Global genomic surveillance of tigecycline resistance gene tet(X) in Salmonella enterica.

OBJECTIVE

The global transmission of plasmid-mediated tigecycline resistance gene tet(X) is a growing concern, yet its distribution in Salmonella remains poorly characterized. This study aimed to determine the prevalence and molecular features of tet(X) in Salmonella isolates from China and elucidate the global population structure and genomic surveillance framework.

METHODS

A total of 865 Salmonella strains collected from diverse sources in China between 2019 and 2024 were screened for genetic analysis of tet(X), along with 89 tet(X)-positive Salmonella isolates from humans, animals, food, and the environment worldwide.

RESULTS

One tet(X4)-positive S. 4,[5],12:i:- ST34 strain was recovered from pig faces among the 865 isolates. The tet(X4) gene was located on the commonly observed IncFIA8-IncHI1/ST17 plasmid. Globally, the 89 tet(X)-positive Salmonella isolates, collected between 2005 and 2025, originated from eight countries, predominantly the United Kingdom (44.94%) and China (22.47%). Most isolates were from humans (67.42%), followed by animals and foods. Among the four identified tet(X) variants, tet(X4) is the most prevalent, representing 83.15% of the isolates. All these isolates carried multiple antibiotic resistance genes and belonged to 16 serovars and 17 sequence types, primarily S. Kentucky ST198 (35.96%) and S. 4,[5],12:i:- ST34 (16.85%). Particularly, both S. Kentucky ST198 and S. 4,[5],12:i:- ST34 strains exhibited a close genetic relatedness within their respective lineages.

DISCUSSION: The global distribution of tet(X)-carrying Salmonella enterica strains across humans, animals, food, and the environment underscores a significant threat to public health. It highlights the urgent need for enhanced global surveillance of tet(X)-positive Salmonella within a One Health framework.