There are seven classical species of Brucella. Which is considered the most virulent Brucella spp. for humans?

There are seven classical species of Brucella. Which is considered the most virulent Brucella spp. for humans?

• A. Abortus
• B. Suis
• C. Melitensis
• D. Canis

Answer: (C)

Brucella melitensis is the most virulent Brucella species for humans. Its high pathogenicity is due to several factors: it requires a very low infectious dose to establish infection, and once inside the body it thrives as an intracellular pathogen, surviving and multiplying within macrophages and spreading to multiple organs such as the liver, spleen, bones, and sometimes the nervous system. This capability leads to more severe and persistent illness, often presenting as undulant fever with systemic symptoms. Historically, melitensis is most strongly associated with goats and sheep and is commonly acquired by humans through consumption of unpasteurized dairy products or direct contact with infected animals. While other Brucella species—those from cattle, swine, or dogs—can also cause disease in people, they generally tend to be less virulent and may require a higher infectious dose or yield somewhat less severe illness on average.

Brucella melitensis is the most virulent Brucella species for humans. Its high pathogenicity is due to several factors: it requires a very low infectious dose to establish infection, and once inside the body it thrives as an intracellular pathogen, surviving and multiplying within macrophages and spreading to multiple organs such as the liver, spleen, bones, and sometimes the nervous system. This capability leads to more severe and persistent illness, often presenting as undulant fever with systemic symptoms.

Historically, melitensis is most strongly associated with goats and sheep and is commonly acquired by humans through consumption of unpasteurized dairy products or direct contact with infected animals. While other Brucella species—those from cattle, swine, or dogs—can also cause disease in people, they generally tend to be less virulent and may require a higher infectious dose or yield somewhat less severe illness on average.