Nationwide surveillance of pESI-positive Salmonella Infantis ST32 in South Korea: Endemic establishment of a dominant lineage across the broiler production chain, 2020-2023.

Authors

Hee-Seung Kang, Md Sekendar Ali, Bo-Youn Moon, Min Young Kim, Yu-Jeong Hwang, Ji-In Kim, Seung-Chun Park, Jae-Myung Kim, Suk-Kyung Lim

Published in

Food microbiology. Volume 141. Pages 105271. Epub Aug 14, 2026.

Abstract

Since 2020, South Korea has seen a rapid surge in multidrug-resistant (MDR) Salmonella Infantis ST32 harboring pESI-like megaplasmids. We investigated the driving forces behind this emergence through a nationwide, four-year surveillance of major broiler slaughterhouses. High-resolution core-genome multi-locus sequence typing (cgMLST) of 57 isolates obtained from chicken feces (n = 29) and carcasses (n = 28) identified three distinct lineages (clades I, II, and III). Further comparative analysis using a minimum spanning tree, incorporating additional human (n = 6) clinical and retail meat (n = 46) isolates from public databases, revealed the broader genetic relationships across the "feces-carcass-retail-human" continuum. Among these, clade III emerged as the dominant endemic lineage, persistently circulating across 14 production networks and maintaining strong genetic linkage from farm-level feces to retail meat. Notably, genomic analysis confirmed that 98.6% of isolates carried bla_CTX-M-65-positive pESI-like megaplasmids, and all 57 isolates (100%) exhibited a highly conserved profile of core chromosomal virulence factors (e.g., SPI-1, SPI-2, and fim operon). Major clades (I-III) exhibited high conjugative transferability (>80%), while non-clade isolates showed significantly lower plasmid transmissibility, suggesting that horizontal transfer efficiency is a key determinant of clonal dominance. Although poultry-derived clades remained genetically divergent from the sampled human clinical isolates, their structural consolidation within the national food supply signifies a robust MDR reservoir with the potential to cause human infection. These findings provide a comprehensive genomic-epidemiological framework for the persistence of pESI-positive lineages, emphasizing the need for targeted, lineage-specific surveillance to mitigate public health risks.

PMID:
42668208
Bibliographic data and abstract were imported from PubMed on 30 Aug 2026.

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