Detection of Virulence-Associated Genes among Brucella melitensis and Brucella abortus Clinical Isolates in Greece, 2001–2022

Brucellosis remains an important zoonotic disease in several parts of the world; in Greece, although it is declining, it is still endemic, affecting both the financial and public health sectors. The current study was undertaken to investigate the presence and distribution of virulence-associated genes among Brucella spp. clinical strains isolated during 2001–2022. Species identification was performed using conventional methodology and Bruce-ladder PCR. The presence of the virulence genes mviN, manA, wbkA, perA, omp19, ure, cbg and virB was investigated using PCR. During the study period, a total of 334 Brucella isolates were identified, of which 328 (98.2%) were detected from positive blood cultures; 315 (94.3%) of the isolates were identified as B. melitensis, whilst the remaining 16 (4.8%) and 3 (0.9%) were identified as B. abortus and B. suis, respectively. Notably, two of the B. melitensis were assigned to the REV-1 vaccine strain type. The presence of the omp19, manA, mviN and perA genes was confirmed in all 315 B. melitensis isolates, while ure, wbkA, cbg and virB genes were detected in all but 9, 2, 1 and 1 of the isolates, respectively. All eight virulence genes were amplified in all B. abortus and B. suis isolates. The detection rate of virulence genes did not differ significantly among species. In conclusion, brucellosis is still considered a prevailing zoonotic disease in Greece, with the majority of the isolates identified as B. melitensis. The eight pathogenicity-associated genes were present in almost all Brucella isolates, although the ure gene was absent from a limited number of B. melitensis isolates.