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

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.

Newly identified variability in Brucella canis fatty-acid content is associated with geographical origin.

This study compared the fatty-acid profiles of Brucella canis blood culture isolates obtained from infected dogs in the UK, Germany, Japan, South Africa, Peru, Mexico, Colombia, and Argentina, and from a human clinical case in Argentina, to a bank of isolates obtained from canine outbreaks in the USA. Analysis of a total of 42 B. canis isolates and one reference strain found a marked variation within the species. Fatty-acid analysis showed that only the isolates from Argentina, Colombia, and Mexico, which included the human B. canis isolate, contained a specific fatty acid, 19:0 cyclopropane (lactobacillic acid), w8c (cis-11,12-methylene octadecanoic acid), and that this fatty acid, when present, made up a large percentage of overall fatty-acid content. Prior to this study, the cellular fatty-acid 19:0 cyclopropane had been identified in all of the species of Brucella considered to be pathogenic to humans (B. abortus, B. melitensis, B. suis) except for B. canis. Discovering that this fatty acid not only occurs in B. canis, but also that it is only present in some strains of the species provides a new focus for investigations aimed at identifying the cause of reported geographical variability in human B. canis infection, and at finding predictors of biological behaviour and human pathogenicity within this Brucella species.