title: Characterization of epidemic clones of Listeria monocytogenes serotype 4b isolated from humans and meat products in Brazil.
abstract: BACKGROUND
  Listeria monocytogenes is an important foodborne pathogen and the 4b serotype is responsible for many cases of human listeriosis reported in Brazil. Several listeriosis outbreaks worldwide have involved a small number of well-defined clonal groups, designated as epidemic clones (ECs).
  
  
  METHODS
  We studied 71 strains of serotype 4b, including 25 isolates from human cases of listeriosis and 46 from meat-based foods, collected in Brazil between 1977 and 2010. The presence of ECs (I and II) markers and virulence genes (inlA, inlB, ilnC, inlJ and actA) were evaluated by PCR assay. The genetic relationship of ECs-positive strains was assessed by pulsed field gel electrophoresis.
  
  
  RESULTS
  ECI and ECII markers were found both in human and food strains, with 19.7% positive for the ECI marker and 40.8% for ECII. Most strains (97.2%) were positive for the virulence genes that were studied. Nevertheless, the actA gene amplicons showed two distinct sizes, with all ECI positive strains exhibiting a 105bp deletion. Pulsed field gel electrophoresis (PFGE) analysis allowed the recognition of highly related strains, particularly from two outbreaks of neonatal listeriosis in São Paulo State occurred in 1992 and 1997, both ECII-positive; and two ECI strains from a human case (1982) and from bovine meat (2009).
  
  
  CONCLUSIONS
  The presence of ECs among clinical samples and beef isolates of serotype 4b from some regions of Brazil highlights the need for rigorous control of production procedures. Furthermore, the association of ECII with two nosocomial outbreaks suggests its ability to spread in these settings.
authors.affiliation: Universidade Federal Fluminense, Niterói, Rio de Janeiro, Brazil. andre_ctbp@yahoo.com.br.
authors.forename: André Victor
authors.initials: AV
authors.lastname: Barbosa
authors.forename: Aloysio De Mello Figueiredo
authors.initials: Ade M
authors.lastname: Cerqueira
authors.forename: Leonardo Alves
authors.initials: LA
authors.lastname: Rusak
authors.forename: Cristhiane Moura Falavina
authors.initials: CM
authors.lastname: Dos Reis
authors.forename: Nilma Cintra
authors.initials: NC
authors.lastname: Leal
authors.forename: Ernesto
authors.initials: E
authors.lastname: Hofer
authors.forename: Deyse Christina
authors.initials: DC
authors.lastname: Vallim
mesh_terms: D000818:Animals; D001938:Brazil / Q000453:epidemiology; D002417:Cattle; D016521:Electrophoresis, Gel, Pulsed-Field; D005819:Genetic Markers; D005838:Genotype; D006801:Humans; D008089:Listeria monocytogenes / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D008088:Listeriosis / Q000453:epidemiology / Q000382:microbiology*; D008461:Meat Products / Q000382:microbiology*; D058889:Molecular Typing; D016133:Polymerase Chain Reaction; D065288:Serogroup; D037521:Virulence Factors / Q000235:genetics
chemical_list: D005819:Genetic Markers; D037521:Virulence Factors