Incidence of virulence genes in predominant Brucella strains among domestic animals in Egypt

Abstract

To investigate the incidence of the virulence genes among predominant Brucella strains in infected cattle, buffaloes, sheep, goats, and camels as well as in humans in Egypt, a total of 263 samples (85 milk, 167 tissue, 11 whole blood samples), yielded 140 (53.2%) Brucella isolates. Confirmation of Brucella isolates was carried out by conventional biotyping and by PCR using IR1/IR2 primers targeting Brucella genus showing an amplicon of 839 bp in all Brucella isolates. Conventional bioty­ping, as well as duplex PCR of the isolated non-repetitive Brucella strains, identified 107 (76.4 %) as B. melitensis with an amplicon of 731 bp and 33 (23.6%) as B. abortus with an amplicon of 498 bp. Out of 87 Brucella strains isolated from cattle, 63 (72.4%) were B. melitensis. No Brucella isolates were obtained from 7 lymph nodes of camels or 11 human blood samples; however, DNA extraction from 7 human sera and 3 camel lymph nodes gave positive PCR yield. All these samples gave PCR products indicating infection with B. melitensis. The distribution of the virulence genes among 33 B. abortus isolates revealed that virB recorded the highest incidence (97%), then followed bvfA, ure, and omp25 (93.9%), wbkA (90.9%), manB (87.9%) and amiC (84.8%). All 107 B. melitensis isolates had the bvfA, virB, and omp25 genes, while the prevalence of ure was 99.1%, that of wbkA: 96.3%, manB: 95.3% and amiC: 94.4%. The obtained results indicated the high incidence of virulence genes among field Brucella strains among farm animals in Egypt.