title: Genetic diversity of Salmonella enteric serovar typhi and paratyphi in Shenzhen, China from 2002 through 2007.
abstract: BACKGROUND
  Typhoid and paratyphoid fever are endemic in China. The objective of this investigation was to determine the molecular features of nalidixic acid-resistant Salmonella enteric serovar Typhi (S. typhi) and Paratyphi (S. paratyphi) from blood isolates in Shenzhen, China.
  
  
  RESULTS
  Twenty-five S. typhi and 66 S. paratyphi were isolated from 91 bacteremic patients between 2002 and 2007 at a hospital in Shenzhen, Southern China. Fifty-two percent (13/25) of S. typhi and 95.3% (61/64) of S. paratyphi A were resistant to nalidixic acid. Sixty-seven isolates of nalidixic acid-resistant Salmonella (NARS) showed decreased susceptibility to ciprofloxacin (MICs of 0.125-1 microg/mL). All 75 NARS isolates had a single substitution in the quinolone resistance-determining region (QRDR) of GyrA (Ser83-->Phe/Pro/Tyr, or Asp87-->Gly/Asn), and 90.7% of these isolates carried the substitution Ser83Phe in GyrA. No mutation was found in the QRDR of gyrB, parC, or parE. Plasmid mediated quinolone resistance genes including qnr and aac(6')-Ib-cr were not detected in any isolate. Twenty-two distinct pulsed field gel electrophoresis (PFGE) patterns were observed among S. typhi. Sixty-four isolates of S. paratyphi A belonged to one clone. Eighty-seven investigated inpatients were infected in the community. Six patients infected by S. paratyphi A had a travel history before infection.
  
  
  CONCLUSIONS
  Nalidixic acid-resistant S. typhi and S. paratyphi A blood isolates were highly prevalent in Shenzhen, China. PFGE showed the variable genetic diversity of nalidixic acid-resistant S. typhi and limited genetic diversity of nalidixic acid -resistant S. paratyphi A.
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences, Beijing 100730, PR China.
authors.forename: Weiyuan
authors.initials: W
authors.lastname: Wu
authors.forename: Hui
authors.initials: H
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Lu
authors.forename: Jinsong
authors.initials: J
authors.lastname: Wu
authors.forename: Minjun
authors.initials: M
authors.lastname: Chen
authors.forename: Yingchun
authors.initials: Y
authors.lastname: Xu
authors.forename: Yuemei
authors.initials: Y
authors.lastname: Lu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D002681:China / Q000453:epidemiology; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D014644:Genetic Variation; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009268:Nalidixic Acid / Q000494:pharmacology; D010284:Paratyphoid Fever / Q000453:epidemiology; D015995:Prevalence; D012482:Salmonella paratyphi A / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D012485:Salmonella typhi / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D014435:Typhoid Fever / Q000453:epidemiology; D055815:Young Adult
chemical_list: D004269:DNA, Bacterial; D009268:Nalidixic Acid