Multidrug-resistant Salmonella enterica serovar paratyphi A harbors IncHI1 plasmids similar to those found in serovar typhi.
Salmonella enterica serovars Typhi and Paratyphi A cause systemic infections in humans which are referred to as enteric fever. Multidrug-resistant (MDR) serovar Typhi isolates emerged in the 1980s, and in recent years MDR serovar Paratyphi A infections have become established as a significant problem across Asia. MDR in serovar Typhi is almost invariably associated with IncHI1 plasmids, but the genetic basis of MDR in serovar Paratyphi A has remained predominantly undefined. The DNA sequence of an IncHI1 plasmid, pAKU_1, encoding MDR in a serovar Paratyphi A strain has been determined. Significantly, this plasmid shares a common IncHI1-associated DNA backbone with the serovar Typhi plasmid pHCM1 and an S. enterica serovar Typhimurium plasmid pR27. Plasmids pAKU_1 and pHCM1 share 14 antibiotic resistance genes encoded within similar mobile elements, which appear to form a 24-kb composite transposon that has transferred as a single unit into different positions into their IncHI1 backbones. Thus, these plasmids have acquired similar antibiotic resistance genes independently via the horizontal transfer of mobile DNA elements. Furthermore, two IncHI1 plasmids from a Vietnamese isolate of serovar Typhi were found to contain features of the backbone sequence of pAKU_1 rather than pHCM1, with the composite transposon inserted in the same location as in the pAKU_1 sequence. Our data show that these serovar Typhi and Paratyphi A IncHI1 plasmids share highly conserved core DNA and have acquired similar mobile elements encoding antibiotic resistance genes in past decades.
Holt
Kathryn E
KE
Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SA, UK.
Thomson
Nicholas R
NR
Wain
John
J
Phan
Minh Duy
MD
Nair
Satheesh
S
Hasan
Rumina
R
Bhutta
Zulfiqar A
ZA
Quail
Michael A
MA
Norbertczak
Halina
H
Walker
Danielle
D
Dougan
Gordon
G
Parkhill
Julian
J
D004251:DNA Transposable Elements / Q000235:genetics; D024901:Drug Resistance, Multiple, Bacterial / Q000235:genetics*; D023061:Gene Order; D022761:Gene Transfer, Horizontal / Q000235:genetics; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010957:Plasmids / Q000737:chemistry / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012482:Salmonella paratyphi A / Q000235:genetics*; D012485:Salmonella typhi / Q000235:genetics*; D017422:Sequence Analysis, DNA
D004251:DNA Transposable Elements