Whole Genome Sequencing for Tracing Geographical Origin of Imported Cases of Human Brucellosis in Sweden.

Sacchini Sacchini,Zilli Zilli,Wahab Wahab,Di Giannatale Di Giannatale,Garofolo Garofolo,Abass Abass,Janowicz Janowicz

doi:10.3390/microorganisms7100398

Abstract

Human infections with Brucella melitensis are occasionally reported in Sweden, despite the fact that the national flocks of sheep and goats are officially free from brucellosis. The aim of our study was to analyze 103 isolates of B. melitensis collected from patients in Sweden between 1994 and 2016 and determine their putative geographic origin using whole genome sequencing (WGS)-based tools. The majority of the strains were assigned to East Mediterranean and African lineages. Both in silico Multiple Loci VNTR (Variable Number of Tandem Repeats) Analysis (MLVA) and core genome Multilocus Sequence Typing (cgMLST) analyses identified countries of the Middle East as the most probable source of origin of the majority of the strains. Isolates collected from patients with travel history to Iraq or Syria were often associated with genotypes from Turkey, as the cgMLST profiles from these countries clustered together. Sixty strains were located within a distance of 20 core genes to related genotypes from the publicly available database, and for eighteen isolates, the closest genotype was different by more than 50 loci. Our study showed that WGS based tools are effective in tracing back the geographic origin of infection of patients with unknown travel status, provided that public sequences from the location of the source are available.

Highlights

IntroductionHalf a million cases of human brucellosis are reported worldwide, but the actual number of cases is estimated to be ten times higher [1,2]
Brucellosis is one of the most widespread bacterial zoonosis globally
Majority of human cases are caused by Brucella melitensis, which is most frequently transmitted through direct contact with infected goats and sheep and through consumption of unpasteurized milk and dairy products contaminated with the bacteria [3,4,5]

Summary

Introduction

Half a million cases of human brucellosis are reported worldwide, but the actual number of cases is estimated to be ten times higher [1,2]. Majority of human cases are caused by Brucella melitensis, which is most frequently transmitted through direct contact with infected goats and sheep and through consumption of unpasteurized milk and dairy products contaminated with the bacteria [3,4,5]. Unspecific clinical presentation and the failure of correct primary diagnosis and treatment often leads to disease progression with genitourinary, neurological, pulmonary, or cardiovascular system involvement, with endocarditis being the most serious of the complications [4,6,7]. For a prompt diagnosis, particular attention should be given to the patient’s history of travel to brucellosis endemic areas and consumption of raw milk products

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Conclusion