Molecular detection and biovar characterization of Brucella melitensis in sera from wright-positive individuals in western Iran

Brucellosis remains a major zoonotic disease and an important public health concern in western Iran. This study aimed to molecularly detect Brucella spp., identify Brucella melitensis , and characterize its biovar in serum samples from Wright-positive individuals in five western provinces of Iran. A total of 100 serum samples from Wright-positive individuals were analyzed by PCR targeting the bcsp31 gene for Brucella spp. and the IS711 gene for B. melitensis . Biovar characterization of B. melitensis -positive samples was performed by PCR-RFLP analysis of the omp2a and omp2b genes using PstI and HinfI restriction enzymes. Brucella DNA was detected in 52/100 (52.0%) samples, of which 20/52 (38.5%) were identified as B. melitensis . PCR positivity was significantly associated with sex ( P = 0.018) and Wright agglutination titer ( P = 0.047), whereas no significant association was observed with age group ( P = 0.119) or province ( P = 0.738). PCR-RFLP analysis revealed the biovar 1 restriction pattern in all molecularly characterized B. melitensis DNA-positive samples. These findings demonstrate that PCR-based molecular assays provide valuable complementary evidence alongside serological testing for the investigation of human brucellosis. Further studies incorporating additional species-specific molecular assays are warranted to characterize the remaining Brucella DNA-positive samples and better define the distribution of Brucella species in western Iran.