Imported human brucellosis in Belgium: Bio and molecular typing of bacterial isolates, 1996-2015

The aim of this study was to characterize by classical biotyping and Multi-Locus variable number tandem repeats (VNTR) Analysis (MLVA) all Brucella spp. derived from human cases in Belgium from 1996 to 2015. Final goals were to determine the species and biovar, to trace-back on genetic grounds the origin of each strain when patient history and risk factors were missing, and to survey for particular trends at the national level.

A total of 37 Brucella strains, isolated from 37 patients in Belgium, were analyzed by both classical biotyping and MLVA, and the genetic patterns compared to those of human strains isolated worldwide.

Classical biotyping revealed that isolates were mainly Brucella melitensis. Most of them belonged to biovar 3, the most abundant biovar in the Mediterranean region. MLVA confirmed that Brucella melitensis is too diverse in VNTRs to be able to make clusters associated to each biovar, but it allowed retrieving precious epidemiological information. The analysis highlighted the imported nature of the strains from all over the world with a dominant part from the Mediterranean countries. Findings of the MLVA11 testing were in line with the travel history of patients coming from Italy, Turkey, Lebanon and Peru. The analysis was particularly useful because it suggested the geographical origin of the infection for 12/16 patients for whom no case history was available.

Classical biotyping and MLVA analysis are not exclusive but remain complementary tools for Brucella melitensis strain surveillance. MLVA11 is sufficient for Brucella-free countries such as Belgium to trace the geographical origin of infection, but complete MLVA16 is needed to search for links with endemic areas.