title: Investigation of a staphylococcal food poisoning outbreak combining case-control, traditional typing and whole genome sequencing methods, Luxembourg, June 2014.
abstract: In June 2014, a staphylococcal food poisoning outbreak occurred at an international equine sports event in Luxembourg requiring the hospitalisation of 31 persons. We conducted a microbiological investigation of patients and buffet items, a case-control study and a carriage study of catering staff. Isolates of Staphylococcus aureus from patients, food and catering staff were characterised and compared using traditional typing methods and whole genome sequencing. Genotypically identical strains (sequence type ST8, spa-type t024, MLVA-type 4698, enterotoxin A FRI100) were isolated in 10 patients, shiitake mushrooms, cured ham, and in three members of staff. The case-control study strongly suggested pasta salad with pesto as the vehicle of infection (p<0.001), but this food item could not be tested, because there were no leftovers. Additional enterotoxigenic strains genetically unrelated to the outbreak strain were found in four members of staff. Non-enterotoxigenic strains with livestock-associated sequence type ST398 were isolated from three food items and two members of staff. The main cause of the outbreak is likely to have been not maintaining the cold chain after food preparation. Whole genome sequencing resulted in phylogenetic clustering which concurred with traditional typing while simultaneously characterising virulence and resistance traits.
authors.affiliation: Laboratoire National de Santé, Dudelange, Luxembourg.
authors.forename: Joël
authors.initials: J
authors.lastname: Mossong
authors.forename: Frédéric
authors.initials: F
authors.lastname: Decruyenaere
authors.forename: Gilbert
authors.initials: G
authors.lastname: Moris
authors.forename: Catherine
authors.initials: C
authors.lastname: Ragimbeau
authors.forename: Christophe M
authors.initials: CM
authors.lastname: Olinger
authors.forename: Sophia
authors.initials: S
authors.lastname: Johler
authors.forename: Monique
authors.initials: M
authors.lastname: Perrin
authors.forename: Patrick
authors.initials: P
authors.lastname: Hau
authors.forename: Pierre
authors.initials: P
authors.lastname: Weicherding
mesh_terms: D000328:Adult; D016022:Case-Control Studies; D004196:Disease Outbreaks; D004768:Enterotoxins / Q000235:genetics*; D005260:Female; D005516:Food Microbiology; D016680:Genome, Bacterial; D005838:Genotype; D006801:Humans; D008189:Luxembourg / Q000453:epidemiology; D008297:Male; D058889:Molecular Typing; D010802:Phylogeny; D017421:Sequence Analysis; D013202:Staphylococcal Food Poisoning / Q000175:diagnosis / Q000453:epidemiology* / Q000382:microbiology; D013203:Staphylococcal Infections / Q000453:epidemiology*; D013211:Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D004768:Enterotoxins
keywords: Luxembourg; Staphylococcus aureus; Whole genome sequencing; case–control study; colonisation; food poisoning