Real-time subtyping via PFGE reveals potential epidemiological relatedness among human salmonellosis cases in Northern Italy

Abstract

Aim: This study aimed to assess the applicability of a combined approach of traditional and molecular epidemiology in order to detect salmonellosis outbreaks in the Piedmont region (Italy), characterized by high Salmonella prevalence.

Methods and results: Pulsed field gel electrophoresis (PFGE) was used in real-time and in combination with clinical surveillance to assess the relatedness of salmonellosis human cases; subsequently, PFGE profiles of clinical isolates were compared with those of isolates from food items collected during the same study period to identify putative food sources of Salmonella. The real-time subtyping approach allowed the identification of an outbreak (21 isolates), which was undetected by epidemiological surveillance.

Conclusions: Traditional epidemiological investigation did not allow the formulation of hypotheses on food items possibly associated with the outbreak owing mainly to patients' difficulties in remembering foods they ate, and the tendency of health-care professionals to direct patient's suspicion towards specific food items.

Significance and impact of the study: This finding highlighted the value of real-time molecular subtyping in salmonellosis outbreak identification. In order to improve national epidemiological investigations implementing public health agency network and planning, information campaigns for health-care professionals are required.