Using molecular tools to identify the geographical origin of a case of human brucellosis

Abstract

Although Malta is historically linked with the zoonosis brucellosis, there had not been a case of the disease in either the human or livestock population for several years. However, in July 2013 a case of human brucellosis was identified on the island. To determine whether this recent case originated in Malta, four isolates from this case were subjected to molecular analysis. Molecular profiles generated using multilocus sequence analysis and multilocus variable number tandem repeat for the recent human case isolates and 11 Brucella melitensis strains of known Maltese origin were compared with others held on in-house and global databases. While the 11 isolates of Maltese origin formed a distinct cluster, the recent human isolation was not associated with these strains but instead clustered with isolates originating from the Horn of Africa. These data was congruent with epidemiological trace-back showed that the individual had travelled to Malta from Eritrea. This work highlights the potential of using molecular typing data to aid in epidemiological trace-back of Brucella isolations and assist in monitoring of the effectiveness of brucellosis control schemes.

Keywords: Brucella; brucellosis; molecular epidemiology.

Fig. 1.

Dendrogram illustrating MLVA-16 profiles of over 700 Brucella melitensis isolates from different parts of the world [, –10]. The green labels represent profiles from strains known to originate in the Horn of Africa. The yellow labels are profiles from the 11 known Maltese strains. The red labels are from the four isolates taken from the recent human case.