title: Tracing isolates from domestic human Campylobacter jejuni infections to chicken slaughter batches and swimming water using whole-genome multilocus sequence typing.
abstract: Campylobacter jejuni is the leading cause of bacterial gastroenteritis and chicken is considered a major reservoir and source of human campylobacteriosis. In this study, we investigated temporally related Finnish human (n=95), chicken (n=83) and swimming water (n=20) C. jejuni isolates collected during the seasonal peak in 2012 using multilocus sequence typing (MLST) and whole-genome MLST (wgMLST). Our objective was to trace domestic human C. jejuni infections to C. jejuni isolates from chicken slaughter batches and swimming water. At MLST level, 79% of the sequence types (STs) of the human isolates overlapped with chicken STs suggesting chicken as an important reservoir. Four STs, the ST-45, ST-230, ST-267 and ST-677, covered 75% of the human and 64% of the chicken isolates. In addition, 50% of the swimming water isolates comprised ST-45, ST-230 and ST-677. Further wgMLST analysis of the isolates within STs, accounting their temporal relationship, revealed that 22 of the human isolates (24%) were traceable back to C. jejuni positive chicken slaughter batches. None of the human isolates were traced back to swimming water, which was rather sporadically sampled. The highly discriminatory wgMLST, together with the patient background information and temporal relationship data with possible sources, offers a new, accurate approach to trace back the origin of domestic campylobacteriosis. Our results suggest that potentially a substantial proportion of campylobacteriosis cases during the seasonal peak most probably are due to other sources than chicken meat consumption. These findings warrant further wgMLST-based studies to reassess the role of other reservoirs in the Campylobacter epidemiology both in Finland and elsewhere.
authors.affiliation: Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
authors.forename: Sara
authors.initials: S
authors.lastname: Kovanen
authors.affiliation: Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
authors.forename: Rauni
authors.initials: R
authors.lastname: Kivistö
authors.affiliation: Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
authors.forename: Ann-Katrin
authors.initials: AK
authors.lastname: Llarena
authors.affiliation: Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
authors.forename: Ji
authors.initials: J
authors.lastname: Zhang
authors.affiliation: Eastern Finland Laboratory Centre Joint Authority Enterprise (ISLAB), Kuopio District Laboratory, Finland.
authors.forename: Ulla-Maija
authors.initials: UM
authors.lastname: Kärkkäinen
authors.affiliation: Eastern Finland Laboratory Centre Joint Authority Enterprise (ISLAB), Mikkeli District Laboratory and University of Helsinki, Department of Bacteriology and Immunology, Helsinki, Finland.
authors.forename: Tamara
authors.initials: T
authors.lastname: Tuuminen
authors.affiliation: Keslab Laboratory, Department of Clinical Microbiology, Central Finland Health Care District, Jyväskylä, Finland and Fimlab Laboratories, Ltd., Jyväskylä, Finland.
authors.forename: Jaakko
authors.initials: J
authors.lastname: Uksila
authors.affiliation: Food and Feed Microbiology Research Unit, Research and Laboratory Department, Finnish Food Safety Authority, Evira, Finland.
authors.forename: Marjaana
authors.initials: M
authors.lastname: Hakkinen
authors.affiliation: Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland.
authors.forename: Mirko
authors.initials: M
authors.lastname: Rossi
authors.affiliation: Department of Food Hygiene and Environmental Health, University of Helsinki, Helsinki, Finland. Electronic address: marja-liisa.hanninen@helsinki.fi.
authors.forename: Marja-Liisa
authors.initials: ML
authors.lastname: Hänninen
mesh_terms: D000818:Animals; D002169:Campylobacter Infections / Q000453:epidemiology / Q000382:microbiology; D016123:Campylobacter jejuni / Q000235:genetics*; D002645:Chickens / Q000382:microbiology*; D005387:Finland / Q000453:epidemiology; D006801:Humans; D058885:Multilocus Sequence Typing; D013550:Swimming; D014871:Water Microbiology
keywords: Chicken; Domestically acquired campylobacteriosis; Source; Summer peak; Surface water