Advancement of Knowledge of Brucella Over the Past 50 Years

Abstract

Fifty years ago, bacteria in the genus Brucella were known to cause infertility and reproductive losses. At that time, the genus was considered to contain only 3 species: Brucella abortus, Brucella melitensis, and Brucella suis. Since the early 1960s, at least 7 new species have been identified as belonging to the Brucella genus (Brucella canis, Brucella ceti, Brucella inopinata, Brucella microti, Brucella neotomae, Brucella ovis, and Brucella pinnipedialis) with several additional new species under consideration for inclusion. Although molecular studies have found such high homology that some authors have proposed that all Brucella are actually 1 species, the epidemiologic and diagnostic benefits for separating the genus based on phenotypic characteristics are more compelling. Although pathogenic Brucella spp have preferred reservoir hosts, their ability to infect numerous mammalian hosts has been increasingly documented. The maintenance of infection in new reservoir hosts, such as wildlife, has become an issue for both public health and animal health regulatory personnel. Since the 1960s, new information on how Brucella enters host cells and modifies their intracellular environment has been gained. Although the pathogenesis and histologic lesions of B. abortus, B. melitensis, and B. suis in their preferred hosts have not changed, additional knowledge on the pathology of these brucellae in new hosts, or of new species of Brucella in their preferred hosts, has been obtained. To this day, brucellosis remains a significant human zoonosis that is emerging or reemerging in many parts of the world.Keywords Brucella, pathogenesis, zoonosis, reservoir hosts, laboratory modelsIn 1966, the first issue of Pathologia Veterinaria-now known as Veterinary Pathology-published an article on the characteristics of Brucella granulomas by K. L. Jacob, and the third issue included a manuscript by B. I. Osburn and P. C. Kennedy describing pathologic and immunologic responses of fetal lambs after infection with Brucella ovis. As the journal embarks on its second half-century of publication, it seems appropriate to assess the advancement of knowledge on this topic since these articles were published in the first issues of the journal.Fifty years ago, bacteria in the genus Brucella were known to cause infertility and reproductive losses with predilection for causing placentitis, fetal pneumonia, and mastitis. At that time, the genus contained only Brucella abortus, Brucella melitensis, and Brucella suis, the 3 classic species of brucellae, and these were generally thought to be somewhat hostspecific pathogens of cattle, sheep and goats, and swine, respectively. They were also known to be zoonotic, with the capability for causing clinical disease in humans. At that time, taxonomy placed the 3 classic species in the family Brucellaceae, with other bacterial genera such as Bordetella, Pasteurella and so on. Although scientific and practical knowledge of brucellosis has increased dramatically, in many countries, brucellosis continu...

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Expression of Brucella Lumazine Synthase Gene in E. coli System

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