title: Characterization of an unusual Salmonella phage type DT7a and report of a foodborne outbreak of salmonellosis.
abstract: Salmonella enterica subsp. enterica serovar 4,[5],12,i:- is a monophasic variant of Salmonella Typhimurium and its occurrence has markedly increased in several European countries in the last ten years. In June 2011, an outbreak of Salmonella 4,[5],12,i:- was reported among attendees of a wedding reception in the North-East of Italy. The source of this outbreak was identified as a cooked pork product served during the wedding reception. All Salmonella isolates from humans and the contaminated pork products were identified as Salmonella 4,[5],12,i:- and phage typed as DT7a. Afterwards, the farm where the pigs were raised was identified and sampled, and Salmonella Typhimurium was isolated from swine fecal samples. Despite the difference in serovar, these Salmonella Typhimurium isolates were also phage typed as DT7a. In the present study, Salmonella isolates from animals, humans and pork products during the outbreak investigation were subtyped by pulsed-field gel electrophoresis (PFGE), Multiple-Locus Variable number tandem repeats Analysis (MLVA), and resistance patterns, aiming to identify the most suitable subtyping methods to characterize isolates associated with this outbreak. In addition, a collection of epidemiologically unrelated strains of Salmonella 4,[5],12,i:- and Salmonella Typhimurium sharing the same phage type (DT7a) was similarly characterized in order to investigate their genetic relationship. This study provides a first snapshot of a rare Salmonella phage type, DT7a, associated with both Salmonella 4,[5],12,i:- and Salmonella Typhimurium. Moreover, the study demonstrated that in this specific context MLVA could be a reliable tool to support outbreak investigations as well as to assess the genetic relatedness among Salmonella isolates.
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: A A
authors.initials: AA
authors.lastname: Lettini
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Saccardin
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Ramon
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: A
authors.initials: A
authors.lastname: Longo
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: E
authors.initials: E
authors.lastname: Cortini
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: M C
authors.initials: MC
authors.lastname: Dalla Pozza
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Barco
authors.affiliation: Federal Institute for Risk Assessment, Department of Biological Safety, Max-Dohrn-Str. 8-10, D - 10589 Berlin, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Guerra
authors.affiliation: Istituto Superiore di Sanità, Department of Infectious, Parasitic and Immunomediated Diseases, Rome, Italy.
authors.forename: I
authors.initials: I
authors.lastname: Luzzi
authors.affiliation: Istituto Zooprofilattico Sperimentale delle Venezie, National Reference Laboratory for Salmonellosis, Legnaro, PD, Italy. Electronic address: aricci@izsvenezie.it.
authors.forename: A
authors.initials: A
authors.lastname: Ricci
mesh_terms: D000818:Animals; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D005243:Feces / Q000382:microbiology; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008460:Meat / Q000382:microbiology*; D018598:Minisatellite Repeats; D010802:Phylogeny; D012478:Salmonella Food Poisoning / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D012480:Salmonella Infections / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission; D012483:Salmonella Phages / Q000235:genetics* / Q000302:isolation & purification; D019779:Salmonella enterica / Q000145:classification / Q000235:genetics* / Q000472:pathogenicity / Q000821:virology; D013552:Swine
keywords: MLVA; Salmonella outbreak; sub-typing methods