The clinical manifestations and laboratory test results of Brucella melitensis and Brucella abortus in acute brucellosis patients

BACKGROUND: Brucellosis is an emerging zoonotic disease worldwide. Brucella melitensis, Brucella abortus, Brucella suis, and Brucella canis are the main etiologic agents causing human brucellosis. It has been considered that Brucella melitensis is the most virulent Brucella species but relative studies are rare. We try to verify this viewpoint by comparing the clinical manifestations and laboratory test results of patients infected with different Brucella species. METHODS: In this study, blood samples of acute brucellosis patients were collected in four locations in China. A culture-independent nested PCR method for simultaneous detection and differentiation of B. melitensis and B. abortus was designed and applied to determine the etiologic Brucella species. The clinical manifestations and laboratory test data of the patients were then collected and analyzed. RESULTS: A total of 349 blood samples were collected and 55 Brucella strains (38 B. melitensis and 17 B. abortus) were identified. For patients infected with B. abortus, the proportions of fatigue, arthralgia, and sweating are apparently higher. For patients infected with B. melitensis, larger proportions of decreased eosinophils and elevated CRP were observed. CONCLUSIONS: Our results indicated that it may not be appropriate to claim that Brucella melitensis is the most virulent Brucella species. Brucella abortus and B. melitensis just result in different clinical manifestations and laboratory test results in humans.