
110 kb of plasmid, and comparative plasmid analysis showed that all of
the MDR Salmonella Enteritidis strains carried a novel fusion
plasmid with genes coding virulence factors and antibiotic resistance
proteins. The almost identical plasmid, with an extra 7.5-kb insertion
sequence was also found in the FORC_019 strain.
These results suggested that the single genetic lineage of MDRSalmonella Enteritidis that can cause salmonellosis in human is
currently contaminating the Korean poultry industry.