title: Antimicrobial-resistant Shigella infections from Iran: an overlooked problem?
abstract: OBJECTIVE
  In this study, we wanted to assess the level of antimicrobial resistance, the presence of genes encoding resistance to cephalosporins and plasmid-mediated quinolone resistance (PMQR), and genetic relatedness among Shigella isolates obtained from Iranian patients.
  
  
  METHODS
  A total of 44 Shigella isolates were collected from Iranian patients admitted to Milad Hospital, Tehran, Iran, during 2008-10. Of these, 37 were serotyped and characterized by MIC determination. A subset of eight suspected extended-spectrum β-lactamase (ESBL) producers (six Shigella sonnei phase II and two Shigella flexneri type 1b) were examined for the presence of genes encoding cephalosporin resistance. The presence of PMQR was assessed in one S. flexneri isolate exhibiting low-level resistance to ciprofloxacin and susceptibility to nalidixic acid. PFGE was performed on 25 S. sonnei phase II isolates.
  
  
  RESULTS
  Of the isolates, 25 (68%) were S. sonnei phase II, with 5 (14%) S. flexneri, 5 (14%) Shigella dysenteriae type 2, and 2 (5%) Shigella boydii type 2. Resistance to at least threeclasses of antimicrobials was detected in all species. The presence of bla(CTX-M-15) and the AmpC β-lactamase producer bla(CMY-2) was confirmed in five and one S. sonnei phase II isolates, respectively. One of the two S. flexneri type 1b that contained bla(CTX-M-15) also harboured a qnrS1 gene. PFGE identified sevenPFGE profiles; the main cluster included 15 of the strains, suggesting low genetic diversity between isolates or the presence of an endemic clone in Iran.
  
  
  CONCLUSIONS
  This is the first known description of ESBL-producing and AmpC β-lactamase-producing Shigella and of PMQR Shigella in Iran. The emergence of CTX-15, CMY-2 and qnrS1 genes may compromise the treatment of shigellosis. Strategies to minimize the spread of ESBL-producing and AmpC-β-lactamase-producing Shigella should be implemented.
authors.affiliation: Research Center for Gastroenterology and Liver Disease, Shahid Beheshti University, Medical Sciences, Tehran, Iran.
authors.forename: Mercedeh
authors.initials: M
authors.lastname: Tajbakhsh
authors.forename: Lourdes
authors.initials: L
authors.lastname: García Migura
authors.forename: Mohammad
authors.initials: M
authors.lastname: Rahbar
authors.forename: Christina Aaby
authors.initials: CA
authors.lastname: Svendsen
authors.forename: Mona
authors.initials: M
authors.lastname: Mohammadzadeh
authors.forename: Mohammad Reza
authors.initials: MR
authors.lastname: Zali
authors.forename: Frank M
authors.initials: FM
authors.lastname: Aarestrup
authors.forename: Rene S
authors.initials: RS
authors.lastname: Hendriksen
mesh_terms: D000293:Adolescent; D000328:Adult; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D024881:Drug Resistance, Bacterial; D004405:Dysentery, Bacillary / Q000382:microbiology*; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D007492:Iran; D008297:Male; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D058889:Molecular Typing; D010957:Plasmids; D015363:Quinolones / Q000494:pharmacology; D012760:Shigella / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification*; D055815:Young Adult
chemical_list: D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D015363:Quinolones