Brucella

A 38-year-old male dairy farmer from Punjab presents with a 3-week history of undulating fever, chills, and generalized malaise. He reports occupational exposure to unpasteurized milk and animal products. Physical examination reveals hepatomegaly (3 cm below costal margin) and mild splenomegaly. Blood cultures remain negative after 48 hours of standard aerobic incubation. Serum agglutination test shows a titre of 1:320 against Brucella. What is the most appropriate next step in management?

A 42-year-old woman from Rajasthan working in a livestock slaughterhouse presents with a 6-week history of recurrent fever (38.5–39.5°C), night sweats, fatigue, and joint pain. She has no hepatosplenomegaly. Blood cultures obtained on day 1 and day 5 are negative. Serum Brucella IgM and IgG agglutination titres are both 1:640. She was treated with doxycycline monotherapy for 4 weeks by a local physician 2 months ago. What is the most likely diagnosis?

Brucella species are characterized by which of the following structural features that distinguishes them from other gram-negative bacteria?

Which of the following is the most characteristic biochemical feature that allows presumptive identification of Brucella in the laboratory?