Abstract
Antibiotic resistance in bacteria is one of the urgent threats to both public and global health. The Salmonella Typhimurium monophasic sequence type 34 (ST34) clone, with its rapid dissemination and resistance to numerous critical antimicrobials, has raised global concerns. Here, we present an updated overview on the emerging infections caused by mobile colistin resistance (mcr)-carrying colistin-resistant ST34 isolates, covering their global dissemination and virulence-associated efficacy. The higher rates of mcr-1-positive ST34 in children in China highlights the increasing threat caused by this pathogen. Most of the ST34 isolates carrying the mcr-1 gene were isolated from animals and food products, indicating the role of foodborne transmission of mcr-1. The emergence of multidrug resistance genes along with various virulence factors and many heavy metal resistance genes on the chromosome and plasmid from ST34 isolates will challenge available therapeutic options. The presence of the colistin resistance gene (mcr-1, mcr-3, and mcr-5) with the multidrug-resistant phenotype in ST34 has spread across different countries, and most of the mcr-1 genes in ST34 isolates were detected in plasmid type IncHI2 followed by IncI2, and IncX4. Together, mcr-carrying S. Typhimurium ST34 may become a new pandemic clone. The fast detection and active surveillance in community, hospital, animal herds, food products and environment are urgently warranted.
Highlights
Salmonella enterica serovars are one of the most common causative pathogens of enteric diseases in humans and animals over the world [1]
The limitation of this review is that only the references with “sequence type 34 (ST34)” have been included here due to the lack of multilocus sequence typing (MLST) data in some studies, which only reported monophasic variants by serological study but did not report the sequence type
The global dissemination of the MDR ST34 clone is likely an emerging threat to both global and public health, and, as such, it warrants being closely monitored in different sectors, including community populations and hospital patients, as well as animal herds, their food products, and their environments [88]
Summary
Salmonella enterica serovars are one of the most common causative pathogens of enteric diseases in humans and animals over the world [1]. The increasing prevalence of MDR Gram-negative bacteria, along with the lack of new antibiotics against such strains, has led to a resurgence in colistin, and it has been recognized as the last-resort antibiotic for numerous MDR bacterial infections [27,29]. The discovery of a plasmid-borne mobile colistin resistance (mcr) gene mcr-1 challenged the use of ‘last-line’ antibiotic colistin in the treatment of bacterial infections, especially by MDR bacteria [31]. Typhimurium ST34 variant is a potential threat to public health due to its global expansion and the emergence of colistin resistance.
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