title: Cost-effective procedure for Streptococcus pyogenes immobilized DNA preparation and miniPFGE subtyping.
abstract: BACKGROUND
  Group A streptococci (GAS) is responsible of several human diseases ranging from mild infection to severe invasive toxin-mediated disease and post-infectious sequelae. Accordingly, a GAS surveillance program based on molecular techniques is advisable for its epidemiological control. Pulsed-field gel electrophoresis (PFGE) is the gold standard for GAS molecular subtyping, but a major disadvantage is the length of the procedure, which takes 1-3 days of work, minimum. The aim of this study was to develop a rapid and cost-effective procedure for PFGE subtyping of GAS isolates.
  
  
  METHODS
  Different incubation times of GAS, immobilized in agarose miniplugs, in solutions containing lysozyme and/or mutanolysine followed by solutions with urea instead of proteinase K, were assayed. DNA was restricted with SmaI and the fingerprints were obtained in clamped homogeneous electric field (CHEF) chambers and minichambers. The modified procedure was used to subtype 22 GAS isolates.
  
  
  RESULTS
  Intact DNA molecules of GAS immobilized in agarose miniplugs were prepared incubating the cells, in situ, with a solution containing lysozyme for 4 hours, followed by the incubation in a non-enzymatic solution with urea for 2 hours. SmaIDNA macrorestriction fragments were well resolved in 5 hours and 14 minutes by electrophoresis in a CHEF minichamber at 10 V/cm. This procedure for GAS DNA preparation was useful for fingerprinting GAS strains in the format of CHEF Mapper (BioRad).
  
  
  CONCLUSIONS
  The procedure took 13 hours for GAS strains subtyping. Both sample preparation and electrophoresis in CHEF minichamber represent an economic alternative for performing massive epidemiological studies of this human pathogen.
authors.affiliation: Cuban Neurosciences Center, La Habana, Cuba. yaumara@cneuro.edu.cu.
authors.forename: Yaumara
authors.initials: Y
authors.lastname: López
authors.forename: Viana
authors.initials: V
authors.lastname: Manrique
authors.forename: Esperanza
authors.initials: E
authors.lastname: Niubo
authors.forename: Margarita
authors.initials: M
authors.lastname: Valdés-Dapena
authors.forename: Julián
authors.initials: J
authors.lastname: Pérez Amarillo
authors.forename: Israel
authors.initials: I
authors.lastname: López
authors.forename: Berenice
authors.initials: B
authors.lastname: Parra
authors.forename: Gerardo
authors.initials: G
authors.lastname: Escalona Venegas
authors.forename: Ana María
authors.initials: AM
authors.lastname: Riverón
authors.forename: Lilia
authors.initials: L
authors.lastname: López-Cánovas
mesh_terms: D003365:Costs and Cost Analysis; D004269:DNA, Bacterial / Q000235:genetics* / Q000302:isolation & purification; D016521:Electrophoresis, Gel, Pulsed-Field / Q000191:economics* / Q000379:methods*; D006801:Humans; D061925:Immobilized Nucleic Acids / Q000235:genetics* / Q000302:isolation & purification; D017720:Molecular Epidemiology / Q000379:methods; D058889:Molecular Typing / Q000191:economics* / Q000379:methods*; D013297:Streptococcus pyogenes / Q000145:classification* / Q000235:genetics; D013997:Time Factors
chemical_list: D004269:DNA, Bacterial; D061925:Immobilized Nucleic Acids