title: Comparison of Salmonella enteritidis phage types isolated from layers and humans in Belgium in 2005.
abstract: OBJECTIVE
  The aim of this study was to investigate the available results for Belgium of the European Union coordinated monitoring program (2004/665 EC) on Salmonella in layers in 2005, as well as the results of the monthly outbreak reports of Salmonella Enteritidis in humans in 2005 to identify a possible statistical significant trend in both populations.
  
  
  METHODS
  Separate descriptive statistics and univariate analysis were carried out and the parametric and/or non-parametric hypothesis tests were conducted. A time cluster analysis was performed for all Salmonella Enteritidis phage types (PTs) isolated. The proportions of each Salmonella Enteritidis PT in layers and in humans were compared and the monthly distribution of the most common PT, isolated in both populations, was evaluated.
  
  
  RESULTS
  The time cluster analysis revealed significant clusters during the months May and June for layers and May, July, August, and September for humans. PT21, the most frequently isolated PT in both populations in 2005, seemed to be responsible of these significant clusters. PT4 was the second most frequently isolated PT. No significant difference was found for the monthly trend evolution of both PT in both populations based on parametric and non-parametric methods.
  
  
  CONCLUSIONS
  A similar monthly trend of PT distribution in humans and layers during the year 2005 was observed. The time cluster analysis and the statistical significance testing confirmed these results. Moreover, the time cluster analysis showed significant clusters during the summer time and slightly delayed in time (humans after layers). These results suggest a common link between the prevalence of Salmonella Enteritidis in layers and the occurrence of the pathogen in humans. Phage typing was confirmed to be a useful tool for identifying temporal trends.
authors.affiliation: Unit for Coordination of Veterinary Diagnostics, Epidemiology and Risk Analysis, Veterinary and Agrochemical Research Centre, Brussels, Belgium. sawel@var.fgov.be
authors.forename: Sarah
authors.initials: S
authors.lastname: Welby
authors.forename: Hein
authors.initials: H
authors.lastname: Imberechts
authors.forename: Flavien
authors.initials: F
authors.lastname: Riocreux
authors.forename: Sophie
authors.initials: S
authors.lastname: Bertrand
authors.forename: Katelijne
authors.initials: K
authors.lastname: Dierick
authors.forename: Christa
authors.initials: C
authors.lastname: Wildemauwe
authors.forename: Jozef
authors.initials: J
authors.lastname: Hooyberghs
authors.forename: Yves
authors.initials: Y
authors.lastname: Van der Stede
mesh_terms: D000818:Animals; D001434:Bacteriophage Typing; D001435:Bacteriophages / Q000145:classification / Q000302:isolation & purification; D001530:Belgium / Q000453:epidemiology; D002645:Chickens / Q000382:microbiology*; D005260:Female; D006801:Humans; D011201:Poultry Diseases / Q000453:epidemiology / Q000382:microbiology*; D012480:Salmonella Infections / Q000453:epidemiology* / Q000382:microbiology; D012481:Salmonella Infections, Animal / Q000453:epidemiology*; D012477:Salmonella enteritidis / Q000145:classification / Q000821:virology*; D012621:Seasons