title: The sudden dominance of blaCTX-M harbouring plasmids in Shigella spp. Circulating in Southern Vietnam.
abstract: BACKGROUND
  Plasmid mediated antimicrobial resistance in the Enterobacteriaceae is a global problem. The rise of CTX-M class extended spectrum beta lactamases (ESBLs) has been well documented in industrialized countries. Vietnam is representative of a typical transitional middle income country where the spectrum of infectious diseases combined with the spread of drug resistance is shifting and bringing new healthcare challenges.
  
  
  METHODS
  We collected hospital admission data from the pediatric population attending the hospital for tropical diseases in Ho Chi Minh City with Shigella infections. Organisms were cultured from all enrolled patients and subjected to antimicrobial susceptibility testing. Those that were ESBL positive were subjected to further investigation. These investigations included PCR amplification for common ESBL genes, plasmid investigation, conjugation, microarray hybridization and DNA sequencing of a bla(CTX-M) encoding plasmid.
  
  
  RESULTS
  We show that two different bla(CTX-M) genes are circulating in this bacterial population in this location. Sequence of one of the ESBL plasmids shows that rather than the gene being integrated into a preexisting MDR plasmid, the bla(CTX-M) gene is located on relatively simple conjugative plasmid. The sequenced plasmid (pEG356) carried the bla(CTX-M-24) gene on an ISEcp1 element and demonstrated considerable sequence homology with other IncFI plasmids.
  
  
  CONCLUSIONS
  The rapid dissemination, spread of antimicrobial resistance and changing population of Shigella spp. concurrent with economic growth are pertinent to many other countries undergoing similar development. Third generation cephalosporins are commonly used empiric antibiotics in Ho Chi Minh City. We recommend that these agents should not be considered for therapy of dysentery in this setting.
authors.affiliation: The Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors.forename: Nhu Thi Khanh
authors.initials: NT
authors.lastname: Nguyen
authors.forename: Vinh
authors.initials: V
authors.lastname: Ha
authors.forename: Nga Vu Thieu
authors.initials: NV
authors.lastname: Tran
authors.forename: Richard
authors.initials: R
authors.lastname: Stabler
authors.forename: Duy Thanh
authors.initials: DT
authors.lastname: Pham
authors.forename: Thi Minh Vien
authors.initials: TM
authors.lastname: Le
authors.forename: H Rogier
authors.initials: HR
authors.lastname: van Doorn
authors.forename: Ana
authors.initials: A
authors.lastname: Cerdeño-Tárraga
authors.forename: Nicholas
authors.initials: N
authors.lastname: Thomson
authors.forename: James
authors.initials: J
authors.lastname: Campbell
authors.forename: Van Minh Hoang
authors.initials: VM
authors.lastname: Nguyen
authors.forename: Thi Thu Nga
authors.initials: TT
authors.lastname: Tran
authors.forename: Minh Van
authors.initials: MV
authors.lastname: Pham
authors.forename: Thuy Thu
authors.initials: TT
authors.lastname: Cao
authors.forename: Brendan
authors.initials: B
authors.lastname: Wren
authors.forename: Jeremy
authors.initials: J
authors.lastname: Farrar
authors.forename: Stephen
authors.initials: S
authors.lastname: Baker
mesh_terms: D000293:Adolescent; D001426:Bacterial Proteins / Q000235:genetics*; D002443:Ceftriaxone / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004405:Dysentery, Bacillary / Q000453:epidemiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D010957:Plasmids / Q000235:genetics*; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D012760:Shigella / Q000187:drug effects / Q000235:genetics* / Q000472:pathogenicity; D014744:Vietnam; D001618:beta-Lactamases / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D002443:Ceftriaxone; D001618:beta-Lactamases