title: Cephalosporin-resistant Shigella flexneri over 9 years (2001-09) in India.
abstract: OBJECTIVE
  To determine the pattern and antimicrobial resistance genes of cephalosporin resistance in Shigella flexneri and Shigella dysenteriae over 9 years.
  
  
  METHODS
  Isolates of Shigella (S. flexneri, n = 119 and S. dysenteriae, n = 24) were tested for resistance to ceftriaxone and cefepime by disc diffusion, for MIC by Etest and for extended-spectrum β-lactamase (ESBL) and AmpC production. The presence of antimicrobial resistance genes was investigated by PCR using specific primers for bla(TEM), bla(OXA-1), bla(CTX-M-15), bla(SHV) and bla(CMY-2) for all the isolates.
  
  
  RESULTS
  Twenty (16.8%) S. flexneri isolates were resistant/intermediately susceptible to ceftriaxone/cefepime, while all S. dysenteriae were susceptible. In S. flexneri isolates, the MIC(50) values of ceftriaxone and cefepime were found to be 0.032 and 0.125 mg/L, respectively, while their MIC(90) values were 12 and 8 mg/L, respectively. The MIC(50) and MIC(90) for S. dysenteriae were below 1 mg/L for ceftriaxone; however, for cefepime the MIC(90) was found to be 4 mg/L. Of the 20 resistant/intermediately susceptible S. flexneri isolates, 9 were positive for ESBL production and 4 for AmpC production by phenotypic tests. All 20 isolates were found to be positive for bla(TEM), 10 for bla(CTX-M-15), 8 for bla(OXA) and 7 for bla(CMY-2); none was positive for bla(SHV).
  
  
  CONCLUSIONS
  We report a high level of cephalosporin resistance with high MICs and ESBL- and AmpC-mediated antibiotic resistance in Shigella from north India.
authors.affiliation: Department of Medical Microbiology, Postgraduate Institute of Medical Education and Research, Chandigarh, India. drneelampgi@yahoo.com
authors.forename: Neelam
authors.initials: N
authors.lastname: Taneja
authors.forename: Abhishek
authors.initials: A
authors.lastname: Mewara
authors.forename: Ajay
authors.initials: A
authors.lastname: Kumar
authors.forename: Garima
authors.initials: G
authors.lastname: Verma
authors.forename: Meera
authors.initials: M
authors.lastname: Sharma
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology*; D002648:Child; D002675:Child, Preschool; D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000235:genetics; D004405:Dysentery, Bacillary / Q000453:epidemiology* / Q000382:microbiology*; D005260:Female; D006801:Humans; D007194:India / Q000453:epidemiology; D007223:Infant; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D016133:Polymerase Chain Reaction; D015995:Prevalence; D012763:Shigella flexneri / Q000187:drug effects* / Q000302:isolation & purification; D055815:Young Adult; D018440:beta-Lactam Resistance; D001618:beta-Lactamases / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D017931:DNA Primers; D004269:DNA, Bacterial; D001618:beta-Lactamases