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Multidrug resistance plasmids underlie clonal expansions and international spread of Salmonella enterica serotype 1,4,[5],12:i:- ST34 in Southeast Asia.

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Pham, Phuong 
Ha Thanh, Tuyen 
Phuong, Linh Vo Kim 
Yen, Nguyen Phuong 


Salmonella enterica serotype 1,4,[5],12:i:- (Typhimurium monophasic variant) of sequence type (ST) 34 has emerged as the predominant pandemic genotype in recent decades. Despite increasing reports of resistance to antimicrobials in Southeast Asia, Salmonella ST34 population structure and evolution remained understudied in the region. Here we performed detailed genomic investigations on 454 ST34 genomes collected from Vietnam and diverse geographical sources to elucidate the pathogen's epidemiology, evolution and antimicrobial resistance. We showed that ST34 has been introduced into Vietnam in at least nine occasions since 2000, forming five co-circulating major clones responsible for paediatric diarrhoea and bloodstream infection. Most expansion events were associated with acquisitions of large multidrug resistance plasmids of IncHI2 or IncA/C2. Particularly, the self-conjugative IncA/C2 pST34VN2 (co-transferring blaCTX-M-55, mcr-3.1, and qnrS1) underlies local expansion and intercontinental spread in two separate ST34 clones. At the global scale, Southeast Asia was identified as a potential hub for the emergence and dissemination of multidrug resistant Salmonella ST34, and mutation analysis suggests of selection in antimicrobial responses and key virulence factors.


Acknowledgements: The authors wish to thank all study participants and their parents/guardians for participating in the study. H.C.T. is a Wellcome International Training Fellow (218726/Z/19/Z). A.E.M. is supported by the Biotechnology and Biological Sciences Research Council (BBSRC) through the BBSRC Institute Strategic Programme Microbes in the Food Chain BB/R012504/1 and its constituent project BBS/E/F/000PR10348 (Theme 1, Epidemiology and Evolution of Pathogens in the Food Chain). S.B. is a Wellcome Senior Research Fellow (215515/Z/19/Z). D.T.P. is supported by the Wellcome International Training Fellowship (222983/Z/21/Z).


Humans, Child, Salmonella enterica, Serogroup, Drug Resistance, Multiple, Bacterial, Plasmids, Salmonella, Asia, Southeastern, Anti-Infective Agents

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Commun Biol

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Springer Science and Business Media LLC
Wellcome Trust (Wellcome) (218726/Z/19/Z)