New Brucella variant isolated from Croatian cattle

Area of Science:

• Veterinary Microbiology
• Infectious Diseases
• Genomics

Background:

• Brucellosis is a significant zoonotic disease affecting livestock and humans.
• A brucellosis eradication program in Croatia detected an unusual Brucella strain in cattle.
• This finding is significant given the historical prevalence of brucellosis in the region.

Observation:

• A dairy cattle herd tested positive for Brucella infection.
• Initial identification suggested B. melitensis and B. abortus, but molecular methods confirmed all isolates as B. melitensis.
• Phylogenetic analysis revealed a novel Brucella variant closely related to strains from the Balkan region.

Findings:

• Two isolates were identified as Brucella melitensis biovar 3.
• A third isolate exhibited a unique phylogenetic profile, growth characteristics, and lacked a specific omp31 gene sequence found in B. melitensis bv. 3.
• Whole-genome sequencing and MLVA confirmed the proximity of the novel variant to regional B. melitensis strains.

Implications:

• The emergence of novel Brucella variants may be linked to high prevalence in animals and humans and suboptimal eradication strategies.
• Further investigation into the zoonotic potential, reservoirs, and transmission routes of this Brucella variant is crucial.
• Understanding these variants is essential for effective control and eradication of brucellosis.